TAILIEUCHUNG - Báo cáo lâm nghiệp:" The key-role of topsoil moisture on CO2 efflux from a Mediterranean Quercus ilex forest"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí lâm nghiệp đề tài:" The key-role of topsoil moisture on CO2 efflux from a Mediterranean Quercus ilex forest" | Ann. For. Sci. 60 2003 519-526 INRA EDP Sciences 2003 DOI forest 2003045 519 Original article The key-role of topsoil moisture on CO2 efflux from a Mediterranean Quercus ilex forest Richard jOFFREa Jean-Marc OuRCIVALa Serge RAMBALa Alain ROCHETEAUa b a Équipe DREAM CEFE-CNRS 1919 Route de Mende 34293 Montpellier Cedex 5 France b Ur CLIFA IRD-CNRS 1919 Route de Mende 34293 Montpellier Cedex 5 France Received 7 October 2002 accepted 1 June 2003 Abstract - CO2 respiratory losses partly determine net carbon ecosystem exchanges. The main objective of this paper was to understand regulation imposed by soil water content and temperature on soil and ecosystem CO2 efflux in a holm oak Quercus ilex L. Mediterranean forest. Soil CO2 efflux was monitored monthly during 1999 and 2001. Moreover experimental water treatments were conducted in 1999 over 9 small plots m1 2 during nine months. Results showed strong decreases of soil CO2 efflux for a relative soil water content below . Ecosystem respiration measured by eddy covariance over a 4-year period showed strong sensitivity to soil water content and temperature. Severe limitations of soil and ecosystem efflux imposed by low values of soil water content occurred on about 90 days per year. The best adjustments of soil and ecosystem CO2 efflux were obtained using regression models where the exponential effect of temperature is linearly related to soil water content r2 and for soil and ecosystem respectively . Our results highlighted strong differences in respiration sensitivity to topsoil moisture between soil and ecosystem. When the relative water content RWC is low an increase of 1 C provokes an increase of soil respiration of and an increase of ecosystem respiration of . For nonlimiting soil water conditions at RWC 1 the increases of respiration caused by a 1 C temperature increase are of and for soil and ecosystem respectively. These results emphasized the probable determinant .

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