Abstract:

Based on monthly MODIS series NDVI data from NASA between February 2000 and December 2022, the vegetation condition index (VCI) was calculated, and combined with land use type data. Methods such as univariate linear regression, the Theil-Sen Median trend test, and the Mann−Kendall test were used to analyze the trend and abrupt change of VCI, the drought proportion, and the drought frequency. The spatiotemporal characteristics of agricultural drought in the Tarim river basin were explored. The results indicated that: (1) the VCI concentration in the Tarim river basin from 2000 to 2022 was between 0.3−0.6 and showed a significant increase trend. The drought proportion was showing a significant decrease trend, with the highest drought proportion being 98.4%, and the lowest being 38.6%. The most severe seasons, annual, and land use types of drought were spring, 2000 and cultivated land, respectively. The years of agricultural drought abrupt changed in the Tarim river basin and its different land use types (cultivated land, wood land, meadow) were in 2011, 2010, 2014, and 2015, respectively. (2) The proportion of VCI spatial changes showed a highly significant increasing trend during the growing season was the highest, accounting for 63.50%. The frequency of agricultural drought in spring, summer, autumn, and growing season was mainly concentrated in the range of 50%−100%. The regions where VCI spatial changes showed a significant increasing trend, mainly distributed in the central and southeastern parts of Kaidu−Kongque river, the central part of Aksu river, the central and northeastern parts of Kashgar river. The low−frequency areas where agricultural drought occurs were mainly distributed in the southern part of Hotan river, the southern part of the small rivers of Crimea river, and the northern and southwestern parts of the small rivers of Chechen river. Overall, the agricultural drought in the Tarim river basin from 2000 to 2022 is mainly characterized by regional drought and shows a decreasing trend year by year.

Key words: Vegetation condition index (VCI), Agricultural drought, Spatiotemporal characteristics, Tarim river basin