Lecture 26: Production Flashcards
Define primary productivity
Amount of energy fixed by autotrophs over an interval of time
Primary production vs primary consumers
Production: fixation of energy by autotrophs in an ecosystem
Consumers: assimilation of organic matter by heterotrophs to produce biomass
Explain redfield ratio
Ratio at which elements are fixed by plants during photosynthesis
Net primary production (npp) vs gross primary primary production (gpp)
NPP: amount of energy fixed by all autotrophs, regardless of the cost associated with fixation (photosynthesis)
Consumer: amount of energy fixed by all autotrophs in the ecosystem, minus respiration
How do you quantify primary production?
- Estimate npp by measuring increase in plant biomass in experimental plots and scaling up to the whole ecosystem
- Remote sensing can quantify the change in primary production overtime using wavelengths that are reflected off of the earth’s surface
What is normalized difference vegetation index (NDVI)?
- Ration of near red to red reflectance
- Assessing chlorophyll concentrations
- used to estimate CO2 uptake and npp
What influences global terrestrial npp?
- limited by temp and moisture
- highest in the tropics, lower at the poles
- actual evapotranspiration (aet): total amount of water that evaporates and transpires every year
- soil fertility and nutrient availability in soil
What is liebig’s law of minimum?
Plant growth is not limited by the total amount of all soil nutrients available but by the soil nutrient variable that is present in the lowest quantity
What influences global aquatic npp?
- nutrient availability is greatest near ocean shores
- freshwater patterns
Define eutrophication
nutrient enrichment in a body of water through natural processes that result in rapid agal growth and reduced oxygen levels
What are dead zones?
Hypoxic areas, mainly caused by nutrient runoff from fertilizer use
