类别 全部 - bacteria - microorganisms - fungi - nitrogen

作者:roslina mustapha 11 年以前

445

Soil Habitat

The presence and activities of microorganisms, particularly bacteria and fungi, play a crucial role in terrestrial ecosystems. These microbes are essential in the conversion of ammonium and nitrate into biomass, thereby stimulating soil population growth.

Soil Habitat

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