Climate Science

Fertilizing Forests with CO2

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Science  06 Jan 2006:
Vol. 311, Issue 5757, pp. 16
DOI: 10.1126/science.311.5757.16d

One of the biggest obstacles to predicting how much climate will be affected by increasing concentrations of atmospheric CO2 is not knowing how much additional carbon uptake from the terrestrial biosphere, stimulated by higher CO2 concentrations, might occur. This sequestration could slow the rate of warming by a significant amount, at least in the short term, so it is important to understand how forests in particular will react to the CO2 “fertilizer” added by fossil fuel burning.

Norby et al. report results from an experiment in which forest stands were exposed to an artificially enhanced level of CO2 and their net primary productivity (NPP)—the net fixation of C by green plants into organic matter—was determined. NPP increased by an average of 23% over a broad range of productivity when CO2 was enriched to a level of 550 parts per million (ppm), approximately 170 ppm above today's value and around what it is expected to be by the end of the 21st century. This study thereby provides a foundation on which questions about more specific and subtle responses of ecosystems to CO2 fertilization, such as how this additional C is allocated and retained in plants and how the availability of other growth-limiting resources might affect NPP, can be addressed. — HJS

Proc. Natl. Acad. Sci. U.S.A. 102, 18052 (2005).

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