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TERRESTRIAL C SEQUESTRATION AT ELEVATED CO 2 AND TEMPERATURE: THE ROLE OF DISSOLVED ORGANIC N LOSS
Author(s) -
Rastetter Edward B.,
Perakis Steven S.,
Shaver Gaius R.,
Ågren Göran I.
Publication year - 2005
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/03-5303
Subject(s) - carbon sequestration , ecosystem , soil water , environmental science , nitrogen , environmental chemistry , organic matter , soil carbon , chemistry , terrestrial ecosystem , soil science , ecology , agronomy , zoology , biology , organic chemistry
We used a simple model of carbon–nitrogen (C–N) interactions in terrestrial ecosystems to examine the responses to elevated CO 2 and to elevated CO 2 plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand in response to elevated CO 2 , but that DON losses cannot. We also examined simulations in which DON losses were held constant, were proportional to the amount of soil organic matter, were proportional to the soil C:N ratio, or were proportional to the rate of decomposition. We found that the mode of N loss made little difference to the short‐term (<60 years) rate of carbon sequestration by the ecosystem, but high DON losses resulted in much lower carbon sequestration in the long term than did low DON losses. In the short term, C sequestration was fueled by an internal redistribution of N from soils to vegetation and by increases in the C:N ratio of soils and vegetation. This sequestration was about three times larger with elevated CO 2 and warming than with elevated CO 2 alone. After year 60, C sequestration was fueled by a net accumulation of N in the ecosystem, and the rate of sequestration was about the same with elevated CO 2 and warming as with elevated CO 2 alone. With high DON losses, the ecosystem either sequestered C slowly after year 60 (when DON losses were constant or proportional to soil organic matter) or lost C (when DON losses were proportional to the soil C:N ratio or to decomposition). We conclude that changes in long‐term C sequestration depend not only on the magnitude of N losses, but also on the form of those losses.