Spatiotemporal Features and Time-Lagged Effects of Drought on Terrestrial Ecosystem in Southwest China

Abstract

With global warming, the increase in the frequency and intensity of droughts have severely affected the balance of terrestrial ecosystems. Although the immediate effects of drought on vegetation growth have been widely studied, the time-lagged effects have been neglected, particularly in ecologically fragile karst areas. We examined the vegetation growth trends and abrupt changes in southwest China from 1990 to 2018 by reconstructing the normalized difference vegetation index (NDVI); we then used the standardized precipitation and evapotranspiration index (SPEI) to explore the drought evolution characteristics and the time-lagged effect of drought on vegetation growth. The results showed that 97% of the study area exhibited a greening trend, which accelerated after 1995. Spring drought increased noticeably. We demonstrated that drought had a time-lagged effect on vegetation growth; 27.28% of the vegetation lands had a lag time of less than 3 months, and the mean lagged time in karst areas was shorter than that in non-karst areas. Compared to other vegetation types, the cultivated vegetation had weaker drought resistance, while the mixed-forest had stronger tolerance to drought. This study contributes to a further understanding of the drought–vegetation relationship and has important implications for optimizing vegetation conservation strategies in southwest China while coping with climate change.