关键词: 土壤有机碳蓄积量, 碳循环, 土壤碳循环

Abstract: Plant leaf stomatal conductance (g) is an important factor controlling the energy and water exchanges between canopy and atmosphere, while air humidity is a key environmental variable controlling the g. In last decade, the stomatal conductance- humidity relationships in Ball-Woodrow-Berry (BWB) and Leuning models were widely used. In this study, a new diagnostic parameter f(H) was adopted to assess the response of g to air humidity. Based on the leaflevel measurements in a cropland ecosystem, the performance of the BWB, Leuning, and newly developed power-h and power-D models was examined. The results showed that the BWB model which employs a linear relationship between g and relative humidity (h_s) led to a larger underestimate of g when the air was wet, while the Leuning model which employs a nonlinear function of water vapor pressure deficit (D_s) decreased this bias but still not adequately captured the significant increase of g under the wet condition. Compared with BWB and Leuning models, the newly developed power-h and power-D models that employ a power function of D_sand a power function of relative humidity deficit (1-h_s), respectively, showed better performance. The results also indicated that the models based on D_s generally performed better, compared with those based on h_s.

Key words: Soil organic carbon storage, Carbon cycle, Soil carbon cycle