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1 Background THE C_i/C_a, the ratio of intercellular and ambient C0_2 partial pressure, is internally controlled by thestomatal conductance and assimilation rate, and is externally affected by the atmospheric CO_2 concentration and climate changes. C_i/C_a can be only estimated by the isotopic fractionation equation of Farquchar. However, this method is limited by the very little observation of atmospheric δ~(13) C before1980. Leavitt had to interpolate the atmospheric δ~(13) C by means of the polynomial. A geochemicalmethod to model C_i/C_a by tree-ring δ~(13)C has been developed to reduce the dependence. By the estimated tree-ring C_i/ C_a, the authors here discuss C0_2 and water exchanges between the atmosphere and biosphere that greatly influence the climate change
1 Background THE C_i / C_a, the ratio of intercellular and ambient C0_2 partial pressure, is internally controlled by the start of conduct conduct and assimilation rate, and is externally affected by the atmospheric CO 2 concentration and climate changes. C_i / C_a can be only estimated by the isotopic fractionation equation of Farquchar. However, this method is limited by the very little observation of atmospheric δ ~ (13) C before 1980. Leavitt had to interpolate the atmospheric δ ~ (13) C by means of the polynomial. A geochemical method to model C_i / C_a by tree-ring δ ~ (13) C has been developed to reduce the dependence. By the estimated tree-ring C_i / C_a, the authors here discuss C0_2 and water exchanges between the atmosphere and biosphere that greatly affect the climate change