Feb 13, 2016
Soil BiologySoil Biology
Who is down Who is down there and what there and what do they dodo they do
Learning Objectives
• List the major groups of soil organisms …• Identify the roles of organisms • Draw a simplified soil food web . ..• Describe the conditions affecting growth…• Discuss the beneficial functions …
Sun
Humus
Producers
ConsumersDecomposers
air water
soil
Important Groups of Soil OrganismsImportant Groups of Soil Organisms
• MacrofloraMacroflora
• MicrofloraMicroflora
• MacrofaunaMacrofauna
Vascular plantsVascular plants, mosses, mosses
Vascular plantsVascular plants, algae, actinomycetes, , algae, actinomycetes, bacteria, and fungi**bacteria, and fungi**
Vertebrates, arthropods, earthworms, Vertebrates, arthropods, earthworms, snails… snails…
** Fungi are actually their own ** Fungi are actually their own separate kingdomseparate kingdom
• MesofaunaMesofauna
• MicrofaunaMicrofauna
Bigger arthropods, wormsBigger arthropods, worms
Nematodes, protazoaNematodes, protazoa
Size/type classSize/type class e.g. and functional group/energy acquisitione.g. and functional group/energy acquisition
Soil Animals – micro, meso, macro
BacteriaMicroflora
Microflora
Nematodes
Protozoa
Microfauna
20-200 kg/ha!20-200 kg/ha!
Mites
Springtails
Mesofauna
Other invertebrates
Mesofauna
Worms
Voles!
Macrofauna
A cup of soil containsA cup of soil contains......
BacteriaBacteria
Fungi*Fungi*
ProtozoaProtozoa
NematodesNematodes
ArthropodsArthropods
EarthwormsEarthworms
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microfaunamicrofauna
macro- and macro- and mesofaunamesofauna
200 billion200 billion
100,000 meters
20 million20 million
100,000100,000
50,00050,000<1<1
Microflora, Microflora, or “microbes”or “microbes”
* Fungi are * Fungi are actually their actually their own separate own separate kingdomkingdom
B – BacteriaA – ActinomycetesMy – MycorrhizaeH – Saprophitic fungusN – NematodeCP – Ciliate protozoaFP – Flagellate protozoaM – Mite
< 1mm
1/10 mm
• Gain energy from nematodesGain energy from nematodes• 3 groups, yeast, mold, mushrooms3 groups, yeast, mold, mushrooms• symbiotic relationships with symbiotic relationships with mostmost
plantsplants• Produce chemicals that are toxicProduce chemicals that are toxic
• The major agent of decay in The major agent of decay in acid environsacid environs• Network of Network of hyphaehyphae: : improves soil structureimproves soil structure• Decomposition of Decomposition of cellulosecellulose!!!!!!• Can Can compete with higher plantscompete with higher plants for N for N
Fungi Fungi – tens of thousands of species– tens of thousands of species
Sun
Humus
Producers
ConsumersDecomposers
Aggregates held together by:
1. Fungal hyphae2. Bacterial “glues”3. Organic matter
sand
silt
hyphaeclay
bacteria
Bacteria – 1 billion -1 trillion/g soil (up to 20,000 spp.)
• Exist in both forest and grassland soils• Most do best under high Ca2+, high pH• Do best when soil temp 20-40C (68-100F)
but seldom killed by temp extremes
Sun
Humus
Producers
ConsumersDecomposers
Fungi vs. bacteriaFungi vs. bacteriaFungiFungi BacteriaBacteria
Tube-like body; hyphae
Generally slower growth rate
Single-celled, can form colonies
Rapid regeneration time (hours); can respond quickly to nutrient additions
Complex, mutually beneficial Complex, mutually beneficial relationshipsrelationships
fungi
bacteria
Amoebae
CiliateFlagellate
• some parasitic• feed on bacteria
and fungi• release plant nutrients –
protozoa KEY for N
Nematode
MicrofaunaMicrofauna
Sun
Humus
Producers
ConsumersDecomposers
MicrofaunaMicrofauna
– Widely distributed in forest soils– Saprophytic and parasitic groups– Some predatory species attack
tree roots and cause damage
• Nematodes (non-segmented, round worms)
sap·ro·phyte An organism, that grows on and derives its nourishment from dead or decaying organic matter.
MicrofaunaMicrofauna
– Most abundant of all soil Most abundant of all soil faunafauna– One-celledOne-celled– Feed on bacteriaFeed on bacteria– Up to 30% of all mineralized N from protozoaUp to 30% of all mineralized N from protozoa
• ProtozoaProtozoa
Collembola (springtails)
Fungus feeding mite
• heterotrophs (detritivores, predators)heterotrophs (detritivores, predators)• feed on fungi, protozoa, nematodes, mitesfeed on fungi, protozoa, nematodes, mites• important in regulating populations of everything important in regulating populations of everything smallersmaller
Nematode feeding mite
MesofaunaMesofauna
Photo by Suzanne Paisley
• shred plant materialshred plant material• feed on bacteria feed on bacteria and fungi associated and fungi associated with organic matterwith organic matter
MacrofaunaMacrofauna
Earthworm middenEarthworm midden
Earthworms Earthworms – (have gizzards!)– (have gizzards!)
• Probably the most important component of Probably the most important component of soil fauna (not in acid soils, not in very dry soil fauna (not in acid soils, not in very dry soils)soils)
• Eat OM & pass as much as 30 tons/ha of Eat OM & pass as much as 30 tons/ha of soil through their bodies (mixing horizons) soil through their bodies (mixing horizons) each yeareach year
• Promote good soil structure and aerationPromote good soil structure and aerationest. wt. of worms in U.S. = 10X wt. of entire human population
Great for fishing! Worm farming - Huge industry!
Sun
Humus
Producers
ConsumersDecomposers
air water
soil
Some generalizations . . .Some generalizations . . .• Forested soils more biologically diverseForested soils more biologically diverse• Forested soils dominated by fungiForested soils dominated by fungi• Faunal biomass (and activity) greater per ha in Faunal biomass (and activity) greater per ha in
grasslandsgrasslands• Cultivated soils least diverse, less biomass, Cultivated soils least diverse, less biomass,
fewer organismsfewer organisms