资源环境科技发展态势分析平台

Located in the subtropical monsoon climate area of China, the Yangtze River Basin (YRB) had been frequently affected by drought events recently. Based on standardized precipitation evapotranspiration Index (SPEI) and enhanced vegetation index (EVI), the characteristics of drought in the YRB and the influence of drought on vegetation in different seasons were investigated by maximum correlation (R-max) between 1981 and 2015. The results showed that: (a) Droughts occurred frequently but had no obvious regularity in the YRB from 1981 to 2015. The drought intensity in autumn and winter were slightly higher than that in spring and summer. The autumn droughts in Sichuan Basin were the most serious, followed by the spring droughts in the middle and lower reaches of the YRB; (b) Annual SPEI series at 102 stations exhibited a downward trend and 72 stations exhibited an upward trend. There was no station showing a significant downward trend and two stations showing a significant upward trend. There was a drying trend in autumn and winter, and a wetting trend in spring and summer. The eastern area of the YRB shows a more arid trend in spring and autumn, as well as in the southwest in winter; (c) 90% of YRB showed a significant positive correlation (p < .05) between SPEI and EVI during the growing season (March-October), and the vegetation was more sensitive to short-term and medium-term drought. However, there were spatial and seasonal differences in the impact of drought on vegetation. Different types of land cover had different responses to droughts. Grasslands and croplands were more sensitive to droughts, grasslands at low elevation was dominated by short-term droughts, while at high elevation was influenced by medium-long- and long-term droughts. Croplands and woodlands were more vulnerable to short-term droughts.