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Start Over Topic carbon cycle Publisher springer netherlands
102 results

36. The Carbon Cycle and Global Forest Ecosystem

Author

Roger A. Sedjo

Subjects
Climatology, Forest ecology, Temperate climate, Environmental science, Carbon sink, Tropics, Temperate forest, Carbon sequestration, Atmospheric sciences, Temperate rainforest, Carbon cycle
Abstract

Attempts to account for the fluxes by quantifying C sources and sinks have provided evidence of a missing C sink (Detwiler and Hall, 1988), which may be located somewhere in the temperate region of the northern hemisphere (Tans et al., 1990). Until recently, most estimates have concluded that the temperate forest is a small C source. Two recent papers (Sedjo, 1992; Kauppi et al., 1992) provided evidence that the temperate forests are substantial C sinks. This paper combines these earlier findings on temeperate forest carbon sequestration with a new estimate of the annual C releases due to tropical deforestation, 1.7 Gt, which is obtained using the FAO estimates of the rate of deforestation in the tropics over the decade of the 1980s and conservative estimates of C releases associated with this deforestation. Finally, to this is added the crude estimate of C export by the global river system found in Hall et al. (1992). Applying these estimates of the C sink function of both temperate and tropical forests to Detwiler and Hall’s alternative C budgets largely eliminates the “missing C” hypothesized by Detwiler and Hall, and Tans et al.

Published
1993

37. Quantifying Feedback Processes In the Response of The Terrestrial Carbon Cycle to Global Change: The Modeling Approach of Image-2

Author

M. Vloedbeld and Rik Leemans

Subjects
Soil respiration, Atmosphere, Meteorology, Climate change, Environmental science, Biosphere, Global change, Land cover, Atmospheric sciences, Greenhouse effect, Carbon cycle
Abstract

The terrestrial biosphere component of the Integrated Model to Assess the Greenhouse Effect (IMAGE 2) uses changes in land cover to compute dynamically the C fluxes between the terrestrial biosphere and the atmosphere. The model explores the potential impact of feedback processes incorporated in the model, which are the enhancement of plant growth (CO2 fertilization) and a more efficient use of water under increased CO2 concentrations in the atmosphere; the temperature response of photosynthesis and respiration of plants; the temperature and soil water response of decomposition processes; and the climate-induced changes in vegetation and agricultural patterns with the consequent changes in land cover. In this paper we discuss the implementation and operation of the different feedback processes in the IMAGE 2 model. Results are shown for each process separately as well as the combined processes. The aim of this paper is to quantify the importance of these feedback processes geographically. The main results are that vegetation shifts due to climatic change and increased water use efficiency, CO2 fertilization decreases net C emissions, while changed decomposition rates strongly increase C emissions to the atmosphere. Changes in the global balance between photosynthesis and respiration make little net difference. With the IPPC business-as-usual scenario the terrestrial biosphere continues to emit C into the atmosphere. This behavior is governed by changes in land-use, caused by a multitude of anthropogenic processes.

Published
1993