近20年新疆荒漠草地动态变化及其对气候变化的响应

荒漠草地是干旱半干旱区陆地生态系统的关键类型,具有重要的生态作用,对气候变化和人类活动敏感.通过确定新疆荒漠草地NDVI阈值,提取荒漠草地范围,结合归一化植被指数(normalized difference vegetation index,NDVI)、植被净初级生产力(net primary productivity...

Desert grassland dynamics in the last 20 years and its response to climate change in Xinjiang

Desert grassland is a key type of land ecosystem in arid and semi-arid areas.Desert grassland has an important ecological role and is sensitive to human activities and global change.In this paper,we studied the dynamic changes in desert grassland in Xinjiang and the responses to different driving factors on different time scales and spatial scales for the period 1999-2018.We first extracted the coverage of desert grassland in Xinjiang and determined the desert grassland threshold values for normalized difference vegetation index(NDVI).Then,we used a unitary linear regression model,correlation analysis and other methods to combine NDVI,net primary productivity(NPP),meteorological factors and other data to study the changes in area of desert grassland and their driving mechanisms.The results showed that:1)There were differences in the distribution of desert grasslands in the North and South of Xinjiang during the study period.Over all the area of desert grassland decreased significantly,while the average NDVI was relatively stable,and the NPP showed an upward trend.2)Meteorological factors over the study period showed different trends at different times of the year.In July and August there were significant differences between North and South Xinjiang.Temperature and precipitation in most regions of Xinjiang increased between 1999 and 2018.3)In terms of interannual changes,precipitation,high evaporation events,and average wind speed are the important factors affecting NDVI of desert grasslands in Xinjiang.The effect of water conditions on NDVI in the growing season is more obvious.There is a significant negative correlation between annual evaporation and desert grassland NPP,and average wind speed and precipitation have a correlation with desert grassland NPP.4)In terms of spatial correlation,the area where temperature and precipitation are positively correlated with the NDVI and NPP of desert grassland is larger than that dominated by other factors,and the area where the precipitation effect dominates is larger than that driven by temperature.It was concluded that the dynamic changes of desert grassland in Xinjiang were the result of the combined effects of multiple meteorological factors.Temperature and precipitation were the main factors of influence,and of these the impact of precipitation was more obvious.Water status is the decisive factor driving dynamic vegetation change in desert grassland.