24. Primary Production Flashcards
primary production
The fixation of energy by autotrophs in an ecosystem
– Biggest source of primary production is photosynthesis by plants, phytoplankton, and
cyanobacteria.
– Also can occur via chemosynthesis by some species of bacteria
primary productivity
amount of energy fixed by autotrophs over an interval of time (rate!)
ex: rate at which energy from the sun used to make sugars by plants
gross primary production (GPP)
The total amount of energy fixedby all the autotrophs
in the ecosystem.
Ex: GPP = Photosynthesis
net primary productino (NPP)
The total amount of energy fixed by all the autotrophs in the ecosystem, minus the cost associated with its fixation = the amount of energy available to consumers in an ecosystem.
Ex: NPP = Photosynthesis - Respiration
remote sensing
used to measure ecosystem-level primary production, sensing and recording reflected or emitted energy
using cameras and sensorsattached to satellites
How temperature and moisture limit NPP in terrestrial ecosystems
- NPP increases with increased precipitation
- NPP increases with added fertilizer
How nutrients limit NPP in aquatic ecosystems
- higher phosphorous concentration = greater algal biomass
- as algal biomass increases so does the rate of primary production
eutrophication
nutrient enrichment of a water body through natural processes or pollution, generally causing rapid algal growth and reduce dissolved oxygen levels
two measures of primary productivity
GPP and NPP
actual evapotranspiration
The total amount of water that evaporates and transpires off a landscape during a given time period,
measured in mm water - Measure that accounts for both temperature and precipitation, as AET is affected by both
hypoxia
when wateroxygen concentration is <2mg O2 L-1
dead zones
hypoxic areas in aquatic ecosystems, typically a consequence of pollution, eutrophication, and high rates of decomposition, that are essentially devoid of life
