Approaches of climate factors affecting the spatial variation of annual gross primary productivity among terrestrial ecosystems in China

Analyzing the approaches that climatic factors affect the spatial variation of annual gross primary productivity (GPP(yr)) would improve our understanding on its spatial pattern. Based on network eddy covariance measurements and published data in literature, we separated GPP(yr) into radiation use efficiency (RUE) and annual absorbed photosynthesis active radiation (APAR(yr)), where APAR(yr) can be regarded as the product of the fraction of absorbed annual photosynthesis active radiation (FPAR(yr)) and annual PAR (PAR(yr)). Given that PAR(yr) affects the spatial variation of GPP(yr) directly through itself, we investigated factors affecting the spatial variations of RUE and FPAR(yr), to reveal how climatic factors affect the spatial variation of GPP(yr). Results suggest that the spatial variation of RUE was directly affected by annual mean air temperature (MAT) and annual mean CO2 mass concentration (rho(cyr)). The increasing MAT and rho(cyr), directly enhanced RUE. The increasing annual precipitation (MAP) directly prompted FPAR(yr). Therefore, MAT and rho(cyr) affected the spatial variation of GPP(yr) through altering RUE while the effect of MAP was achieved through altering FPAR(yr). Our study could also provide an alternative way for regional GPP(yr) assessment. (C) 2015 Elsevier Ltd. All rights reserved