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SOIL BIOLOGY LIFE IN THE SOIL SOIL BIOLOGY There are a DIVERSITY of ORGANISMS in SOIL SIZE What they EAT or PRODUCE MICROORGANISMS MACROORGANISMS PRODUCERS HERBIVORES PREDATORS PARASITES DECOMPOSERS PREFERRED ENVIRONMENT AEROBIC – O2 ANAEROBIC – without O2 SOIL BIOLOGY CYCLES Focus on NUTRIENT CYCLING and the PROCESS SOIL BIOLOGY WEBS Focus on ORGANISMS within the WEB SOIL BIOLOGY WEBS COMPLEX SOIL BIOLOGY SOIL ORGANIC MATTER - FOOD for the WEB ORGANIC MATTER is the portion of soil that contains PLANT and ANIMAL RESIDUES at various levels of DECAY SOIL BIOLOGY Most OM is made of CHEMICALLY COMPLEX C Compounds CARBOHYDRATES – long chains of simple sugars SUGARS STARCHES CELLULOSE – primary cell walls of live cells LIGNIN - secondary cell walls that make cells rigid, dead cells PROTEINS – long chains of N containing compounds (amino acids) SOIL BIOLOGY ORGANIC MATTER DECOMPOSITION ACTIVE OM - OM easily DECOMPOSED by MICROBES ORGANIC COMPOUNDS leaked from roots Sloughed off ROOT PARTS DEAD OM MICROBES use RESPIRATION to break down OM OM + O2 →→→→ CO2 + H2O + HUMUS (respiration) Occurs RAPIDLY – weeks to months SOIL BIOLOGY HUMUS – OM that RESISTS DECAY HUMUS is DARK and made of tiny, CLAY sized particles OXIDATION – chemical decomposition of HUMUS HUMUS + O2 →→→→ CO2 + H2O (oxidation) Occurs SLOWLY - 1-3% loss of HUMUS / year SOIL BIOLOGY NUTRIENT CYCLING of OM PLANTS can only use NUTRIENTS in simple INORGANIC IONS When NUTRIENTS are TIED UP in the BODIES of living ORGANISMS or in FRESH OM they cannot be used by plants This is called IMMOBILIZATION Keeps NUTRIENTS from LEACHING When MICROBES break down COMPLEX ORGANIC FORMS to SIMPLER INORGANIC FORMS that PLANTS CAN USE This is called MINERALIZATION When MICROBES EXCRETE, DIE, or are EATEN by another ORGANISM they will RELEASE NUTRIENTS that plants can use SOIL BIOLOGY DISTRIBUTION of SOIL BIOLOGY Top 2’ of SOIL – O and A Horizons Most O2 Most H2O Most OM Best SOIL STRUCTURE RHIZOSPHERE Where LEAKING and SLOUGHING occurs BACTERIAL dominated SOIL BIOLOGY DISTRIBUTION of SOIL BIOLOGY LITTER LAYER and in HUMUS FUNGAL dominated where COMPLEX C compounds SOIL PORES Protozoa and Nematodes in water films Arthropods, Earthworms in air spaces SOIL BIOLOGY SOIL ORGANISM ACTIVITY DEPENDS on MOISTURE and TEMP As MOISTURE & TEMPERATURE increases, ACTIVITY increases SOME ORGANISM is always ACTIVE SOIL BIOLOGY - MICROORGANISMS BACTERIA MOST ABUNDANT SINGLE CELLED MICROSCOPIC organisms RHIZOSPHERE 4 MAJOR DECOMPOSERS – consume SIMPLE C compounds SAPROPHYTIC MUTUALISTS – N FIXERS BENEFICIAL relationship with PLANTS Reside in ROOT NODULES Take atmospheric N2 and convert to NH4+ PLANTS get NH4+ and BACTERIA get simple sugars SOIL BIOLOGY - MICROORGANISMS BACTERIA 4 MAJOR PATHOGENS - FEED on plant ROOTS CHEMOTROPHS (or LITHOTROPHS) FEED on INORGANIC COMPOUNDS of N, S, Fe, or H Important to N CYCLE Some good at DEGRADING POLLUTANTS SOIL BIOLOGY - MICROORGANISMS BACTERIA 2 ODD BALLS PHOTOSYNTHETIC CYANOBACTERIA PRODUCERS Increase OM in soils Live in WATER FILMS ACTINOMYCETES FILAMENTOUS bacteria Give soil EARTHY SMELL (geosmins) DEGRADE COMPLEX C compounds PRODUCE ANTIBIOTICS that can inhibit growth Tolerant of DRY, HIGH TEMP and HIGH pH soils Most are SAPROPHYTIC, some PARASITIC SOIL BIOLOGY - MICROORGANISMS BACTERIA IMPORTANT ROLES of BACTERIA IMMOBILIZATION / MINERALIZATION of NUTRIENTS Produce GUMS that BIND soil particles and BUILD SOIL STRUCTURE Some FILTER and DEGRADE POLLUTANTS DOMINANT in NEUTRAL pH soils and GRASSLANDS SOIL BIOLOGY - MICROORGANISMS FUNGI FEWER numbers of FUNGI in soil, but makes up the LARGEST MASS FILAMENTOUS, MULTI-CELLULAR organisms HYPHAE MYCELIUM 4 TYPES DECOMPOSERS – SAPROPHYTIC COMPLEX C compounds Excrete organic ACIDS which increase HUMUS SOIL BIOLOGY - MICROORGANISMS 4 TYPES MUTUALISTS - MYCORRHIZAE (fungus – root) ECTOmycorrhizae ENDOmycorrhizae – AM (VAM) Grows INTO CELLS of roots and forms ARBUSCLES (nutrient transfer), VESCICLES (storage) Cannot be artificially grown ECENDOmycorrhizae (minor type) Forms a MANTLE surrounding ROOT and IN BETWEEN CELLS Artificially grown and INOCULATED Intermediate type seen in nurseries and after forest fires Thin mantle and some cell penetration, but turns into ECTO as matures Increases ABSORPTION of P, Zn, Cu, H2O Some PROTECT PLANT from diseases causing PATHOGENS SOIL BIOLOGY - MICROORGANISMS SOIL BIOLOGY - MICROORGANISMS FUNGI 4 TYPES PATHOGENS - DISEASE causing organisms PREDATORS NEMATODE eating fungi SOIL BIOLOGY - MICROORGANISMS FUNGI IMPORTANT CHARACTERISTICS of FUNGI O Horizon for COMPLEX C compounds AEROBIC soils DOMINATE ACID soils, FOREST soils DETRIMENTAL HABITATS TILLAGE FUNGICIDE use High N or P FERTILIZER use Fallowed FIELDS Non-Mycorrhizae CROPS SOIL BIOLOGY - MICROORGANISMS PROTOZOA SINGLE CELLED organisms 3 TYPES CILIATES AMOEBA FLAGELLATES FEED on BACTERIA C : N ratio BACTERIA, 4 - 5: 1 C : N ratio PROTOZOA , 10 : 1 As feed on bacteria EXCRETE excess N as NH4+ (mineralization) SOIL BIOLOGY - MACROORGANISMS NEMATODES Non – segmented, EEL-LIKE WORMS, 1/20” long MULTI-CELLULAR organisms PRODUCE EGGS in masses SOIL BIOLOGY - MACROORGANISMS NEMATODES 5 TYPES – based on what they FEED on BACTERIAL feeders FUNGAL feeders PREDATORS OMNIVORES PLANT ROOT feeders – PARASITIC Puncture roots with STYLET, hollow needle Can be ENTRY POINT for other organisms SOIL BIOLOGY - MACROORGANISMS NEMATODES IMPORTANT CHARACTERISTICS Most common in POROUS SOILS DISTRIBUTE Bacteria and Fungi throughout soil USEFUL INDICATORS of a HEALTHY SOIL FOOD WEB The greater DIVERSITY of NEMATODES in a soil, means there are a lot of DIFFERENT CRITTERS to FEED on SOIL BIOLOGY - MACROORGANISMS ARTHROPODS MULTI-CELLULAR INVERTEBRATES (no skeleton) JOINTED LEGS EXOSKELETONS 4 TYPES INSECTS – Springtails, Beetles, Ants CRUSTACEANS – Sow bugs ARACHNIDS – Spiders, Mites MYRAPODS – Centipedes, Millipedes, scorpions SOIL BIOLOGY - MACROORGANISMS ARTHROPODS IMPORTANT CHARACTERISTICS Exist in the TOP 3” of SOIL SHRED and MIX OM, breaks down faster IMPROVES SOIL STRUCTURE by BURROWING and adding FECAL PELLETS SOIL BIOLOGY - MACROORGANISMS EARTHWORMS Segmented INVERTEBRATES MULTI-CELLULAR organisms Sexual REPRODUCTION 3 TYPES EPIGEIC – LITTER dwellers ENDOGEIC - SHALLOW soil (top to 12” down) Compost piles - Red Wigglers Not permanent burrows ANECIC – DEEP BURROWING (to 6’ down) Night crawlers Permanent BURROWS SOIL BIOLOGY - MACROORGANISMS EARTHWORMS IMPORTANT CHARACTERISTICS TURN SOIL OVER IMPROVE SOIL STRUCTURE with BURROWS (biopores) Most abundant in LOAM, where MOISTURE, O2, and NEUTRAL pH SOIL BIOLOGY - MACROORGANISMS MAMMALS RODENTS Highest concentration in UNDISTURBED SOILS Gophers, Woodchucks, Prairie Dogs, Moles, Voles Pasture, Forest, Prairie IMPORTANT CHARACTERISTICS REJUVENATION of soil by BURROWING and MIXING SOIL HORIZONS SUMMARY - SOILFOOD WEB Researchers have not defined how much or what kind of DIVERSITY is BEST for the SOIL FOOD WEB WHAT WE DO KNOW: Greater BIODIVERSITY = Greater STABILITY of the WEB NUTRIENT CYCLING - More ORGANISMS – FASTER cycling NUTRIENT RETENTION IMPROVED STRUCTURE DISEASE SUPPRESSION DEGRADE POLLUTANTS SUMMARY - SOILFOOD WEB WHAT does this mean for LAND MANAGEMENT? Less FERTILIZER Greater INFILTRATION, Less EROSION Less PESTICIDES Greater WATER QUALITY