The Princeton Guide to Ecology

The characterization and understanding of carbon flows in aquatic and terrestrial ecosystems are topics of paramount importance for several disciplines, such as ecology, biogeochemistry, oceanography, and climatology. Scientists have been studying such flows in many diverse ecosystems for decades, and sufficient information is now available to investigate whether any patterns are evident in how carbon flows in ecosystems and to determine the factors responsible for those patterns. In particular, a wealth of information exists on the movement of carbon through the activity of herbivores and consumers of detritus (i.e., decomposers and detritivores), two of the major agents of carbon flows in ecosystems. This chapter analyzes the transference of carbon through herbivory and decomposition in aquatic and terrestrial ecosystems, documents the nature and implications of salient patterns, and explains why those patterns emerge.

absolute decomposition. The amount (in g C-m^–2year^–1) of detritus consumed by microbial decomposers (e.g., bacteria, fungi) and detritivores, which range from detritivorous micro-, macro-, and gelatinous zooplankton in pelagic systems to micro(<100 μm), meio- (100–500 μm), and macrofauna (>500 μm) in benthic and terrestrial systems

decomposition rate. The proportion of detrital mass decomposed per unit time (e.g., day⁻), often estimated by fitting the following single exponential equation to the pattern of detritus decay observed in experimental incubations, DM_t = DM_t0e^–k(t–t0), where k is the decomposition rate, DMt is the detrital mass remaining in the experimental incubation at time t, DM_t0, is the initial detrital mass, and (t – t₀) is the incubation time

detrital production. The amount (in g C-m^–2-year^–1) of net primary production not consumed by herbivores, which senesces and enters the detrital compartment

detritus. Dead primary producer material, which normally becomes detached from the primary producer after senescence

herbivory. The amount (in g C·m^–2 ·year^–1) of net primary production ingested or removed, including primary producer biomass discarded by herbivores

net primary production. The amount (in g C·m^–2· year^–1) of carbon assimilated through photosynthesis and not respired by the producer

nutrient concentration (producer or detritus). The percentage of nitrogen and phosphorus within producer biomass or detritus on a dry weight basis

Carbon enters the biotic component of an ecosystem when inorganic carbon, often carbon dioxide, is taken up and converted into organic compounds. With the rare exception of chemosynthetic organisms, the energy for this conversion comes from photosynthesis. Once inorganic carbon has been converted into organic compounds, it is considered fixed. This production of fixed carbon is known as primary production, and those organisms that can fix carbon are primary producers. Gross primary production is the entire amount of carbon fixed by a primary producer. Net primary production is gross primary production minus

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