Abstract:

Using monthly temperature and precipitation data from Zhaosu County meteorological station in the Ili River Valley from 1956 to 2022, as well as data on the growth period of grasslands, the standardized precipitation evapotranspiration index (SPEI), regression analysis, Mann-Kendall test, and other methods were adopted to analyze the drought variation characteristics during the growing season (April to August) of alpine grasslands in the high-altitude areas of the Ili River Valley. The results showed that the annual average temperature in Zhaosu County from 1956 to 2022 was 3.5°C, with a significant upward trend of 0.3°C/10 years. The annual precipitation was 509.3 mm, showing significant interannual variability but no significant increasing trend. The drought frequency during the entire growth period of grasslands in Zhaosu County was 16.4%, with a probability of severe drought occurrence at 7.5%. The drought frequencies during the greening, tillering, heading, and flowering stages were 13.4%, 16.4%, 22.3%, and 22.4% respectively. The greening stage showed no significant drought trend, while the tillering, heading, and flowering stages exhibited significant drought trends. The results are expected to provide a scientific theoretical basis for monitoring, early warning, and defense against grassland drought disasters in Zhaosu County.

Key words: Zhaosu County, grassland, drought, SPEI, high-altitude areas, drought frequency, drought changes, Mann-Kendall Test