Potential exam question #1
What is the difference between NEE and NEP?
NEE, or Net Ecosystem Exchange, is an instantaneous measurement of the inward and outward flows of carbon within an ecosystem. NEE is measured by eddy-flux towers to determine the amount of CO2 entering an ecosystem and the amount of carbon being lost through respiration simultaneously.
NEP, or Net Ecosystem Production, is a measurement of the net gain (or loss) of energy/carbon in a system over a period of time. NEP, therefore, is NPP minus energy lost through heterotrophic respiration. NEP is expressed in flux units (g/m2yr) and is estimated based on long-term averages of NEE measurements.
Potential exam question #2
Explain the differences between an upland and bottomland terrestrial ecosystem in regards to rate of decompositon, rate of production, and potential for Carbon storage.
Upland ecosystems tend to have increased rates of decompostion and lower rates of production. Bottomland ecosystems tend to have lower rates of decompostion (due to standing water and thus lack of oxygen impeding decomposition) and higher rates of production due to an increased presence of H2O. The potential for Carbon storage is greater in bottomland ecosystems due to the low rate of decomposition and high rate of production.
Potential exam question #3
Describe the major components of the global terrestrial carbon uptake and release.
Photosynthesis removes carbon from the atmosphere (this is gross primary production, or GPP). Plants use some of the energy produced in photosynthesis for individual growth and they respire CO2 into the atmosphere (this is autotrophic respiration, or RA). Together, GPP minus RA is the short-term carbon uptake by plants (net primary production, NPP).
In the medium-term, heterotrophic respiration (RH) releases carbon to the atmosphere via soil decomposers (mainly fungi and bacteria), herbivores, and other animals. Taking the short-term NPP and subtracting RH, the release from heterotrophic respiration, gives you net ecosystem production (NEP).
Disturbances also release stored carbon over the long-term. Examples include fire, flooding, insect irruptions (the gypsy moth, for example), windthrow, and ice storms. NEP minus the carbon released from disturbances results in net biome production (NBP). NBP would also include scaling up across all ecosystems in the landscape, which means averaging across different community types and successional stages.
potential exam question #4
Define the term succession and distinguish between its two types.
Succession is the tendency of a community's species composition to be replaced over time in a sequence of changes, known as seres, to progress towards a stable state. Secondary succession occurs in a habitat that has been disturbed, but in which some aspects of community remain. Primary succession is different in that it occurs in a newly formed or exposed habitat devoid of life, such as after a lava flow or a glacier retreat. Primary succession is the establishment of a community wheras secondary succession is the regeneration of a community. (If you have heard of r- and k-selected species, it may help to remember that r-selected species are typically primary successors, and k-selected species are secondary successors. R-selected species do very well in disturbed and unstable environments and reproduce quickly. K-selected species reproduce much less quickly, are more competitive, and require more stable environments in which to grow.)