Energy, Biomass, Productivity Flashcards
What is an ecosystem?
Biological community together with the abiotic environment.
What is biomass?
Mass of organisms per unit area (J m-2)
What is primary productivity?
Rate at which biomass is produced per unit area by plants (J m-2 day-1)
What is secondary productivity?
Rate at which biomass is produced by heterotrophs (bacteria, fungi and animals)
What is gross primary productivity (GPP)?
Total fixation of energy by photosynthesis.
What is autotrophic respiration (RA)?
Proportion of GPP lost from plant community as respiratory heat.
What is net primary productivity (NPP)?
Rate of production of new biomass that is available for consumption.
NPP = GPP - RA
What is ecosystem respiration? (RE)
Ecosystem Respiration (RE) - respiratory heat loss from both autotrophs (RA) and heterotrophs (RH).
RE = RA + RH
What is net ecosystem productivity (NEP)?
Balance between carbon fixation and ecosystem respiration.
NEP = GPP - RE
Under what conditions does NPP lead to carbon sinks and carbon storage?
Carbon sink = when GPP > RE
Carbon source = when GPP < RE
What are the factors determining NPP?
Solar radiation
Heat
Water
Nutrients
CO2
What is the relationship between latitude and NPP?
Generally, NPP decreases with latitude with the tropics being the most productive ecosystems, however there is some debate whether higher latitudes in the summer have a higher NPP than lower regions.
What is autochthonous and allochthonous productivity?
Autochthonous - Organic carbon made in situ from photosynthesis e.g. shallow waters.
Allochthonous - Organic carbon made from elsewhere e.g. rivers.
Describe biomass:NPP relationships
In terrestrial ecosystems (compared with aquatic):
- Greater ratio of biomass:NPP
- More support tissue in primary producers
- Lower rates of biomass turnover
What is photosynthetic efficiency?
Efficiency of light interception by leaves and conversion. Depends on photosynthetically active radiation (PAR) and abundance of resources.
