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
