Soil Biology – A PrimerWho 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

http://commtechlab.msu.edu/sites/dlc-me/zoo/zdrr0101.html

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

hyphaeclay

bacteria

Microflora –

Amoebae

CiliateFlagellate

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 ReserveKwaZulu 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 WebEcosystem Function –

Influence of soil biota on soil processesNutrient cycling Soil 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