| 摘 要： |
Temperature response of gross primary productivity (GPP) is a well-known property of ecosystem, but GPP at the optimum temperature (GPP_T-opt) has not been fully discussed. Our understanding of how GPP_T(opt )responds to warming and water availability is highly limited. In this study, we analyzed data at 326 globally distributed eddy covariance sites (79(o)N-37(o)S), to identify controlling factors of GPP_Topt. Although GPP_Topt was significantly influenced by soil moisture, global solar radiation, mean annual temperature, and vapor pressure deficit in a non-linear pattern (R-2 = 0.47), the direction and magnitude of these climate variables' effects on GPP_T-opt depend on the dryness index (DI), a ratio of potential evapotranspiration to precipitation. The spatial pattern showed that soil moisture did not affect GPP_T(opt )across energy-limited sites with DI < 1 while dominated GPP_T-opt across water-limited sites with DI > 1. The temporal pattern showed that GPP_T-opt was lowered by warming or low precipitation in water-limited sites while energy-limited sites tended to maintain a stable GPP_T-opt regardless of changes in air temperature. Vegetation types in humid climates tended to have higher GPP_T(opt )and were more likely to benefit from a warmer climate since it was not restricted by water conditions. This study highlights that the response of GPP_T-opt to global warming depends on the dryness conditions, which explains the nonlinear control of water and temperature over GPP_T-opt. Our finding is essential to realistic prediction of terrestrial carbon uptake under future climate and vegetation conditions. |
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