Factors Affecting The Temperature Sensitivity Of Gross Primary Productivity In Typical Forests Of China

Temperature response and temperature sensibility of ecosystem carbon cycle is one of the major topics in the research field of global change ecology.One of the imperative ways to explore the temperature sensitivity of ecosystem is by means of exploring the response and acclimation mechanism of forest ecosystem productivity to temperature.The temperature response of gross primary productivity(GPP)usually shows that GPP increases with temperature in the lower temperature range to reach a maximum growth rate(DGPP/dt),and then grows slowly as temperature increases further to obtain a maximum GPP(GPPmax)at the optimal temperature(TGPPopt).All these three factors are key ecological indexes to characterize the temperature sensitivity of carbon cycle,while our understanding on the spatial and temporal patterns and main controlling factors of TGPPopt,DGPP/dt,GPP max in forest ecosystems are still limited.In this study,five typical forest ecosystems(temperate coniferous and broad-leaved mixed forest of Changbaishan,subtropical Chinese fir plantation of Huitong,subtropical evergreen coniferous forests of Qianyanzhou,subtropical evergreen broad-leaf and coniferous mixed forest of Dinghushan and tropical rain forest of Xishuangbanna)were selected in China,which covers broad climate zones including temperate,subtropical and tropical zones.The temporal and spatial distribution of TGPPopt,DGPP/dt,GPPmax and main influencing factors were analyzed based on flux data in above forest ecosystems.The main results of our study were as followed:(1)The temperature response of GPP followed a one-peak curve with GPPmax occurring at the optimum temperature in each year for all ecosystems.TGPPopt declined with the increasing latitude,while GPPmax and DGPP/dt increased with the increasing latitude.(2)GPPmax and DGPP/dt existed a similar spatial pattern.Temperature and precipitation played important roles in causing the spatial patterns of GPPmax across sites,with GPPmax decreasing with the increasing temperature,while the distribution of TGPPopt was mainly influenced by VPD.(3)The factors that dominate TGPPopt,GPPmax and DGPP/dt of each forest ecosystem varied from temporal scale.Temperature is well correlated with TGPPopt,GPPmax and DGPP/dt in the forest of Changbaishan.Our findings described the temporal and spatial variation patterns of the temperature sensitivity of GPP in China's typical forests for the first time,which benefits the understanding of GPP variation under climate change and provided experimental evidence and parameter basis for accurate simulation of carbon cycle.