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Soil Biodiversity & Function > Soil 8 - Coil C and OM > Flashcards

Soil 8 - Coil C and OM Flashcards

1
Q

What is soil health?

A

the continued capacity of a soil to function
- intersection of biological, physical, chemical qualities

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2
Q

What are some soil ecosystem services?

A

Nutrient cycling, water/air, support/plant medium, habitat/biodiversity:

  • carbon storage
  • GHG uptake
  • food/fuel/fibre
  • pollination, wildlife habitat
  • water purification
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3
Q

What environmental crises does agriculture concern?

A
  • biodiversity crisis
  • soil carbon crisis
  • climate crisis
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4
Q

where does the long-term carbon cycle happen?

A
  • tectonics (volcanoes, seafloor spread, weathering)
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5
Q

Where does the short-term carbon cycle take place?

A

terrestrial! soil, plants, animals, atmosphere

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6
Q

What is SOM?

A

soil organic matter
- plant/animal/organic matter in various stages of decomposition

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7
Q

What breaks down in decomposition?

A

bonds in molecules
- proteins, sugars/starches, structural polysaccharides

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8
Q

What is the equation for decomposition?

A

Lt = L0 * e^-kt
(L = leaching)

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9
Q

What are the 4 phases of decomposition?

A
  1. Leaching of soluble cells
  2. fragmentation/chemical alteration/leaching of decay products
  3. chemical alteration
  4. mixing/adherance to mineral surfaces (MAON)
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10
Q

What environmental factors influence decomposition?

A
  • temperature, moisture, access to substrate
  • substrate quality/quantity
  • biological drivers
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11
Q

What are other terms for ‘rapid’ and ‘slow’ decomposing molecules?

A

rapid = labile
slow = recalcitrant

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12
Q

What happens as OM decreases in particle size in decomposition?

A

decomposition slows down!
- more opportunities to protect against future decomposition

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13
Q

Why is humus maybe not a thing?

A

no experimental evidence supports the formation of large, persistent ‘humic substances’ in soil

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14
Q

What is the main shift in our modern understanding of SOC?

A

Traditionally thought that SOC comes from leaf litter, but soil microbes are a bigger carbon pool and flow than we thought

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15
Q

What is the rhizosphere?

A

all the soil directly on the roots, which provide nutrients for soil microbes
- contrast with low C bulk soil, in a natural state of starvation

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16
Q

What are root exudates?

A

low-weight compounds released into the root environment
- differ depending on plant species, crop development, abiotic factors

17
Q

What is the importance of biota in the C cycle?

A
  • Carbon pump microbes
  • macrofauna bring nutrients downward, leave more extracellular substances (ex worm slime)
  • also chewing + shredding - macrofauna mix the soil!
18
Q

What are 3 ways soil C is destabilized?

A
  • more CO2 in air
  • C desorption (becomes dissolved C)
  • increased microbial C metabolism
19
Q

What are 4 ways climate change impacts the C cycle?

A
  • more CO2 affects photosynthesis
  • change in freeze-thaw cycles
  • drought timing/intensity
  • temperature
20
Q

How permanent is soil C?

A

depends on the upper limit of mineral capacity to hold C (C can cycle between mineral, dissolved, organic sites), and plant/microbe biomass

21
Q

What are the 2 main global changes affecting soils?

A
  • agriculture
  • climate change
22
Q

What are the 2 new ‘knowns’ in C cycling?

A
  1. low molecular weight, labile molecules (usually from microbes) persist longer than chemically recalcitrant C structures when protected by organo-mineral complexation (ie when C attaches to soil minerals)
  2. Each soil type has a finite limit to how much C it can store on mineral surfaces
23
Q

What is the MEMS model of soil C cycling?

A

Microbial Efficiency Matrix Stabilization
- set of pools and flows in atmosphere, soil, deep soil

24
Q

What part of regenerative agriculture techniques is accurate?

A

changing grazing and rotations does affect SOC

25
Q

What are 2 goals for increasing SOC in regenerative agriculture?

A
  • improve soil health and biodiversity
  • non-inorganic amendments and living roots
26
Q

Are SOC increases predictable and linear?

A

no to both!

27
Q

What are the 2 main influences in C storage capacity?

A
  • OM inputs
  • soil texture
28
Q

Where are the greatest opportunities to increase SOC?

A

low-yielding regions

29
Q

What are 4 soil management regenerative practices?

A
  • keep soil in place/covered
  • minimize disturbances and extremes
  • maximize living roots
  • return residues to soil
30
Q

What do good soil management practices do for the microbiome?

A

increase abundance (capacity) and diversity (resilience) of community

31
Q

What is a big future debate in SOC management?

A

hoard it or use it? (build an ecosystem or a farm?)

32
Q

How is Miscanthus grass relevant to N cycles?

A

lots of Nosz genes, so takes up a lot of N

33
Q

What model does decomposition follow?

A

Continuum model!

Soil Biodiversity & Function (7 decks)

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