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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 CO 2 mass concentration ( ρ cyr ). The increasing MAT and ρ cyr directly enhanced RUE. The increasing annual precipitation (MAP) directly prompted FPAR yr . Therefore, MAT and ρ 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. [ABSTRACT FROM AUTHOR]

Accurate quantifying the magnitudes and distributions of carbon budgets is helpful for strategies in mitigating global climate change. Based on spatial patterns of carbon fluxes (gross ecosystem productivity (GEP), ecosystem respiration (ER) and net ecosystem productivity (NEP)) and their drivers, we constructed geographical statistical assessment schemes and quantified the magnitudes of carbon fluxes in China. The optimal assessment scheme was then validated with observed eddy covariance data to analyze the spatial distributions of carbon fluxes. Using climate-based geographical statistical assessment schemes, our estimates of GEP, ER and NEP in China during 2000s were 7.51±0.51, 5.82±0.16 and 1.91±0.15PgCyr−1, corresponding to 4.29%–6.80%, 5.65%–6.06% and 9.10%–12.73% of global annual carbon fluxes, respectively. The spatial distributions of GEP, ER and NEP, generated from the optimal scheme, were similar, following a southeast–northwest decreasing gradient. The maximum values for GEP, ER and NEP were 1790, 1300 and 490gCm−2 yr−1, respectively, which occurred in Central subtropics and Southern subtropics. Climate-based geographical statistical assessment schemes provided an independent dataset for the regional carbon budget assessment, which can be deemed as the potential carbon fluxes. Meanwhile, most areas in China were potential carbon sink especially Eastern China and the largest potential carbon sink appeared in Central subtropics and Southern subtropics. [ABSTRACT FROM AUTHOR]