CODIT Shigo

Page 1 COMPARTMENTALIZATION OF DECAY IN TREES Forest Service U.S. Department of Agriculture Agriculture Information Bulletin No. 405 July 1977 Page 2 Watercolor illustrations by David M. Carroll, Warner, New Hampshire. * u.s. GOVERNMENT PRINTING OFFICE, 19n 0-23 1-254 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. '20402 · Price S1.85 Stock No. OOHlOIH3671-8 Page 3 COMPARTMENTALIZATION OF DECAY IN TREES Alex L. Shiga Plant Pathologist, U,S, Department of Agriculture, Forest Service, Northeastern Forest Experiment Station, Durham, New Hampshire and Harold G, Marx Research Applications Staff Assistant, U,S, Department of Agriculture, Forest Service, Washington, D,C, Forest Service U.S. Department of Agriculture Agriculture Information Bulletin No. 405 July 1977 Page 4 INTRODUCTION The science of tree pathology emerged from studies on decay almost a century ago. Many of the concepts developed then have changed little over the years. But, in the last few dec­ ades some additional information on the decay process in trees has been developed. This new information has added to the basic story of decay without subtr acting anything important from it The new expanded concept of decay is simply more complete. And this new, more complete concept gives us a better opportunity to regulate and control decay. Dr. George H. Hepting made the first sound observations on compartmentalization of decay in trees in 1935. His ideas acted as a trigger for the work that followed. The work presented here is an expansion of his ideas. The informati on in this pub­ lication is based on 16 years of research by Dr. Shiga that in­ volved complete dissections of approximately 10,000 trees­ mostly deciduous hardwoods, at least 1,000 conifers, and 17 tropical species. Details of these stUdies have been published elsewhere. The purpose of this publication is to show how most columns of discolored and decayed wood associated with trunk wounds in trees are compartmentalized . A great number of confusing terms are given to a wide variety of defects caused by discolora­ tions and decays in trees. This book describes a system that makes it possible for forest managers to understand how most of these defects develop. To understand the system, the 2 report must be studied very care­ fully. The system is called CODIT Compartmentalization Of Decay In Trees When the system is learned, it will act as the code for under­ standing a wide variety of defects on most tree species. The CODIT system is based on two major points. First, a tree is a highly compartmented plant Second, after a tree is wounded, the resulting defects are compartmentalized . To apply the CODIT system it is necessary to understand that the new expanded decay concept developed in the last few decades include s: 1) Successions of microorganisms associated with discoloration and decay, and 2) Compartmentalization of dis· colored and decayed wood associated with trunk wounds. To begi n with , decay of wood is a natural process caused by microorganisms, mainly fun gi, that enter trees throu gh wounds. Tree wounds are usually inflicted by fire, weather, insects, birds, small or large animals, or man and his activit ies. These wounds start the processes that can lead to decay, and decay is a major cause of damage to trees. While wood decay is most often caused by decay-causing fungi, these fungi are often intimately asso· ciated with bacteria and non­ decay fungi in the process. Decay is the breakdown or de­ composition of dead organic matter. It is also essential to new life. To understand how trees react to wounding and the associated defects by compartmentalizing the defects, it is necessary to reevaluate our concept of how a tree is constructed. A tree is considered here as a highly compartmented plant In a sense, a tree is made up of many trees; each growth ring is a "tree." Each " tree" is divided into many compartments. A compartment can be thought of as a "room," with side walls made up of rays and front and back walls made up of cells that are the last to form in each growth ring. The top and bottom of the compart­ ment is formed after wounding when the elements that transport liquids plug up. The compart­ ment is the least common de­ nominator of the tree. All the types of cells found in the woody stem of a tree will be found in each compartment When microorgani sms invade tree stems through wounds, they do so in successions. Bacteria, nondecay fungi , and decay fungi are often intimately associated in this invasion process. When microorganisms invade, they first surmount the chemical protec· tive barriers set up by the tree and then move into the tree from compartment to compartment The weakest walls of a compart­ ment are the tops and bottoms, and the inner walls. The side walls are fairly strong . When all these walls fall to the invadin g microorganisms, there is another wall that begins to form. The wall formed by the cambium after wounding is the barrier zone. This wall confines the in· vasion to the wood present at the time of wounding. The new "trees" or rings that continue to form are then protected from invasion unless new wounds are inflicted. When new wounds are inflicted at later times, multiple columns of defect develop. An understanding of CODIT will help to clarify many mis­ conceptions about decay. Page 5 Decay is a natural process. The breakdown of dead organic matter is essential for new life. Fungi are the major group of microorganisms that decay wood. In many cases fung i accomplish this only in association with other organisms, especially bacteria. -"" - / 3 Page 6 Wood-inhabiting microorgan­ isms enter trees through wounds. Wounds start the processes that can lead to decay. And decay is a major cause of damage to trees. 4 Decay Page 8 1,p.,.ci,jU()US hardwoods and tinJoical trees Page 10 Small animals Insects ~ I , 8 Page 11 Fire Large anima ls 9 Page 12 10 But, before explaining how • start the decay process, necessary to understand a tree is constructed. A highly compartmented p.laij1!i~ " -' · <i'~,'Vr P.< do not replace i as anima ls do. A tree is a compartmented plant Page 13 "15 ", ee ,...' . Diagrammatic drawing of a tree. In a sense, a tree is made up of many trees. Each growth ring can be thought of as a separate tree, \ \ " 11 Page 14 12 Pith Ray cells form side walls of In a diagrammatic way, here is how a tree is constructed. (The drawings are designed to give a general impression of compartments in trees and they are not intended as technical anatomical descriptions of cell types and arrangements.) The rays define the side walls of the compartments. The last few series of cells in the growth ring define the inner walls. The compartment has holes in the top and bottom walls because the flow of materials is main­ tained in a vertical direction. But, one of the first events that happens after wounding is a plugging of this system above and below the injury. Complete tops and bottoms then begin to develop on the compartments. (The term "walls" is used here in a very loose sense only to give the mental impression of "rooms" or compartments in the tree.) compartments. 3 -----;------- -.11 ~tH-+-_ Last cells to form in growth ring form inner walls of compartment. 2 Top and bottom of compartment form when vertical elements plug after wounding. 1 ------r-ll~fSt;-:~~l::tJ=::_-\~ Compartment I .l Page 15 In wood present at the time of wounding, the tops and bottoms of the compartments are the weakest walls. These we will call Wall 1. The inner walls are the second in weakness-Wall 2. The side walls are fairly strong­ Wall 3. The strongest wall is the one formed by the cambium after wounding-Wall 4. Wall 1 is incomplete in living sapwood because the conduct­ ing elements-vessels, tracheids -conduct liquids in a vertical direction. But as heartwood forms , or after wounds are inflicted , pits close or the con- ducting elements are plugged. The rate and degree of pit closure and element plugging depend on many factors. Completion of Wall 1 is the result of a dynamic process. The plugging will then set the limits for the vertical extension of each compartment. When plugging occurs rapidly, short compartments form , but when plugging is slow, long compartments form. Wall 2 is continuous around every growth ring, and from the top to bottom of the tree. Wall 3 is discontinuous be­ cause sheets of ray cells are not continuous radially and longi­ tudinally throughout the tree. Wall 4 is a much stronger, more localized version of Wall 2. The area-longitudinal, tangential -covered by Wall 4 will depend on many factors: Wound size, type, position, severity, time of year when wounding occurs, and intrin sic genetic potential to respond to wounds. Wall 2 is continuous around growth~j~~~~;~~~i~:~~5~~~~i~~~:~:~~j ring and from top to bottom of the tree. Side Walls 3 are the strongest walls. Present at time of wounding. ---....;f.------ -.;;:§ Inner Walls 2 are the next weakest walls. ------------.!j--~l----!j-- Wall 1 is incomplete until heartwood forms or after wounding. It is not planar. ----------....:.L.._ Top and bottom Walls 1 are the weakest walls. Wall 3 is discontinuous. Sheets of ray cells may end abruptly both radially and 10ngitUdinaIlY.·:::::::==~~j~~~~W~::==::;~l~~~1 Each growth ring is made up of many compartments. 13 Page 16 14 Walls 2 are continuous arou ndi~t~h:e1:~~~i~~~i~:~~~;~;~;~.~ rings and from top to bottom. A compartment _;;.---'-;---- Wall 3 ,...,.... ........ -r-__ ~ Wa ll 2 +'+it- ....... "-.r-F-S-,... Wall 1 is incomplete until after wounding. _________ ,.....I;j.:. Walls 3 are discontinuous inward and up and down. A compartme nt Vascular elements plug after wounding and complete Wall 1. Page 17 Each growth ring is made up of many compartments. A tree is a highly compartmented plant. Discontinuou s Walls 3 Discontinuous Walls 3 Continuous Walls 2 Continuous Walls 2 15 Page 18 16 .u.Ii+4lill. Section B lO·year·old wound on maple Barrier zone Wall 4 formed atter illlli.lL wou 11d in g B Barrier zone After wounding, the cambium forms Wall 4. Thi s wall is called a barrier zone. It separates wood formed before wounding from wood that forms after wounding. Color key to all drawings RED-Host response to wounding, chemical reactions to STOP invasion. GREEN-Invasion processes by microorganisms GO through the barriers set up by the tree. BLUE-Infection of dead and dying tissues on wound surface. BROWN-Decay processes. Page 19 _____ Bark 1-Top and bottom walls are weakest walls 4-Barrier zone equals strongest wall Section A 2-lnner wall 3-Raywall 17 Page 20 Deep experimental i wound Host response Mapl e After wounding, the tree reacts. Chemical barriers de· velop around the injured tis sues. Some wood·inhabiting micro· organisms surmount these barri ers and begin to interact with the tree . The tree exerts a livin g protective force to keep the invaders out, and the invaders exert a strong force to get into the tree through the wound. When microorganisms are able to get in, they move from com· partment to compartment. And 18 when the walls of the compart· ments begin to fall to the force of the invaders, the tops and bottoms (Wall 1) go first, then the inner walls (Wall 2), and then the side walls (Wall 3). But, most of the time the barrier zone (Wall 4) holds, and confines the invaders to the wood present at the time of wounding. The figures 1, 2, 3, and 4, in addi· tion to naming the wall, also indicate the relative strength of each wall. It must be emphasized that the walls are not absolute in their compartmentalizing capacities and given enough time, even the barrier zone (Wall 4) will fall. Page 21 Wood formed after wounding lO·year·old wou Barrier zone Wall 4 I Ii Ii 4 -I1HlIH Wall-l Weakest -2 -3 -4 Strongest Barrier zone WaIl 4 --~~ 19 Page 22 r; Wood altered slightly-NOT \ ..--~ heartwood I Barrier zone Wall 4 Red maple 20 3 The type, severity, and posi· tion of the wound will affect the extent of compartmenta lization. Here are some of the most typica l examples. \-+-_4 Barrier zona l-i'--_ Wall 4 Page 24 22 A basal wound of moderate severity . The entire "group of trees" present at the time of wounding was altered slightly, and were confined by the barrier zone. The side walls, or rays, held here and the column was wedge-shaped in cross­ section. The jagged vertical edge was due to variat ion in confining ability of compartment tops and bottoms in different growth rings. Page 25 A slight basal wound. The entire column of wood present at the time of wounding was altered very littl e, but it was still confined by the barrier zone. The inner walls and side walls held firm here and only a "moon ring" formed. Very faint discoloration =:::====:====f~4~_~~ Diameter of tree whenwounded:::::===:=~~~~~ ___ ~~ Slight wound I , ~ .• " l,l I., . . 23 Page 26 24 In general, the same types of columns occur in trees that have a heartwood core. Discolored and decayed wood is compart­ mentalized in heartwood. When a mechanical wound penetrates the sapwood to the heartwood, the column develops most rapidly along the sapwood· heartwood boundary . f------ Heartwood Heartwood ---4 111 Sapwood Sapwood ---110 , Wound -.+-IP Young red oak Page 27 RED-Host response to wounding BLUE-Surface infection GREEN-Discolor ation BROWN-Decay YELLOW-Heartwood 2 Injured cambium -----------------Injured cambium Host response _________________ Injured cambium \ 25 Page 28 26 Heartwood --Hl~*,,~ Slightly altered Heartwood formation stalled near wound. Barrier zone in heartwood 4 4 4 Page 29 f/J.-------- Injured cambium _---- Large broken branches Young 4 4_~+- Discolored and decayed wood associated with poorly healed large branch stub s is compart· mentalized in heartwood. Central column s of defect in heartwood· formi ng t rees are often asso· ciated with poorly healed branch stubs. 4 27 Page 30 28 altered wood 3 Here are the basic patterns of compartmentalized columns of discolored and decayed wood associated with a singl e wound and with several wounds at one tim e shown on cross section in nonheartwood·forming trees. r - *--4 central core Slightly ....... ~ ... A/1~" altered Page 31 Here are some basic patterns for heartwood-forming trees . Slightly altered heartwood ---;H~"" Discolored heartwood 29 Page 32 30 Injured cambium Injured ---- cambium Large broken branch Most trees receive many wounds during their lives. Every tre e has some branches that die. When the branches are small and the wounds close rapidly , very little internal defect foll ows. But, when large branches die and healing is slow, trouble starts for the tree. Add to this the injuri es caused by other types of wounds at irre gular time intervals and a pattern of multiple columns begins to de· velop. But again the tree com­ partmentalizes the injuries and each column is separated from the others. Page 33 Wound Injured cambium, new barrier zone forming Injured cambium 31 Page 34 1 1 Barrier zone 32 4 Old barrier zone Wall 4 New barrier e forming Old barrier Page 35 ! 30-year-old branch stub wounds Lu-yei,,-cHo wound zone Wall 4 O-vear-old wound Hr.ttHtttt Barrier zone 4 33 Page 36 34 Diameter when first 4 Open branch stub ~;(I;Ir::J'P 4 ~~,.,..-.,. Wound . , .- central column. • "- Multiple columns are common in trees. A minor wound may set up a central colum n of discolored wood and later large branches die and heal slowly. The decay associated with the branch stubs does not penetrate the inner column of compartmenta lized discolored wood. Page 37 A central column of compart· mentalized discolored wood may be associated with large branch stubs that healed slowly, but did close before decay set in. Additional columns of discolored and decayed wood could develop later, for example, from severe mechanical wounds on the trunk. Stub rl-f_IJ IO barrier zone 4 -,I-BarrIEi " zone Wall 4 35 Page 38 4 4 4 36 4 4 4 Here are some typical patterns of multiple colum ns found in nonheartwood ·forming trees . Page 39 In heartwood·forming trees the patterns are the same, but they are sometimes difficult to see because they are often contained in heartwood that is already dark in color. Compartmentali· zation explains how columns of discolored and decayed wood can be found in ring patterns separated by sound wood. 4 4 4 37 Page 40 A major obstacle in understand­ ing multiple columns of com­ partmentalized decay is the difficulty in "seeing" them in three dimensions. Here are some examples: Birch-Column of discoloration and decay associated with a wound developing around a central column of discoloration associated with branch stubs. 4 ---i---Ht R Stub --+--ll.. = 4 ___ --1 Old wound --; 4 38 :-__ .... __ Barrier zone Central column 1--+---;----·01 discolored wood 1-__ -4 ~!i!t-_-4 IIHIItfllll--- 4 Page 41 Maple-Column of discoloration and decay associated with a wound developing around a central column of discoloration. The entire column of wood present at the time of wounding has been altered slightly. When this wood is dried, it will be a different shade from the wood that formed after wounding. Wood altered slightly __ ~ .... ....,,,,, Central column of discolored wood ---IF- .... -fltt"t Wound Barrier zone - ...... .""Im'! 39 Page 42 Pine-Column of discolored and decayed wood associated with a wound developing around a central column of discolored heartwood associated with poorly healed branch stubs. Barrier zone ---I"""" Wound 4 40 Central column of discolored ....;.,r-;..::;#H~-- heartwood ,!f '~!I-- H ea rtwood Page 46 Fornes pini 44 Page 47 _ ...... ____ Heartwood ;'-__ .J... _________ Discolored heartwood Sporophore of L __ ~":li&:_-F'on~es pini White pine New column of defect not in sapwood 45 Page 48 The " holding power" of column s of discolored wood can be shown by wound s that penetrate th e column s. The new column th at form s remains separate from the inner colum ns. When th e second wound is severe, decay may develop in th e new column . Thi s occurs in nonhea rtwood· for ming t rees. New barrier zone Wall 4 Deep drill wound into sapwood and established central column discolored wood column Nonheartwood·forming tree 46 Injured cambium Individual column in each growth ring Old column New column Page 49 1 Decay did not penetrate discolored column. 4 47 Page 50 And in heartwood· formin g trees. 48 Deep drill wound penetrates sapwood, heartwood, and central column of discolored heartwood. Injured cambium When new wounds penetrate old columns of decay, the decay process proceeds rapidly in the new col umn . Page 51 4 --1)_ 49 Page 52 There are some patterns of defects that on first inspection do not appear to fit the concept of compartmentalization. How­ ever, they do. The most notable are the defects associated with canker rots. Canker rot fungi, once established in a tree, keep the wound open by slowly killing some living tissues around the wound. This process is the same as re-wounding. And, when the new wound is made, a new 50 column begins to develop. An intricate pattern of multiple columns is associated with canker rot. New columns form as cambium is killed each year. Some fungi produce sterile fungus material. Diameter of trunk when branch died. Fungus kills cambium and new ---4l~ wounds form. Page 53 Mass of fungus material Cambium killed Q!l7W17r1I. 'f?.z.... 51 Page 54 4 Ring shake zone Slightly altered wood 4 large, old open wound -~ .. 52 ~ Barrier zone Another type of defect that does not appear to fit the concept are ring shakes-separation of the wood along the rings. The prob· lem here is that the barr ier zone associated with the wounds often form s far beyond the visible column of defect. The barrier zone acts as a partition between the wood present at the time of wounding and the new wood formed after. When growth stresses or other stresses are applied, the wood sometimes pulls apart along the barrier zone. Most shakes are associated with wounds, but not all wounds result in shakes. Page 55 Wound Barrier Wall 4 i \ : I UrV~ _ ,', l,. 4 And, yet another type of defect pattern that appears not to fit the compartmentalization concept is the "island" pattern or streak pattern often spoken of as mineral streak. Wounds indeed start these processes. A pattern type that can be termed "palm and fingers" develops. Near the wound all the columns in the indi vidual growt h ring are coalesced to form the "pa lm." As the discolored columns de­ velop vertical ly above and below the wound, Walls 1, or the tops and bottoms of the compartments in individual growth rings, react in different degrees to the wound and the invading micro­ organisms . When such a "palm and finger" column is viewed in cross section at increasing distances above and below the wound, islands of defect appear. Often, a few " fingers" will develop far beyond all the others . Wood formed after wounding 53 Page 56 In sugar maple, for example, the "palm and finger" pattern is the mineral streak pattern asso· ciated with sugar maple borer wounds. This insect is a major cause of minera l st reak in sugar maple. 54 Page 57 , \ I i 55 Page 58 The yellow-bellied sapsucker (see page 7) inflicts several types of wound patterns on many species of trees. In one type of wound pattern a large wound is the result, and the "palm and finger" defect pattern develops. Again, th e "fingers" may extend great distances above and below the wound. And cross sections of trunks made throu gh the "fingers" will show islands of defect, or mineral streaks. \ ~ I .. 56 .. ~ Page 59 , H ¥ :; , 1 )1 ;; , 1 ! 1 , 1 I I I Sapsucker The "pa lm and finger" defect pattern is also associated with some other wounding patterns made by the sapsuckers. wounds-- ________ _ ~~per birch 57 Page 60 Palm and finger 58 Page 61 Sapsuckers will often wound one area on a trunk . On paper birch a swollen black band will form at these sites. Not only will discolored streaks of the "pa lm and finger" pattern develop from such wounds, but the barrier zone that develops after wounding may pull apart from the inner rings to form a complete ring shake which is sometimes called cup shake or loose heart . 59 Page 62 On some trees, such as eastern hemlock, the yellow-belli ed sapsucker inflicts many wounds over large areas of the trunk, 60 " ....-Ik--- Page 63 The barrier zones that form after wounding act as partitions be· tween wood present at the time of woundi ng and wood that forms after wounding. When growth stresses and other stresses develop over long periods, the wood may separate along the barrier zones, and multiple ring shakes form. 4 Ring shake zone 4 4 - ~ -- y '----'--.,.....-_._.- Ring shake zone 61 Page 64 The " palm and finger" pattern of defect and barrier zones that form shake are commonly associated with wounds made by larger animal,s such as beavers and porcupines (see page 9 ), When wounds are severe, Walls 1 and 2 may fall to invading microorganisms . 62 I I ! I ~ , \ , ! \ ',., r. I 1\' ~l ! / C-17 r -1 -\ I i -. ..) .; \. Ring shake 4 Page 65 Squirrels wound young, smooth· barked trees in several genera (see page 8 ). The typical "palm and finger" defect pattern reo suits. In some species these defects are called mineral streaks. 63 Page 66 Insects wound trees (see page 8) and small islands of defects form. Each island of defect is a small "palm and finger" column. The columns usually penetrate only to the depth of the hole made by the insect. Insect hole I ,.=-:- ~;-~ Tubes from scale insect ~, ... -1fO., __ Scale insect that lives in old insect lS!it:::::t"'O;;"-fff------=:;---4-holes .. - --;..;;...: ...... =} I ~ -..."..., "-"===== 64 Insect holes =: :. -:-:U ::-.c.? Page 67 - ~ C"~~ -- I -- ._ . - - ~-- ---- . " I I I When many insects attack a tree at the same time, a barrier zone may develop around the entire tree. All the wood present at the time of wounding will be slightly altered. When dried, the wood present at the time of wounding will be a different shade from the wood that formed after wounding. .. ' •• 65 Page 68 The cambium miner is a small larva of a type of fly that eats its way down the cambial region of some trees . The "tracks" of the larvae are compartmentalized as very long narrow streaks of discolored wood within growth rings. 66 Page 69 On some trees the wounds are not visible. This is common with small basal wounds, especially those caused by fire when the tree was very young and now the healed wound is hidden by forest litter. The barrier zone still forms around such wounds and often results in ring shake. Also, the inrolled callus serves as a weak spot on the tree that may continue to split vertically. Addi· tional cracks may form from the barrier zone outward into the wood that forms after wound· ing. When the cross section of a trunk with such a pattern of internal defect is viewed above the base, a star·shaped pattern of cracks radiating out from the center will be seen. l ~ , 67 Page 70 With some basal wounds, long internal cracks, called seams, form at right angles to the wounds at the points where the calius inrolis. 68 -~/ Page 72 Seams will also form from mechanical wounds on trunl<s. Once a seam begins to form, it will usually continue to enlarge throughout the life of the tree. 70 Page 73 -'-'~{ . ,I , J.I ' -.. -- . - ' '': .... ..... ,... . • -I _ .... 'I/'...s,.." ':--"" ,0 ,-.. \ 71 Page 74 In summary, the compartmental · ization of defects in trees is a survival system that is effect ive most of the time-not all of the time ! And after the tree dies, 72 the powerful decay processes cont inue to decompose the wood. The decaying wood pro­ vides nourishment for a wide variety of organisms. Page 75 The decomposed wood provides nourishment for new trees. 73 Page 76 [This page intentionally left blank.]