25 - Microorganisms in Terrestrial Ecosystems Flashcards
1
Q
Anoxic
A
Absence of oxygen in waterlogged soils
2
Q
Effect of plant and microbial activity on soil environment
A
consume O2 and release CO2
3
Q
Soil structure
A
Arrangement of solid parts of soil and the pore space located between them
4
Q
Pore space
A
Allows for movement of water, gases, nutrients, roots and microorganisms
5
Q
Factors effecting soil microorganisms
A
- Moisture (saturated soils stimulate anaerobic microbes. Dry soils limit all microbial activity)
- Temperature (major environmental factor)
- Aeration (essential for gas exchange)
- pH
- Available nutrients (mineral soils < 20% organic C, organic soils > 20%)
- Microbial interactions (positive and negative)
6
Q
Soil Organic Matter
A
- Organic matter component of soil
- Retains nutrients
- Contributes to soil structure
- ## Holds water for plant use
7
Q
Three general pools of SOM
A
- Living biomass (microorganisms, plant roots, animals)
- Decomposing residues of living things and added organic wastes
- humus
8
Q
Important activities of microbes in soil
A
- Decompose (‘remineralise’) soil organic matter
- Major roles in biogeochemical cycling
- Support the soil food web
- Contribute to soil structure
- Form associations with plants that determine plant survival
9
Q
How to microbes contribute to soil structure
A
- Soil stabilisation by microbes
- Binding of soil particles to bacteria due to electrostatic charges
- Humus formation by microbes (soil organic matter –> humus)
10
Q
Humus
A
Sponge like material, retains H20, organic and inorganic chemicals in the soil and is important for soil fertility
11
Q
Mycorrhizal (fungus root) associations
A
- Mutualistic fungus-plant association
- Develops between most plants and a limited
number of fungal species
