1.C - the carbon cycle as a system Flashcards
1
Q
what is N.P.P?
A
- NET PRIMARY PRODUCTIVITY
- the amount of energy accumulated and stored in plants
- photosynthesis minus respiration = N.P.P
2
Q
what is N.P.P like in rainforest compared to grazing land?
A
- rainforest = high N.P.P
- stores 400 tonnes carbon per hectare
- grazing land = 30 tonnes carbon p h
3
Q
CARBON
A
- makes up organic compounds
- used as an economic resource
> fossil fuels, eg. coal, oil, natural gas
> oil used as a raw material in the manufacture of products - contained in multiple greenhouse gases
- stored in carbonate rocks in its largest store
- combustion = CO2 increasing sharply in atmospheric concentration
- 600 billion tonnes of carbon in atmosphere
- land use change decreases our ability to store carbon (e.g. deforestation)
4
Q
stores of global carbon: ATMOSPHERE
A
- 0.53%
- stored as the gas carbon dioxide and to a lesser extent methane
5
Q
stores of global carbon: BIOSPHERE
A
- plants: 0.42%
- soils: 1.12%
- stored in organic molecules in living and dead plants and animals.
- in the soil it is stored as organic matter from dead plant material and the activity of microorganisms
- the decay process releases carbon dioxide back into the atmosphere
6
Q
stores of global carbon: OCEAN
A
- 28%
- stored as dissolved carbon dioxide, but also as calcium carbonate in the shells of marine life, which can fall to the sea floor and become marine sediments.
- much of the oceanic carbon store is located at great depths
- only 4% is found near upper ocean surface
7
Q
stores of global carbon: LITHOSPHERE
A
- 70%
- stored as fossil fuels (coal, oil and gas) and also in sedimentary rocks such as chalk and limestone
- this is the largest store of carbon
8
Q
what are rainforests in terms of carbon?
A
REALLY EFFECTIVE CARBON SINKS
9
Q
how do levels of CO2 change throughout the year?
A
- spring and summer = photosynthesis ↑ = much less CO2 in atmosphere (trees are v. effective at soaking up CO2)
- winter = opposite
- temporal change over time
10
Q
what is TUNDRA’S NPP like?
A
- low NPP
- limited seasons
- soils in tundra = really important store of carbon
11
Q
what is NPP?
A
- Net primary productivity measures the amount of carbon that ecosystems sequester.
- it is the difference between what is taken in by photosynthesis and what is given out by respiration
12
Q
what is HOT DESERT’S NPP like?
A
- low NPP
- very little organic matter can survive the LACK OF WATER/NUTRIENTS (and the extreme temps)
- plants cant photosynthesis
13
Q
what is TROPICAL RAINFOREST’S NPP like?
A
- high NPP
- loads of plants and trees = photosynthesis is more than respiration = carbon accumulates
14
Q
how is the ocean a part of the carbon cycle?
A
- carbon dioxide can dissolve in sea water
- phytoplankton - basis of ocean food chain
15
Q
how do phytoplankton play a crucial role in the carbon cycle?
A
- through photosynthesis they absorb CO2 from the atmosphere and combine it w/ water to make carbohydrates (sugars/glucose)
- photosynthesis = foundation of food chain
- decomposition of dead organic material by microbial activity also returns CO2 to the atmosphere
16
Q
how is the LITHOSPHERE a part of the carbon cycle?
A
- long term store. typical residence time = 150 mill yrs
- the lithosphere contains by far the largest amount of carbon on earth, much of which is stored in sedimentary rocks within the planets crust
17
Q
how are carbon containing rocks in the lithosphere produced?
A
- the hardening of mud (containing organic matter) into shale over geological time
- the collection of calcium carbonate particles, from the shells and skeletons of marine organisms
18
Q
how is the EARTH’S CRUST a part of the carbon cycle?
A
- another 4100 GtC is stored in the Earth’s crust as hydrocarbons formed over millions of years from ancient living organisms under intense temperature and pressure.
- these hydrocarbons are commonly known as fossil fuels such as coal, oil and gas
19
Q
how can carbon return to the atmosphere from the lithosphere?
A
- melting of carbonate rocks = rising magma = outgasing of CO2 (volcanoes erupting).
- composite volcanoes are very eruptive
- combustion of fossil fuels
20
Q
what is precipitation in the carbon cycle?
A
- this can dissolve atmospheric CO2 and this can form a weak carbonic acid
- anthropogenic emissions of CO2 can increase the acidity of rainfall.
- this can have devastating effects on vegetation, human structures and fish stocks in lakes and rivers
21
Q
what is photosynthesis in the carbon cycle?
A
the process by which green plants and certain other organisms transform light energy into chemical energy
22
Q
what is respiration in the carbon cycle?
A
defined as the movement of oxygen from the outside air to cells within tissues, and the transport of carbon dioxide in the opposite direction
23
Q
what is decomposition in the carbon cycle?
A
- micro organisms such as bacteria and fungi break down organic matter, extracting energy and releasing CO2 into the atmosphere
24
Q
what is weathering in the carbon cycle?
A
- the in situ breakdown of rocks
- when it involves the chemical action of rainwater, occurs because the water is a weak carbonic acid, which is able to dissolve limestone and chalk by carbonation
25
what is combustion in the carbon cycle?
- occurs when organic material (containing carbon) reacts or burns in the presence of oxygen
- the process will release CO2 into the atmosphere
26
the flows of the carbon cycle - WEATHERING
- the *in situ* breakdown of rocks at the earth's surface, by the action of rainwater, extremes of temperature and biological activity
- it does not involve the removal of rock material
- weathering that involves the chemical action of rainwater on the calcium carbonate in the chalk is known as **carbonation**
27
what is carbonation?
weathering that involves the chemical action of rainwater on the calcium carbonate in the chalk is known as **carbonation**
28
how is carbonation significant?
- weak carbonic acid can react with calcium carbonate to form a BICARBONATE
- the bicarbonate is SOLUBLE
- this allows streams and rivers to absorb the carbon in the soluble bicarbonate.
- this transfers huge amounts of carbon back to the oceans
29
the flows of the carbon cycle - DECOMPOSITION
- micro organisms such as bacteria and fungi break down organic matter, extracting energy and releasing CO2 into the atmosphere
- decomposition occurs fastest in warmer, wet climates
30
the flows of the carbon cycle - COMBUSTION
- occurs when organic material (containing carbon) reacts or burns in the presence of oxygen
- the process will release CO2 into the atmosphere
31
how might COMBUSTION occur naturally?
- **wildfires**
- caused by lightning strikes are essential to the health of some ecosystems.
- long winters slow decompostition = build up on forest floor
- combustion shifts this jam, freeing carbon and nutrients previously inaccessible to forest trees
- also opens forest canopy, creating new habitats and ↑ biodiversity
32
the flows of the carbon cycle - SEQUESTRATION
- the oceans take up carbon by two mechanisms:
- the physical pump
- and the biological pump
33
what is the physical pump?
- involves the mixing of surface and deep ocean waters by vertical currents, creating a more even distribution of carbon, both geographically and vertically, in the oceans
34
how does the physical ocean pump work?
- initially CO2 enters the oceans from the atmosphere by diffusion
- surface ocean currents then transport the water and its dissolved CO2 polewards where it cools, becomes more dense and sinks
- this downwelling only occurs in certain places.
- eventually deep ocean currents transport the carbon to areas of upwelling
- there cold, carbon rich water rises to the surface and CO2 diffuses back into the atmosphere
35
what is the biological pump?
- carbon is also exchanged between the atmosphere and the oceans through actions of marine organisms
- globally nearly **1/2** of all carbon fixation by photosynthesis takes place in the oceans.
- around **50 GT** of carbon is drawn from the atmosphere by the BIO pump every year
36
how does the BIOLOGICAL ocean pump work?
- marine organisms drive the bio pump
- phytoplankton, floating near ocean surface combines sunlight, water and dissolved CO2 to produce organic material
- whether consumes by animals in the marine food chain, or through natural death, carbon locked in the phytoplankton either accumulates in sediments on the ocean floor or is decomposed and released into the ocean as CO2
- other marine organisms, such as tiny coccolithophores, extract carbonate and calcium ions from sea water to manufacture plates, shells and skeletons of calcium carbonate
- most of this carbon-rich material eventually ends up in ocean sediments and is lithified
37
upwelling vs downwelling
upwelling occurs in areas of carbon source, and downwelling occurs in areas of carbon sink
38
what is natural sequestration?
- happens when carbon is stored in the natural environment
- this includes what are known as "carbon sinks", such as forests, grasslands, soil, oceans and other bodies of water
- also known as passive/indirect sequestraiton
39
how long does carbon stay in a slow carbon store?
- total amount of carbon circulated = between 10-100 million tonnes/yr
- carbon held in rocks residence time = 150 mill yrs
40
how long does carbon stay in a fast carbon store?
- transfers are between 10 and 1000 times faster than slow C.C
- natural sequestration in oceans for 350 yrs
