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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]

Evapotranspiration (ET), which is comprised by evaporation from soil surface ( E ), transpiration ( T ) and evaporation from the intercepted water by canopy (EI), plays an important role in maintaining global energy balance and regulating climate. Quantifying the spatiotemporal variations of T /ET (the ratio of T to ET) can improve our understandings on the role of vegetation ecophysiological processes in climate regulation. Using eddy covariance measurements at three forest ecosystems (Changbaishan temperate broad-leaved Korean pine mixed forest (CBS), Qianyanzhou subtropical coniferous plantation (QYZ) and Dinghushan subtropical evergreen mixed forest (DHS)) in north–south transect of Eastern China (NSTEC), we run the revised Shuttleworth–Wallace model (S–W model), validated its performance with the water vapor fluxes measured at two layers, and quantified the spatiotemporal variations of T /ET. The S–W model performed well in simulating ET and T /ET. The mean value of annual T /ET at three forests during the observation period all exceeded 0.6. The diurnal variation of canopy stomal conductance ( G c ) dominated that of T /ET. The seasonal dynamics of T /ET was mainly shaped by that of leaf area index (LAI), vapor pressure deficit (VPD) and air temperature ( T a ) through altering G c and the portion that the energy absorbed by canopy ( P EC ) at temperate forest (CBS), while the seasonal dynamics of T /ET at subtropical forests (QYZ and DHS) were mainly affected by T a , net radiation, VPD, and soil water content through altering G c and soil surface conductance ( G s ). The variation of mean annual G c governed the interannual varaition and spatial variation of T /ET. Therefore, forests in Eastern China played an important role in regulating climate through T and G c primarily affected the spatial and temproal variations of the role of forest T in regulating climate. [ABSTRACT FROM AUTHOR]