Slide 1 Soil Biota LHAP 105 Slide 2 What is Soil Biota? “micro-organisms (bacteria, archaea, fungi, and algae), soil animals (protozoa, nematodes, mites, springtails, spiders, insects, and earthworms) and plants living all or part of their lives in or on the soil or pedosphere.” Fortuna, A. (2012) The Soil Biota. Nature Education Knowledge 3(10):1 - Glossary https://www.nature.com/scitable/knowledge/library/the-soil-biota-84078125/ Slide 3 Slide 4 What do Soil Organisms do? They grow and reproduce They feed on by-products from roots (exudates) and plant and animal residue and feed on each other. Slide 5 What do soil organisms need? Air - oxygen Water Food - carbon, nitrogen pH Non toxic environment https://canvas.instructure.com/courses/1286132/pages/unit-1-part-4-soil-biological-properties?module_item_id=16052970 Slide 6 What do Soil Organisms give ? decompose organic matter cycle nutrients Add nutrients to the soil build soil structure control populations of soil organisms (predators) Slide 7 Photo from Natural Resource Conservation Service USDA Slide 8 C:N ratios Bacteria 5:1 Protozoa 30:1 If one protozoa eats 6 bacteria it will consume 30 carbons but will also consume 6 nitrogens. The excessive 5 nitrogens is expelled into the soil to be taken up by plants or eaten by other organisms. Nutrient Cycling Slide 9 Macro animals - Burrowing animals, slugs, worms, insects Shredders and mixers Ingest smaller organisms Soil Organisms include: Slide 10 Arthropods springtails, beetles, ants, crustaceans, myriapods, scorpions Slide 11 Earthworms decompose organic matter, casts contain nutrients and micro-organisms, create burrows in soil Do not release earthworms in the Boreal Forest Slide 12 Living Organisms: bacteria, fungi, nematodes, protozoa, earthworms, arthropods, and living roots Soil Organic Matter includes: Slide 13 Plant Material Soil Biota includes: Create carbohydrates, sugars etc through photosynthesis Convert nitrates and phosphorus etc. to organic compounds In Rhizosphere Contribute organic compounds (exudates) which provide a food source for microorganisms https://jr.brainpop.com/science/plants/plantlifecycle/ Slide 14 Micro plants Algae - Blue green (Cyanobacteria) Present where moisture and sunlight are available - photosynthesis Small impact on Soil organic matter Convert atmospheric N to a plant available form Soil Biota includes: https://www.pthorticulture.com/en/training-center/controlling-algae-on-growing-media/ Slide 15 Micro-animals nematodes, protozoa ( include amoeba, flagellates, ciliates) Feed on smaller organisms (bacteria) nematodes feed on larvae of insectsand fungi as well as bacteria Soil Biota includes: Slide 16 Bacteria Very small - round or rod shaped (1 micrometer) Covered in slime Don’t move much Advantage is reproductive rate (Can double every 20 minutes) Diversity important Slide 17 Bacteria Decomposers (Heterotrophs - carbon from OM) Contain enzymes that break down sugars, carbohydrates, proteins Chemoautotrophs Transform nutrients from carbon in the airImportant in nitrogen cycling and degrading pollutants Mutualists (Rhizobium) Pathogens https://en.wikipedia.org/wiki/Bacillus_megaterium Slide 18 Bacteria Create micro- aggregates Affects water movement Improve water holding capacity Compete with disease causing organisms Rhizobium - Heterotroph Nitrifying and denitrifying bacteria - N cycle Actinomycetes - earth smell chitin and cellulose at high pH levels Slide 19 Fungi Form Hyphae Mycellium Grow from apex of “root” Generally create acid soils Slide 20 Fungi Decomposers - have the ability to break down complex compounds other organisms can’t Form stable macroaggregates Retain and release nutrients in plant available form. Help increase humus by production of organic acids PHOTO: Kirill Ignatyev/Flickr Slide 21 Fungi Mutualists - mycorrhizae Pathogens and parasites Mycorrhizae Slide 22 Where do soil organisms live? around the roots - Rhizosphere Root Cap Meristem Zone of Elongation Slide 23 The Rhizosphere The Bacteria and fungi feed on plant exudates they decompose organic substances Slide 24 The Rhizosphere Protozoa graze on bacteria Nematodes eat bacteria and fungi Slide 25 In Litter Fungi - complex, hard-to-decompose carbon Bacteria & Fungi attack plant residue shredders break up litter Slide 26 In Litter Shredders - earthworms millipedes leaf-eating insects other arthropods Slide 27 Where do soil organisms live? On the Surface of Soil Aggregates Slide 28 And in spaces between aggregates https://www.agric.wa.gov.au/dispersive-and-sodic-soils/soil-aggregate-stability Slide 29 The importance of soil organisms and the role of carbon - Dr Graham Stirling