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Ecology - Soil Science > Microbial Processes > Flashcards

Microbial Processes Flashcards

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1
Q

Subtrates microbes degrade…

A

Petroleum, rubber, plastics, natural fibers, celluloid, DDR, 2-4D, BHC, PHB and Cynamide

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2
Q

Polyuronides

A

Polymeric substances consiting of uronic acid with glycosidic linkages of monosaccharides

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3
Q

Lignin/cellulose degradation…

A

Bacterial/Fungal extracellular enzymes requiring high energy and containing low N

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4
Q

How does physical states determine decompostability?

A

Dry/wet, tight structuring, easy of microbial entry, O2 and nutrients

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5
Q

Process of deocmposition…

A

Plant material colonised by fast-growing bacteria/fungi, absorbing simple compounds, more complex digested by animals, humus released as residual matter

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6
Q

How is CO2 formed?

A

Aerobic respiration
Anaerobic fermentation

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7
Q

How does CO2 lower pH?

A

Carbonic acid formation

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8
Q

What does CO2 acidification promote?

A

Mineral weathering and plant nutrient release

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9
Q

What does lowered O2 in soils promote?

A

Root diseases organisms, bacterial production of inhibitors like ethylene

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10
Q

Humus

A

Product of colloidal organic decay products accumulating due to slow decay

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11
Q

What is the process of Humification?

A

Breakdown of large polymers
Aggregation due to humic colloids binding to clay particles
Phenolic compounds main component
Cationic chelation

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12
Q

What’s derived from H+ release aciditiy?

A

Cationic chelation, pH buffering, pH dependent suraface charge with oxidation increasing carboxyl groups in tandem with reactions wit phenolic OH groups

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13
Q

How do carboxyl/phenol groups regulate acidity?

A

Carboxyl release/accept H at pH between 4-6.5 whilst phenolic at 7-9

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14
Q

CEC increase with humus?

A

When humus releases H+ raising pH, and vice versa with decreasing pH

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15
Q

Humus and metal immobilizaiton…

A

Negative group chelation of Cu, Zn, Co, Ni and Mn

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16
Q

Organic matter decay and nitrogen release…

A

N as free ions, ammonium, NH4 or immobilised N as ammonium and Nitrate

17
Q

What does N release to soil depend on?

A

How much N is provided to decomposers, N resulting from residual overcompensation.

18
Q

Effects of nitrogen deficiency

A

Limited plant growth, microbial growth and decay process

19
Q

How can N net release/immobilisation be predicted?

A

C/N ratio, below 20 or percentage above 2.5 is released

20
Q

Importance of Nitrogen?

A

Plant growth, leaving a layer of mulch on the topsoil seperating soil water and altering N decay

21
Q

Plant decay and C/N ratio…

A

It allows soil microbes to lower C/N ratio to release nitrogen again.

22
Q

What does decay rate depend on?

A

Properties of OM, amount of OM and environmental factors

23
Q

How does environment infleunce decay?

A

Water increases decay with wetter soils, dry limiting bacterial activity.
Temperature decreasing respiration below 20C and increase 2x for every 10C
O2 concentration at 10% slows aerobic decomposition
Accessbility, organisms within pore spaces being too small for bacteria to enter

24
Q

Why is soil OM management important?

A

Disposing OM like crop residues/urban waste
Improving N/S supply, water/cation retetnion, soil structure
Alleviate clay and poor structure effects on water infiltiration and aeration

25
Q

How can OM levels be increased?

A

promotion of soil erosion
selection of kind of OM added
Optimising evnironmental conditions for decaying microbes, providing warm, moist conditions

26
Q

Examples of OM inputs…

A

Organic wastes, composts and manures

27
Q

How are redox reactions facilitated?

A

Oxidation of ammonium and sulfur through energy provision to chemoautotrophic bacteria

28
Q

Nitrate and Suflate oxidation…

A

Move in soils due to no adsorption to acolloids, nor form insoluble compounds

29
Q

Ammonium in oxidation

A

Held by cation exchange, sulfate insoluble and sulfide precpitates with Cu, Zn and Fe or vaporises and hydrogen sulfide

30
Q

How does oxidation lower pH?

A

H+ ion production

31
Q

What leads to anoxia?

A

Promotion of respiration by warmth, moisture and readily decomposble OM

32
Q

What may limit O2 diffusion?

A

Pores filled with water, increasing anaerobic respiration resulting in gaseous by products

33
Q

What are the three main carbon stores in soils?

A

Detrital OM pools
Food chains of different organism groupd
Seperate pools of structural, storage and metabolite compounds

34
Q

What is central to N cycling?

A

Release/assimilation of ammonium, released in the decay of OM, assimialted by bacteria and plants for N

35
Q

What is N cycling complicated by?

A

Nitrification and ntirate assimilation

36
Q

Nitrification

A

Oxidation of ammonium to nitrate, plants/microbes uptake ntirate and reduce it to organic N compoiunds, releasing N2

37
Q
A

Ecology - Soil Science (12 decks)

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