BISC 204 Lecture Notes - Lecture 16: Terrestrial Ecosystem, Freshwater Ecosystem, Nitrogen Fixation
12 Dec 2017
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Document Summary
Ecosystems ii nutrient cycling: the productivity of any ecosystem is regulated by herbivory, climate, and the availability of limiting nutrients such as p, n, si, and fe, odum"s mass-balance approach champions the importance of. Energy as the key currency: but we know that things other than energy can limit metabolism and growth, studies of nutrient cycling characterize the flows of these nutrients among the living and non-living components of ecosystems. The biota play an enormous role in nutrient availability to plants in nearly all ecosystems: key physical processes regulate the rates and locations of nutrient cycling in different ecosystems. The largest reservoir of nitrogen is in the atmosphere as gaseous n but this form is not available for uptake by most primary producers: many reduced and oxidized forms of n complicate cycle. Nitrogen fixation is the process whereby bacteria and cyanobacteria convert n2 into ammonia that is then biologically available for other organisms.
