ENVI 202 Complete Module

Page 1 Tree BiologyTr e e B i o l o g y ENVI 202ENVI 202 Student NotesStudent Notes Page 2 ENVI 202 - TREE BIOLOGY Developed by: Anita Schill, Land & Horticultural Sciences, Olds College Course Editing: Learning Enhancement Services, Olds College Desktop Publishing: Bonnie Rice, Land & Horticultural Sciences, Olds College © Copyright Olds College 1997 Available from the Olds College Bookstore 4500-50 Street, Olds, Alberta T4H 1R6 Published by Land Sciences Centre, Olds College Printed by Duplicating Services, Olds College All Rights Reserved The contents of ENVI 202 - Tree Biology or any part thereof must not be reproduced in any form without the written permission of the publisher. 1st Edition, 1st Printing - September 1997 Page 3 i ENVI 202 - Tree Biology Table of Contents Table of Contents Module A1 Tree Health .........................................................................................................................................1 Requirements of a Healthy Tree .........................................................................................................................................2 Symplast and Apoplast .......................................................................................................................................................2 Differences Between Plants and Animals in Reaching Old Age ........................................................................................3 Module A2 Communication ...................................................................................................................................5 Roots and Crown Support Each Other ................................................................................................................................6 Signals to Maintain Order ...................................................................................................................................................7 The Root:Crown Balance ...................................................................................................................................................7 Module B1 The Tree in 3-D ...................................................................................................................................9 Investigation .....................................................................................................................................................................10 Tissues in a Transverse Section ........................................................................................................................................10 Apply I2KI .......................................................................................................................................................................12 Radial and Tangential Sections .........................................................................................................................................14 Module B2 Growth ..............................................................................................................................................17 Bark, Its Growth and Function .........................................................................................................................................18 The Vascular Cambium and Its Products ..........................................................................................................................21 Sapwood vs Heartwood ....................................................................................................................................................24 Module B3 Coniferous and Hardwood ................................................................................................................27 Resin Ducts .......................................................................................................................................................................28 Vessels and Tracheids .......................................................................................................................................................28 Ring porous and diffuse-porous ........................................................................................................................................29 Module C1 Mass vs Energy ................................................................................................................................31 Dynamic and Static Mass .................................................................................................................................................32 Young, Mature and Old Trees ...........................................................................................................................................33 Parts of the Tree — First Energy Demand to the Least ....................................................................................................34 Symptoms of Energy Status in a Tree ...............................................................................................................................35 Module C2 Energy From the Sun ........................................................................................................................37 Light Energy .....................................................................................................................................................................38 Photosynthesis ..................................................................................................................................................................39 Potential and Kinetic Energy ............................................................................................................................................41 Module C3 Phenology .........................................................................................................................................43 Phenological Stages ..........................................................................................................................................................44 Differences Among Species and Climates ........................................................................................................................48 Energy Reserves ...............................................................................................................................................................50 Module C4 Stress vs Strain .................................................................................................................................53 System Disorder ................................................................................................................................................................54 Tree Condition ..................................................................................................................................................................55 Module D1 Branch Attachments ..........................................................................................................................57 Bud Development .............................................................................................................................................................58 How Branches are Attached ..............................................................................................................................................59 Page 4 ENVI 202 - Tree Biology Table of Contents ii Module D2 Branch Anatomy ................................................................................................................................61 Bud Development .............................................................................................................................................................62 Branch Attachments ..........................................................................................................................................................63 Branch Protection Zone ....................................................................................................................................................63 Module D3 Included Bark and Codominant Stems .............................................................................................65 Codominant Stems ............................................................................................................................................................66 Pruning a Codominant Stem .............................................................................................................................................66 Included Bark ....................................................................................................................................................................67 Pruning a Branch/Stem Attachment with Included Bark ..................................................................................................67 Module D4 Pruning Responses ...........................................................................................................................69 Tree Response to Pruning at Various Stages .....................................................................................................................70 Epicormics ........................................................................................................................................................................71 Flush Cuts .........................................................................................................................................................................72 Correct Pruning .................................................................................................................................................................72 Woundwood ......................................................................................................................................................................74 Topping .............................................................................................................................................................................75 Module D5 Training Young Trees ........................................................................................................................77 Pruning a Young Tree .......................................................................................................................................................78 Module E1 Root Comparison ..............................................................................................................................79 Root Development ............................................................................................................................................................80 Woody and Non-woody Roots ..........................................................................................................................................81 Root Location ...................................................................................................................................................................83 Module E2 Root Response .................................................................................................................................85 Root Pruning .....................................................................................................................................................................86 Root Condition Assessment ..............................................................................................................................................86 Digging and Planting ........................................................................................................................................................88 Module F1 Defence .............................................................................................................................................89 Energy Demand ................................................................................................................................................................90 Response to Wounding .....................................................................................................................................................90 Compartmentalization .......................................................................................................................................................92 Module F2 Wounds and Decay ...........................................................................................................................95 Dating a Wound ................................................................................................................................................................96 Cracks ...............................................................................................................................................................................97 Good and Bad Compartmentalizers ..................................................................................................................................98 False Heartwood ...............................................................................................................................................................99 Module G1 Environmental Stress ......................................................................................................................101 Drought ...........................................................................................................................................................................102 Temperature ....................................................................................................................................................................103 Oxygen Deficiency .........................................................................................................................................................103 Module G2 Tree Selection .................................................................................................................................105 Species and Growth Characteristics ...............................................................................................................................106 Root Inspection ...............................................................................................................................................................107 Crown Inspection ............................................................................................................................................................108 Page 5 iii ENVI 202 - Tree Biology Table of Contents Module G3 Soil and Fertilization ........................................................................................................................111 Fertilization .....................................................................................................................................................................112 With Nitrogen .................................................................................................................................................................113 Fertilizing a Tree in Decline ...........................................................................................................................................115 Herbicides, Soil Compaction and Competition ..............................................................................................................116 Accurate Records and Follow-up ...................................................................................................................................117 Module G4 Planting ...........................................................................................................................................119 Design Considerations ....................................................................................................................................................120 Handling Trees ................................................................................................................................................................121 Planting ...........................................................................................................................................................................122 Postplanting Care ............................................................................................................................................................126 Establishment ..................................................................................................................................................................129 Module G5 Industry Practices ...........................................................................................................................131 Injections .........................................................................................................................................................................132 Wrapping Trees ...............................................................................................................................................................133 Planting Annuals and Bulbs ............................................................................................................................................133 Weed Whips ....................................................................................................................................................................133 References ........................................................................................................................................................135 Page 6 ENVI 202 - Tree Biology Table of Contents iv Page 7 1 ENVI 202 - Tree Biology Module A1 Module A1 Identify and explain the factors that determine a “healthy” tree. Tree Health In order to recognize a healthy tree, you will be able to: • Describe the requirements of trees to be healthy • Differentiate between symplast and apoplast • Compare tree systems to animal systems Image source: Olds College Page 8 ENVI 202 - Tree Biology Module A1 2  Describe the requirements of trees to be healthy  Differentiate between sym - plast and apoplast Compare tree systems to animal systems Requirements of a Healthy Tree Trees have needs that must be met to ensure good health. Trees need to rest. This necessity must not be disturbed by practices such as water- ing at the wrong time, or incorrect fertilization. Good nutrition is mandatory for the health of any living organism, including trees. Trees must be allowed the opportunity to maximize the amount of photosynthesis they can possibly manage to ensure a good food supply. Trees make their own food (carbohydrates with high en- ergy yielding bonds), so we cannot “feed” a tree. Through fertilization, we supply elements (not nutrients) that can be taken up by the root system. Once in the tree, the elements combine with an energy source (carbohydrates) to form nutrients. Sanitation is critically important in ensuring tree health. Any method of preventing the entry of insects and disease-causing organisms is recommended to ensure the health of a tree. Trees require exercise to be healthy. Trees in shopping malls are found to benefit from regular washing and pulling to make the leaves, twigs and the branches move and sway. Consider all the movement a tree un- dergoes in the wind, rain and snow. These activities determine where growth is required to strengthen tree parts that must contend with what nature throws at them(34a). Symplast and Apoplast Symplast: The symplast is the connection of all living cells in a tree. The symplast consists of the phellogen in the bark, phloem rays, wood rays and axial parenchyma. Plasmodesmata strands connect the pro- toplasm of all the living cells resulting in a live network. To move anything from cell to cell within the symplast requires high amounts of energy. There is always that price to pay so that work can be done, such as the movement of water and minerals. Apoplast: The apoplast consists of all the dead, empty tissues in a tree. Vessels, fibres, and cell walls are part of the apoplast(33). Page 9 3 ENVI 202 - Tree Biology Module A1 Differences Between Plants and Animals in Reaching Old Age People have regenerating systems that have parts that move and even- tually wear out. They have the ability to “heal”, to repair and replace cells. People eat daily, 365 days per year, and not much energy is stored. They grow until they become adult size and growth stops. Trees, on the other hand, are generating systems. They generate and add on more cells. Trees put “new parts in new places” and get bigger and bigger. Trees store the energy that they were able to manufacture during the growing season. If this energy becomes depleted the tree is in big trouble; it cannot be fed as it must manufacture its own food. As a tree puts new parts in new places, it grows bigger and bigger. The extent of growth therefore is limited to the energy available(34). Trees cannot heal their wounds, rather, they “seal” them off with walls of new wood(34). Every system, whether plant or animal, must undergo similar natu- ral processes. Every system must rest and then be able to start again. Energy must be consumed to maintain order. Organisms must grow, defend themselves and reproduce. A system is a collection of parts and processes that are highly ordered so that they have a predetermined product and service. Describe the requirements of trees to be healthy Differentiate between sym - plast and apoplast  Compare tree systems to animal systems Page 10 ENVI 202 - Tree Biology Module A1 4 Self-Check 1. What is tree food? 2. Comment on the landscape industry practice of “deep-root feeding”. 3. Explain how large trees may seem completely hollowed out (can drive through some giant redwood trees) yet still very much alive. 4. a) List the tissues that make up the symplast, or living network. b) What is required for these tissues to function, to work? Answers 1. “Tree food” is sugar, often stored as carbohydrates. The photosynthe- sis process manufactures this sugar - the tree feeds itself. 2. We cannot feed trees - we can only ensure that required minerals are available. When the minerals enter the plant via the root, they combine with sugars to form nutrients. 3. The active cells that function in transport and energy storage are all contained within the last few years of growth. New parts are produced on top of old parts. 4. a) phloem axial and radial parenchyma plasmodesmata phellogen b) energy Page 11 5 ENVI 202 - Tree Biology Module A2 Module A2 Explain how tree parts communicate their health status to other parts. Communication In order to describe how a tree communicates messages from one part to another, you will be able to: • Explain the function of the roots and the crown • Describe the role of auxin and cytokinin for signal communication • Explain the importance of maintaining the root:crown balance Image source: Olds College Page 12 ENVI 202 - Tree Biology Module A2 6  Explain the function of the roots and the crown Describe the role of auxin and cytokinin for signal communi - cation Explain the importance of maintaining the root:crown balance Roots and Crown Support Each Other Roots and shoots depend on each other for growth. Roots are able to send messages to the shoots, and shoots equally send messages to the roots. This communication reveals the health and growth status throughout the entire tree(5). Roots Provide Water and Minerals to the Crown The roots gather minerals and water to supply the roots and the crown. Sugars combine with the minerals, like nitrogen, to form nutrients, or the building blocks. This results in increased growth and develop- ment(33). The Crown Provides Sugar to the Roots The crown supplies the entire tree with sugars, including the roots since roots do not photosynthesize. This way, roots are able to grow and develop in balance with the crown development. The crown is like an upper oscillating pump and the roots as a low- er oscillating pump. One pump receives energy and the other pump moves water. Water must be moved against a gradient, like moving uphill, so a pump is necessary. There exists a dynamic equilibrium that continually oscillates back and forth. Balance is not the goal. Where there is balance, there is equalization of opposing forces. It is better for the pumps to be at different points all the time. Figure A2-1. Oscillating pumps. Image source: Olds College Page 13 7 ENVI 202 - Tree Biology Module A2 Signals to Maintain Order It is through concentrations of plant growth regulators, or hormones, that roots and shoots communicate their health and growth status to each other. Growth regulators maintain order within the entire tree; they bring messages to all living cells. Once the message is received by a cell, it can respond appropriately. The hormones act like a switch - turn them on to accomplish a specific job(5). Cells must be healthy in order for the job to be performed. They re- quire lots of water and enough food for energy to complete tasks suc- cessfully. The signal may be received but if the resources aren’t there, the job won’t get done. Auxins, a hormonal growth regulator, are produced in the shoots and are transported down to the roots, cell - to - cell. Only living cells can pass the message on. Cytokinins, produced in the roots, are transported up to the shoots. These hormones provide signals of root health and its status of mineral uptake to the shoot(5). The changes in the ratio of auxin and cytokinin concentrations de- termines what changes will occur in the tree. The amount of auxin produced will affect how much cytokinin is produced in the roots. The root status message from the cytokinin affects the amount of auxin produced in the shoot. The Root:Crown Balance A given root is directly connected to a particular set of branches, usu- ally on the same side of the tree(30). If some roots die or are removed, there is less demand for sugars. Corresponding leaves and branches may die.(30) The root:crown balance can be physically disrupted by branch remov- al, transplanting, or physiologically disrupted through the effects of drought, flooding, vascular constriction, excessive transpiration, etc. (47). A small root system will inhibit the growth of shoots; a reduction in shoot development will limit root growth(20). If water is in short supply, stomata close, photosynthesis slows down, and sugar production is reduced. Fewer and smaller leaves often result. Explain the function of the roots and the crown  Describe the role of auxin and cytokinin for signal communication  Explain the importance of maintaining the root:crown balance Page 14 ENVI 202 - Tree Biology Module A2 8 If a photosynthesis portion of the tree is destroyed (from pruning, defoliation), some roots will die back. Many other physiological func- tions are seriously affected(30). Loss of roots or root function has the most serious effect on the bal - ance. Increased crown size does not lead to better root development! When nitrogen is applied too heavily, more shoot growth is stimu - lated compared to root growth. The root:crown ratio is decreased. A lower level of fertility leads to the best balance between roots and crown.(47, 49) To restore root:crown balance - mulch and improve soil aeration. Effort should be focused on root health and how to improve the soil environment for tree roots, instead of trying to make the tree grow faster and bigger(47). Self-Check 1. Why do roots store such large quantities of carbohydrates com- pared to the rest of the tree? 2. Describe where auxins and cytokinins are produced and what their roles as messengers entail. 3. Why is it unadvisable to fertilize with the purpose of increasing the crown size? 4. How do the roots support the crown? How does the crown support the roots? 5. How can mulching improve the root:crown balance? Answers 1. Roots do not photosynthesize, and therefore cannot make their own food. The crown feeds the roots with sugars to be stored and easily accessed as the roots need it. 2. Auxins are produced by the shoots. They will move down to tell the roots about the health status of the crown. Cytokinins are produced in the roots and relate to the rest of the tree, whether or not the roots are in good health. 3. This will disrupt the root:crown ratio. Increased crown does not result in a larger root system. 4. The roots provide water and min- erals to the crown and the crown produces sugar for the roots. 5. Pay more attention to the health of the roots instead of the crown. Mulching provides aeration and drainage. Oxygen is required by the roots for normal, efficient respi- ration to occur. Page 15 9 ENVI 202 - Tree Biology Module B1 Module B1 Illustrate and label tree sections in the transverse, radial and tangential views. The Tree in 3-D In order to be able to visualize the tree three dimensionally, you will be able to: • Identify and locate the different tissues found in a transverse section of oak or elm wood • Illustrate and describe the significance of the results after the application of I2KI to the wood surface • Identify and locate the tissues from the radial and tangential views Image source: Olds College Page 16 ENVI 202 - Tree Biology Module B1 10  Identify and locate the different tissues found in a transverse section of oak or elm wood Illustrate and describe the significance of the results after the application of I 2KI to the wood surface Identify and locate the tissues from the radial and tangential views Investigation Purpose To cleanly and clearly expose tissues found in the woody sections of trees for study. Materials Required • Hand saw • Sharp knife - like a hunting knife • Single or one-edged razor blades • Bread board to perform cutting • First-aid kit • Rubber gloves The procedure to follow is described below. Tissues in a Transverse Section Cutting a Transverse Section Saw a slice of wood from the branch or trunk provided, using a hand saw. The slice should be near 1.5 cm in thickness. Do not sand the wood. By using an electric planer or a sharp knife - use extreme caution - slice/clean off the surface of one side of the wood to expose the vessels. Do another slicing this time with a one-edged razor blade. The entire surface need not be cleaned. (A pie-section should be clean, the pith being the center point.) Check with your instructor to see if the exposure is clear enough. Otherwise nothing will be seen and it will be a most frustrating experience. Page 17 11 ENVI 202 - Tree Biology Module B1 Identify the following tissues: Bark/Epidermis Phellum-outer bark, bark cambium or phel- logen-greasy looking, phelloderm Cortex tissue Green layer. Phloem Grit cells like crystals. Vascular Cambium Xylem Vessels The vessels are arranged in and axial di- rection (up and down) so in the transverse section view, they appear as large and small holes. Only the most recent year will have open vessels that function in mineral and water transport. Pith Will appear shiny and flaky, like sponge toffee. Growth Increment Earlywood/Latewood Large vessels indicate those formed at the beginning of the growing season. Smaller vessels develop later in the season. The large vessels are earlywood, the small are late- wood. In elm, the wood will have character- istic white, “wormy” lines throughout. These are latewood vessels in elm. Illustrate and label the tissues listed above: Page 18 ENVI 202 - Tree Biology Module B1 12 Apply I2KI Apply the I2KI (Iodine in Potassium Iodide) to a “Pie Section” of the Transverse Section Mix 0.3 g I crystal, 1.5 g KI solution, in 100 ml H2O. Shake well. This solution will stain only the starch that are in living cells. The stain is purple. This solution is extremely poisonous - do not allow contact with skin and do not ingest. Wash hands thoroughly after application especially before eating, drinking, smoking, etc. Draw and colour a diagram of your observations. The I2KI solution, when applied to the wood, will turn bluish-purple Identify and locate the different tissues found in a transverse section of oak or elm wood  Illustrate and describe the significance of the results after the application of I 2KI to the wood surface Identify and locate the tissues from the radial and tangential views Image source: Olds College Observations after I2KI Application Image source: Olds College Page 19 13 ENVI 202 - Tree Biology Module B1 when there is a presence of starch. Starch (carbohydrates) will only be stored in living cells called parenchyma cells. Looking at the “purple” reveals the network of symplastic compartments - boxes within boxes within boxes. The purple dots are the cross-section of the axial paren- chyma. Most of the purple will be in the last five or six rings. Every purple dot is a battery of stored energy. The cambial zone will not show any purple. (If it is, check with the instructor to ensure a better cleaning of the sample.) The cambial zone does not store energy - it uses energy. The vascular cambium is widest and therefore best viewed in the spring during active growth. In the spring, the vascular cambium is several layers thick and can be seen easily with the aid of a dissect- ing microscope. At any time, the vascular cambium can be witnessed by pushing the cross-section of wood with an inward push using the thumbs and forefingers. A clear watery gel-like substance will be squeezed out revealing the location of the vascular cambium layer. The vessels themselves will not have any purple but they are surround- ed by parenchyma cells that will be purple, full of stored energy. Page 20 ENVI 202 - Tree Biology Module B1 14 Radial and Tangential Sections Cutting the Radial and Tangential Sections Take the transverse section of wood you have been investigating and cut it across through the pith. Lay the sharp edge of the large knife an top of the wood and gently hit the knife downwards through the wood with a mallet or sledge. This exposes the radial view. Discard one of the pieces of wood. Take the knife and cut down at the edge of the piece, cutting just with- in the last one or two growth increments. Do not clean or shave these views. Apply the I2KI immediately. Illustrate and label from the radial view: Fibres Are arranged axially and remain clear Vessel Elements Plugged and unplugged Radial and Axial Parenchyma Weaves in and out like a basket Pith Identify and locate the different tissues found in a transverse section of oak or elm wood Illustrate and describe the significance of the results after the application of I 2KI to the wood surface  Identify and locate the tissues from the radial and tangential views Image source: Olds College Page 21 15 ENVI 202 - Tree Biology Module B1 Illustrate and label from the tangential view. Ray Parenchyma Appear as basket weaving. Image source: Olds College Page 22 ENVI 202 - Tree Biology Module B1 16 Self-Check 1. What does I2KI test for? 2. Give two reasons why the vessels themselves do not show any purple stain. 3. Which living cells store starch? 4. a) Which tissues are arranged axially? b) which are arranged radially? Answers 1. The presence of starch (stored sugar). 2. Vessels are cells that are not living and they do not store any starch. 3. Parenchyma 4. a) vessels axial parenchyma fibres b) radial parenchyma Page 23 17 ENVI 202 - Tree Biology Module B2 Module B2 Describe the formation and function of specific tissues found in trees. Growth In order to understand how a tree produces woody tissue, you will: • Explain how bark functions and grows to compensate for the new growth increment • Describe the function of vascular cambium and the function of its products • Distinguish between sapwood and heartwood in function and appearance Image source: Olds College Page 24 ENVI 202 - Tree Biology Module B2 18  Explain how bark functions and grows to compensate for the new growth incre - ment Describe the function of vascular cambium and the function of its products Distinguish between sapwood and heartwood in function and appearance Bark, Its Growth and Function In young trees, the epidermis appears as a waxy outer layer. This layer eventually splits off as the tree increases in girth. Older trees have bark. The cells of bark are always moving during the expansion of the circumference of the tree. The meristematic cells, called phellogen, produce cork cells that make up the bark. These cells are made of suberin. On the outside of the phellogen, phellem is produced. On the inner side of the phellogen is the phelloderm. Phellogen is still sym- plast. The bark cambial cells divide in two directions. There is a periclinal division which produces radial parenchyma resulting in an increase in girth. Then there is also an anticlinal division which produces axial parenchyma. These increase the tree’s circumference. Bark often cannot keep up with the increase in girth. Some trees have bark cambium that often only divides periclinally. There is no cir- cumferential growth so splits and fissures form on the trunk. Elms for example, have a characteristic diamond pattern of trunk because of splits and fissures due to its inability to keep up with wood production. Birch, on the other hand, has a smooth tight bark. This is an indication that new bark will be produced as fast as the new wood. Birch and beech are exceptions, they have extensive anticlinal division. Bark fissures prove that the symplast is never more than 0.5 cm. away. Defence boundaries in bark only hold for a year compared to the boundaries formed in the wood. One must then question the practices of injections. Can the active vessels be easily and accurately located? Often injections are inserted under pressure. Some of the treatments used in the industry are like “applying a tourniquet around the neck to stop a nosebleed”(34a). Image source: Olds College Page 25 19 ENVI 202 - Tree Biology Module B2 We think that tree trunks are invulnerable. Looking at how close the bark is to the active transport system and growth centre brings one to realize that even slight bark damage could adversely affect tree health. Trees with very thick bark still have fissures. These fissures are only millimeters away from the active phloem, cambium and xylem. Lawn- mower and weedwhip damage can quickly kill a tree. In young trees, there is a thin green layer of cortex tissue under the bark. Where there is green pigment, there is potential for photosyn- thesis. Young trees are able to actively photosynthesize with this large amount of chorophyll just under the bark. In mature trees, this green cortex will appear only as small pockets under bark where there are fissures and cracks. Old trees will have no green cortex under the bark at all. Image source: Olds College Image source: Olds College Page 26 ENVI 202 - Tree Biology Module B2 20 Image source: Olds College Page 27 21 ENVI 202 - Tree Biology Module B2 The Vascular Cambium and Its Products Just under the bark there are several layers (years) of old phloem that are closely condensed together providing a spongy, insulating protec- tion from damage. These layers do not have the capacity to transport sugars. These old layers of phloem are often referred to as “inner bark”. Along with the bark, the old phloem layers help protect the ac- tive phloem, the vascular cambium and the active xylem vessels. “Active” Phloem The active phloem cells, produced by the vascular cambium, are engaged in “active transport” of sugars. These cells move sugars to all parts of the tree requiring this energy at any point in time. The sugars move from the production site, the leaves, to where energy is required (source to sink) at the time, or are placed within storage cells (paren- chyma cells). The Cambial Zone The vascular cambium consists of cells are meristematic and are responsible for the increase of a tree’s girth. There is a ring of these cells under the bark. The thicker the cambium zone, the more vital (not vigorous) is the tree. The vascular cambium does not store energy - it uses energy. All the energy required must come from the stored reserves in the wood until the new leaves have fully expanded. When energy reserves are low, the tree is more susceptible to insects and diseases. It has no more in the budget for defence spending. Once the new leaves have fully expand- ed, the tree is no longer dependent on reserves. The vascular cambium cells divide to produce new cells that differenti- ate and organize into “active” phloem tissue (towards the outside) and xylem vessels (deposited towards the inside). Parenchyma cells, both axial and radial as well as wood fibres, are also produced by the vascu- lar cambium. Only with a continuous supply of the growth regulator hormones, auxins and gibberellins, will xylem vessels and phloem develop. To sustain enough vascular cambium growth, the tree depends on getting enough newly produced growth regulators from the shoot tips. Explain how bark functions and grows to compensate for the new growth increment  Describe the function of vascular cambium and the function of its products Distinguish between sapwood and heartwood in function and appearance Page 28 ENVI 202 - Tree Biology Module B2 22 Xylem Vessels The xylem vessels start forming in early spring. In the spring, it is easy to remove the bark; we say the bark is “slipping”. Actually the slippery material under the bark is the new wood being formed; wood which has not yet lignified. It takes three to four weeks for xylem cells to die so wait a few weeks. Strip the bark off; narrow hard ridges will be present. These vessels are lignified and functional. These new vessels have the major function of water uptake. Roots absorb water and minerals and send these to all living cells of the plant. This is possible because of the xylem vessels in the wood that water can be pulled up to the top. In species such as elm and oak, looking at the transverse view, large holes or vessels can be seen immediately following the dark line of the ring. These spring vessels grow very quickly. This is called earlywood. This early development of large vessels is an advantage for water uptake but pathogens also take advantage of these large open vessels. With many tree species, once these new vessels become functional that is, they are able to transport water, the previous year of vessels are plugged. This plugging of last year’s vessels is called tylosis. The purpose of plugging up these vessels is to prevent easy entry for microorganisms via the transport system. Some of the parenchyma cells that surround the xylem vessels exude their contents like a bubble to fill and plug up the old vessels. It is a simple method of defence. The cell contents of the parenchyma consist of phenolic compounds that will help deter the development and spread of disease-causing organisms within the vessel elements. As the season progresses, vessels are produced that are much smaller in size, yet still functional for water transport. This is called latewood. Every wood “ring” or growth increment of a healthy tree will consist of both earlywood and latewood. These vessels can easily be destroyed from lawn mower bashing or string trimmers. The tree cannot repair cells that are damaged or de- stroyed. Birch have vessel that are the same size throughout the growth ring. Early wood appears lighter in colour than that grown later in the grow- ing season. This is why there are distinguishable lines between the years. Late wood grows more slowly; the cells are more compressed, hence the darker colouration. Page 29 23 ENVI 202 - Tree Biology Module B2 Image source: Olds College In the first year of a tree’s life, the year of germination, it must produce a layer of wood to store sugar to ensure its winter survival. The first year includes the pith plus the first growth ring. Successive years can be calculated simply by counting the subsequent rings. Old xylem vessels help provide strength and rigidity to the tree for support but are no longer involved in movement of water and minerals. Wood is equally as strong for its weight as steel. 90% of growth incre- ment (annual ring) occurs 6-8 weeks after leaves emerge(33). In elm, looking at the transverse section (Module B1), the wood will have characteristic white, “wormy” lines throughout. These are late- wood vessels in elm. Page 30 ENVI 202 - Tree Biology Module B2 24 Explain how bark functions and grows to compensate for the new growth increment Describe the function of vascular cambium and the function of its products  Distinguish between sap - wood and heartwood in function and appearance Fibres and Parenchyma Cells The vascular cambium produces axial cells that differentiate into fibres, vessels and axial parenchyma. The radial cell production differ- entiate into radial parenchyma. Fibres may live for one week to several months. Some parenchyma may live for 150 years! Parenchyma cells are the living cells that store starch (as indicated by the purple colour after the I2KI solution was applied) (Module B1). Axial parenchyma cells are arranged in an axial direction, and radial parenchyma are arranged in a radial direction. There are only thin links from living cells, a continuous network that connects sugar formation in the leaves to sugar movement, energy storage, water movement and cell growth throughout the entire tree system. Without the thin connections of living cells in wood, active transport of water and food to various parts of the tree is disrupted, perhaps fatally. Movement of these transported substances require en- ergy. The energy can only be stored in living parenchyma cells(38). Sapwood vs Heartwood Sapwood is the wood that transports water and minerals, stores energy in the live parenchyma, provides mechanical support and maintains the defence and protection system. Heartwood is age-altered wood that provides mechanical support and maintains a defence and protection system. Heartwood is often wrong- ly thought to be dead wood. If heartwood is wounded, a protection boundary will be formed. An enzyme system is maintained within the heartwood, and chemicals may be released upon entry of pathogens. The energy level is not at its lowest point in heartwood - some energy is maintained so it can react. Heartwood is like a cocked mousetrap. Discolouration of heartwood is proof that reactions have taken place. The wood has been altered to a higher protection state that the sap- wood. This protection wood is genetic - it contains certain extractives such as gums, phenols or terpenes. The static mass of older trees need this protection ability since the priority of an old tree is to maintain mechanical support. Page 31 25 ENVI 202 - Tree Biology Module B2 Image source: Olds College Heartwood is different from discoloured wood (see Module F2). Image source: Olds College Page 32 ENVI 202 - Tree Biology Module B2 26 Self-Check 1. Explain how the growth of bark attempts to keep up with the annu- al increase in a tree’s girth. 2. Why do some trees have prominent splits and fissures in the bark?. 3. What is the purpose of the cortex layer under the bark of young trees? 4. Explain why heartwood should not be considered as dead wood? 5. List the advantages and disadvantages of large early spring vessels, such as in oak, compared to small vessels, such as in birch. Answers 1. The cells of bark are always moving during the expansion of the circumference of the tree. The mer- istematic cells, called phellogen, produce cork cells that make up the bark. On the outside of the phello- gen, phellem is produced. On the inner side of the phellogen is the phelloderm. The bark cambial cells divide in two directions. There is periclinal division which produces radial parenchyma resulting in an increase in girth. Then there is also anticlinal division which produces axial parenchyma. These increase the tree’ s circumference. 2. Some trees have bark cambium that often only divides periclinal- ly. There is no circumferential growth so splits and fissures form on the trunk. Birch and beech are exceptions; they have extensive anticlinal division. 3. This gives the young tree the ad- vantage of being able to photosyn- thesize and produce sugar under the bark tissue. 4. An enzyme system is maintained within the heartwood and chemicals may be released upon entry of path- ogens. Discolouration of heartwood is proof that reactions have taken place. The wood has been altered to a higher protection state that the sapwood. The static mass of older trees need this protection ability since the priority of an old tree is to maintain mechanical support. 5. Large vessels are an advantage for water uptake but are more suscep- tible to pathogens. Birch, therefore, are less susceptible to pathogens moving up and down the xylem vessels but are more susceptible to drought and water stress that a tree such as elm. Elm would fall quicker to pathogens but are better able to put up with some water stress. Page 33 27 ENVI 202 - Tree Biology Module B3 Module B3 Compare transverse sections of various coniferous and hardwood trees. Coniferous and Hardwood In order to compare physical differences among and between hardwoods and conifers, the student will be able to: • Identify resin ducts and list trees that are resinous • Compare the water transport method of conifers with that of hardwoods • Explain the differences between ring-porous and diffuse porous hardwood trees Image source: Olds College Page 34 ENVI 202 - Tree Biology Module B3 28  Identify resin ducts and list trees that are resinous  Compare the water transport method of conifers with that of hardwoods Explain the differences be - tween ring-porous and diffuse porous hardwood trees Resin Ducts Gymnosperms may be resinous or non-resinous. Some coniferous trees have resin ducts which are enlarged parenchyma cells. Hemlock and spruce are generally non-resinous. Spruce may have a few resin ducts. They will only produce resin when wounded. Pine is resinous. The late wood contains most of the axial and radial resin ducts. Most of the rays are only one-cell thick. Many conifers store starch in the phloem which is why they are often attacked by bark beetles. Large resin ducts will be noticeable in the bark. (Epidermis-cortex-resin ducts-crushed phloem-cambial zone- wood-pith). There are a lot of axial parenchyma around the resin ducts therefore a lot of energy storage (lots of purple). Vessels and Tracheids Tracheids are present in conifers instead of fibres and vessels found in hardwoods. Tracheids have open pits and water moves up like a snake. Image source: Olds College Page 35 29 ENVI 202 - Tree Biology Module B3 It is the tracheids that produce the pulp in the production of paper. Jack pine and Lodgepole Pine and Balsam Fir are prime wood for pulp processing. Wood pulp means the removal or extraction of the lignin leaving only the cellulose (the wall of the tracheid). It is inadvisable to inject a conifer since they have no vessels. Ring porous and diffuse-porous Since conifers do not have vessels, it is only with hardwoods that the terms ring-porous and diffuse porous apply. Ring porous species tylose all vessels except the last year’s growth. They have large vessels that form when the leaves are forming, early in the season. The latewood vessels formed are much smaller. Diffuse porous species have open, functional vessels from many years. Vessels are of equal size and they are scattered equally throughout the growth increment. It is more difficult to distinguish individual growth increments. At the end of each growth increment, there is marginal parenchyma which is a different kind of axial parenchyma. Many thin parenchyma rays are present. Examples of ring porous trees: Quercus, Ulmus, Chestnut, Locust. Examples of diffuse porous trees: Fraxinus, Acer, Populus, Betula. Identify resin ducts and list trees that are resinous Compare the water transport method of conifers with that of hardwoods  Explain the differences between ring-porous and diffuse porous hardwood trees Page 36 ENVI 202 - Tree Biology Module B3 30 Self-Check 1. Diagram where you would find resin ducts in conifers? (Teacher should provide a sample) 2. Is a spruce ring-porous? diffuse-porous? 3. Is poplar a hardwood? Explain. 4. How would you distinguish between earlywood and latewood in diffuse porous trees? Answers 1. Between the cortex and the crushed phloem 2. Neither. Conifers have tracheids therefore those terms apply only to hardwoods. 3. Poplars are considered weak, soft, disease-susceptible, etc., but nevertheless they are classified as a hardwood. Conifers are softwoods; all deciduous trees are hardwoods. 4. Look for the marginal parenchyma. Wood produced right after this would be spring or earlywood. Page 37 31 ENVI 202 - Tree Biology Module C1 Module C1 Compare dynamic and static mass with respect to the mass:energy ratio. Mass vs Energy In order to evaluate the health status of a tree with regards to its energy, you will be able to: • Differentiate between dynamic and static mass • Describe the differences between young, mature and old trees with regards to mass and ener- gy • List the parts of the tree in the order of first energy demand to the least • Identify symptoms that help determine the energy status of a tree Image source: Olds College Page 38 ENVI 202 - Tree Biology Module C1 32  Differentiate between dy - namic and static mass Describe the differences between young, mature and old trees with regards to mass and energy List the parts of the tree in the order of first energy demand to the least Identify symptoms that help determine the energy status of a tree Dynamic and Static Mass Mass/Energy Ratio Dynamic mass is the total amount of cells in the tree that are alive. Static mass refers to all of the non-living cells within a tree. The mass of a tree can only increase within the limits of available energy. No system can get larger than the amount of energy available to support it. As age increases, parenchyma cells begin to die. The dynamic mass to static mass ratio changes. The central core of an older tree has non-liv- ing cells. Industry practices drastically affect the ratio of dynamic mass and available energy. Pruning (decreases mass, both static and dynamic) and fertilizing (increases mass) regulates mass. The tree has two choices to manipulate its mass/energy ratio. To im- prove the ratio, the tree can get more energy or it can decrease its mass. As a tree matures it will start to shed some mass. Image source: Olds College Page 39 33 ENVI 202 - Tree Biology Module C1 Young, Mature and Old Trees Young trees are often considered to be 100% dynamic, that is, all cells that can be alive are alive. “Every place there can be a living cell there is a living cell” (33a). This explains why young trees have so much surplus energy. The ratio of dynamic mass to static mass in a young tree can be written as: (Dynamic) (Static) Stems of young trees are capable of photosynthesis as well as the leaves. The amount of available energy is high and since the tree is of low mass, not much energy is required. A mature tree can be described as having equal amounts of dynamic and static mass. (Dynamic) (Static) Parenchyma cells begin to die and the central core of the tree has mainly non-living cells. To diagnose and prescribe treatment for ma- ture trees is more difficult and more critical than with young trees. Watch and record the effects of treatments. This will help with future diagnosis of mature trees. The tree is now of considerable mass and the amount of energy re- quired is much more than with a young tree. Mature trees reproduce which takes a large amount of energy. Wounds occur and much energy must be spent on defence. More energy must be stored every year to cope with the energy demands of the following spring. To help reduce the increasing energy demand every year, the tree starts to shed, wall off and alter wood to a more protective state. It literally tries to make itself smaller. Trees have figured out ways to do this naturally. Losing a leader, for example, gives multiple chances for survival. We have taken trees out of their natural state, out of the forest. They grow much larger in an urban setting than in the forest. Old trees will have 90% of their mass that is non-living or static. (Dynamic) (Static) Only the leaves of older trees can trap energy. There is no longer chlo- rophyll under the bark. Differentiate between dynamic and static mass  Describe the differences between young, mature and old trees with regards to mass and energy List the parts of the tree in the order of first energy demand to the least Identify symptoms that help determine the energy status of a tree 100 1 1 1 5-10 100 Page 40 ENVI 202 - Tree Biology Module C1 34 Parts of the Tree — First Energy Demand to the Least What Gets Shed First? In business, it is unwise to buy a product and turn around to sell it at the same price - the business will not last long. When the dynamic mass becomes near the level of energy required to support it, it must find ways to decrease itself. A tree’s first demands it to take care of its roots, then the stem, next the branches and finally its leaves. At a 1/1 ratio: Image source: Olds College As soon as a tree’s mass exceeds the energy required, branches will die back a little. Meanwhile, the tree is a generating system. It must increase its mass and the skin must cover the static mass. As a tree gets older, bigger and bigger parts begin to die so that new growth can live. The last you see of life are sprouts (epicormics). Heavy sprouters are the exception. Poplar trees are heavy sprouters - they tolerate our mis- treatments (topping) better than other trees. It is still not a wise thing to do to a tree. Let the tree be your guide! It is of the best interest of the old tree to prune only deadwood - not living wood. In the spring, after the leaves have fully emerged, it is very easy to determine what needs to be pruned. Prune out only those branches that have no leaves! Be sure to wait until all of the leaves on the tree have expanded fully before pruning out any deadwood. Differentiate between dynamic and static mass Describe the differences between young, mature and old trees with regards to mass and energy  List the parts of the tree in the order of first energy demand to the least Identify symptoms that help determine the energy status of a tree Page 41 35 ENVI 202 - Tree Biology Module C1 Symptoms of Energy Status in a Tree Visible Symptoms of Low Energy Look for the following symptoms and signs that reveal that a tree is low in energy: • leaves are changing colour but staying on the tree • fall colouration occurs before other trees • general dieback • dead spots, cankers • boring insects (as in holes & tunnels, not in disposition) • sucking insects (aphids, mealybugs, scale insects, etc.) • sprout formation near the end of the season • bigger than normal leaves • leaves are not falling from the top down Test the tree for purple using the IKI solution on a small core sam- ple. A tree may appear in great health but if it has few reserves for the following year it may die. A bad-looking, beat up tree may still have a lot of energy reserves and will not die. Differentiate between dynamic and static mass Describe the differences between young, mature and old trees with regards to mass and energy List the parts of the tree in the order of first energy demand to the least  Identify symptoms that help determine the energy status of a tree Page 42 ENVI 202 - Tree Biology Module C1 36 Self-Check 1. How does the dynamic:static mass change over time? Explain why. 2. The presence of sucking insects is a sign of low energy. It is also a result of heavy N fertilization. Explain. 3. What is the easiest way to test the level of energy reserves availa- ble to the tree? 4. What organ will the tree provide energy for first? last? 5. Your client wants you to prune a very old tree to “open it up” or “shape it” or just for the sake of it “not been pruned in a while”. How would you respond? Answers 1. Static mass increases over time so the ratio approaches 1 as a tree matures and <1 as it grows older yet. Cells die. New cells must be produced to cover the dead ones (not replace). 2. N fertilization produces weak, lush growth, with no energy for defence from disease or insects. 3. Use I2KI. If the tree is actively growing as in spring, test lower down in the tree since reserves get used up first at the top. 4. Roots first, leaves last. 5. Prune in the late dormant season or after the leaves have fully expanded. Prune only what is dead and dying. Leave everything else alone. The tree will tell you what needs to be removed. How can you make that judgement? With a younger tree it doesn’t matter, since the dynamic mass is much greater than the static mass. Page 43 37 ENVI 202 - Tree Biology Module C2 Module C2 Explain how energy is trapped and stored in trees. Energy From the Sun In order to describe how energy is trapped, stored and utilized, you will be able to: • Explain how light energy is formed • Describe how light energy is converted into chemical energy and is stored • Compare potential and kinetic energy with regards to sugar storage Image source: Olds College Page 44 ENVI 202 - Tree Biology Module C2 38  Explain how light energy is formed Describe how light energy is converted into chemical ener - gy and is stored Compare potential and kinetic energy with regards to sugar storage Light Energy The sun is very hot and the hydrogen gases are under very high pres- sure. The hydrogen mass gets squeezed under these high pressures and fusion occurs. A new substance, helium, is produced. 4 Hydrogen atoms under pressure - results in - one Helium (total atomic weight of 4.0032) (atomic weight of 4.026) Somehow an atomic mass of 0.0008 is lost somewhere - destroyed? No. Mass cannot be made or destroyed. E = mc2 Energy = mass (speed of light)2 Energy and mass can vibrate and become one or the other (just like fish oscillating back and forth in a fish tank). Energy that is released during fusion are little particles (photons) or little waves. Page 45 39 ENVI 202 - Tree Biology Module C2 Photosynthesis These energy waves hit chlorophyll. Chlorophyll “a” has thousands of receptive “antennae”. The magnesium electrons of chlorophyll are excited and pushed out of orbit into a new one. Like a rubber band, these electrons want to come back to their initial orbit. As the electrons are returning to their original orbit, the energy is trapped into a molecules called ATP (Adenosine triphosphate). Each molecule of ATP has two extremely high energy bonds. 4.032 4.024 .008 e- Fusion 4H+ = He + ? left over Mass = amount of matter per unit volume Can’t create it; can’t destroy it. So, Energy = mc2 Move mass fast enough and it becomes energy. Some of the energy is released (from fusion) from the sun = light. .1% of this energy is trapped. Trees trap 50% of this .1%. Photosynthesis — energy trapping process. Chlorophyll Mg + Photon hits particle — moves it to a higher energy orbit. Energy is: Spring - CO2 + H2O Bond bolted together CHO Glucose 6CO2 + 6H2O C6H12O6 + 6O2 Glucose bond is the metabolism. This bond is the tree food; the trapped food moves parts of our cells metabolism. The spring catches the ball on its way down (light energy trapped as the electron jumps back to its original, lower orbit). Photosynthesis is an energy trapping process. Glucose is the result of photosynthesis. During the formation of this sugar, the sun’s energy is trapped as ATP in the chemical bonds of the glucose. The high energy bonds are locked so they cannot break. light chlorophyll Explain how light energy is formed  Describe how light energy is converted into chemical energy and is stored Compare potential and kinetic energy with regards to sugar storage Image source: Olds College Page 46 ENVI 202 - Tree Biology Module C2 40 The spring holds the lead ball and holds the energy power. The spring (the bonds) is soluble in water, breaks apart, releasing the energy so that work can be done, something can move — metabolism! The glucose bond is the metabolism. Sugars dissolves easily in water and water is present in all cells for chemical reactions to occur. This bond is the tree food, the trapped energy. Light energy is convert- ed to a storable chemical energy. During the process of photosynthesis, water is split. The splitting of water is performed by an enzyme of Mn and Fe. If these elements are deficient, then the amount of photosynthesis will, of course, decrease. 6CO2 + 6H2O —————————— C 6H12O6 + 6O2 CO2 & water The stomata must stay open to get CO2 from the atmosphere. If the concentration of CO2 is too high, the stomata will close. If water becomes unavailable the stomata will close. Carbohydrates To be storable, the sugars must combine to form insoluble carbohy- drates such as starch, oils and fats. The presence an concentration of carbohydrates is what is tested with the I2KI solution (Module B1). This is tree food. A tree makes its own food - we cannot feed it. Page 47 41 ENVI 202 - Tree Biology Module C2 Potential and Kinetic Energy The stored energy in the living parenchyma cells is potential energy - the money saved in the bank. Parenchyma cells are located in the wood throughout the tree including the roots, stems, branches and buds. As long as a parenchyma cell is living, it will have the capacity to store sugars (carbohydrates, starch). The potential energy runs the defense system. In the spring, the parenchyma cells are ready to unload the energy - first from the top (you’ll see only a little purple) and last from the bottom (see lots of purple). This demonstrates that the potential energy (purple) is being converted to kinetic energy. This is when the stored reserves are changed to sugar that is soluble in water. Energy can then be released to do work. Test a small sample of the tree for energy reserves with the use of I2KI. This is like using a dipstick. As potential energy, the reserves are stored as starch which is insoluble in water. Explain how light energy is formed Describe how light energy is converted into chemical ener - gy and is stored  Compare potential and kinetic energy with regards to sugar storage Page 48 ENVI 202 - Tree Biology Module C2 42 Self-Check 1. Where is energy stored in the sugar molecule. 2. In what form is sugar stored if it is not required immediately by the tree? 3. How is the sun’s energy trapped by the chlorophyll? 4. What elements are required for water to split in the process of pho- tosynthesis? 5. How come light energy comes to us from the sun? Answers 1. Energy is stored in the high energy bonds. 2. Sugar is stored in water-insoluble forms such as carbohydrates, starch, lipids (fats). 3. The Mg electron gets excited when hit by light energy photons and the electron jumps up to another orbit. As it jumps back to its original lower orbit, ATP holds the energy and is stored in the end product of photosynthesis - the sugar. 4. Iron and Manganese 5. Energy is released during the pro- cess of fusion where four hydrogen fuse to form one helium. The “loss” of mass is converted to light energy and is released. Page 49 43 ENVI 202 - Tree Biology Module C3 Module C3 Identify the annual phenological stages that occur and the relative energy available at each stage. Phenology In order to describe the stages that a tree undergoes annually, you will be able to: • List and explain each phenological stage regarding the tree’s activity during each phase and the energy demands • Identify the differences in timing of each stage with reference to deciduous, evergreen, tropi- cal and temperate species • Describe what physiological processes require the utilization of energy reserves Image source: Olds College Page 50 ENVI 202 - Tree Biology Module C3 44  List and explain each phe - nological stage regarding the tree’s activity during each phase and the energy demands Identify the differences in timing of each stage with reference to deciduous, ever - green, tropical and temperate species Describe what physiological processes require the utiliza - tion of energy reserves Phenological Stages Trees undergo five visually distinctive periods during each year. Start- ing in the spring, when the buds begin to swell, is the stage called onset of growth (1). The second stage quickly follows where new leaves begin to form. This period is called foliation (2). Throughout these two stages, all of the energy required to perform all of the nec- essary physiological processes depend totally on reserve energy that is stored in the system. Once the high photosynthetic period (3) begins, when the leaves have fully expanded, the tree will be manufacturing new food. The tree can then use this rather than further depleting the energy reserves. New wood and bark are formed during the fourth stage, called wood formation and storage (4). All excess energy from photosynthesis can be stored in the new living parenchyma to ensure survival for another season. Dormancy (5), the final stage, gives the tree a rest period. The following graph indicated the typical use of energy reserves at each period throughout the year. Phenological Stages and Energy Use The tree has the lowest energy reserves at 2* and is, at this time has lit- tle energy for defence. Any practice that affects the mass:energy ratio should be avoided at this time (pruning). The other Achilles Heel* occurs when bark is being formed. The tree is vulnerable to insects and diseases that invade the bark. Image source: Olds College Page 51 45 ENVI 202 - Tree Biology Module C3 It is important to consider the stages that insects and microorganisms undergo in relation to that of the tree. At 2, when trees are most sus- ceptible, insects and microorganisms voraciously use available energy sources prior to thir stage of rapid reprduction. At the tree’s stage 4 , insects and microorganisms move to new potential growth and over- wintering sites prior o their dormancy. A. Onset of Growth (wake up) After the long winter, energy is required to get growth started again in the spring. First a tree has to “start up” in the spring, much like getting out of bed in the morning(33). Metabolic activity increases. Energy is made available to the new growing points, the buds. B. Foliation (get dressed) The buds open and the shoots begin to elongate. Leaves emerge. A tremendous amount of energy is required at this time of accelerated growth. When shoot elongation begins, hormonal growth regulators are produced. One such chemical produced in the shoot is auxin. Aux- ins move from the stem tips down to the roots. This gives a signal to initiate root development(5). Roots absorb water and minerals for the stems and leaves. Roots are stimulated to produce hormones as well and translocate these back to the shoot. One of these hormones, cytokinin, is produced only in the roots. Cytokinin is sent up to the shoot tips and the developing shoot to activate cell division and cell expansion(20). During ONSET and FOLIATION, energy reserves are used for res- piration, root development, leaf development, new bud formation and possibly even for reproduction (flower and seed production as in elms). Page 52 ENVI 202 - Tree Biology Module C3 46 C. High Photosynthesis Period (get something to eat)(33a) All trees must replenish the energy that was expended in the spring growth flush in order to survive another year. If there are no more sav- ings (reserves) left in the bank the tree may die(47). Photosynthesis is the ability to trap energy from the sun. Trees need an adequate supply of water and carbon dioxide before solar energy can be converted into chemical energy (sugar). The CO2 comes from the surrounding air, but water must be taken up via the roots and transport- ed to the leaves. When photosynthesis begins, the tree is able to use these newly formed sugars to fulfill energy demands required for growth, etc., at that time. The remaining energy reserves, if any, can stay stored in the living parenchyma cells. D. New Wood (go to work)(33a) A good season of growth will allow the tree to replenish and increase its carbohydrates reserves. If energy reserves are replenished from photosynthesis, and sugar production exceeds sugar utilization, wood production will happen. The annual rings in a branch or stem reveal how much growth occurred from one year to the next. A good season will be reflected in a wide growth ring. After wood has been formed and new energy stored, roots begin to elongate again. In the fall, the soil is warmer than it is in the spring and aeration is better. There is a great energy demand at this time of year. The tree is more susceptible to insects and diseases at this time. Do not injure the tree in any way (pruning, etc.). Reserves in the roots are used mainly to supply the demands of the root only, since roots are unable to make their own food. The twigs, branches and trunk supply the crown and the root system with energy for growth and development. Hopefully, there is enough stored to supply the tree until after leaves have expanded in the following spring when carbohydrates are being produced, used, and stored again. Page 53 47 ENVI 202 - Tree Biology Module C3 E. Dormancy (get ready for bed)(33) The tree dormancy period in cold, temperate climates is very long compared to dormancy periods in warmer climates. Winter survival mainly depends on adequate storage of carbohydrates in living paren- chyma cells in the shoots, trunk and roots. If dormancy is prematurely interrupted, by fall planting for example - the tree will experience major problems. There is no sure way to tell when trees are finally dormant. Some reputable nursery growers on the prairies, through experience, know which trees will survive fall digging and fall planting. Most would probably agree that early spring planting is still any tree’s best chance for survival. Birch for example, are best dug in the spring as well as planted in the spring. This species is most sensitive to any disruption of the dormant period(44). Dormancy (acclimation) is also a period that does require some energy from reserves. Page 54 ENVI 202 - Tree Biology Module C3 48 Differences Among Species and Climates Compare Species The graph will differ among trees of different species. Oak will be barely at 1, onset, when maydays are at 2, foliation. To plan activities using days of a calendar such as “fertilize all trees the first week in June” is not sound. Look at the phenological stages of every tree, to determine when to fertilize, when to prune, etc. Decisions in tree care for trees anywhere in the world can be made by observing the tree’s phenology. Compare Deciduous and Coniferous Trees Since conifers retain most of their needles throughout the year, they are capable of undergoing photosynthesis whenever conditions are good. Deciduous trees drop all their leaves in the fall and must wait until the leaves are fully expanded before photosynthesis can occur. Those deciduous trees that have green cortex tissue under the bark are capable of some limited photosynthesis throughout the year. Coniferous phenology chart vs. deciduous Image source: Olds College List and explain each phe - nological stage regarding the tree’s activity during each phase and the energy demands  Identify the differences in timing of each stage with reference to deciduous, evergreen, tropical and temperate species Describe what physiological processes require the utiliza - tion of energy reserves Page 55 49 ENVI 202 - Tree Biology Module C3 Compare Tropical Trees with Temperate Trees The period of wood formation 4 for trees in the tropics is much longer there than for trees in the temperate areas such as Olds: 1 = onset 2 = foliation 3 = photosynthesis 4 = wood formation and energy storage 5 = dormancy Image source: Olds College Tropical trees differ from temperate in that they continually form leaves, flowers and fruit. Most leaves on temperate trees are formed from start to finish then flower and finally fruit from start to finish. With tropical trees there rarely is a baseline. One can usually find a flower somewhere. Image source: Olds College Page 56 ENVI 202 - Tree Biology Module C3 50 Energy Reserves Trees do not have grocery stores to turn to when they need energy. Trees must make their own food by trapping the sun’s energy and changing it to chemical energy, sugar. The more sugar a tree can produce the more energy it can store away into energy reserves - like putting money in the bank(33, 34). A tree uses energy for: Growth building new parts in new places (new leaves, roots) Metabolism makes biological processes go (cellular reac- tions) Reproduction produces flowers, fruit and seeds (high energy demand) Energy Storage sugar stored as carbohydrates, stored in the wood Defence protection from decay If a tree has few energy reserves, the active processes will be limited. If a tree can’t replenish its energy reserves every year, it will start to decline in health. The tree will be more susceptible to decay-causing organisms. It usually takes several years for a tree to die. The amount of stored energy reserves are more critical in deciduous trees than in evergreen trees for survival and growth. Deciduous trees are dependent on its reserves for every activity until new leaves begin to produce new sugar. This occurs once the leaves have fully expand- ed, not before. Since evergreens maintain many of their needles, they List and explain each phe - nological stage regarding the tree’s activity during each phase and the energy demands Identify the differences in timing of each stage with reference to deciduous, ever - green, tropical and temperate species  Describe what physiological processes require the utili - zation of energy reserves Successive Weak Years Image source: Olds College Page 57 51 ENVI 202 - Tree Biology Module C3 are capable of producing new sugars much sooner than deciduous trees(22). Environmental and man-made stresses often contribute to tree decline and death. Drought, soil compaction, flooding, transplanting, pruning, insects and disease are examples of stresses that affect the tree’s usage of its energy reserves. After successive years of withdrawing energy from the reserve bank the tree finally may not have enough to complete another season. Energy is not only required for growth and metabolism. Great amounts of energy are also required for processes such as reproduction, de- fence, hormone production and transport, etc. Page 58 ENVI 202 - Tree Biology Module C3 52 Self-Check 1. During the stage of foliation and the time of wood formation just before dormancy begins, the tree is most susceptible to insects and diseases. Why is this the case? 2. Advice in a magazine suggests that you fertilize your trees 3 times over the summer, every six weeks. How would you interpret this information for the prairies? 3. How can you tell whether a tree has had a good growing season? 4. Compare the periods 4 and 5 of trees in Calgary compared to those in San Francisco? 5. Looking at the phenology of a tree with respect to its reserve ener- gy, when is it best to plant a tree? Answers 1. During foliation the tree is lowest in reserve energy. There may be little to no energy available for defence. In late summer, the bark has not yet grown over all of the new wood that was produced and insects and diseases, at this time, are looking for overwintering sites. Just under the bark is an excellent place to overwinter. 2. On the prairies, fertilization should be half rate. Wait until the trees have expanded their leaves completely. Fertilize twice; wait three weeks before the second application. Assess this treatment and adjust for the following year. 3. The size of its growth ring-the amount of wood its been able to make that will store sugars. 4. Our period 4 is much shorter in du- ration and period 5 is much longer in duration. 5. Early spring before the buds swell (before foliation). Page 59 53 ENVI 202 - Tree Biology Module C4 Module C4 Differentiate between stress and strain on a tree system. Stress vs Strain In order to evaluate the condition of a tree, you will be able to: • Define stress and strain • Describe the indicators that are used during the assessment to evaluate a tree’s condition Image source: Olds College Page 60 ENVI 202 - Tree Biology Module C4 54  Define stress and strain Describe the indicators that are used during the assess - ment to evaluate a tree’s condition System Disorder Health is the ability to resist strain. Vigour is the capacity to resist strain. The capacity is genetic. Ability displays what is done with ca- pacity. Tree health depends on energy reserves. Any system not getting enough energy will head towards disorder and the system starts to wobble. Wobble leads to stress. Stress is a condition where energy reserves become limiting or drains and a system begins to operate near the limits for which it was designed. Stress is reversible. It simply indicates that something has gone wrong with the flow of energy. The system begins to operate near the limits. While the wobbling is hap- pening, the tree slows itself down. A tree under extreme stress may use its limited reserves to build xylem vessels only. It cannot even think about making any wood. If stress is allowed to continue, and goes beyond its limits, stress turns to strain. Strain is indicative of the system breaking. Strain is not re- versible. Trees show strain by dieback, general decline. If you do not take care of a system the result is greater disorder. You cannot win, just try to break even. A tree cannot live forever. How long any system lives depends on its condition. Good condition is attainable - perfect quality is not. A bigger tree is not a healthier tree(34a). Pathogens and insects, like trees, have phenological patterns too. With any treatments such as pruning, fertilizing, etc. the energy/mass ratio is affected. The arborist must also realize that the associates (beneficial and harmful) are affected as well! The good associates include micro- organisms that help the tree’s mineral absorption from the roots and beneficial insects and microorganisms that are predators or parasites of pathogens. Page 61 55 ENVI 202 - Tree Biology Module C4 Tree Condition(17a) Tree valuation and tree hazard assessments require the arborist to ob- serve the condition of a tree. General condition, as well as specific indicators are used. • Leaf appearance, colour, density, size and shape are assessed. The presence of insects and diseases are noted. • Twig growth condition is analysed by observing the size and shape of the buds, the colouration of sapwood, the shedding of twigs and the presence of insects and diseases. • Branches are assessed for percentage of deadwood, crown location and observation of previous pruning, wounds and any structural weakness. • The trunk observations include the presence of cavities, cracks, mechanical injury, loose bark and the presence of insects and dis- ease. • Roots assessment should not be neglected. The colour of absorbing roots are recorded. Girdling roots, mechanical injury and again, the presence of insects and diseases are worth noting. • Other assessments include soil analysis and previous treatments are investigated. The above symptoms of tree condition help determine whether the tree is under stress, and steps taken to improve the condition. Define stress and strain  Describe the indicators that are used during the assess - ment to evaluate a tree’s condition Page 62 ENVI 202 - Tree Biology Module C4 56 Self-Check 1. What would you consider to be signs of stress? 2. A bigger tree is not a better tree. Explain. 3. Draw the transverse section of an oak tree that would indicate that the tree has been stressed for four or five years? 4. What is a good indicator that the tree is not under stress? 5. What is the difference between vigour and vitality with respect to tree health? Answers 1. Answers may vary - presence of epicormic buds, slow growth, small buds and leaves, etc. 2. Root:shoot balance could be distorted. Energy reserves could be low. Defence system could be very susceptible. 3. The section should show the development of only large spring vessels for four or five years. There was not enough energy from season to season to try to make any wood for storage - each year the tree barely had enough energy to make new xylem so that water could be transported. 4. Healthy buds, large growth incre- ment, lots of sugar storage. 5. A vital tree means a healthy tree - a vigourous tree means a fast-grow- ing tree which does not mean it is healthy. Page 63 57 ENVI 202 - Tree Biology Module D1 Module D1 Dissect branch attachments to determine their formation, structure and function. Branch Attachments In order to list and dissect branch attachments to determine their formation, structure and function, you will be able to: • Describe the characteristics of healthy buds, twigs and stems • Illustrate how branches are attached Image source: Olds College Page 64 ENVI 202 - Tree Biology Module D1 58  Describe the characteristics of healthy buds, twigs and stems Illustrate how branches are attached Bud Development Buds are developed as the leaves are still emerging in the spring. They are formed in the leaf axils at the base of the petiole. Image source: Olds College By the end of the season, buds should be well formed and large, sup- ported by strong stems. The largest buds are located at the branch tip, the terminal buds. If a tree is stressed, the buds at the tips will not develop. There are carbohydrates (starch) stored at the base of the bud which provides the energy in the spring to start growth(33). Dissect a twig and a bud longitudinally. Note the pith of the bud does not connect with the pith of the stem. Add some I2KI to see where the starch is accumulated. Illustrate your observations: Image source: Olds College Page 65 59 ENVI 202 - Tree Biology Module D1 How Branches are Attached Inspect the branch/stem attachments provided for this investigation. Locate the Branch Bark Ridge and the collar. Make a simple drawing of these features. Inspect the branch/stem attachment that has been cut through the center to reveal the pith. Note here again that the pith from the branch does not connect to the pith of the stem. Observe the collar, the branch bark ridge and branch protection zone. Illustrate your observations. Image source: Olds College Describe the characteristics of healthy buds, twigs and stems  Illustrate how branches are attached Image source: Olds College Page 66 ENVI 202 - Tree Biology Module D1 60 Answers 1. Branches are separate entities; individual trees, if you will. 2. At the base of the bud to provide the bud with the needed energy to develop and grow to the point where new leaves are fully expand- ed and can produce sugars on their own. 3. The branch bark ridge follows the top of the collar; the collars appear as curves. 4. The strength is the result of the overlapping rings first from the branch and then from the stem year after year. Self-Check 1. What is the significance of the fact that the pith of branches and that of stems are not connected? 2. When the bud/twig were dissected longitudinally, where was most of the starch being stored? Why? 3. Describe or illustrate the appearance of the branch bark ridge and the collar from the longitudinal view that shows the pith, etc. 4. How does a branch collar provide so much strength and support to a tree’s mechanical structure? Page 67 61 ENVI 202 - Tree Biology Module D2 Module D2 Identify the anatomy and the physiology of branch attachments. Branch Anatomy In order to describe how branches function, you will be able to: • Describe how buds develop • Explain how branch attachments are formed • Relate the significance of the branch protection zone Image source: Olds College Page 68 ENVI 202 - Tree Biology Module D2 62  Describe how buds develop Explain how branch attach - ments are formed Relate the significance of the branch protection zone Bud Development Different species experience different types of bud development. Pines and spruce have predetermined growth. These trees develop buds that contain a complete year’s growth very early in the season. They are more influenced by droughts of the previous growing seasons dur- ing the time their buds are forming. If the buds are stunted, the effects will be seen in the following growing season — shorter shoots, less foliage. Trees such as birch, poplar, elm, apple, and ashes have shoots that are not completely formed in the winter bud; this is called heterophyllous growth. The leaves that expand first are well formed in the winter bud. Later in the growing season, new leaves develop. These continue to grow and form during the current growing season. If there is a drought, this second flush of growth will stop. The tree canopy appears thinner than normal or growth may appear stunted(39). Drought or other environmental stresses may result in less leaves. Less food would be produced and stored as energy reserves. The following season is affected as well since buds formed under moisture stress conditions will be fewer and smaller. If there has been a water deficit (or flooding-poor oxygen availability), during bud formation of the previous year, the internode length be- tween the buds will be shorter. Leaves are thicker and smaller. Current summer droughts will reduce current shoot elongation. Shoot elon- gation only occurs with the combined action of the hormonal growth regulators, auxin and gibberelins. Smaller buds will be formed for next year resulting in smaller leaves (needles) even if water availability is good at that time(20). Page 69 63 ENVI 202 - Tree Biology Module D2 Branch Attachments In looking at a branch attachment, a few signs for a healthy union should be evident. The branch bark ridge, or BBR, is the raised bark resulting from the contact of the new wood and bark where the branch and the stem meet at a crotch. At the base of the branch there is a distinctive bulge called the branch collar. This bulge is actually made up of several branch collars. Every year a new layer of wood is added around the base of the branch. Soon after, the trunk adds a layer of wood that encircles the branch collar that was just formed. This interlocking system has extraordinary strength and resiliency and yet there is no real attachment. Branch Protection Zone Trees provide their own chemicals that resist pathogens. Do not use wound dressings. The dark-coloured “V” found in the longitudi- nal-section view in Module D1 is the branch protection zone. This darkened area contains an extra chemical protection barrier that aids in the protection of the stem from decay that develops in the branch. To describe the extent of protection provided by the branch protection zone, the decay pattern is labelled as A, B or C where A shows the best protection and C reveals very little. Image source: Olds College Describe how buds develop  Explain how branch attach - ments are formed  Relate the significance of the branch protection zone Page 70 ENVI 202 - Tree Biology Module D2 64 Self-Check 1. Illustrate a type “B” decay. 2. If branches and stems are not connected by the pith, how does the branch get its water and mineral requirements, and how does the stem get the sugars that are produced in the leaves? 3. Many biology books indicate branch and stem attachments as fol- lows: With your knowledge of how branches are attached, why is this impossible? 4. You have been asked to predict whether a tree, planted in the spring two seasons ago, will survive. You are looking at the tree in late September. What indicators do you observe? What do you expect to see if the tree is established and healthy? Image source: Olds College Answers 1. Insert Graphic?? 2. At the base of the branch and stem collars, xylem and phloem are attached. 3. The collars make it impossible for this to occur. The common diagram in texts, as above, describes how codominant stems appear, not branches. 4. Buds — should be large, plump and dormant. Twigs — showing adequate growth from the species, stout. I2KI sample — to measure amounts of carbohydrates stored. Page 71 65 ENVI 202 - Tree Biology Module D4 Module D3 Compare normal branching with included bark and codominant stems. Included Bark and Codominant Stems In order to identify included bark and codominant stems, you will be able to: • Describe physical appearance of codominant stems • Illustrate how to prune a codominant stem • Describe the physical appearance of included bark • Illustrate how to prune a branch/stem attachment with included bark Image source: Olds College Page 72 ENVI 202 - Tree Biology Module D4 66  Describe physical appear - ance of codominant stems  Illustrate how to prune a codominant stem Describe the physical appear - ance of included bark Illustrate how to prune a branch/stem attachment with included bark Codominant Stems Codominant stems appear as a fork, two stems that are connected to half of the stem below. With codominant stems, there is no branch protections zone nor a branch collar since the stems are exactly that - stems. Pruning one of the codominants opens the tree to pests and diseases. Pruning a Codominant Stem To prune a codominant stem, start beside the top of the stem bark ridge and end the cut directly across from the bottom of the ridge. Image source: Olds College Page 73 67 ENVI 202 - Tree Biology Module D4 Describe physical appearance of codominant stems Illustrate how to prune a codominant stem  Describe the physical ap - pearance of included bark  Illustrate how to prune a branch/stem attachment with included bark Included Bark Branches that grow close to the tree may develop included bark. The branch collar is weakened and instead of a branch bark ridge at the crotch, the bark actually rolls inward. Branches with included bark should be removed when small. Otherwise, every year the bark is trapped in the crotch. As the weight of the branch increases, the branch may pull away from the tree. The branch will eventually tear away. Pruning a Branch/Stem Attachment with Included Bark If you see that the branch has no branch bark ridge, prune the branch out. There is no possible way that a branch attachment of included bark can get anything but worse. Page 74 ENVI 202 - Tree Biology Module D4 68 Self-Check 1. Illustrate how water, minerals and sugars move in codominant stems. 2. Why can a branch/stem attachment with included bark only get worse? 3. Illustrate the appearance of a branch attachment with included bark. Answers 1. 2. As weight and girth increases in both the stem and the branch, splitting at the crotch is inevitable. 3. Page 75 69 ENVI 202 - Tree Biology Module D4 Module D4 Describe the growth response to pruning, topping, pollarding and flush cuts. Pruning Responses In order to predict a tree’s response to pruning, you will be able to: • Explain how the tree responds to pruning at various stages in its phenology • Define and describe the development of epicormic sprouts • Define a flush cut and describe its effect on the health of a tree • Illustrate correct pruning • Describe the patterns of woundwood resulting after branch removal • Describe the tree’s response to topping Image source: Olds College Page 76 ENVI 202 - Tree Biology Module D4 70  Explain how the tree responds to pruning at vari - ous stages in its phenology Define and describe the devel - opment of epicormic sprouts Define a flush cut and de - scribe its effect on the health of a tree Illustrate correct pruning Describe the patterns of woundwood resulting after branch removal Describe the tree’s response to topping Tree Response to Pruning at Various Stages Timing of Pruning Once there is an understanding of a tree’s phenology, and the mass:en- ergy ratio, decisions as to when to prune are easy to make once the desired effects are determined(34). Desired Response Time to Prune To stimulate leader growth Just before buds break To regulate growth (slow it down) Right after leaves are fully formed To kill a tree At 2 - just when the leaves are emerging To get a lot of copious growth At 5 - dormancy To cut sprouts and discourage them from growing back Just after 4? Pruning is still wounding. How branches are cut depends on how well the tree will be able to defend itself. The best time to prune is in late dormancy. The tree has the greatest reserves and is ready to grow. Prune before the buds begin to swell. The next best time to prune is in the growing season, after the leaves have fully expanded. If a tree is low in reserves for one reason or another, do not prune. Wait a year or two once reserves have a chance to build up, and the tree can defend itself. Pruning for Fireblight The bacterium moves down to the branch crotches. There is natural rupturing of the bark where branch and trunk meet. Tissues are ex- posed to the surface at the time of wood building. Cankers start in the crotch of the tree. It is recommended to prune out the infected wood. Sterilization of the pruning equipment prior to every cut is required to prevent the spread of the bacterium. Do not use alcohol, as it breaks the water tension. Use a 10% bleach solution. Do not fertilize with nitrogen (see Module G2)(34). Page 77 71 ENVI 202 - Tree Biology Module D4 Epicormics Epicormic means “on the trunk.” If sprouts emerge from dormant buds, they are called dormant sprouts. These are always there, and arise from the meristematic cone that is constantly pushing outward. If the sprouts emerge from callus, then they are called adventitious sprouts. These were not there before. Figure D4-1. Epicormic branch following the tree horizontally com- pared to normal branch development. Image source: Olds College To decrease the amount of sprouting, cut in the late spring and sum- mer; to increase the sprouts, prune in the dormant season. If you remove the enlarged bump from the base of a sprout, you will get many more sprouts at that same location. Overfertilization stimulates the development of epicormics. When sprouts develop, the tree has an energy problem. Unfortunately, tree sprouts grow and they end up in the shade, up against a building, etc. They cannot produce food for the tree, yet that was the purpose of them sprouting in the first place — to help the tree in a desperate situation. If the sprouts develop in full sun, a sprout bush develops. Epicormics often result from overfertilization. Elite vs Suppressed Epicormics Suppressed epicormics are weaker, more spindly than elite epicormics. When pruning a previously topped tree, epicormics may be all there is to prune. Select the elite epicormics over the suppressed. Prunus — a genus that does not like to be pruned. It will contain large amounts of false heartwood and only a small amount of energy stor- age. They are fairly short-lived and have no branch boundary. Populus — have no branch boundary either. Explain how the tree responds to pruning at various stages in its phenology  Define and describe the development of epicormic sprouts Define a flush cut and de - scribe its effect on the health of a tree Illustrate correct pruning Describe the patterns of woundwood resulting after branch removal Describe the tree’s response to topping Page 78 ENVI 202 - Tree Biology Module D4 72 Flush Cuts Flush cuts take the defence system away. It was previously thought that fast callus formation meant good “healing.” Flush cuts do pro- mote callus development. Research has recently demonstrated that flush cuts remove the important protective barrier (of phenolic com- pounds) called the branch protection zone, and decay spreads quickly throughout. On the outside, the tree appears “healed” since the wound is covered up. Flush cuts force the tree to use up substantial amounts of reserves of energy and consequently large amounts of wood. Correct Pruning Leave the branch collar intact. Make the pruning cut close to the collar without cutting into it. Any bit of stub left will feed pathogens, allowing them to build up populations that may push past the branch protection zone. If the branch collar cannot easily be located, drop a plumb line from the outer edge of the branch bark ridge and measure the angle of the ridge. Repeat this angle on the other side and cut following that line. Explain how the tree responds to pruning at various stages in its phenology Define and describe the devel - opment of epicormic sprouts  Define a flush cut and de - scribe its effect on the health of a tree  Illustrate correct pruning Describe the patterns of woundwood resulting after branch removal Describe the tree’s response to topping Image source: Olds College Image source: Olds College Page 79 73 ENVI 202 - Tree Biology Module D4 If you can’t see the collar: Stub the branch first to eliminate the chance of the branch tearing away and ripping the tissues at the bottom of the branch collar and down along the trunk. Image source: Olds College Image source: Olds College Page 80 ENVI 202 - Tree Biology Module D4 74 Explain how the tree responds to pruning at various stages in its phenology Define and describe the devel - opment of epicormic sprouts Define a flush cut and de - scribe its effect on the health of a tree Illustrate correct pruning  Describe the patterns of woundwood resulting after branch removal Describe the tree’s response to topping Woundwood (After Pruning) Callus is formed first. If the cut is correctly made during a branch removal, the woundwood will develop evenly. If an incorrect cut was made: BBR Removed Collar Damaged Collar and BBR Damaged Image source: Olds College Flush cuts cause the woundwood to curl under onto itself and cracks develop. Page 81 75 ENVI 202 - Tree Biology Module D4 Topping Topping involves the cutting back (shortening) of large branches, resulting in the profuse development of epicormics. Rotting is rampant below the topping wounds and the epicormics are weakly attached. Epicormic branches develop from dormant (latent) buds just under the bark, or new buds that develop around the wound (adventitious buds). As the epicormic branches increase in size, decay spreads under them. These branches may eventually tear away. Topping is often mistakenly referred to as pollarding. Pruning a Previously Topped Tree If only epicormics remain from a previous topping, choose to retain the larger, stronger ones and prune out the smaller, weaker epicormic branches. Pollarding Pollarding is a respected style of pruning, much like bonsai, topiary, etc. With starter pollards, a framework is established when tree is young and all sprouts are cut back to the original framework. Wine grapes are pruned as pollards. Explain how the tree responds to pruning at various stages in its phenology Define and describe the devel - opment of epicormic sprouts Define a flush cut and de - scribe its effect on the health of a tree Illustrate correct pruning Describe the patterns of woundwood resulting after branch removal  Describe the tree’s response to topping Page 82 ENVI 202 - Tree Biology Module D4 76 Answers 1. 2. Flush cuts remove the branch pro- tection zone opening up the tree to decay-causing organisms. CODIT still does apply, but the defence system is greatly lessened with the loss of the branch protection zone. 3. Prune dogwoods in the dormant season and Shuberts after leaves have fully expanded. 4. Topping will encourage weak attachments. If the tree is healthy, leave it alone. Roots do not seek out water pipes; they simply grow where there is oxygen and water. If you pipes aren’t leaking, do not worry. Self-Check 1. Locate five trees on campus and evaluate previous pruning wounds as to the woundwood patterns present. Make a chart listing the spe- cies of tree, location on campus, location of previous wound and draw the woundwood pattern. 2. “Flush cuts take the defence system away.” Doesn’t CODIT still apply? Why is this statement valid? 3. When should you prune to encourage the development of new red stems in dogwoods? When should you prune to discourage epicor- mic sprouts forming on Hawthorn of Shubert chokecherries? 4. A client wants you to top their large poplar because it is too big. It will fall on their house and the roots will invade the water pipes. How would you respond? Page 83 77 ENVI 202 - Tree Biology Module D5 Module D5 Explain training techniques for the growth and development of young trees. Training Young Trees In order to explain the pruning of young trees, you will be able to: • Describe the difference of pruning a small branch compared to those on large trees Image source: Olds College Page 84 ENVI 202 - Tree Biology Module D5 78  Describe the difference of pruning a small branch com-pared to those on large trees Pruning a Young Tree It is wrong to attempt to prune a big tree in the hopes of getting a healthy, small tree. Instead, it is more successful to keep a small tree healthy by correct pruning. Our profession should be aiming this way, in pruning little trees. We should be staying away from the big tree business. Branch collars on young trees are usually quite prominent. Do not remove the collar, even though it looks odd to leave them on younger trees. The tree nurseries often prune up the branches to make them more high-headed. Check to see if collars are intact. If there are many branches in one area along a trunk, and they all require pruning, limit the pruning to only one or two of those branches one year. Do a couple a year later, etc. Module G2 describes how to choose a tree from the nursery. Be- sides looking at general condition of the tree, look for included bark, wounds, sprouts from the branches and from the roots. The most important thing to do to keep a tree healthy is to plant it in the right place. Self-Check 1. Why is it preferred to plant small trees instead of large caliper trees? 2. If you leave the collar intact when pruning small trees, the collar is unsightly. Your client wants you to get rid of it. What is your response? Answers 1. Roots respond quicker; there is less catching up to do. 2. Tell the customer about the branch protection zone, and also that as the tree matures, the collar will not be obvious any more. Page 85 79 ENVI 202 - Tree Biology Module E1 Module E1 Compare woody roots, non- woody roots and mycorrhizae. Root Comparison In order to list and describe various types of tree roots and how they grow, you will be able to: • Identify the conditions for root growth to occur • Define and describe the characteristics of woody and non-woody roots • Identify where roots are located Image source: Olds College Page 86 ENVI 202 - Tree Biology Module E1 80  Identify the conditions for root growth to occur Define and describe the characteristics of woody and non-woody roots Identify where roots are located Root Development Roots grow as shoots are developing. Most tree species must have developing buds on the twigs before roots will begin to grow. For root elongation to continue, the leaves must be actively growing(15). Roots also need a continuous supply of growth regulator hormones for new root formation and elongation. Auxins are particularly necessary for rooting. The terminal buds on shoots contain the highest concentra- tion of auxins. This is one reason why thinning is a healthier alterna- tive for trees than shearing. Roots need to grow enough every year to maintain a balance with the crown. Most roots start growing in the spring as soon as the soil tem- perature increases to at least 5° C. There needs to be adequate moisture available at this time. Trees on the prairies, especially along the Chi- nook belt, must be watered well in the fall to ensure enough moisture is available to the roots in the spring. A healthy root system requires good aeration and a good water supply for growth. It can then support the upper portions of the tree with all of its needs including the capacity to supply any new growth from the new stems, including flowers, fruit and seed production. Healthy, well-developed roots are firm and well-branched. The woody roots appear dark-brown with light-brown or white tips. Microscopic root hairs are formed in the spring to aid in the absorption of water and minerals(19). Roots have a low level of cold tolerance. They cannot survive tem- peratures below the temperature range of -4° to -7° C. Snow cover or mulch in temperate climates will insulate and protect the roots. Stressed and dying roots are most vulnerable to attacks from diseases. The roots need stored reserves for defence. Page 87 81 ENVI 202 - Tree Biology Module E1 Woody and Non-woody Roots Woody Roots Major roots are perennial and contain wood. Woody roots function as storage of energy and mechanical support for the entire tree. Roots do not store all of the energy for a tree. It a misconception that when sugars are produced, it all moves down to be stored by the roots. This is accurate for perennials that shed their crowns every year, i.e. del- phiniums. Trees store sugars wherever there are live parenchyma cells: in the wood of branches, trunks and roots. To prove this, simply cut a branch from a flowering shrub in the dormant season and put it in water and light. Flowers and leaves will emerge. This activity of course requires much energy which is supplied only by the branch since no roots are present. Woody roots do store a tremendous amount of sugar, much more than the branches. This is simply because roots cannot make their own food. The roots are totally dependent on the crowns to supply it with energy. In return, the crown totally relies on the roots to provide water and essential elements. Fall digging of trees shouldn’t be done until perennial roots have fin- ished their development. This time is very difficult to predict with trees on the prairies. Growth seasons are short. Maximum time should be made available for this root development as this will be assurance of successful spring growth the following year. Non-woody Roots The fine, non-woody roots function as absorbing roots. Non-woody roots absorb water and minerals. Root hairs and mycorrhizae are microscopic and deciduous; both are shed in the fall during leaf drop. Absorbing roots include both root hairs and mycorrhizae. New mycorrhizae associations begin to develop and grow immediately in the fall but root hairs won’t develop until the following spring. Both are shed in the fall during leaf drop(29, 33, 34). Root hairs develop just behind the root tips. These microscopic hairs are extensions of epidermal cells of the root. These increase the sur- face area and the absorptive capacity of the root by many times. Where there is enough water and oxygen in the soil, roots may form associations with a fungus. This symbiotic relationship is called my- corrhizae. Myco means fungus; rhiza means root. The fungus infects the root and may stay on the outside. These are called ectomycorrhiza. Identify the conditions for root growth to occur  Define and describe the characteristics of woody and non-woody roots Identify where roots are located Page 88 ENVI 202 - Tree Biology Module E1 82 Those fungi that infect and develop on the inside of the root are called endomycorrhiza. Mycorrhizae depend on the tree for food, but in return, the mycor- rhizae make minerals readily available to the tree. Mycorrhizae absorb phosphorus, potassium and other slow moving elements one hundred times more efficiently than the root could itself. Phosphorus is very sluggish because it is round and has a very weak charge. The myc- orrhizae, with its very thin membrane easily absorb phosphorus and other slow moving elements such as manganese and zinc(29). In the fall, mycorrhizae load the elements, in the spring, the root hairs load water. Mycorrhizae also form important growth regulating hormones for the tree (and may buffer the effects of substance toxicities(9, 24). In order for mycorrhizae associations to grow and thrive, they require a healthy tree and a favourable soil that has good aeration, moisture, normal pH, adequate nutrients and high organic matter content(25). Figure E1-1. Compare mycorrhiza size with root hair Image source: Olds College Page 89 83 ENVI 202 - Tree Biology Module E1 Root Location Roots are located within the top 30 cm and extend four to seven times larger an area than the crown. Open grown trees often have roots that spread far beyond the edge of the branches (dripline)(30). Roots grow parallel to the surface of the soil . Sloping root systems ac- tually grow uphill. More roots grow on the north side of a tree. When replanting the tree, maintain this orientation. There is no such thing as a shallow-rooted or deep-rooted species(29, 30). Roots are opportunists. They will grow where there is room to grow, where there is oxygen and water. They do not seek out water! They will grow if conditions are good for them to grow. Pipes that have roots growing through them were probably cracked and leaky in the first place thus providing an excellent moist habitat for roots. Identify the conditions for root growth to occur Define and describe the characteristics of woody and non-woody roots  Identify where roots are located Page 90 ENVI 202 - Tree Biology Module E1 84 Page 91 85 ENVI 202 - Tree Biology Module E2 Module E2 Explain a tree’s response to root pruning, crushed roots, girdling and roots grown in containers Root Response In order to provide the best chance of survival during digging and planting, the student will be able to: • Describe the purpose of root pruning • Explain the criteria used to inspect the condition of tree roots during digging and planting operations • List methods to prevent root damage while handling Image source: Olds College Page 92 ENVI 202 - Tree Biology Module E2 86  Describe the purpose of root pruning  Explain the criteria used to inspect the condition of tree roots during digging and planting operations List methods to prevent root damage while handling Root Pruning Chances for success are greatly increased if root pruning can be done one to three years in advance. Root pruning increases the amount of absorbing roots that will be contained within the root ball. New roots will be clustered at the cut ends so be sure not to recut at the original cut location. Trees that have been root pruned a few years prior to transplanting show less stress than freshly dug trees(12, 40, 46). Root Condition Assessment Inspect trees to be planted since some roots will be broken or ragged at the tips. Cut these with a very sharp knife. Make clean, sharp cuts on roots to ensure the development of callus. Callus tissue is meris- tematic, non-lignified and undifferentiated (soft, gel-like). New roots will generate from the callus because it is meristematic (adventitious). They will generate from just behind cut ends. New roots will not form behind crushed roots(20, 48). Crushed roots from construction damage for example, will not form callus so no adventitious roots will develop. Roots from bareroot stock and small container-grown stock can be inspected more easily than balled-in-burlap or large container-grown plants. Container grown and containerized plants are often exposed to temperatures that are too high or too low. The temperatures of the soil in a container may be hotter or colder than the surrounding air and roots die. The roots on the south-west sides of the containers are affected the most(1). Girdling Roots Normally, roots grow in a lateral direction away from the trunk. Gir- dling roots are roots that circle a tree trunk. They may eventually choke or squeeze the stem tissue as the trunk and root increase in girth. The growth of the stem is restricted(15, 42). Girdling roots are usually found at or near the soil surface in balled-in- burlap plants. Some species characteristically girdle (Norway Maple). Often, there will be one side of the trunk that is flattened at the base of the tree(42). Page 93 87 ENVI 202 - Tree Biology Module E2 It is generally suggested to remove the girdling roots, if they are small. New research is indicating that pruning girdling roots might actually worsen the situation. When a root is pruned, the terminal and laterals grow faster. Since laterals roots are positioned at a perpendicular posi- tion from the trunk, multiple girdling roots may result where only one existed before(42). Girdling roots will happen in the forest too. Circling Roots Circling roots are often found in container-grown trees where roots have grown to follow the container perimeter. A container grown tree has the advantage of having all of its roots intact for transplanting, compared to dug trees that have most of their roots severed. The dis- advantage occurs if the tree is left too long in its container. If the roots contact the wall, they may continue to grow horizontally along the side of the pot circling round and round. If the tree is planted in this man- ner, the circling roots may eventually girdle the tree. Sometimes, circling roots are difficult to see. If the tree was in a small- er pot and developed circling roots and was later transplanted in a larger pot, the circling roots will be hidden by new soil and new roots. Look at other trees around and see if any are growing faster. This is a clue that girdling or circling roots may be present(42). Circling roots often can be corrected at planting by spreading the roots outward and providing enough area in the planting hole to accommo- date the straightened roots. Roots that are left in containers, whether plastic or burlap, must have the covering slit to ensure root spread. Otherwise, roots will not push out. Never twist a root ball to squeeze the root into a small hole. Some- times the roots are in their containers for too long. The resulting roots appear as entwined, large masses at the bottom and around the root ball. If the crown is vigorous, the roots are probably not potbound(15). Avoid trees in containers with straight, slick sides. Pots that have ver- tical ribbing help direct roots downward rather than around. Some pots are lined with a copper-based material which helps prevent the devel- opment of circling roots(42). Kinked Roots Trees with kinked roots should also be avoided. These are roots that are sharply bent back on themselves. These cannot be corrected(15). Page 94 ENVI 202 - Tree Biology Module E2 88 Digging and Planting During digging, a large portion of the absorptive area of the root sys- tem is severed. As much as 95 - 97% of the roots may be lost. Water must be made readily available. The plants must be protected from desiccation and temperature extremes(17). Handle the trees by the roots not the trunk. Tie chains and ropes around the root ball for support. Never stand on the inside of the ball during digging as the ball can fall apart. A backhoe works well for digging - be sure to stop and cut the roots by hand.(41) The roots should be kept cool and moist, especially if they are bare- root or in dark-coloured containers. In the spring, bark is particularly vulnerable to damage(15, 31). Antitranspirants are effective during warm, windy days(15, 31, 40). Describe the purpose of root pruning Explain the criteria used to inspect the condition of tree roots during digging and plant - ing operations  List methods to prevent root damage while handling Page 95 89 ENVI 202 - Tree Biology Module F1 Module F1 Explain the CODIT concept. Defence In order to describe how energy is trapped, stored and utilized, you will be able to: • Explain how energy is required to enable a tree to have a defence system • Describe the tree’s response to wounding • Explain CODIT by illustrating each wall and its function Image source: Olds College Page 96 ENVI 202 - Tree Biology Module F1 90  Explain how energy is required to enable a tree to have a defence system  Describe the tree’s response to wounding Explain CODIT by illustrating each wall and its function Energy Demand The ability for a tree to defend itself from microorganisms primarily come from the purple, the stored energy reserves. As energy reserves decrease, a weak defence system results. Expect root rotting problems, borers, etc. Knowing that bark splits and moves every year to compensate for the new growth increment, it is understandable that at this time the tree is very susceptible to insects and diseases that invade bark. This is a temporary weak time for the tree. An attack of a pathogen can only be walled off by the existing, living cambium. This wall, a boundary of wood, attempts to resist the spread of the pathogen. The growth increment may result in being very thin, without enough stored energy to resist further attack. The tree may end up not having enough parenchyma cells to store energy, and may simply run out of energy. If the can keep up with the pathogen by generating new tissue faster than the pathogen, the tree will survive. Response to Wounding When wounding does occur, the tree reacts immediately. It is unable to repair dead and dying cells but it can grow cells on top of old ones. This takes a lot of energy, energy that would otherwise be used for growth, metabolism and storage. A tree compartmentalizes, or walls off, decay. It builds walls to con- tain the injured wood from all directions to prevent the spread of pathogens. Even though the spread of decay may eventually appear to have been completely stopped by the walls, that wood will never be as structurally sound as it was prior to the injury. If the decay organisms are not stopped, the tree must then start building new barriers, new walls, using more energy. Some species of trees are better compartmentalizers than others. Some trees even within a species are stronger than others. The seriousness of the injury and the amount of energy (carbohydrates) available for defence will determine the ability of a tree to compartmentalize decay. Any time that cells are used in defence, they are no longer available for future energy storage. Each cell in defence exudes its contents of phenols or tannins to prevents further invasion of decay. These now Page 97 91 ENVI 202 - Tree Biology Module F1 dead cells result in disruption of the living links. Messages, hormones, water, minerals, sugars, and nutrients all have less available routes to travel if some cells have been used for defence purposes. When tissue, normally used for energy storage is compartmentalized, there is less space in the tree for the storage of starch. Defence uses energy and loses storage space, decreasing the chances of injury to maximize storage capacity(28). Intentional wounds requiring a strong defensive response come from pruning, topping, injections, cavity filling and hardware installa- tion(38). Where there is injury there is infection - ALWAYS. One organism lives on another. Host - Pathogen. If there is so much infection so that visible signs and symptoms are expressed, then we call it a disease. The system is wobbling - stress - reversible. strain - some parts break. Boundaries that are formed by a tree after injury: • defend the mechanical support system • defend the storage system • defend the transport system • resist the spread of the pathogen Carbohydrates are what build the boundaries. They are used to make phenols (or terpenes). When a tree needs more food, it cannot go out to the store and buy it. As we make a tree “bigger” its demands for growth, reproduction, metabolism and defence also increase. Page 98 ENVI 202 - Tree Biology Module F1 92 Compartmentalization Compartmentalization is a two-part process. After an injury the tree first produces a chemical all over. Pathogens move in and try to get through. The reaction zone is the wood that is present at the time of injury. The barrier zone is the new wood formed after the injury. Wall 1 - plugging up vessels (tylosis) forming chemicals only in tis- sues present at the time of injury Wall 2 - preventing inward spread Wall 3 - preventing radial (lateral) spread Wall 4 - new wood Explain how energy is required to enable a tree to have a defence system Describe the tree’s response to wounding  Explain CODIT by illus - trating each wall and its function Image source: Olds College Image source: Olds College Page 99 93 ENVI 202 - Tree Biology Module F1 Callus formation is very fast, like a young tree. If it grows too fast the result will be cracking. All of the wood is changed somewhat after a wound is inflicted. Other barriers besides barrier zone and reaction zone: • branch protection zones (Module D) • miccorrhizae base attachment • leaf abscission • wetwood - an anaerobic bacteria - better to have one fox eating otherwise poplar get cankers all over • NAA - naphalene acetic acid - do not use to reduce seed pro- duction- knocks the pulp out of the tree Image source: Olds College Page 100 ENVI 202 - Tree Biology Module F1 94 Page 101 95 ENVI 202 - Tree Biology Module F2 Module F2 Inspect wounded wood to date the wound and identify characteristics and consequences of wounds. Wounds and Decay In order to date wounds and analyze a tree’s defence capabilities, you will be able to: • Identify the year, season and even the month in which a wound occurred • Investigate trees where cracking has occurred and diagnose the cause • Distinguish between good and bad compartmentalizers • Compare heartwood and false heartwood Image source: Olds College Page 102 ENVI 202 - Tree Biology Module F2 96  Identify the year, season and even the month in which a wound occurred Investigate trees where cracking has occurred and diagnose the cause Distinguish between good and bad compartmentalizers Compare heartwood and false heartwood Dating a Wound To date a wound, look at the barrier zone and count the growth rings. Determine the year and the season of wound occurrence. The reaction zone is the wood that was present at the time of injury. Decide whether the wound is located within the growth ring, or is it at the end of the growth increment. Consider that by mid to late May the leaves are fully expanded by this time. Growth rings develop within 6-8 weeks. On several samples of wounds, attempt to determine which month the wound had occurred. Page 103 97 ENVI 202 - Tree Biology Module F2 Identify the year, season and even the month in which a wound occurred  Investigate trees where cracking has occurred and diagnose the cause Distinguish between good and bad compartmentalizers Compare heartwood and false heartwood Cracks Sun and frost cracks are just what fires the shot. The tree is usually predisposed to cracking from a previous wound, such as a flush cut or root damage. Internal cracking is often caused by ramshorning. This is are often cause by long narrow wounds on fast growing closure on a fast grow- ing tree. The callus continues to roll in on itself. Birch ramshorning, primary and secondary cracks Image source: Olds College Image source: Olds College Page 104 ENVI 202 - Tree Biology Module F2 98 Good and Bad Compartmentalizers Poor Compartmentalizers Poplars are poor compartmentalizers. They have a poor defense sys- tem. In contrast, they have an excellent reproduction system. These type of trees grow very fast - they make it and spend it. Storage occurs only in the phloem. Maples store a lot of sugar so there is a lot of sap flow in the spring. The starch is converted to glucose very early in the spring. Birch can also be tapped to make “birch beer” (root beer; add a bit of winter- green). Maple syrup only drips during the daytime, not at night. Some trees will flow, others will not. Parenchyma begin to oxidize; when you respire, CO2 is given off - CO2 builds up and sets up pres- sures. Good Compartmentalizers Birch Oak has a very strong wall 3. They may show large frost cracks since they have very large parenchyma rays. Many tropical hardwoods have leaves with high concentrations of tannins so that insects will not feed on them. (Conifers contain terpe- nes instead.) Proteins are like spirals held together with toothpicks. The phenols knock out the toothpicks preventing any entry of en- zymes. No longer is this protein digestible (like tanned leather). Image source: Olds College 40° C - tanning leaves so insects won’t eat it. Proteins (C-N Amino Acids) + Phenol (Hardwoods). Terpenes (Conifers). Identify the year, season and even the month in which a wound occurred Investigate trees where cracking has occurred and diagnose the cause  Distinguish between good and bad compartmentalizers Compare heartwood and false heartwood Page 105 99 ENVI 202 - Tree Biology Module F2 Identify the year, season and even the month in which a wound occurred Investigate trees where cracking has occurred and diagnose the cause Distinguish between good and bad compartmentalizers  Compare heartwood and false heartwood Our southwest coastal trees - biggest, fastest growing trees in south- western British Columbia and California. Trees can only take so much CO2 also. Require both light and temper- ature. Flush cuts - take defense system. away. We thought that callus formation means good ‘healing.’ Big callus = strong healing. (Oxymo- ron - doesn’t make sense.) Woundwood not callus; sealing not healing. False Heartwood False heartwood, as in Ash, is associated with the death of branches. Tissues in the branch lose all of their energy reserves, starve to death, discolour and die. False heartwood does not react to wounding as heartwood does(34). Page 106 ENVI 202 - Tree Biology Module F2 100 Page 107 101 ENVI 202 - Tree Biology Module G1 Module G1 Explain how trees respond to environmental stress. Environmental Stress In order to predict a tree’s response to common environmental problems, you will be able to: • Explain how lack of water affects the tree system • List the temperature range that is ideal for root development • Describe the effect of oxygen deficiency on tree roots Image source: Olds College Page 108 ENVI 202 - Tree Biology Module G1 102  Explain how lack of water affects the tree system List the temperature range that is ideal for root develop - ment Describe the effect of oxygen deficiency on tree roots Drought Lack of water can be due to lack of irrigation, drought on unirrigated soils, compacted soils, or root removal from transplanting or construc- tion. If there is a lack of water, the root will send a signal (hormone) to the shoot informing it to take preventative measures so that injury will not be so severe. The consequences of drought are that transpiration is reduced, and photosynthesis slows down. This results in a loss of valuable production time(23). If carbohydrate production is decreased, that also means less wood is formed. The annual ring will be smaller than normal with less capacity to store sugars in its parenchyma cells. Less energy storage means less energy available for spring flush demands. As water deficiencies increase, temporary wilting during the day will occur, but will recover throughout the night. At night, transpiration is much less and the roots have a chance to “catch up” in supplying the crown with water. If drought conditions persist, permanent wilting occurs, meaning that recovery is no longer possible. The tree may even start going into a dormant phase. Leaves may colour up and shed much earlier than normal. Symptoms of water stress are poor colouration and a decrease in tur- gor. This often goes by unnoticed. Damage to evergreen needles from drought stress is greatest in the winter. The soil water cannot be absorbed, yet water loss occurs through transpiration since the air temperature may rise considerably. Needles may dry up and turn brown. If water is not available in early spring, entire branches may die(39). Mulching aids in holding soil moisture. Excessive mulch depth (greater than 10-15 cm.) will cut off the oxy- gen supply and could kill trees. Page 109 103 ENVI 202 - Tree Biology Module G1 Temperature Soil temperatures of 22-25° C result in an increase in root initiation. In early spring, temporarily move any mulch aside to allow soil temper- atures to rise to improve water absorption and root production. Then, when summer heat becomes a problem, return the mulch around the trees. During the hot summer months, mulch will lower soil temper- atures and decrease the amount of evaporation form the soil surface. Since soil temperatures stay more moderate, late into the fall, woody roots and mycorrhizae will grow even after the leaves fall, since the soil temperature is ideal at this time. Make sure water is available for root development in the fall, but do not allow any flooding, even for a short period of time(20). Oxygen Deficiency Oxygen deficiency will result in an immediate reaction from in the roots. If drainage is poor and water has a chance to sit, roots will be ef- fected immediately. Do not allow flooding during the growing season. Prior to planting, ensure good drainage at the site. Install weeping tiles, etc., if necessary. Without oxygen: • shoot elongation will decrease; • leaf initiation and expansion will cease; • cambial growth will be reduced; • hormonal balance in the tree will be disrupted; • mycorrhizae may be destroyed; • harmful fungi will attack the roots; • root rot results; • root growth is at a standstill; • leaves become yellow and die; • stem growth is reduced. Flooding can cause a water deficit. If roots are in too much water, oxy- gen is not available for the root to do work, and roots rot and die. Less roots mean less water is absorbed and transported to the crown. Explain how lack of water affects the tree system  List the temperature range that is ideal for root devel - opment  Describe the effect of oxy - gen deficiency on tree roots Page 110 ENVI 202 - Tree Biology Module G1 104 Page 111 105 ENVI 202 - Tree Biology Module G2 Module G2 Describe the criteria used to select a healthy tree from a nursery. Tree Selection In order to be able to select high quality trees from the nursery, you will: • Describe the importance of knowing the tree species and how they were grown in the nursery • Explain how roots are to be inspected from container stock • Explain how the crown of the tree is inspected Image source: Olds College Page 112 ENVI 202 - Tree Biology Module G2 106  Describe the importance of knowing the tree species and how it was grown in the nursery Explain how roots are to be inspected from container stock Explain how the crown of the tree is inspected Species and Growth Characteristics Individual growth characteristics of tree species will help determine a tree’s suitability to a site. Be sure that the tree is correctly identi- fied(29). The tree should be a species that is easy to move, that grows well in that location, and will satisfy the requirements of the design(15). Never try to make the tree fit or tolerate a site. Provide the tree with its needs and an environment that it has been used to(15). Observe how the trees were grown at the nursery. A tree that has been grown in full sun, and an exposed site will probably do well in a protected, less sunny location. However, trees that have been grown in shaded and protected sites will not do well when planted in sunny, exposed sites(15). Twigs should show adequate growth and leaf colour, and size should be characteristic for the species. Have the north side of the trees marked so that this orientation may be maintained when planted in the new site. Trees must be healthy to begin with. Careful inspection of the trees is critical to the success of the landscape project. The transplanting and establishment period is very stressful for trees to undertake. Weak trees will greatly decrease the chances of survival. This is especially true for large trees. Inspection is more suitably done at the nursery rather than at the planting site, in case there is a need for substitutions or replace- ments(15, 29, 41). Written specifications, clearly describing the condition of the roots and the crown, will ensure good quality selection. Use the Canadian Stand- ards for Nursery Stock as a guideline to compare root ball size and trunk caliper to tree height. High quality trees are expensive but worth the money. It will save time and money in the long run by not having to replace the trees in the future. Page 113 107 ENVI 202 - Tree Biology Module G2 Root Inspection Root systems should be well-developed and well-branched. Roots should be firm and dark brown with tips that are a lighter brown or white. Do not select trees whose root tips are crushed or soggy. Do not select a tree if, when the trunk is lifted slowly, the root ball moves up 25 - 50 mm before the container and soil do(15). The root flare is located where the stem and the root join. The soil level in the container or in the field should not be above the root flare. Often roots have been buried too deep in the pot, probably so that the tree would not blow over. Trees whose root flares are well below the soil level and have been in the container for a long time should not be selected. If the tree has been recently potted, the media in the pot will still be very loose and light. Planting at the appropriate level is still possible. Roots are not easily visible in containers from the nursery or from balled-in-burlap material. Locate the tree’s main roots by gently brush- ing the soil away from the trunk. A container-grown plant has three sections of the root ball that should be inspected. These zones repre- sent the previous containers the roots were grown in(15): Zone 1: from the liner pot, 50 mm from the trunk Zone 2: the centre root zone from the intermediate container(s) Zone 3: the edge and bottom of the root ball, called the peripheral root zone. Inspection of the peripheral zone can be easily done simply by remov- ing the container(25). Replace the container as soon as possible to prevent root exposure to sunlight and the dry surrounding air. Describe the importance of knowing the tree species and how it was grown in the nurs - ery  Explain how roots are to be inspected from container stock Explain how the crown of the tree is inspected Image source: Olds College Page 114 ENVI 202 - Tree Biology Module G2 108 Inspecting the centre zones involves washing the soil from the roots, which is very damaging. Perform this inspection on only a small sam- ple of plants, and replace the soil immediately. Purchase these trees as the supplier should not be made responsible for those trees after this type of inspection(15). Balled-in-burlap trees can best be inspected at the time of planting. Crown Inspection The crown, or above-ground parts should be well-formed and charac- teristic of the species. One-half or more of the foliage should be on branches originating on the lower two-thirds of the trunk(15). Lower branches shade the trunk and supply it with energy. A tree with greater caliper and taper results. Lower branches can gradually be shortened and finally removed as the tree increases in size and the crown is large enough to shade the trunk(15). Follow the Canadian Nursery Trades Association Standards for height relationship to caliper of deciduous trees(21). Describe the importance of knowing the tree species and how it was grown in the nurs - ery Explain how roots are to be inspected from container stock  Explain how the crown of the tree is inspected Image source: Olds College Page 115 109 ENVI 202 - Tree Biology Module G2 Here are some examples: Caliper Overall Height Min. # of Branches 45 mm 300 - 350 cm 9 50 mm 350 - 400 cm 10 70 mm 400 - 450 cm 12 100 mm 500 - 600 cm 15 Source: (Canadian Standards p.18) Taper is the decrease in trunk caliper with increasing height. Staking and severe pruning result in trees with little to no taper. A tapered trunk of an unstaked tree will bend uniformly along the stem in strong winds. The stress is evenly distributed along the lower two-thirds of the trunk and decreases toward the tip. The possibility of breakage is reduced(15). Test for taper by deflecting the tree with the hand and see if the tree can return to an upright position(15). Twigs should not be weak and spindly. Twigs should show adequate growth over the past 3-5 years(34). Buds should be well-formed. Knowledge of individual species characteristics is required for twig inspection. Leaf turgidity indicates correct watering of the tree. Leaf colour should be characteristic to the species and the time of year. Leaf size should also be characteristic to the species. Oversized leaves indicate heavy use of nitrogen fertilizer predisposing the tree to insects and diseases. If the leaves are smaller than normal after spring growth is completed, the tree is under stress(15). Image source: Olds College Page 116 ENVI 202 - Tree Biology Module G2 110 Comparing normal to small and large leaves Do not accept trees that have flush cut branches, that is, cuts that are within the BBR and the branch collar (see Module D4). Avoid trees with branch attachments that have included bark. Includ- ed bark occurs when bark of the branch and trunk squeeze together. Branches with included bark are easy to identify by the lack of a branch bark ridge. They have very weak attachments to the trunk and it progressively gets worse as the tree grows. If the tree has only one or two small branches with included bark, just remove them(17, 33). Inspect for any injuries. Do not select trees where there are branch stubs, leader stubs, painted wounds, trunks covered with wrap, cracks, cankers and wounds. Bark should be firm. Look for bark that has been exposed to the afternoon sun. Sunburned trunks are slow to recover and are very susceptible to borers(15, 17). Inspect for insects and diseases. It is not unusual to see newly plant- ed trees with large galls from diseases such as Western Gall Rust or Blacknot. A quick inspection would ensure that these trees would not be planted at all(17). Image source: Olds College Page 117 111 ENVI 202 - Tree Biology Module G3 Module G3 Explain the growth effects of soil treatments such as N fertilization, compaction, and flooding. Soil and Fertilization In order to accurately assess the fertilization needs of trees, you will: • Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root • Explain the effects of nitrogen fertilization with respect to a tree’s defence system • Describe how to treat a tree in decline • Describe the effects of turfgrass herbicides, soil compaction and competition to trees • List what type of records would provide excellent information to be able to assess a tree’s response to treatments Image source: Olds College Page 118 ENVI 202 - Tree Biology Module G3 112  Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root Explain the effects of nitrogen fertilization with respect to a tree’s defence system Describe how to treat a tree in decline Describe the effects of turf - grass herbicides, soil compac - tion and competition to trees List what type of records would provide excellent infor - mation to be able to assess a tree’s response to treatments Fertilization Fast release fertilizers are in a highly soluble state which is absorbed very quickly by the roots. Ionization is almost immediate. Some slow release fertilizers are granule-coated that must be weathered to remove the coating. The thickness of the coating varies, allowing for gradual gradation and element release. Do not use slow-release fertilizers if there is a potential for root rot problems. If root-rot pathogens are present, you will be feeding them rather than supplying the tree. Overfertilizing (oversalting) results in plasmolysis. Carbohydrates + one or more elements = NUTRIENT produces energy building block building block + energy We do not feed trees when we fertilize. We provide them with the min- erals (elements) that combine with carbohydrates to result in a nutrient. Green plants make their own food. Find out what mineral deficiencies there are in a soil. Nitrogen tends to get misused and the other twelve elements are underused or ignored. The other elements besides Nitrogen (N) that are essential for growth are Phosphorus (P), Potassium (K), Sulfur (S), Calcium (Ca), Man- ganese (Mn), Magnesium (Mg), Iron (Fe), Copper (Cu), Zinc (Z) and Molybdenum (Mb). Elements do not carry any energy, but they are building blocks. They do not come with a bond. It is the sugar, the energy that elements bond to. Page 119 113 ENVI 202 - Tree Biology Module G3 With Nitrogen Nitrogen is important in the production of chlorophyll. If there is more chlorophyll, the tree can produce more food, but there is a tremendous initial investment of energy to consider first. Fertilization takes away the purple. Nitrogen, a soil mineral, is required by the tree to combine with car- bohydrates to form amino acids, proteins, amino acids, etc. which are required to build new parts for the tree. Wait until there is adequate energy reserves before fertilizing with nitrogen. Nitrogen must combine with carbohydrates. For every four atoms of Nitrogen, 52 Carbons (carbohydrates) must be combined with them to make one molecule of chlorophyll. In early spring, these carbohydrates must come from the stored energy reserves. There is only so much energy in reserve. N enters the plant as NO2. This is soluble in water, enters the root and combines with carbohydrates (energy). Proteins are formed (proto- plasm). The result is bigger leaves but low storage in these leaves. Energy for growth is important but should not be used at the expense of reproduction and defence. High nitrogen fertilization may result in plants (even turfgrass) that cannot defend themselves. Pesticides and herbicides must then be used to help the plant in defence. If the plant had not been weakened by the demand for energy from fertilizing with Nitrogen, it could defend itself, and pesticides and other treatment. would probably not have to be applied nearly as much as we see in the industry today. Nitrogen fertilization stimulates growth at the expense of the tree’s defence system. Fertilizing with nitrogen is an investment in the future but it does require an initial outlay of energy $$. Many carbon atoms (52) are required to combine with four nitrogen atoms. It may be a long time before the tree can benefit from its rewards, e.g. new leaves for photosynthesis. If energy $$ run out before the returns start coming in, the tree will have nothing left for defence from injuries, insects and diseases. Do not let the amount of growth induced through fertilization take away energy reserves. If a tree is already low in energy reserves and it is stimulated to grow, the energy to grow must come from stored energy. The kinetic energy is from the leaves, but first the engine must be start- ed by the batteries, the stored (potential) energy in living parenchyma. Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root  Explain the effects of nitro - gen fertilization with respect to a tree’s defence system Describe how to treat a tree in decline Describe the effects of turf - grass herbicides, soil compac - tion and competition to trees List what type of records would provide excellent infor - mation to be able to assess a tree’s response to treatments Page 120 ENVI 202 - Tree Biology Module G3 114 A sure sign that too much nitrogen has been applied is the presence of sucking insects. Also check the length of the internodes for another indication of too much nitrogen. Trees that are infected with fireblight should not be fertilized. Ferti- lization would result in only more tissue that has no protection. The fireblight causing organism, Erwinia amylovora, is a bacterium; amy- lovora means “I love to eat starch”. High nitrogen applications for turf may adversely affect the trees. Growth may be too lush and rapid, making it very susceptible insects such as aphids and diseases. Sooty mold will be evident on trees that have been exposed to high nitrogen levels. Aphids attack the lush growth, and the sooty mold is attracted to the sweet exudate released by the aphids. Do not fertilize with Nitrogen in period 4 (wood formation); otherwise, frost injury may occur. Wait until everything is truly dormant (between period 5 and 1). Use lower doses and fertilize more often instead of one or two large doses. Some trees are capable of fixing nitrogen from the atmosphere. Alder and Douglas-Fir are examples of trees that are nitrogen fixers. Many of the associates found in the forests among trees are also capable. It may be wise to simulate a more natural environment by including several of the species that associate with trees in their natural state. Page 121 115 ENVI 202 - Tree Biology Module G3 Fertilizing a Tree in Decline Apply two to three separate applications of fertilizer, using low doses before period 4 begins. This is more dangerous in areas with very short growing seasons. Perhaps only two applications can be accommodat- ed. Start with the lowest possible dose. Return later to assess the tree and measure the response. Adjust the dosage accordingly. Always water first to ensure fertilizer availability in the top 25 cm of soil. Image source: Olds College Repeat this practice for another year or two. Hopefully, the energy reserves will eventually increase and the tree will be well on its way to recovery. Image source: Olds College Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root Explain the effects of nitrogen fertilization with respect to a tree’s defence system  Describe how to treat a tree in decline Describe the effects of turf - grass herbicides, soil compac - tion and competition to trees List what type of records would provide excellent infor - mation to be able to assess a tree’s response to treatments Page 122 ENVI 202 - Tree Biology Module G3 116 Herbicides, Soil Compaction and Competition Herbicides Since roots extend far beyond the dripline of a tree, applications of fer- tilizers that also contain herbicides can kill trees. Tree roots grow with the turf and easily absorb 2,4-D and other commonly used broadleaf herbicides. Roundup® is supposedly “deactivated” once it touches the soil surface. However, Round-Up® does not necessarily touch the soil before contacting with tree roots(30). Soil Compaction Soil compaction reduces oxygen and water content of a soil. A de- crease in soil oxygen from compaction will decrease the number of functional roots. This will alter the root:crown balance, since the remaining roots are unable to support the entire crown with water and minerals. Dying branches will result and photosynthesis will decrease. Soil compaction also creates a build-up of CO2 in the soil, which may be toxic to roots. Competition Grass growing around trees can reduce the tree’s growth by 75%. The competition for water and nutrients restricts the tree’s ability to pro- duce absorbing roots. A smaller, less vigorous tree is the result. It is also more susceptible to environmental stresses such as drought, and is more prone to insect and disease. Young trees are especially sensi- tive(1). Another major consequence of grass growing close to trees is mechan- ical damage from mowing equipment, weed whips, hoes, etc. Lawns are often watered frequently and shallowly. This may cause rot at the tree flare area. Since turfgrass prefer full sun, it often grows poorly under trees. To improve the condition of the grass, people tend to strip up (remove) the lower tree branches, which is harmful to the health of the trees. This practice only hurts the tree; the growth of the grass is rarely improved. Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root Explain the effects of nitrogen fertilization with respect to a tree’s defence system Describe how to treat a tree in decline  Describe the effects of turfgrass herbicides, soil compaction and competition to trees List what type of records would provide excellent infor - mation to be able to assess a tree’s response to treatments Page 123 117 ENVI 202 - Tree Biology Module G3 Differentiate between a nutrient and a mineral and describe what happens when a mineral enters the root Explain the effects of nitrogen fertilization with respect to a tree’s defence system Describe how to treat a tree in decline Describe the effects of turf - grass herbicides, soil compac - tion and competition to trees  List what type of records would provide excellent information to be able to assess a tree’s response to treatments Accurate Records and Follow-up People in the tree industry are very active in diagnosing problems and prescribing treatments. Unfortunately, few arborists return to assess the treatment to make adjustments for next time. This would involve accurate record-keeping of what was done, when it was done, and an evaluation. Investigate the amount of energy reserves, measure the internodes, and inspect the buds or the leaves. Make recommendations for the future. This is where a true “tree care professional” is required, one who has the knowledge and experience to accurately assess a tree’s condition, and make recommendations for that particular tree. There should be maps of the trees and their locations with records that indicate the timing and the amounts used. Page 124 ENVI 202 - Tree Biology Module G3 118 Page 125 119 ENVI 202 - Tree Biology Module G4 Module G4 Describe planting techniques that improve the chances of a tree’s future development. Planting In order to successfully plant trees to ensure their future health and establishment, you will be able to: • Identify design recommendations that are helpful in ensuring quality plant material • List and describe the methods of handling tree stock • Describe planting techniques and considerations that will result in correctly planted trees • Describe how trees should be treated following the planting process • Explain the criteria used to determine if a tree is “established” in its new site Image source: Olds College Page 126 ENVI 202 - Tree Biology Module G4 120  Identify design recommen - dations that are helpful in ensuring quality plant material List and describe the methods of handling tree stock Describe planting techniques and considerations that will re - sult in correctly planted trees Describe how trees should be treated following the planting process Explain the criteria used to determine if a tree is “estab - lished” in its new site Design Considerations Planting plans should have the trees drawn to mature size, so that enough space is provided for each tree to grow. Large shade trees such as oaks may require a 15 m spacing from other trees; smaller trees like hawthorn may only need 5 m. In this way, mistakes in plant placement can be avoided. It also ensures that trees will be placed at the correct angles from each other as drawn on the scale drawing to ensure the natural or a formal placement requested by the designer. Trees are often placed too close to buildings. Trees should be planted at least one-half their ultimate height away from buildings(18). Designs should also have all of the trees specifically labelled as to ge- nus, species, and cultivar, if applicable. Many plans used today simply say “26 deciduous trees” and “22 evergreen shrubs”, etc. Some plans are more specific, yet still do not describe enough: “15 Pines” and “8 Crabapples”. This allows too much leeway for the contractor and the tree supplier to make selection decisions. It also leaves no recourse for the maintenance contractor or the property manager to have plant material changed, moved or replaced. Each plant should be listed on a Plant List on the plan, describing its size and caliper specifications. Additional comments such as “mul- tistemmed” or “specimen tree” are helpful to describe the expected quality of specific trees on the plan. Written specifications should also be available with the planting plan describing the quality expectations of the plant material. The specifi- cations provide the guidelines for the receiver to accept or reject trees that have been delivered to the site. It also provides the supplier with the project’s expectations of the quality of trees expected. The name of the supplier(s) should also be included so the designer or the represent- ative can inspect the trees at the nursery before choosing a contractor for the job installation. Page 127 121 ENVI 202 - Tree Biology Module G4 Handling Trees Bareroot stock have roots that have little to no soil. The crown is kept dormant.(15) These trees should be planted prior to budbreak(15). Balled-in-burlap plants have a longer planting season than bareroot but should still be planted before spring. Nearly all evergreens can be balled-in-burlap. Deciduous trees with calipers over 5 cm can be balled in burlap as well. Use this method for trees that are difficult to transplant. When planting, fold the burlap down as far as possible prior to backfilling. If the burlap has any plastic content, remove it(15, 41). Many trees are wire-basketed for ease of handling. Otherwise, care for it as a balled in burlap tree by wrapping the ball and keeping the roots moist. Wirebaskets should be cut to allow for root growth(15). Container-grown trees have made it possible to plant all season long(15). Planting large specimens is becoming more and more popular. Plants are grown to a large size in the nursery, and then are dug mechanically. The tree spade allows the tree to be wrapped, or placed immediately into the new landscape. The most important reason transplants fail from tree spades is that a SHARP spade is not used. A sharp space is needed to cleanly cut the roots. Bent, crushed and torn roots just rot. A tree should not be moved if its size exceeds the size limitations of the machine being used(15, 40, 41). Trees that are dug manually are usually inspected closely prior to dig- ging to ensure their quality. Since tree spades make digging faster and easier, unsuitable trees may be dug. Installers may give less attention to spade-dug trees, since so much of the tree’s original soil comes with the tree. These problems have given tree spades a bad name. If spades are correctly used, they will move large trees well(7). Spaded trees respond similarly to balled-in-burlap trees. Ensure that the sides of the planting hole are not glazed. Otherwise roots will have difficulty penetrating. Enlarge the hole to accommodate loosened backfill soil(12).  Identify design recommen - dations that are helpful in ensuring quality plant material List and describe the methods of handling tree stock Describe planting techniques and considerations that will re - sult in correctly planted trees Describe how trees should be treated following the planting process Explain the criteria used to determine if a tree is “estab - lished” in its new site Page 128 ENVI 202 - Tree Biology Module G4 122 Planting Follow the minimum rootball standards set out by the Canadian Stand- ards for Nursery Stock 1994 p. 20. For example, for deciduous trees a 300 cm tree with a calipre of 40 mm should have a root ball diameter of 60 cm minimum. Container size should be of minimum standard in size as listed in the same publication. A tree that has a height of 350 cm should have a calipre of 45 - 50 mm and the container should have a top diameter of 38 - 45 cm. The larger the root area that is planted, the better. To ensure establish- ment, have at least 30 cm root ball diameter for every 2.5 cm diameter at 1.4 m (dbh)(17). A tree will run into problems after being transplanted if it is low in reserve energy. It is better to use parent material rather than adding any soil amend- ments. Loosen up the parent material. If there is only topsoil and no mixing with parent material, the roots will just grow round and round, spiralling, to eventually girdle the tree. Tree are often than not planted too deeply. To compensate, roots must grow upward and then they begin to wrap around the trunk. Plant trees on mounds to avoid sidewalk problems. Be sure to give corner trees enough room. The roots should be kept cool and moist, especially if they are bareroot or in dark-coloured containers. Bark is particularly vulnerable to dam- age in the spring(15, 31). Antitranspirants are effective during warm, windy days(40). Trees that have been root pruned a few years prior to transplanting show less stress than freshly dug trees(12). Site Preparation The planting hole should not be deeper than the root ball. Dig the hole 2 to 3 times as wide as the root ball and slope the sides. This improves the aeration for new developing roots. Faster root generation is pos- sible in the loosened backfill soil if the planting hole is wide. Backfill should be the soil removed from the planting hole(16, 18, 51). Identify design recommen - dations that are helpful in ensuring quality plant material List and describe the methods of handling tree stock  Describe planting tech - niques and considerations that will result in correctly planted trees Describe how trees should be treated following the planting process Explain the criteria used to determine if a tree is “estab - lished” in its new site Page 129 123 ENVI 202 - Tree Biology Module G4 Water must be readily available. The plants must be protected from dessication and temperature extremes. Handle the trees by the roots not the trunk. Tie chains and ropes around the root ball for support. Never stand on the inside of the ball during digging as the ball can fall apart(41). A backhoe works well for digging - be sure to stop and cut the roots by hand before backfilling in(41). Crown Pruning Crown pruning should be limited to the removal of broken, dead or damaged branches. Do not remove branches to compensate for root loss at transplanting. Auxins are concentrated predominantly in the terminal buds. Auxin is the signal for roots to initiate growth. If terminal buds are removed, root initiation will be inhibited. By removing terminal buds, excessive growth of lateral shoots is encouraged. Sugar reserves are then directed to the developing shoots rather than roots. When there is intense shoot growth, new root formation is reduced(14). Many texts will wrongly recommend that when transplanting a tree, one third of the crown should be removed to compensate for root loss. It has been many years now that this practice has been discouraged. It is the hormones in the terminal buds that produce signals of communi- cation to the root to stimulate root initiation, growth and development. Try to keep as many terminal buds intact as possible. The only pruning that should be done to the crown is the removal of any dead, damaged or diseased branches. Roots, should be inspected at planting. If there are any crushed roots cut these clean to encourage the production of adventitious roots. Roots will not form on crushed roots. Pruning also delays hardening off, resulting in winter injury. Respect and understand the consequences of the short growing season on the prairies. Overcompensate for this fact by minimal pruning and mini- mal nitrogen fertilization. Trees should not be headed back (terminals cut back) as the natural form of the tree may be ruined. Trees that have been headed have many evident stubs. These stubs provide a perfect environment for decay-causing organisms to get established and possi- bly advance through to the rest of the tree(15). Avoid taking major limbs at all costs. Trees do better when there was is no pruning done(41). Page 130 ENVI 202 - Tree Biology Module G4 124 Placement When setting the tree into the hole, lift the tree by the root ball, never by the trunk. The trunk does not support the weight of the root ball, and the roots will break off. The cambium layer beneath the bark can easily be crushed from the lifting. If the tree is balled in burlap, cut the string or wire and remove this material from the hole. It is generally accepted throughout the indus- try that all containers must be removed at planting. Removal of wire baskets is recommended. Some suggest to simply bend back or remove the wire loops. In this case, the top horizontal wire should be bent down to at least 20 cm below the top of the root ball. Having to grow through and around the wires injures the roots. This uses up energy reserves, and the capacity to store energy is reduced(16, 18, 27). With wide planting holes it is possible to cut and bend the wire back under so that the top 20 - 30 cm. can be wire-free. This also provides an opportunity to cut cleanly any crushed or damaged roots before backfilling. This extra care can only improve the tree’s chances of quickly establishing itself in its new environment. One common reason for leaving baskets completely intact is for easy removal if the tree dies. Tree removal should be the last consideration, not the first! Plant a good quality tree into a site with good aeration and drainage. Plant it correctly to provide the tree with the best chance for establishment. Provide consistent aftercare. If this is done, tree remov- al should not be required. Depth of Planting If the soil is sandy, set the tree level to the ground. If it is heavy clay soil, plant the tree 10-15 cm higher than ground level. Trees die be- cause they have been planted too deep. The root flare should be visible at soil level after planting. Otherwise, moisture is in direct contact with the stem. Living cells die. This promotes decay. Sometimes, the nurs- ery fills the containers too high with soil. The installer takes these trees and often plants them even deeper(37, 41)). Fill the hole by gently firming the backfill around the tree to hold it in place and to eliminate air pockets. Settle the soil with water. Water the root ball, not just the surrounding backfill(27). Page 131 125 ENVI 202 - Tree Biology Module G4 When to Plant Planting should be done immediately upon receipt of the trees. Trees must survive the digging, the storage, the hardening off, the handling and the transport. Dessication of trees occurs most often between the time of delivery and the time of planting. If planting cannot be done immediately, store the trees in a cool, moist place(8). If trees are to be subjected to winds, which is likely in the prairies at almost any location, transplant trees in early spring as soon as the soil can be worked (after the disappearance of frost and before the bud- break). The advantage to planting in the spring is that there is ample soil moisture at this time of the year. Roots will have the entire grow- ing season to establish before freezing weather. Birch move best in the spring, always! Pine prefer to move in the spring as well(17, 41). Avoid transplanting when the leaf growth is rapid. This is the time energy reserves are being drained. Wait until spring shoot and leaf growth are complete(17). Summer planting of trees in containers will provide favourable soil temperatures for root development but irrigation will be necessary. Avoid the hottest part of summer for transplanting any trees. Evergreens can be successfully transplanted in the spring or fall. Ever- green trees can be transplanted a little later in the spring and earlier in the fall than deciduous trees(17). Planting deciduous trees in the fall is risky on the prairies since there is little time for new roots to be generated before freeze up. Soil tempera- tures ideally should be 15-21° C for root generation. Tree Size Larger trees do provide a more instant landscape appearance but if you want what is best for the tree, plant smaller trees. Smaller trees do suc- ceed better than larger trees after transplanting. Choose smaller trees if irrigation will be limited. Smaller trees can establish more quickly and soon surpass trees that were planted as larger specimens(12, 16, 17, 48). Page 132 ENVI 202 - Tree Biology Module G4 126 Postplanting Care Tree Quality A tree’s chance to overcome transplanting depends on the amount of carbohydrates the tree has stored, the tree’s ability to tolerate dessi- cation and its ability to function while the roots develop. Promoting root development must be given top priority to establish newly planted trees, especially big trees. In favourable conditions, good air and water movement, pH level and nutrient availability, roots will spread 2 to 3 times further than the branches(16, 49). “Transplanted trees do not produce significant shoot growth until the previous pre-transplant root:shoot ratio has been re-established.” It is best not to fertilize with any fertilizer high in nitrogen. When one atom of nitrogen is taken in by the roots, several molecules of carbohydrates must combine with it. If carbohydrate reserves are limited, it may be better to limit the amount of nitrogen fertilization. It is water stress that is the major cause of transplant failure(16). Unfortunately, customers look for the lowest price more often than for the tree quality and aftercare(10) The tree must be of good quality to begin with. Spending any amount of money on a poor quality tree is still a waste of money. Pay for good quality. Pay for good planting site conditions. Pay for quality aftercare! It is difficult for tree suppliers to sell their stock to companies they know will not take care of the trees, especially if they are to guarantee the trees for any length of time. The first two years are the most critical for newly planted trees. Specifications documenting the maintenance regime for aftercare should clearly state expectations for watering, etc. This will provide maintenance companies a clear basis for their bid- ding and provide the owner with the level of the quality care that is to be expected. Watering Water stress is the most limiting factor is tree establishment. Correct watering is critical for newly transplanted trees, large or small. Sub- surface drainage should be installed so that excess water moves away from the trees. Consider soil types and exposure to determine the watering schedule required(40, 48). Water the root ball - not just the surrounding soil. Be sure there is good drainage to avoid flooding. Trees that have been grown in containers are more sensitive to dessication since they have many more fine roots Identify design recommen - dations that are helpful in ensuring quality plant material List and describe the methods of handling tree stock Describe planting techniques and considerations that will re - sult in correctly planted trees  Describe how trees should be treated following the planting process Explain the criteria used to determine if a tree is “estab - lished” in its new site Page 133 127 ENVI 202 - Tree Biology Module G4 than trees harvested from the field. Daily irrigation, especially for trees with calipers greater than 5 cm, may be required for several weeks after planting(12, 41). Try to apply approximately 5 cm. of water at each watering. The small absorbing roots must be kept alive. If these die, it decreases the capac- ity to absorb water. Energy reserves also must be used to replace the dying roots. Fine roots will quickly die if they are flooded, exposed to drought conditions and temperature extremes. On slopes use a soaker hose, and on very steep slopes, use a watering needle(49). Frequent watering with less water is recommended prior to the estab- lishment of trees. This is opposite to the usual recommendation for established landscapes to provide the occasional watering with large volumes of water(12). If there is good air and water movement, pH level and nutrient availa- bility, roots will spread 2 to 3 times further than the branches. Fertilizer It is not recommended to fertilize newly transplanted trees with Nitro- gen, especially before the leaves have emerged and fully expanded. Fungi, (rot-causing) are waiting. They will feed on the Nitrogen and this will aid in their population to infect the tree. Soil Temperature Initial root generation is from the elongation of existing roots first, and secondly from adventitious roots. Budbreak occurs before root genera- tion in dormant-transplanted stock. It would be advantageous to de- crease the time between budbreak and root generation. Applying auxin to the roots prior to transplanting may have some success in promoting root development(43). Mulch Mulch has proven beneficial to trees in many ways. Micorrhizae associations are encouraged. Soil temperatures are moderated. Weed growth is inhibited. Compaction of the soil is greatly reduced. Soil moisture retention is improved. Nutrient availability is improved(49). Be aware of the type of mulch you are applying. To be sure that mulch is “good”, smell it. It should smell like freshly cut wood or fertile Page 134 ENVI 202 - Tree Biology Module G4 128 garden compost. Sour mulch will produce toxins that may be detri- mental to the trees. Sour mulch smell like ammonia or vinegar, sulphur or silage. Sour mulch occurs if the mulch pile is too large for good air penetration(45). To avoid sour mulch from developing mix the particle sizes so that there are large pieces in with small. This will help aeration. This is why sawdust and mushroom compost often go sour. There is less oxy- gen between the small particles and compression occurs. Never cover a mulch pile with plastic as this will further deter oxygen penetration. Be sure that mulch is no more than 2.5 cm deep next to the tree trunk and only 10 cm deep beyond(37, 45). Type of Mulch Depth (cm) Fine sand or fine bark 2.5 Coarse sand or coarse bark 5.0 Mixture fine & coarse 5.0 Pea gravel 7.5 Brush chips 7.5 - 10.0 Bark nuggets 10.0 Chart taken from (18) Kessel, C. 1992. Planting Habits. Landscape Trades. July/August Mulch should not be applied over plastic. Oxygen and water availabili- ty to the trees are severely restricted(18). Tree Wraps Tree wraps do not moderate the fluctuations in temperature that trunks are exposed to. Tree wraps retain excessive moisture against the trunk. This promotes the development of cankers and other fungal problems and also predisposes the bark to further injury. Wrap has been used to discourage rodents and to protect the bark from mechanical injury. Instead, keep mulch 2.5 cm away from the trunks of trees, and don’t allow grass to grow to the trunk. Mechanical damage from weed whips and mowers will thus be prevented(18). Staking Choose trees that can stand alone so that staking will not be necessary. Stake only if the tree will be injured in heavy winds and rains. If a tree has been grown in the nursery with adequate space and without staking or severe pruning, it should be capable of supporting itself, even in high winds(15, 18). Page 135 129 ENVI 202 - Tree Biology Module G4 If staking is necessary, do not use wire in a hose to secure around the trunk. Bark injury will occur. Instead, use strapping that is wide and belt-like. As soon as the tree is stable and secure, remove the stak- ing(35). In any case, remove the stakes after one year. Do not ever plant the tree too deep just to avoid having to stake the tree(35). Establishment The establishment period is the time required to completely replace the root system to the same size as it was before transplanting. Another in- dication is when shoot growth rate matches that of the tree’s pre-trans- plant years(11). In the south and central United States, it takes one year for every 2.5 cm. of trunk diameter to become established. This establishment peri- od is even longer in the northern climates as experienced in the Cana- dian prairie provinces. For this reason, a small tree will establish more quickly and grow more rapidly than a larger tree. Plants not receiving ideal irrigation will take even longer to establish(11, 49, 51). Short guarantee periods of 30 to 90 days are not very useful. Water stress is inevitable in the first season due to transplant shock. Growth is decreased that season. Buds developed the year of transplanting will be very small so growth the following season will also be less than normal. Waiting until the end of the second full growing season would give a better indication of the tree’s success at establishment into the new site. By this time, root growth should be equal to pre-transplant levels. This will correspond to normal shoot growth and bud develop- ment as well(51). Identify design recommen - dations that are helpful in ensuring quality plant material List and describe the methods of handling tree stock Describe planting techniques and considerations that will re - sult in correctly planted trees Describe how trees should be treated following the planting process  Explain the criteria used to determine if a tree is “estab - lished” in its new site Page 136 ENVI 202 - Tree Biology Module G4 130 Page 137 131 ENVI 202 - Tree Biology Module G5 Module G5 Explain the effects of various landscape practices. Industry Practices In order to explain the effects of various landscape practices, you will: • Explain the effects of injections • Explain the effects of wrapping trees • Explain the effects of planting annuals and bulbs • Explain the effects of weed whip Image source: Olds College Page 138 ENVI 202 - Tree Biology Module G5 132  Explain the effects of injec - tions Explain the effects of wrap - ping trees Explain the effects of planting annuals and bulbs Explain the effects of weed whip Injections Injections for micronutrients, insecticides, fungicides, etc., is a con- troversial subject amongst arborists. Consider the location of active xylem. Only the current season vessels are involved in uptake. Drilling holes, injecting with caps, using pressure — How does one know that the active vessels are even being accessed? Xylem vessels allow water to “snake” its way upward through co- hesion, adhesion and transpirational pull. If there is any air in any of these vessels, wouldn’t this pulling effect be broken? This is probably why injections are often force up the tree with the use of pressurized equipment. Injury to wood and encouragement of decay organisms is often the re- sult of injections. Trees that are injected are usually those in ill health, in decline. Is it wise to injure it further, open it to decay-causing organ- isms? Why not concentrate on root uptake of the required elements? That is where the problem may lie - pH, compaction, flooding, etc. Iron, (Fe), is important for trees, as it is responsible for splitting the water molecule during photosynthesis. The tree must constantly be making more chlorophyll. Add iron chelates to the soil to allow for root uptake. Within three or four years, the green will be back. Foliar “feeding” is probably successful only because it drips off the leaves and enters the soil, and is available for the roots to absorb(Shigo work- shop). Do not grow a tree in soils with pH of 7 or 8 if the tree’s natural habi- tat is in a soil with the pH of 5! Maple trees are constantly being wounded by inserting the drain spouts into trunk to gather the syrup in the springtime. Maple trees are dy- ing. Most are blaming the deaths on high concentrations of SO2 in the atmosphere. Consider how maples production has changed over the years. The associates that grew amongst the maples are removed. Many roads have been installed to access all trees with large equip- ment (compaction). Many, many holes are inserted and the sugar is extracted by vacuum suction. SO2 is a problem but would maples have a better chance of defending themselves if they weren’t already in such a weakened, depressed state due to our infliction? Page 139 133 ENVI 202 - Tree Biology Module G5 Wrapping Trees Wrapping trees will cover the green cortex layer just under the bark, thus preventing photosynthesis along the trunk. It also promotes the collection of moisture under the wrap, therefore encouraging the development of decay-causing organisms. Some arborists claim that tree wrap protects the tree from sunscald and damage from rodents. Surely other material such as wire mesh around the lower trunk (but not touching it) would prevent rodent damage. To prevent sunscald, keep the lower branches on the tree to shade the trunk until the tree is established. These branches may be gradually pruned back until they are removed entirely. In the interim, the leaves on these lower branches contribute to the food production and the build-up of energy reserves. Planting Annuals and Bulbs Don’t plant close to tree roots. It is better to plant groundcovers or ap- ply a mulch at the time the tree is planted. Roots will do poorly if they are constantly being wounded from the weeding, hoeing and digging required by annuals and perennials. Weed Whips If you want to kill a tree with a 50 mm calliper in five seconds, use a whip around it. It is amazing how ignorant we are as to how suscepti- ble and vulnerable the cambium zone is just under the bark. Explain the effects of injec - tions  Explain the effects of wrap - ping trees  Explain the effects of plant - ing annuals and bulbs  Explain the effects of weed whip Page 140 ENVI 202 - Tree Biology Module G5 134 Page 141 135 ENVI 202 - Tree Biology References References 1. Borland, J., 1994. An Alternative container-growing System. American Nurseryman, 180(1):127-133 2. Calgary Parks and Recreation (no author) 1995. Development Guidelines and Standard Specifications Landscape Construction. 3. Chong, C., Lumis, G.P. and Cline, R.A., 1989. Effects of Fabric Containers. American Nurseryman. 170(11):51-55 4. Clark. J.R. and Ham. D.L., 1993. Maintaining Tree/Turf Associations. Arborist News; 2(3):33-37 5. Coder. K.D. and Lilly. S., 1994. Regulation of Tree Growth: Keeping the Green Side Up. Arborist News. 3(1):33-37 6. Cutler, D.F., 1993. Interactions between Tree Roots and Construction Work. Arboricultural Journal. 17:47-55 7. Davis, R.K., 1984. How a Tree is Replanted Affects its Chances for Survival. American Nurseryman. Nov 1, 1984:83-85 8. Englert, J.M., Fuchigami, L.H. and Chen, T.H.H., 1993. Effects of Storage Temperatures and Duration on the Perfor- mance of Bare-root Deciduous Hardwood Trees. J. Arboric. 19(2):106-112 9. Garbaye, J. and Churin, J.L., 1996. Effects of Ectomycorrhizal Inoculation at Planting on Growth and Foliage Quali- ty of Tilia tomentosa. J. Arboric. 22 (1):29-34 10. Gerstenberger, P., 1992. Trees on the Move. Tree Care Industry. 3(4):4-6 11. Gilman, E.F., 1992. Effect of Root Pruning Prior to Transplanting on Establishment of Southern Magnolia in the Landscape. J. Arboric. 18(4):197-200 12. Gilman, E.F. 1994. The Landscape Below Ground:Establishing Trees in the Landscape. The International Society of Arboriculture. pp.69-77 13. Grainger, G., 1991. Transplanting Alberta Trees and Shrubs. AgDex 275. Print Media Branch. 14. Hall, L.D., 1994. To Prune or not to Prune. American Nurseryman 179(7):53-57 15. Harris, J.R., 1992. Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines. Prentice-Hall, Inc., Toronto. 16. Harris,J.R.,Bassuk, N.,1993. Tree Planting Fundamentals. J. Arboric. 19(2):164-170 17. Himelick, E.B. 1988. Tree and Shrub Transplanting Manual. International Society of Arboriculture. 17a. International Society of Arboriculture, 1988. Valuation of landscape trees, shrubs and other plants. Seventh Edi- tion. p. 10-21. 18. Kessel, C., 1992. Planting Habits. Landscape Trades. July/August 19. Kessel, C. 1994 Always Check Out the Roots. Landscape Trades. Nov./Dec 20. Kramer, P.J. and Kozlowski, T.T., 1979. Physiology of Woody Plants. Academic Press, Inc., New York. 21. Landscape Canada, 1994. Canadian Standards for Nursery Stock, Canadian Nursery Trades Association - Com- modity Groups, Fourth edition 22. Loescher, W.H., McCamant, T. and Keller, J.D., 1990. Carbohydrate Reserves, Translocation, and Storage in Woody Plant Roots. HortScience. Vol. 25(3):274-279 23. Markhart, III, A.H. and Smit, B., 1990. Measurement of Root Hydraulic Conductance. HortScience. Vol. 25(3):282- 287 24. Marks, G.C. and Kozlowski, T.T., 1973. Ectomycorrhizae: Their Ecology and Physiology, Physiological Ecology. Academic Press, New York and London.pp.153- Page 142 ENVI 202 - Tree Biology References 136 25. Marx, D.H., Pettway, M.D. and Mellick. R.D., 1995. Study Focuses on Ectomycorrhizal Fungi. Tree Care Industry 6(8):29-32 26. Murray, C. , Lumis, G. and Chong, C., 1992. In-ground Container Production of Shade Trees. Landscape Trades 14(5):24 27. New Tree Planting. 1995. Arborist News. 4(1):39-42 28. Ossenbruggen, H.S., 1989. Tree Energy Systems. J. Arboric. 15 (3):53-58 29. Perry, T.O., 1989. Tree Roots: Facts and Fallacies. Arnoldia; Vol. 49 #4:3-21 30. Perry, T.O., 1982. The Ecology of Tree Roots and the Practical Significance Thereof. J. of Arboric. 8(8):197-211 31. Reinartz, W., 1994. Signs of Maturity American Nurseryman. 179(11):32-37 32. Shigo, A.L., 1989. A New Tree Biology. Shigo and Trees, Associates, Durham, NH. 33. Shigo, A.L., 1991. Modern Arboriculture.Shigo and Trees, Associates, Durham, NH. 34. Shigo, A.L., 1990. A New Tree Biology Workshop. June 6, 1990. Olds, Alberta. 34a. Shigo, A.L., 1988. A New Tree Biology Workshop. Nov, 1988. Boone, NC. 35. Shigo, A.L., 1993. 100 Tree Myths. Shigo and Trees, Associates, Durham, NH. 36. Shigo, A.L., 1994. Tree Anatomy. Shigo and Trees, Associates, Durham, NH. 37. Smiley, E.T., 1991. Improper Planting is Killing Trees. Arbor Age. 11(12):38-39 38. Smith, K.T. 1995. Trees at Risk from Good Intentions. Arborist News. 4(5):27-29 39. Smith, R.C. 1989. Stressed Out. American Nurseryman. Dec.15, 1989 40. Stone, H.M., 1992. Big Trees on the Move. Arbor Age. 12(9):18-20 41. Stone, H.M., 1993. Moving Trees: A Guide to Success. Arbor Age. 13(8):10-13 42. Stone, H.M., 1993. Girdling Tree Roots: The Hidden Cause of Tree Failure. Arbor Age. 13(10):8-12 43. Struve, D.K., 1990. Root Regeneration in Transplanted Deciduous Nursery Stock. HortScience. 25(3):266-269 44. Sutton, R.F. 1990. Root Growth Capacity in Coniferous Forest Trees. HortScience, 25(3):259-264 45. Svenson, S.E. and Witte, W.T., 1989. Mulch Toxicity. American Nurseryman. 169(2):45-46. 46. Swartzell, D., 1993. How Trees Respond to Root Pruning. Arbor Age. 13(1):24-25 47. Watson, G.W., 1991. Attaining Root:Crown Balance in Landscape Trees, J. of Arboric. 17(8):211-216 48. Watson, G.W. 1993. The Landscape Below Ground: Root Development after Transplanting. International Society of Arboriculture. 54-68 49. Watson, G.W. 1993., Root System Care. Arborist News. 2(6):33-38 50. Watson, G.W. and Himelick,E.B., 1982. Root Distribution of Nursery Trees and its Relationship to Transplanting Success. J. Arboric. 8(9):225-229 51. Watson, G., Kupkowski, G. and von der Heide-Spravka, K. G., 1992. The Effect of Backfill Soil Texture and Planting Hole Shape on Root Regeneration of Transplanted Green Ash. J. Arboric. 18(3):130-135