Soil Habitat

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Microorganisms in Terrestrial Ecosystem

Mycorrhizae

Arbuscular Mycorrhizae (AM)

can increase plant's competiveness

provides ammonium to host

transfer phosphorus to roots

Ectomycorrhizae (ECM)

transfer essential nutrients (phosphorus/nitrigen) to roots

formed by ascomycete&basidomycete fungi

Functions of soil fungi

Pathogens/parasites

Roles of microbes in Rhizosphere & Rhizoplane

associative nitrogen fixation

promotion of plant growth

synthesis & degradation of organic matter

source of nutrients, creating microbial loop

Microbe plants interactions

endophytes

microbes that colonize internal plant tissues

epiphytes

microbes live on the surface of plants

Soil Population

Bacteria

Filamentous

Anaerobic

Aerobic

Microbial Loop

plants or insects released degradative enzymes do not rapidly diffuse away

differs than in open ocean

plants rather than microbes account for most primary production

Nitrogen

nitrogen saturation point

point beyond which any nitrogen added to soil won't be incorporated into organic matter and will remain in mobile form

C/N Ratios

convert ammonium and nitrate to biomass

stimulate growth

the subsurface biosphere

make up one-third of biomass on Earth

subsurface zones

methanogenic zones

coal, kerogen, oil 7 gas containing region

shallow subsurfaces

Protozoa

functions

food source

mineralizing nutrients

Mycorrhizal associations

ectomycorrhizae

fungi that reman extracellular, forming a sheath of interconnecting filaments around the root

endomycorrhizae

fungi that enter the root hairs

Functional group of soil bacteria

Litotrophs or chemoautotrophs

Pathogens

Mutualists

Decomposers

Conditions affecting microbial populations

Soil atmosphere

influenced by soil particle size

well drained soil-- well aerated

Acidity&Allkalinity

influenced by

previous cropping hysory

climate

time of the year

microbial metabolic activity

usually pH 4-8.5

temperature

varies depend on

latitude & altitude

depth

Water (-- moisture)

Depends on

drainage

particle size

rainfall

Thin water films-- oxygen at high level+easily replenish

Surfaces

Soil Organic Matter (SOM)

maintains soil structure

hold water (plant use)

retains nutrients

Categories of Soil

organic soil

posesses at least 20% organic carbon

mineral oil

most of Earth's soils

contains less than 20% organic carbon