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BIOL 215 > Lecture 25 - Carbon cycle > Flashcards

Lecture 25 - Carbon cycle Flashcards

1
Q

Explain the C cycle. Which transfers from atmosphere are fast and which ones are slow?

A

fast: terrestrial, ocean
slow: sedimentation, organic matter

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2
Q

Rank the pools of CO2

A

Sedimentation
65000000 *10^15g
CACO2

organic matter
16000000*10^15g

in oceans, dissolved CO2
38000*10^15g

Terrestrial
1e prod 600 *10^15g
soil 1400 *10^15g

atmosphere
750*10^15g

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3
Q

At what rate is CO2 rising, what’s mostly causing this?

A

CO2 is now rising at 1.0 ppm (0.5%) per year. Most of this increase comes from burning fossil fuels.

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4
Q

Explain the Greenhouse gases. What gases does it consist of?

A

Atmosphere’s ability to absorb infra-red energy – a “blanket”

Without it, the average temperature on earth would be 33 degrees cooler than what it is now.

Composed of gases:
Water vapor (H2O)
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Chlorofluorocarbons (CFCs)
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5
Q

Explain the greenhouse effect

A

Blanket becomes “thicker”

global warming: increase in temperature, 1.4–5.5°C over the next 100 year

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6
Q

What human sources are increasing CO2 in atmosphere?

A
  1. fossil fuels

2. land use change (cutting down forest)

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7
Q

Define atmospheric storage

A

Atmospheric storage = Human input (fossil, land use)- Biosphere uptake (ocean uptake, unidentified sink)

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8
Q

What is the unidentified CO2 sink suspected to be

A

Increased forest growth

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9
Q

Explain the experiment that determined the missing CO2 sink

A

Evidence that forest uptake is part of that missing stink:
• Experiment measured increase in carbon in the Amazonian forest.
• Examined over 6k trees and found a way to estimate the amount of carbon increasing in the tree.
• 0.6 pG is being taken up by plants (About 25% of the unidentified sink)
• Experiment don’t account for the below ground processes because plants have roots.
• Reason: hard measurement to make.
• Supported by NPP from satellites.
• Ex: in tropical systems, plants are close to their temperature optimum. We expected then, as you increase temperature, respiration will be enhanced to a greater extent than photosynthesis. Net effect will be a decrease in photosynthesis. Prediction is that the plants in the tropics will respond negatively to a change in temperature.
High latitudes: increase in temperature might increase the growing season which increases the NPP that we have.
Tropic plants will start moving to the north.

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10
Q

What are 4 causes of soil organic matter buildup?

A
  1. Root biomass increase
  2. Litter fall
  3. Transfer of C-rich compounds from plants to soil microbes
  4. Humus is produced biologically and chemically (recalcitrant form of SOC)
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11
Q

How much has NPP grown in 18 years in 20th century? How can we account for the increased NPP?

A

Global average shows an increase of about 6% in NPP over 18 years – note that this is opposite to the pattern for NPP in the sea

Enzymatic reactons like photosynthesis are temperature dependent –> more plants!

CO2 fertilization?

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12
Q

What’s the optimal temperature for net photosynthesis?

A

25 C

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13
Q

What are the two types of photosynthesis? Which one is CO2 limited?

A

C3 photosynthesis

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14
Q

Other resources for growth such as ___, ___ and ___, must be present in excess to observe the (sustained) effect of elevated CO2 levels

A

water, light and nutrients

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15
Q

What was the Free Air Carbon Enrichment (FACE) experiment? What did it show?

what were its limitations?

A

Free Air Carbon Enrichment (FACE) experiment - more realistic:
• Plots of natural forest.
• Tower equipped of nozzles that shoot CO2 into the middle of the forest plot.
• Plots are naturally exposed to nutrients.
• Comparing the increase yield of C3 and C4 to the ones in the greenhouse, it’s much less.
• 12-14% (C3) and 0% (C4) vs 20-30% (C3 and C4)

Limitations: only carried on for a decade (short time) but we are interested in identifying a sink might respond over a much longer time.

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16
Q

Why is the NPP also increasing in the high latitude?

A
  • Nitrogen in fossil fuel, so when we burn it, it releases into the atmosphere (enhancing the nitrogen cycle)
  • When it rains, nitrates fall into the ground and act as a source of nitrogen for the plants.
  • Northern hemisphere acting fertilizing the planet with nitrogen.
  • More nitrogen deposition → high values of NEP
17
Q

Define Net Ecosystem Production (NEP)

A 
NEP = NPP - R(decomp) - R(other heterotrophs) or 
NEP = GPP - R(total)
  • NPP takes up carbon, respiration by decomposers and heterotrophs release carbon.
  • In order for an ecosystem to take up C carbon NEP has to be positive.
  • If there is more R than NPP, losing carbon to the atmosphere.
  • NPP> R, than the ecosystem will take up CO2.
  • How does increase in CO2 affect R?
18
Q

How does increase in T affect R?
NEP = NPP - R(decomp) - R(other heterotrophs)

What were 2 experiments that showed this?

A
  • Decrease in photosynthesis as T increases.
  • Enhancement in respiration as T increases.
  • Respiration responds slowly to increase in T.

Experiment: Artificially heated plots of land in the forest using heat cables.
• Compared amount of carbon released by respiration by decomposers.
• Heated plots released 25% more carbon.
• On the short term, heating the soil enhances decomposition of the organic matter. Decreasing caused by reduction of content in the soil → if u reduce all the organic C , there’s nothing left for the microbes to break down → concern for northern hemisphere as the temperature rises.

Another experiment: Heated little ponds, measure the NEP.
• When ecosystem respiration (ER) = gross primary production (GPP), then carbon out = carbon in.
• ER > GPP , more respiration occurring. Source of CO2 to the atmosphere.
• ER < GPP, System is absorbing CO2
• Heating ecosystem makes it less efficient at absorbing carbon.

19
Q

What is the impact of CO2 on consumers?

A
  • Indirect response.
  • Herbivores: High co2, less herbivores.
  • When growing plants under high CO2, increase C:N ratio. Increase the ratio, less protein rich → poor quality food for consumers.
  • Animals are not able to convert as much of the food they ingest into their own biomass → animals eat more. Survival drops, Abundance drops.Conversion efficiency • • (CE) = Production/Ingestion
20
Q

What are the effects of CO2 on ocean pH

A
  • CO2 dissolves in water causes decrease in pH, but ph is still way above neutral. Produces H+ protons.
  • Ocean contains high amount of carbonate and so as you produce more protons, you reduce the concentration of carbonates.
  • Issue because organisms use the carbonates to make hard shells, hard parts, etc.

BIOL 215 (14 decks)

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