Dissolved Organic Carbon in Terrestrial Ecosystems: Synthesis and a Model |
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Authors: | Jason C Neff Gregory P Asner |
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Institution: | (1) Department of Biological Sciences, Stanford University, Stanford, California 94305, USA; and, US;(2) Department of Geological Sciences and Environmental Studies Program, University of Colorado, Boulder, Colorado 80309, USA, US |
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Abstract: | The movement of dissolved organic carbon (DOC) through soils is an important process for the transport of carbon within ecosystems
and the formation of soil organic matter. In some cases, DOC fluxes may also contribute to the carbon balance of terrestrial
ecosystems; in most ecosystems, they are an important source of energy, carbon, and nutrient transfers from terrestrial to
aquatic ecosystems. Despite their importance for terrestrial and aquatic biogeochemistry, these fluxes are rarely represented
in conceptual or numerical models of terrestrial biogeochemistry. In part, this is due to the lack of a comprehensive understanding
of the suite of processes that control DOC dynamics in soils. In this article, we synthesize information on the geochemical
and biological factors that control DOC fluxes through soils. We focus on conceptual issues and quantitative evaluations of
key process rates to present a general numerical model of DOC dynamics. We then test the sensitivity of the model to variation
in the controlling parameters to highlight both the significance of DOC fluxes to terrestrial carbon processes and the key
uncertainties that require additional experiments and data. Simulation model results indicate the importance of representing
both root carbon inputs and soluble carbon fluxes to predict the quantity and distribution of soil carbon in soil layers.
For a test case in a temperate forest, DOC contributed 25% of the total soil profile carbon, whereas roots provided the remainder.
The analysis also shows that physical factors—most notably, sorption dynamics and hydrology—play the dominant role in regulating
DOC losses from terrestrial ecosystems but that interactions between hydrology and microbial–DOC relationships are important
in regulating the fluxes of DOC in the litter and surface soil horizons. The model also indicates that DOC fluxes to deeper
soil layers can support a large fraction (up to 30%) of microbial activity below 40 cm.
Received 14 January 2000; accepted 6 September 2000 |
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Keywords: | : DOC dissolved carbon fluxes soil model |
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