#14 Decomposition, Nutrient Cycling, & Biogeochemical Cycles Flashcards

1
Q

what is nutrient cycling?

A

the transformation of organic nutrients into mineral form and back into organisms through decomposition and mineralization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define decompositon

A

the breakdown of chemical bonds in organic molecules, resulting in energy, carbon dioxide, and water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

which 4 processes make up decomposition

A
  • leaching
  • fragmentation
  • structure changes (physical and chemical)
  • ingestion/excretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Decomposers are categorized based on ______?

A

size and function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

______ are used to examine the decomposition of plant litter

A

litter bags

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are litter bags used by ecologists

A

a fixed amount of litter is put into the bags. The mass of litter remaining decreases continuously as time progresses and the rate of decomposition is related to the litter quality.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do these carbon forms affect the decomposition rates:
- glucose and other simple sugars
- Cellulose and hemicellulose
- lignin (and others)

A
  • glucose and other simple sugars: small, high quality sources of carbon, high-energy bonds.
  • Cellulose and hemicellulose: structurally complex, more energy required to break bonds, moderate quality
  • lignin (and others): very large and complex molecules, slow to decompose, low quality
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the only group that can decompose lignin?

A

Basidiomycetes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

For the following, what is their % carbon and how long does it take to break down?
- Proteins, simple sugars, soluble compounds
- Cellulose and hemicellulose
- Lignins

A

Proteins, simple sugars, soluble compounds: 15% carbon - decompose very quickly and non remaining in a few days

Cellulose and hemicellulose: 60% carbon - decomposed more slowly and were completely broken down in three weeks

Lignins: 20% carbon - the majority remained intact by day 80

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

the rate of organic decay is related to what three things?

A
  1. plant litter quality
  2. soil properties (texture and pH)
  3. climate (temperature and precipitation).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

net mineralization rate

A

the difference between the rates of mineralization and immobilization.
NMR = mineralization rate - immobillization rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

mineralization

A

the transformation of nutrients contained in organic compounds into inorganic forms
- minerals in the soil to usable inorganic forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Immobilization

A

the uptake and assimilation of minerals by microbial decomposers
(immobilizing and digesting the nutrients)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is nitrogen released into the soil with respect to litter breakdown and mineralization/ immobilization

A
  1. Nitrogen starts at 100
  2. Nitrogen decreases as water soluble compounds are leached from the litter
  3. Nitrogen increases as decomposers immobilize nitrogen from outside the litter.
  4. The mineralization rate exceeds the immobilization rate and nitrogen is released into the soil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the (bio)geochemical cycle

A

the cyclic flow of nutrients from the nonliving to the living and back to nonliving components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the two types of biogeochemical cycles

A

Gaseous: the main pools of nutrients are the atmosphere and the oceans.
- nitrogen, carbon dioxide, and oxygen

Sedimentary: Soil, rocks, and minerals
- inorganic sources of minerals are released to living animals through weathering and erosion
- phosphorous

17
Q

both biogeochemical cycles are driven by ______ and could not exist without the _____ cycle.

A

flow of energy
water cycle

18
Q

nutrients with a gaseous cycle enter via the ______, while nutrients with the sedimentary cycle enter via the _______?

A

nutrients with a gaseous cycle enter via the atmosphere, while nutrients with the sedimentary cycle enter via the weathering of rocks and minerals?

19
Q

the earth contains _____ gigatons of carbon

A

100 million gigatons or 10^23 grams. all but a small fraction is buried in sedimentary rock and not actively involved in the carbon cycle

20
Q

nitrogen is available to plants in which two forms?

A

ammonium (NH4+)
nitrate (NO3-)

21
Q

the Earths atmosphere is ___% nitrogen in the form of N2?

A

80%, which is unavailable to plants for assimilation

22
Q

List the five basic steps of the nitrogen cycle

A
  1. Nitrogen fixation (from N2)
  2. Nitrification: from ammonia to nitrates by aerobic bacteria
  3. Assimilation: plants assimilate nitrogen
  4. Ammonification (mineralization): the formation of ammonia through decomposition
  5. Denitrification: the reverse of nitrogen fixation from nitrates to gaseous nitrogen (anaerobic bacteria)
23
Q

phosphorous can only be cycled from ___ to ____?

A

land to sea

24
Q

what are the main reservoirs of phosphorous?
How is it released?

A

rock and natural phosphate deposits.
Released through weathering, leaching, erosion, and mining
- in soils, only a small fraction is available to plants

25
Q

can phosphorous be returned to the biogeochemical cycle - why or why not?

A

no, its in short supply under undisturbed conditions, can only be cycled from land to sea.