Impact Of Drought In Xilin Gol Grassland On Net Primary Productivity From 2001 To 2018

Vegetation net primary productivity(NPP)is an important indicator reflecting the vegetation growth status of terrestrial ecosystems,and can intuitively reflect the impact of drought on vegetation productivity.In recent years,the drought in Xilinguole grassland has been widespread,which has caused a great impact on the production of vegetation.By discussing the impact of drought on the net primary productivity of vegetation in the Xilinguole grassland,it can reveal how the drought has affected the grassland ecosystem,providing a reference for regional ecological construction and sustainable economic development.In the study,MODIS remote sensing data,meteorological data,and field measured data were used to simulate the drought conditions and vegetation NPP in the growing season of Xilinguole grassland from 2001 to 2018.After analysis,the impact of drought on vegetation NPP was finally discussed.The conclusions are as follows:(1)From 2001 to 2018,the Xilinguole grassland was mainly light drought,followed by moderate drought,and less severe drought.The areas with high drought accumulation intensity in the study area are mainly distributed in the typical steppe regions in the middle east and the desert steppe regions in the west.Months with a wide drought area and high cumulative intensity include May,June,and July.From 2001 to 2018,the interannual change of the proportion of the cumulative area of drought in the Xilinguole grassland showed a downward trend,which indicates that the drought in the study area is alleviating,with each month being mainly light drought.(2)Based on the least square method,the maximum light energy utilization rate ?max of the sandy land in Xilinguole grassland was simulated.The maximum light energy utilization rate of the obtained sandy vegetation was 0.561 gc MJ-1.It was verified by field data.Simulation of grassland sandy vegetation NPP.(3)The vegetation NPP in Xilinguole grassland showed an overall increasing trend from 2001 to 2018.The interannual variability of NPP was consistent with the variability of precipitation and the opposite of the variability of temperature.There is a certain difference in the correlation between the NPP and temperature and precipitation of the four vegetation types: The meadow NPP,typical steppe,desert steppe,and sandy land have a significant positive correlation with precipitation.Land> Meadow Steppe> Desert Steppe.NPPs in meadow steppe and desert steppe have a negative correlation with temperature;NPPs in typical steppe and sandy land have no significant correlation with temperature.For different vegetation types,the effects of temperature and precipitation on vegetation NPP also differ in different months.(4)The NPP of Xilinguole grassland has obvious differences from east to west,and gradually decreases from east to west.The spatial distribution characteristics are consistent with the vegetation types and consistent with the spatial distribution characteristics of precipitation.The vegetation NPP in most areas of the study area is affected by precipitation.The vegetation types mainly include most typical steppe,sandy land,and a small part of meadow steppe.The areas affected by temperature and precipitation are mainly distributed in the western desert steppe,most meadow steppe,and the north and northeast of typical steppe.The area where temperature only plays a decisive role in NPP is small,scattered in desert grasslands and typical grasslands in the east.Areas determined by other factors are found in all types of vegetation and occupy a small area.(5)Vegetation NPP in most areas of Xilinguole grassland will be affected by drought,and the occurrence of drought will inhibit vegetation NPP productivity to varying degrees.After the drought,the area that will inevitably lead to the decline of vegetation NPP accounts for about 32.4% of the total area of the study area.The vegetation types mainly include meadow grasslands,typical grasslands in the east and south.(6)Drought frequency will have a certain impact on vegetation NPP,and there are differences in the impact on different types of vegetation: for desert steppe,the more frequent the drought,the smaller the impact on vegetation NPP;and for other vegetation,Especially in the typical steppe of central and eastern China,the higher the frequency of drought,the greater the impact on vegetation NPP.(7)With the increase of drought intensity,the decline of vegetation NPP also increased.Different periods of light drought,moderate drought and severe drought have different impacts on vegetation NPP.In different vegetation coverage areas,except for the mean distance of meadow NPP vegetation NPP and drought intensity were not significantly related,the vegetation NPP of typical steppe,desert grassland,and sandy land showed a downward trend with increasing drought intensity.During the growing season of Xilinguole grassland,the proportion of accumulated area of drought was opposite to that of vegetation NPP.The proportion of accumulated area of drought area was higher and the vegetation NPP was lower.