Spatial And Temporal Variations Of Terrestrial Gross Primary Productivity And Underlying Driving Factors In China

Terrestrial ecosystem carbon cycle is an important part of the global carbon cycle,has important effects on atmospheric CO2 concentration and climate change.Terrestrial gross primary productivity?GPP?is an important component of terrestrial ecosystem carbon cycle,and reflect terrestrial ecosystem productivity levels in natural environment.Spatial and temporal variation of terrestrial ecosystems GPP in China monitoring and analysis of its response to the climate factors such as temperature and precipitation,will help to understand the ecosystem carbon cycle on the response of the climate change.Paper with two-leaf light use efficiency model?TL-LUE?as the tool,based on the MODIS data and eddy flux measurement GPP in China during the period of 2001-2014?spatial resolution is 500 m,temporal resolution for the day?,analyze its spatial and temporal variation and its response to climate factors such as temperature and precipitation changes,revealing the canopy sunlit GPP and shaded GPP contribution to the GPP.The research content and conclusions are as follows:?1?Spatial and temporal variations of GPPThere was a significant spatial difference in the terrestrial ecosystem GPP inChina due to the combined effects of climate,LAI and vegetation types during the period of 2001-2014,in range of GPP change 0-3000 g C m-2a^-1.In the Qinghai Tibet Plateau,northwest China and the central and western regions of Inner Mongolia,due to the restriction of precipitation,the vegetation is sparse and the value of GPP is below 500 g C m-2a^-1.The vegetation growth in northeast China is mainly restricted by temperature,and the average value of GPP is between 500 g C m-2a^-1 to 1500 g C m-2a^-1 in the whole year.The GPP in the North China Plain and the Huai River Basin is obviously higher than that in the surrounding area,and the GPP value is about 2500 g C m-2a^-1.The average change rate of GPP in terrestrial ecosystem is concentrated in the interval-25-25 g C m-2a^-1,and the coefficient of variation is basically stable 0.02-0.4.The North China and northwest,Tibetan Plateau and the border of Yunnan and Guizhou,GPP fluctuation greatly?high coefficient of variation?,the northeast,south and central part of North China,eastern and southern China,southwest of GPP less fluctuation?lower coefficient of variation?.?2?spatial and temporal variation of sunlit GPP and shaded GPP with their contributionOn the whole,the value of shaded GPP?GPPshade?was higher than that of sunlit GPP?GPPsun?,the range of GPPsun was 0^-1350 g C m-2a^-1,while GPPshade was 0-2200 g C m-2a^-1,and the maximum value of GPPshade was 1.6 times higher than that of GPPsun.Tibet,Xinjiang,Inner Mongolia and Qinghai,GPPsun was lower than 450 g C m-2a^-1,while GPPshade was lower than 1000 g C m-2a^-1.In Huaihai River Basin and Southern China,GPPshade was above 900 g C m-2a^-1,and GPPsun was above 1500 g C m-2a^-1.In the northeast,central,southwest and southeast regions is relatively concentrated,and the range of GPPsun is 450-900 g C m-2a^-1,GPPshade is 800^-1600 g C m-2a^-1 The average annual rate of change of GPPsun was^-15^-15g C m-2a^-1,and the average annual rate of change of GPPshade was-25-25g C m-2a^-1.The annual GPP in China varied between 5.8 Pg C a^-1 and 6.2 Pg C a^-1,annual GPPsun of China varied between 1.8 Pg C a^-1 and 2.0 Pg C a^-1,annual GPPsahde in China varied between 4.0 Pg C a^-1 and 4.2 Pg C a^-1.Nationally,GPPsun accounted for about 32%of all GPP,GPPshade accounting for about 68%of all GPP.The interannual fluctuation of GPP terrestrial ecosystem in China is mainly caused by the fluctuation of GPPshade.?3?Effects of different factors on temporal and spatial variation of GPPIn 70.4%of the vegetation areas,the rise in LAI will lead to an increase in GPP.In 78%of the grassland,71%of cropland and 61%of the forest,LAI promoted the increased of GPP.In the arid and semi-arid areas of the northwest,Inner Mongolia,western Liaoning,western Jilin and North China,the increase of precipitation will lead to the increase of GPP?p<0.05?;In most parts of Inner Mongolia,Greater Khingan Range and Heilongjiang,annual precipitation increases,leading to a marked decline in GPP?p<0.001?.In eastern Jilin,Eastern Liaoning,Tibet,Anhui,Jiangsu,western Sichuan,Zhejiang,Fujian,Guangdong,northern Yunnan,eastern Guangxi,southern Shaanxi,western Hubei and Henan and other southern regions,precipitation rise will cause the loss of GPP?p<0.05?.The spatial pattern of rainfall and the effect of temperature on GPP on the contrary,in the southeast cormer of Tibet,eastern Inner Mongolia,eastern Gansu,Tianshan Mountain and Altai Mountains of Xinjiang,northern Shanxi,Hebei,northern Shaanxi and Northern Shandong,GPP negatively correlated with temperature?p<0.1?.In most parts of China,GPP is positively related to temperature,in which the correlation coefficient between GPP and annual mean temperature in central and western of Sichuan,central China,Southern China and southeast China is reached p<0.1,At the junction of Qinghai and Sichuan,the coefficient of correlation coefficient between GPP and temperature reached a significant level ofp<0.001.