APS124 Papers Flashcards
The primary source of carbon dioxide released to the atmosphere by human activities derives from..
fossil fuels fixed by prehistoric photosynthesis
Globally and annually, photosynthesis fixes an order of magnitude more CO2 than..
is released by human activities
Gross Primary Production (GPP) refers to the photosynthetic conversion of solar radiation to produce … and …
ATP, NADPH
- rate of production of chemical energy
NPP is taken as…
the energy remaining for CO2 fixation, after its use for photorespiration and the reduction of nitrate and sulphate
NPP = GPP - autotrophic respiration
Net ecosystem production (NEP) =
NPP - heterotrophic respiration
Net biome production (NBP) =
NEP - losses through disturbance
Biomass =
Sum of(NPP - losses through litterfall)
Per unit … or …
surface area, time
Over a year, only about … of GPP is fixed into …
half, biomass
- the other half is lost by respiratory processes, which defines NPP
Biomass is the key product of NPP as…
this is now available for consumption by secondary consumers
The NPP of a single plant can be measured by..
enclosing the whole plant (including roots) in an airtight and air conditioned container, while constantly recording changes in CO2 concentration
(Daytime photosynthetic uptake of CO2 will be followed by nocturnal release of CO2 by respiration)
On land, NPP can be calculated in the field for a larger sample of plants by measuring the biomass increment over a year. This approach may miss…
unaccounted losses of new biomass through litterfall, and other possible losses such as through herbivory or root exudates, and so would underestimate NPP.
NPP =
photosynthetic biomass x growth efficiency x light
Photosynthetic biomass is made up of either green leaves or chlorophyll in algal cells and expressed per…
unit area of surface.
Light is solar radiation (mol day^-1) in…
the photosynthetically active waveband (400-700nm)
Radiometric measurements by satellites of radiation reflected from the earth’s surface can be used to quantify…
critical components of the NPP model
Ocean light depth =
euphotic zone
Terrestrial NPP per unit area is on average…
3 times that of the oceans
However the total NPP by the 2 biospheres is … …
approximately equal
- 60PgC.yr^-1 for terrestrial biosphere
- 65PgC.yr^-1 for oceanic biosphere
High oceanic NPP is observed in areas where there is…
coastal upwelling of nutrients, such as off the coasts of South America and Africa
(these regions account for about 14-30% of oceanic NPP)
On land, NPP is highest…
in the rainforests between the tropics
Seasonal variations of temperature or precipitation…
reduce NPP
Over Europe NPP is reduced by about … for every 1C reduction in mean annual temperature
4%
Accounting for heterotrophic respiration reduces global NPP considerably from 125PgC.yr^-1 to…
11 for oceans and 5 for the land - similar to the 9 from human derived emissions
It is likely that carbon sequestration by the biological pump is a…
relatively small fraction of emissions
CO2 solubility is greatest in..
the cold waters of high latitude oceans
- where the dense water sinks, removing CO2 to depth
Rising atmospheric CO2 concentrations increase the dissolved CO2 concentration in sea water, but…
warming reduces this solubility
It is estimated that the oceanic NPP by the biological pump has declined by about 6% over the last 20 years and this is strongly correlated with…
an increase in global sea surface temperatures of 0.2C
The contemporary solubility pump is already working at a…
25-40% reduction in efficiency compared to before the industrial revolution
Atmospheric carbon accumulation : atmospheric CO2 concentrations : Global warming
200:100:1
Experiments have demonstrated that increasing CO2 concentrations stimulate…
NPP on land
- doubling CO2 concentration stimulates NPP by about 20%
If the whole of the UK were reforested this would be equivalent to a C sequestration of about…
1PgC
Global mitigation of climatic change can only be achieved by…
internationally concerted action to reduce carbon emissions
The oceanic and terrestrial carbon sinks currently sequester … of anthropogenic emissions
60%
- likely to decline through the 21st century
Brazil produces ethanol from sugar can that replaces 20-25%…
of petrol in fuel
