Impact Of Diffuse Radiation On GPP Simulation Of Terrestrial Ecosystem In China

Terrestrial ecosystem carbon cycle is one of the hot spots in global change.It has a significant impact on climate change system and a close relationship with the biosphere and human circle of Earth system.Level of vegetation productivity is an important indicator of carbon budget of terrestrial ecosystems,which is of great significance for simulation of carbon budget and vegetation productivity.Gross Primary Productivity(GPP)is not only one of main criteria for carbon exchange in the atmosphere and terrestrial ecosystems,but also an important indicator of plant carbon sequestration and function.It is very important to study the GPP of site and region accurately and analyze temporal and spatial pattern of land and ecosystem.It is very important to study the response of terrestrial ecosystem carbon budget to human activities and climate change.(1)Cloudiness index coefficient light use efficiency model(CI-LUE)construction and validation.On the basis of MOD 17 GPP arithmetic,by increasing clouds can change characterization of scattered radiation coefficient CI,CI-LUE GPP estimation model is constructed.CI-LUE model is applied to simulate the flux of 7 stations.(2)Simulation and analysis of Chinese terrestrial ecosystem GPP based on CI-LUE Model.Based on the CI-LUE model,GPP with 1km resolution of Chinese terrestrial ecosystem at the regional scale was simulated with meteorological data,remote sensing data and measured flux data in 2003-2012.Time scales were 8 days and years respectively,and the time and space of GPP were analyzed Pattern distribution characteristics.The temporal and spatial distribution pattern of GPP is similar,and the GPP value in North China and Northeast China is obviously higher than that in northwest China,and there is increasing trend of northwest inland to southeast coast.(3)Based on the terrestrial ecosystem of China,the GPP of terrestrial ecosystem from 2003 to 2012 was analyzed by eight types of ecosystems.GPP was quantitatively analyzed and verified by BEPS model and GLCV model(m-2 yr-1).The results show that simulation results of CI-LUE model are better than GLCV model and BEPS model,and the model of diffuse radiation can improve the simulation level of GPP.10 years GPP average is 4.75Pg C,2003-2012 GPP annual total value increased first and then lower trend,2007 GPP total value reached the maximum.Broad-leaved forest is the most fixed forest ecosystem,followed by mixed forest,the least is the grass.(4)Impact of Climate Change on GPP.The dynamic trend of GPP in terrestrial ecosystems was analyzed year by year from 2003 to 2012.The results showed that GPP showed a seasonal trend of increasing first and then decreasing,and it could respond to the dynamic changes of single peak season.GPP value and photosynthetically active radiation(PAR)showed a consistent trend from 2003 to 2012.It was found that the maximum value of GPP was always concentrated around the first 200 days.The response of meteorological factor temperature and precipitation to interannual GPP changes was discussed.The change of temperature and GPP tends to be consistent with time and precipitation has a hysteresis effect on the inhibition and enhancement of vegetation GPP.