Response And Sensitivity Analysis Of Phenology Of Alpine Grassland To Climate Change In The Tibetan Plateau

Plant phenology is one of the best indicators of the response of terrestrial ecosystems to climate change.As a sensitive region of global climate change,the ecosystem of Tibetan Plateau is especially fragile.Therefore,it is of great significance to study the phenology of alpine grassland in Tibetan Plateau and its response and sensitivity to climate change.Based on GIMMS NDVI data and climate factors(annual average temperature,annual precipitation and annual radiation)of alpine grassland in the Tibetan Plateau from 1982 to 2013,this study studied the temporal and spatial changes of phenology and climate of alpine grassland in the Tibetan Plateau from 1982 to 2013,and further discussed the response and sensitivity analysis of phenology of alpine grassland in the Tibetan Plateau to climate change.The main results and conclusions are as follows:(1)Due to the influence of climate and topography,the spatial distribution of the average phenological mean of alpine grassland in the Tibetan Plateau is quite different.From southeast to northwest,the Start of growing season(SOS)of vegetation is gradually delayed.In addition,the Peak value of growing season(POS)in the Tibetan Plateau is gradually postponed from north to south.From northeast to southwest of the Tibetan Plateau,the End of growing season(EOS)shows a trend of gradually postponing,while the Length of growing season(LOS)shows a trend of gradually extending.In different phenological stages,the differences between southwest and northwest are obvious.(2)From 1982 to 2013,the overall interannual trend of phenology of alpine grassland vegetation on the Tibetan Plateau was shown as SOS delay,with a delay range of 0.08d/a(R~2=0.1001,P=0.08).POS generally shows an advance trend,and the advance range is 0.08d/a(R~2=0.06,P=0.16).Overall,EOS showed a significant advance trend,with the advance range of 0.28d/a(R~2=0.21,P=0.008).Overall,LOS showed a significant trend of shortening,with a shortening range of 0.26d/a(R~2=0.31,P<0.001).(3)From 1982 to 2013,the phenology of alpine grassland vegetation on the Tibetan Plateau was significantly different in space,and the advance trend of SOS increased from northwest to southeast of the Tibetan Plateau.The advance trend of POS and EOS in the southeast,central and northern regions of the Tibetan Plateau was greater than that in the southwest and northeast.Under the combined action of SOS and EOS,the shortening trend of LOS in the northeast and southwest regions is less than that in the central and northern regions.(4)The annual average precipitation of the Tibetan Plateau from 1982 to 2013 was mainly distributed in the southeast,the annual average temperature in the southwest and southeast was higher than that in other regions,and the annual average radiation was mainly distributed in the western and northern regions.From 1982 to 2013,the annual precipitation and annual average temperature on the Tibetan Plateau increased significantly,and the annual radiation decreased significantly.In terms of space,the annual precipitation in the southwest of the Tibetan Plateau shows an increasing trend,the annual average temperature in the northwest and north shows an increasing trend,and the radiation in the northwest shows an increasing trend.(5)In regions with higher average annual temperature,more sufficient annual precipitation and more sufficient annual radiation,SOS of alpine grassland vegetation is usually delayed.The influence of annual average temperature on POS of alpine grassland vegetation is greater than that of annual precipitation and annual radiation.The higher the annual average temperature,the earlier the vegetation POS.The more abundant the annual precipitation and annual radiation,the later the vegetation POS.The effect of annual average temperature on EOS of alpine grassland was greater than that of annual precipitation and annual radiation.The higher the average annual temperature,the earlier the vegetation EOS.The more abundant the annual precipitation and radiation,the later the EOS is usually.The influence of annual average moderate annual precipitation on alpine grassland vegetation LOS is greater than that of annual radiation.Vegetation LOS tended to shorten with the increase of annual average temperature and sufficient annual precipitation,while vegetation LOS tended to lengthen with the increase of radiation.In general,the influence of annual average temperature and annual radiation on different phenological stages of alpine grassland vegetation is relatively greater than that of annual precipitation and annual radiation.However,the effects of annual average temperature,annual precipitation and annual radiation on phenological changes of alpine grassland at different growth stages were limited.(6)From 1982 to 2013,SOS precipitation sensitivity,SOS temperature sensitivity and SOS radiation sensitivity on the Tibetan Plateau all showed a decreasing trend with the interannual variation,of which SOS precipitation sensitivity(R~2=0.13,P<0.05)and SOS radiation sensitivity(R~2=0.12,P<0.05)showed a significantly decreasing trend.POS precipitation sensitivity and POS radiation sensitivity showed a slight decreasing trend with the interannual variation,while POS temperature sensitivity showed a significant increasing trend(R~2=0.16,P<0.05).EOS precipitation sensitivity and EOS temperature sensitivity showed an increasing trend with the interannual variation,in which EOS temperature sensitivity showed a significant increasing trend(R~2=0.33,P<0.05),and EOS radiation sensitivity showed a decreasing trend.The interannual variation of LOS precipitation sensitivity and LOS temperature sensitivity showed an increasing trend,of which LOS temperature sensitivity showed a significant increasing trend(R~2=0.26,P<0.05),and LOS radiation sensitivity showed a decreasing trend.