Theme C Flashcards
Why is the northern hemisphere producing more carbon dioxide than the southern hemisphere?
- It has more land mass and is more industrialised
Why is there correspondence between el nino records and C02 concentrations?
- El Nino caused by climatic oscillations
- C02 spikes in El nino years because tropics become sources rather than sinks
In what ways is carbon lost due to disturbance?
Photosynthesis (respiration)
Fires
Deforestation
What makes a terrestrial sink a terrestrial sink
Carbon sink means photosynthesis has to be > than respiration year after year
The last thing a carbon sink needs means is that the carbon has to be stored with a slow turnover rate (soils,trees etc)
How does demography cause ecosystems to act as carbon sinks?
- young trees grow fast in new forests
- Younger, regenerating forests in mid lats
- Old growth forests in tropic and high lats
How does physiology cause ecosystems to act as carbon sinks?
Hotter weather = increases in productivity, but not in drought
- Evidence of weakening amazon carbon sink, increasing productivity but increased tree turnover
- In African forests there is a net positive trend with increased productivity and no change in mortality
What is helicopter science?
Scientists wouldn’t engage with scientists in the country they were working in
How does C02 fertilisation of growth depend globally on mycorrhizas?
- Mutualistic relationship increases plant C uptake
- High N negatively impacts AMF and good levels of P is needed for AMF to work properly
How do droughts weaken tropical carbon sinks?
- Peak mortality of trees correlate to el nino events
- In the southern, dry amazon, the species adapted to wet climates are at higher risk of mortality
Which processes control carbon sinks in mature tropical forests?
- Rising C02 boosts photosynthesis if there is nutrient bioavailability
- Rising temps and drought limit wood production - could cause saturation of Amazonia C sink
- El Nino increasing tree mortality
- African forests less impacted by heatwaves as they are at higher altitude
When is amazon deforestation aiming to end by?
2030
Why do tropical forests surprisingly remain more intact than other ecosystems?
- They havent yet been transformed
- Savannas are used for pasture land and temperate ecosystems have had much more transformation over a much longer period of time
When did deforestation for agriculture begin and how can we tell?
- intensive land use beginning 3000-1000 BC
- Pollen evidence of olive cultivation from 6000 BC decline of Oak pollen at the same time as well as bones of livestock farming
E.g. Yellow river region in China where there is evidence of land clearance for agriculture 5000-3000 years BC
How is carbon emitted from deforestation?
Decay of felled trees
Disturbance releases soil carbon
Burning to clear the felled area
How much has deforestation been responsible for human C02 emissions?
A third
What are the feedbacks from deforestation mediated via surface energy balance?
The amount of dissipated longwave energy from the sun depends on albedo
High albedo= reflectance (ice)
Low albedo = absorbance (ocean)
Deforestation increases albedo and cools the land
Also a cooling effect as loss of trees=loss of evapotranspiration (significant as convectional rainfall recycles 80% of water over tropical forests)
