Soil Microbes and Nutrient Cycling
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What is taxonomy based on?
rRNA differences
Classifications of soil organisms…
Microbiota Mesobiota Macrobiota
Macrobiota
Include fungi, soil and the protozoa and algae, being less than 200 micrometres in size
Bacteria function for rhizosphere……
Surround plant roots where bacteria surrounded by mucilagenous film protecting the bacteria, binding soil particles to bufefring capacity and high cations
Function of Actinomycetes…
Resistant material decomposition, can withstand drought and synthesise antibiotics
Function of cyanobacteria…
Able to photosynthesise and fixate nitrogen
How can fungi survive harsh conditions…
Incrcease cell wall thikness, form chlamydospores or sclerotium production, with a hyphal mass that can germinate producing fruiting pores
Importance of Fungi in decomposition?
Difficult material like lignin, preferring acidic conditions
Functions of algae?
Found in top horizon with ability to photosynthesise and primary colonisers of rock surfaces in inital soil formation stages
What do protozoa include?
Flagellates, amoebae and ciliates, based on form of locomotion, important in bacterial graing
Mesobiota
Nematodes, rotifers, springtails, mites, organisms larger than 200-10000 micrometres
Macrobiota
Include earthworms, slugs, snails and insects, being larger than 1cm
Classification based on ecological roles…
Auto/heterotrophs or chemotrophs/photosynthetic Aerobic/Anaerobic
Why are faculatiative aerobes important?
Use NO3 or CH4 instead of O2, whilst anaerobes in water-saturated soils that are O2 degraded
When can micro-organisms colonise soil?
When plant/animal residues enter, breaking down easiest ocmpounds first
What happens in humification?
Resistant plant residues and microbial waste combines to form humus
Why are microorganisms important in soils?
Nutrient recycling, residues entering soil require breakdown for plant growth
Nutrient Cycle
Groups micro-organism species into a singular organism, tracing nutrient passage from atmosphere to soil to atmosphere
How can we assess nutrient cycle?
How microbial biomass changes relating to C/N present in the soil
What is microbial biomass proportional too?
Soil organic matter, thus carbon inputs
States of soil microbes..
Majorly inactive, either zymogenous or autochtonous
What regulates nitrogen cycle?
Microbiota and soil inpts
What does diatomic nitrogen require to break?
400c and 200-350 bars pressure
How is nitrogen cytcling solved?
Enzyme nitrogenase requriing low O2 condiitons and ready supply of carbon