Soil Biology – A Primer Who is who & What do they do? Elizabeth Sulzman, Oregon State & T. Kittel

Important Groups of Soil Organisms Macroflora Microflora Macrofauna Vascular plants, mosses (autotrophs) Vascular plants (root hairs), algae, actinomycetes, bacteria, and fungi (auto- and heterotrophs) Vertebrates, arthropods, earthworms, snails… (herbivores, detritivores, predators) Size, functional groups: Mesofauna Microfauna Arthropods, worms (detritivores, predators) Nematodes, protazoa… (detritivores, fungivores, bacterivores, predators)

Relative Sizes Animated gif – view in slideshow mode Note ruler for scale

heterotrophs (bacteria, fungi) & autotrophs (algae, cyanobacteria) the primary decomposers release plant available nutrients stabilize soil aggregates Microflora Soil fungiSoil bacteria

Aggregates held together by: –Fungal hyphae –Bacterial “glues” –Organic matter sand silt hyphae clay bacteria Microflora –

Amoebae Ciliate Flagellate Nematode heterotrophs; some parasitic feed on bacteria and fungi release plant nutrients – protozoa KEY for N Nematode Microfauna eeee!

Collembola (springtails) Fungus feeding mite heterotrophs (detritivores, predators) feed on fungi, protozoa, nematodes, mites important in regulating populations of everything smaller Nematode feeding mite Mesofauna

Photo by Suzanne Paisley heterotrophs shred plant material feed on bacteria and fungi associated with organic matter Macrofauna

Addo National Park, South Africa Tembe Elephant Reserve KwaZulu Natal, South Africa Dung Beetles Amboseli National Park, Kenya Macrofauna – Key disposer of elephant dung  and so a protected species! (you can imagine the ‘or else’…)

Soil Food Web Ecosystem Function –

Influence of soil biota on soil processes Nutrient cyclingSoil structure Microflora Microfauna Mesofauna Macrofauna Break up O.M., mineralize and immobilize nutrients Bind aggregates, hyphae entangle particles Regulate bacterial and fungal populations Indirectly affect structure Regulate above pops.; fragment plant tissue Fecal pellets, pores Fragment plant tissue Mix O.M. and mineral soil; pores; feces Ecosystem Function –

Recall: Rate of decomposition depends on – Physical and chemical nature of the litter material Temperature and moisture of the soil environment Aeration (vs. anaerobic) The kinds and numbers of soil fauna  More bugs, and more different kinds of bugs, means more decomposition Ecosystem Function –

– Mendenhall