Soil Microbes and Nutrient Cycling

Question 1

What is taxonomy based on?

Answer 1

rRNA differences

Question 2

Classifications of soil organisms…

Answer 2

Microbiota
Mesobiota
Macrobiota

Question 3

Macrobiota

Answer 3

Include fungi, soil and the protozoa and algae, being less than 200 micrometres in size

Question 4

Bacteria function for rhizosphere……

Answer 4

Surround plant roots where bacteria surrounded by mucilagenous film protecting the bacteria, binding soil particles to bufefring capacity and high cations

Question 5

Function of Actinomycetes…

Answer 5

Resistant material decomposition, can withstand drought and synthesise antibiotics

Question 6

Function of cyanobacteria…

Answer 6

Able to photosynthesise and fixate nitrogen

Question 7

How can fungi survive harsh conditions…

Answer 7

Incrcease cell wall thikness, form chlamydospores or sclerotium production, with a hyphal mass that can germinate producing fruiting pores

Question 8

Importance of Fungi in decomposition?

Answer 8

Difficult material like lignin, preferring acidic conditions

Question 9

Functions of algae?

Answer 9

Found in top horizon with ability to photosynthesise and primary colonisers of rock surfaces in inital soil formation stages

Question 10

What do protozoa include?

Answer 10

Flagellates, amoebae and ciliates, based on form of locomotion, important in bacterial graing

Question 11

Mesobiota

Answer 11

Nematodes, rotifers, springtails, mites, organisms larger than 200-10000 micrometres

Question 12

Macrobiota

Answer 12

Include earthworms, slugs, snails and insects, being larger than 1cm

Question 13

Classification based on ecological roles…

Answer 13

Auto/heterotrophs or chemotrophs/photosynthetic
Aerobic/Anaerobic

Question 14

Why are faculatiative aerobes important?

Answer 14

Use NO3 or CH4 instead of O2, whilst anaerobes in water-saturated soils that are O2 degraded

Question 15

When can micro-organisms colonise soil?

Answer 15

When plant/animal residues enter, breaking down easiest ocmpounds first

Question 16

What happens in humification?

Answer 16

Resistant plant residues and microbial waste combines to form humus

Question 17

Why are microorganisms important in soils?

Answer 17

Nutrient recycling, residues entering soil require breakdown for plant growth

Question 18

Nutrient Cycle

Answer 18

Groups micro-organism species into a singular organism, tracing nutrient passage from atmosphere to soil to atmosphere

Question 19

How can we assess nutrient cycle?

Answer 19

How microbial biomass changes relating to C/N present in the soil

Question 20

What is microbial biomass proportional too?

Answer 20

Soil organic matter, thus carbon inputs

Question 21

States of soil microbes..

Answer 21

Majorly inactive, either zymogenous or autochtonous

Question 22

What regulates nitrogen cycle?

Answer 22

Microbiota and soil inpts

Question 23

What does diatomic nitrogen require to break?

Answer 23

400c and 200-350 bars pressure

Question 24

How is nitrogen cytcling solved?

Answer 24

Enzyme nitrogenase requriing low O2 condiitons and ready supply of carbon

Question 25

What is an example of nitrogen fixation?

Answer 25

Rhizobium symbiotic relationship with legumes, forming nodules, obtaining fixated C from photosynthesis and fixing N2 to incorporate into tissues

Question 26

Nitrogen degradation…

Answer 26

When plant dies, series of reactions, supplying nitrogen pool

Question 27

What does nitrogen compound degradation depend on?

Answer 27

Ease of mineralisation and C/N ratio

Question 28

Example of C/N ratios…

Answer 28

Bacteria C/N ratio of 5:1 whilst straw 100:1 so microbes must balance this ratio consuuming carbon with colony expansion meaning more N found to balance the ratio

Question 29

Why is animal manure used for soils?

Answer 29

Lower C/N ratio