NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology1NRES 201Soil Organisms & Ecology1“We know more about the movement of celestial bodies than about the soil underfoot.”Leonardo da Vinci, 16thcenturyThis 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.2NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology2“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.”Brady and Weil (2010)Source: Lowenfels and Lewis (2006)Business end of fungus-eating nematode34Today’s lecture topics- The diversity of soil organisms- The food web- Organism abundance & metabolic activitySoil Organisms & EcologyNRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology3The diversity of soil organismsTypes of organisms- Animals versus plants- Fauna = animals- Flora = plants + nonanimal microbes- Domains- Eukarya = plants, animals, and fungi- Bacteria- Archaeamicrobes5- 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 CO2for carbon• Energy from photosynthesis or chemicaloxidation6NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology4Source: Brady and Weil (2010)Macro: > 2 mmMeso: 0.1-2 mmMicro: < 0.1 mm7Diversity and isolation- Species diversity vastly greater for soils thanfor aquatic environments, owing to:- A nearly limitless food variety- And a much wider range of habitat conditions- Soil aggregates isolate meso- andmicroorganisms8Source: Troeh and Thompson (2005)NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology5Importance 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 rangeof environmental conditions- Benefits of biological diversity- For soil quality- For ecosystem stability and resilience- Soil processes remain active and recoverfrom disturbance9Implications for global biodiversity- Soil is a major storehouse of genetic information- Because so many species live underground- Mankind has learned to utilize some of thisinformation in making:- Antibiotics- Yogurt- And beer- The soil DNA bank is a valuable resource forgenetic engineering- Microbial genes utilized for plant or animal improvement 10NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology6The food web11Source: http://www.nrcs.usda.gov(Primary producers)(Primary consumers)(Secondary consumers)(Tertiary consumers) (Higher level consumers)Note: Earthworms are important for shredding and as a consumer at and above the second trophic level.Source of energy and carbonSource: Brady and Weil (2010)Humans fit here12NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology7Primary producers- At the base ofthe food web - Mainly vascularplants- But also:- Mosses-Algae- Lichens- And some bacteria- Most are capable of photosynthesis- CO2is converted to organic substrates- These substrates supply other organisms with:-Organic C- And chemical energy13Primary consumers- Animals and microflora that feed on planttissues - Herbivores eat live plants- Examples include:• Nematodes•Ants•Mice• Rabbits- Most are considered pestsbut some do more goodthan harm• Such as cicadas, whichimprove soil drainageand promote root growthCicadaSource: http://nationalgeographic.comLeaf-cutter ant14NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology8- Detritivores eat plant debris- Examples include:• Mites• Springtails• Earthworms- Their shredding actionsincrease exposure tomicrobial attack- And the microbes areconsumed along withthe plant debrisOribatid miteSource: Nardi (2007)SpringtailSource: Lowenfels and Lewis (2006)0.5 mm15- 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 consumers16NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology9Secondary consumers- Soil microflora can feed on primary consumers- This group also includes carnivores that consumeother animals, such as:- Centipedes- Mites- Springtails- Predatory nematodes- Spiders- Snails- Their grazing can stimulatemicrobial growth and activity- Or kill off microbial coloniesSource: http://animal-world.comCentipede17- Meso- and macrofauna enhance microfloral decomposition because:- Their chewing action fragments plant litter andcuts through waxy coatings- Chewed tissues are mixed with microbes inthe animal gut- Animal movement disperses microbes and exposes them to new food sources18NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology10Tertiary consumers- Other carnivores prey on secondary consumers- Examples include:- Ants that eat:• Centipedes• Spiders• Mites• And other insects- Robins that pullearthworms fromtheir burrows- Predation releasesnutrientsSource: http://berkeley.eduTrap-jaw antSource: http://www.telegraph.co.ukEuropean Robin19- Soil microflora are the ultimate decomposers- They function as tertiary consumers:- In animal digestive tracts- In animal feces- In decomposing dead animal bodiesSource: http://researchmagazine.uga.edu20NRES 201 Lectures 32-34 (Fall 2014):Soil Organisms & Ecology11Ecosystem engineers- Some organisms create new habitats for others by altering their environment- Examples include:- Microbial crusts thatconserve water in desert soils- Soil inversion by antsor termites- Burrowing by:• Earthworms• Gophers•Moles• Prairie dogsSource: http://www.public.asu.eduMicrobial crust in the southwestern U.S.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:• Conservesnutrients• Controls flies• Enriches thesoil food webSource: