Temperature and precipitation control of the spatial variation of terrestrial ecosystem carbon exchange in the Asian region

Carbon exchange between terrestrial ecosystems and the atmosphere is one of the most important processes in the global carbon cycle. Understanding the spatial variation and controlling factors of carbon exchange fluxes is helpful for accurately predicting and evaluating the global carbon budget. In this study, we quantified the carbon exchange fluxes of different terrestrial ecosystems in the Asian region, and analyzed their spatial variation and controlling factors based on long-term observation data from ChinaFLUX (19 sites) and published data from AsiaFlux (37 sites) and 32 other sites in Asia. The results indicated that the majority of Asian terrestrial ecosystems are currently large carbon sinks. The average net ecosystem production (NEP) values were 325 ± 187, 274 ± 207, 236 ± 260, 89 ± 134 g C m−2 yr−1 in cropland, forest, wetland and grassland ecosystems, respectively. The spatial variation of gross primary production (GPP) and ecosystem respiration (Re) were mainly controlled by the mean annual temperature (MAT) and the mean annual precipitation (MAP) in the Asian region. There was a clear linear relationship between GPP and MAT, and a strong sigmoid relationship between GPP and MAP. Re was exponentially related to MAT and linearly related to MAP. Interestingly, those response modes were consistent across different ecosystem types. The different responses of GPP and Re to MAT and MAP determined the spatial variation of NEP. The combined effects of MAT and MAP contributed 85%, 81% and 36% to the spatial variations of GPP, Re and NEP, respectively. Our findings confirmed that the spatial variation of carbon exchange fluxes was mainly controlled by climatic factors, which further strongly supports the use of the climate-driven theory in the Asian region.