| Forest ecosystem is the major component of terrestrial ecosystems.The carbon and water cycles of forest ecosystem have a crucial influence on all spheres of the earth.In recent years,research on the relationship between carbon and water of forest ecosystem has become a hot topic of eco-hydrology.However,the response mechanism and adaptation method of the water-carbon coupling relationship in China’s forest ecosystem under global changes are still not fully understood.Water use efficiency（WUE）reflects the carbon-water cycle of ecosystems,which is an important indicator to understand the coupling relationship between the carbon-water cycle of the ecosystems.Therefore,researching on WUE of forest ecosystem of China under the climate change can not only provide new information for the coupling relationship of water and carbon of forest ecosystem of China,but also provide strategies for the successful implementation of forest management in the future.In this study,the LPJ（Lund-Potsdam-Jena）global vegetation dynamics model was used to estimate the NPP（Net Primary Productivity）and ET（Evapotranspiration）of forest ecosystem of China from 1961 to 2013.Based on the estimated results of NPP and ET by LPJ model,the temporal and spatial characteristics of NPP,ET and WUE in Chinese forest ecosystem were analyzed.At last,the effects of climate change on WUE was discussed in this paper.The main results are as follows:（1）LPJ model can simulate NPP of forest ecosystem of China well.The annual mean NPP of Chinese forest ecosystem from 1961 to 2013 was 459.38 gC·m-2·a-1.There is a trend of decreasing from southeast to northwest.The order of annual mean NPP in three forest areas of China is:Southwest forest area>Southeast forest area>Northeast forest area.The NPP of Chinese forest ecosystem showed a significant increase in time from 1961 to 2013.（2）LPJ model can simulate ET of Chinese forest ecosystem well.The annual mean ET of Chinese forest ecosystem from 1961 to 2013 was 535.33 mm.The overall trend is also decreasing from southeast to northwest.The order of annual mean ET in three forest areas of China is:Southeast forest area>Southwest forest area>Northeast forest area.The ET of Chinese forest ecosystem from 1961 to 2013 shows a slight upward trend in time.（3）The annual mean WUE for Chinese forest ecosystem from 1961 to 2013 was 0.88gC·mm-1 m-2.WUE has spatial heterogeneity.The order of annual mean WUE in three forest areas of China is:Northeast forest area>Southwest forest area>Southeast forest area.The WUE of forest ecosystem of China shows a significant upward trend in time from 1961 to 2013.（4）The annual precipitation of Chinese forest ecosystem in 1961-2013 shows the spatial distribution of the decline from the southeast coast to the northwest inland.The spatial distribution characteristics of the annual mean temperature of Chinese forest ecosystem decreasing from South to North.The temperature of forest ecosystem in China have gradually increased over the past 50 years,and the precipitation of forest ecosystem in China showed a slight decrease with time.（5）64.96%regional forest ecosystem in China air temperature is positively correlated with WUE.However,in the south of the southwest China,south of Guangdong and Guangxi of the south China,the north of the north China,and the west of the northeast China,WUE is significantly positive correlated with temperature.The precipitation is basically the opposite,where WUE is positively correlated with precipitation,it is negatively correlated with temperature.（6）In three forest areas of China,WUE is sensitive to temperature and precipitation,but WUE is less sensitive to temperature,and WUE is more sensitive to precipitation.With the relative increase in precipitation,the relative change of NPP tends to increase slowly and the trend of relative increase in ET is more obvious,the relative change of WUE tends to decrease.The relative change of WUE is mainly negatively correlated with the relative change of precipitation. |
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