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Moyano, Fernando E.; Atkin, Owen K.; Bahn, Michael; Bruhn, Dan; Burton, Andrew J.; Heinemeyer, Andreas; Kutsch, Werner L. and Wieser, Gerhard
(2010).
URL: http://www.cambridge.org/gb/academic/subjects/life...
Abstract
The largest flux in the global carbon cycle is the uptake of CO2 by plants as photosynthesis. Estimates of gross primary production (GPP), or total amount of CO2 assimilated by terrestrial plants, range between about 109 and 120 Pg C per year at the global scale (Schlesinger, 1997; Zhao et al., 2005). Except for carbon that remains stored in passive organic matter pools, as fossil fuel, and an estimated 0.2 Pg C per year sedimenting on the ocean floors, assimilated carbon is eventually returned to the atmosphere by respiration, either by plants or by heterotrophic organism. The time between the fixation of a carbon atom by the plant and its conversion back to CO2 is extremely variable, ranging between a few hours and thousands of years. How long it remains part of organic compounds will depend on its turnover within the plant and, eventually as part of soil organic matter.