NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology NRES 201 Soil Organisms Ecology 1 We know more about the movement of celestial bodies than about the soil underfoot Leonardo da Vinci 16th century This quotation is still true today We know very little about who lives in the soil Less than 0 1 of soil microbes can be cultured 2 1 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology If our bodies were small enough to enter the tiny passages in the soil we would discover a world populated by a wild array of creatures all fiercely competing for every leaf root fecal pellet and dead body that reaches the soil We would also find predators of all kinds lurking in the dark some with fearsome jaws to snatch unwary victims others whose jellylike bodies simply engulf and digest their prey Business end of fungus eating nematode Source Lowenfels and Lewis 2006 Brady and Weil 2010 3 Soil Organisms Ecology Today s lecture topics The diversity of soil organisms The food web Organism abundance metabolic activity 4 2 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology The diversity of soil organisms Types of organisms Animals versus plants Fauna animals Flora plants nonanimal microbes Domains Eukarya plants animals and fungi Bacteria microbes Archaea 5 Food source Herbivores eat living plants Detritivores eat dead plant debris Predators eat other animals Fungivores eat fungi Bacterivores eat bacteria Parasites feed on other organisms without killing them Carbon and energy sources Heterotrophs use organic compounds Autotrophs use CO2 for carbon Energy from photosynthesis or chemical oxidation 6 3 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Macro 2 mm Meso 0 1 2 mm Micro 0 1 mm Source Brady and Weil 2010 7 Diversity and isolation Species diversity vastly greater for soils than for aquatic environments owing to A nearly limitless food variety And a much wider range of habitat conditions Soil aggregates isolate meso and microorganisms Source Troeh and Thompson 2005 8 4 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Importance of diversity The presence of more species increases Functional diversity A wider variety of substrates can be used to carry out a wider array of processes Functional redundancy A given process occurs under a wider range of environmental conditions Benefits of biological diversity For soil quality For ecosystem stability and resilience Soil processes remain active and recover from disturbance 9 Implications for global biodiversity Soil is a major storehouse of genetic information Because so many species live underground Mankind has learned to utilize some of this information in making Antibiotics Yogurt And beer The soil DNA bank is a valuable resource for genetic engineering Microbial genes utilized for plant or animal improvement 10 5 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology The food web Primary producers Tertiary consumers Secondary consumers Higher level consumers Primary consumers Note Earthworms are important for shredding and as a consumer at and above the second trophic level Source http www nrcs usda gov 11 Source of energy and carbon Humans fit here Source Brady and Weil 2010 12 6 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Primary producers At the base of the food web Mainly vascular plants But also Mosses Algae Lichens And some bacteria Most are capable of photosynthesis CO2 is converted to organic substrates These substrates supply other organisms with Organic C And chemical energy 13 Primary consumers Animals and microflora that feed on plant tissues Leaf cutter ant Herbivores eat live plants Examples include Nematodes Ants Mice Source http nationalgeographic com Rabbits Most are considered pests Cicada but some do more good than harm Such as cicadas which improve soil drainage and promote root growth 14 7 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Detritivores eat plant debris Examples include Mites Springtails Earthworms Their shredding actions increase exposure to microbial attack And the microbes are consumed along with the plant debris Oribatid mite Source Nardi 2007 Springtail 0 5 mm Source Lowenfels and Lewis 2006 15 Saprophytes feed on dead plant debris And also on animal feces and corpses This group consists of the soil microflora including Bacteria Actinomycetes Fungi Decomposition is their business But they also feed many secondary consumers 16 8 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Secondary consumers Soil microflora can feed on primary consumers This group also includes carnivores that consume other animals such as Centipede Centipedes Mites Springtails Predatory nematodes Spiders Source http animal world com Snails Their grazing can stimulate microbial growth and activity Or kill off microbial colonies 17 Meso and macrofauna enhance microfloral decomposition because Their chewing action fragments plant litter and cuts through waxy coatings Chewed tissues are mixed with microbes in the animal gut Animal movement disperses microbes and exposes them to new food sources 18 9 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Tertiary consumers Other carnivores prey on secondary consumers Examples include Trap jaw ant Ants that eat Centipedes Spiders Mites And other insects Source http berkeley edu Robins that pull European Robin earthworms from their burrows Predation releases nutrients Source http www telegraph co uk 19 Soil microflora are the ultimate decomposers They function as tertiary consumers In animal digestive tracts In animal feces In decomposing dead animal bodies Source http researchmagazine uga edu 20 10 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Ecosystem engineers Some organisms create new habitats for others by altering their environment Examples include Microbial crusts that Microbial crust in the southwestern U S conserve water in desert soils Soil inversion by ants or termites Burrowing by Earthworms Gophers Moles Source http www public asu edu Prairie dogs 21 Dung beetles bury animal dung in upper soil horizons The dung is cut into round balls that can be rolled The female lays her eggs in the dung ball Dung burial Conserves nutrients Controls flies Enriches the soil food web Source http torch cs dal ca 22 11 NRES 201 Lectures 32 34 Fall 2014 Soil Organisms Ecology Organism abundance metabolic activity Populations and biomass Controlled by Food supply Quantity and quality Physical factors Moisture and temperature