Vegetation Dynamic And Responses To Climate Change In Four Greater Sandy Lands Of China

Four greater sandy lands are the most serious areas of sandification in China,which are highly sensitive to climate change and one of the key areas for vegetation construction in China.Understanding the response of vegetation to climate change,and quantitatively predicting possible changes of vegetation under climate change are the key road for desertification prevention and restoration of the ecological environment.Based on the historical meteorological data and the GIMMS NDVI3g data during 1982?2013,the responses of vegetation ecosystem to climate change are analyzed.Then,the possible changes of future NDVI are further estimated by the future climate scenario data.It aims to adapt to the climate change and seek benefits and avoid harm.The main conclusions are as follows:(1)Precipitation in the Mu Us Sandy Land continuously increased(0.61 mm·yr-1)from 1982 to 2013,while the other three Sandy Lands have shown a decreasing trend.For mean temperature,warming trends occurred in the historical period for four greater sandy lands,the change-rate is the largest in Mu Us Sandy Land with 0.049?·yr-1,the smallest in Horqin with 0.021?·yr-1.For potential evapotranspiration,the decreasing trend occurred in the Horqin Sandy Land,and the other three Sandy Lands all show an increasing trend in the historical period.(2)Under different climate scenarios,the annual precipitation in four greater sandy lands showed an increasing trend.Relative to the baseline period,changes in precipitation in the four greater sandy lands generally rose for four scenarios,the largest increase in the Horqin Sandy Land,rose by 9.75%,10.96%and 10.61%by 2050,for RCP2.6,RCP4.5 and RCP8.5,respectively;the smallest in the Mu Us Sandy Land,by 9.63%?10.30%?9.30%and 9.97%,respectively.For mean temperature,warming trends were projected to persist into the future;the most strongly in the Horqin sandy land rose by 1.81??1.97??1.90? and 2.15? under four scenarios.The simulated temperature increased with the most strongly changes for RCP8.5 and the smallest magnitudes for RCP2.6,when compared with the observations.Compared with the baseline period,the potential evapotranspiration increased in the Otindag Sandy Land and Mu Us Sandy Land under different scenarios,decreased in the Hulunbeir Sandy Land and Horqin Sandy Land.However,the annual increase in potential evapotranspiration in four greater sandy lands under different climate scenarios was very significant.(3)The spatial distribution of vegetation in four greater sandy lands shows a"stepwise" decline pattern from east to west in vegetation cover(NDVI),with the highest in the Hulunbuir Sandy Land and the lowest in the Mu Us Sandy Land.The trends of annual maximum NDVI and annual average NDVI are consistent in the same Sandy Land,decreasing trends accure in the Hulunbeier Sandy Land and Otindag Sandy Land,and increasing trends in the Horqin Sandy Land and Mu Us Sandy Land.Except for the areas where NDVI is stable,the areas of improvements in annual maximum NDVI for four greater sandy lands are larger than those in the degraded areas.The annual NDVI variability is the strongest and the stability is the worst in the Mu Us Sandy Land.In general,the interannual variability of NDVI in four greater sandy lands showed an increase with drought,and increased interannual variability in NDVI.(4)The average annual NPP is 164.55?529.14 gC·m-2·yr-1 in the Hulun Buir Sandy Land,75.82?453.02 gC·m-2·yr-1 in the Horqin Sandy Land,31.54?305.59 gC·m-2·yr-1 in the Otindag Sandy Land,28.65?231.17 gC·m-2·yr-1 in the Mu Us Sandy Land.The interannual changes of the NPP in four greater sandy lands showed increasing trend,a significant increase in the Mu Us Sandy Land.Spatially,the annual NPP in most areas of the Hulun Buir Sand Land shows an increasing trend,all regions of the other three Sand Lands showed increasing trend.(5)NDVI is positively linked with summer precipitation in four greater sandy lands,and there is no significant lag effect.The autumn precipitation in four greater sandy lands is also a positive effect on NDVI,but they are more closely relate to pre-precipitation in autumn.Autumn precipitation has less impact on NDVI than summer.For mean temperature,NDVI is positively correlated with temperature in spring,mostly negatively correlated with temperature in summer and autumn,but lower correlation shows that response is not sensitive to mean temperature.For potential evapotranspiration,in summer,NDVI and potential evapotranspiration show significant negative correlation,and there is a lag effect.In addition,the correlation coefficient between NDVI and potential evapotranspiration is generally lower than the correlation coefficient with precipitation in summer.It can be seen that precipitation is the main driving factor for NDVI change,followed by potential evapotranspiration,and the least sensitive to temperature.(6)Under RCP4.5 and RCP8.5,the multi-annual average of annual maximum NDVI for four greater sandy lands is higher than the average for the historical period,especially under RCP8.5.Among them,the Hulun Buir Sandy Land increased the most strongly,and the Otindag Sand Land had the smallest change.Spatially,spatial patterns of the change in the annual maximum NDVI for the same Sand Land under RCP4.5 and RCP8.5 are generally the consistent,but the proportion of the amplitude changes is different.