Coupled Influences and Lagged Effects of Climate and Topography on Vegetation Dynamics in Yiliang County

In order to further study the spatiotemporal dynamic changes of vegetation in Yiliang County, explore the multiple factors affecting vegetation coverage and the hysteresis of precipitation and temperature on NDVI, the Landsat8 dataset from 2014 to 2024 was selected to calculate the annual, seasonal, and monthly mean values of NDVI using the mean method and explore the interannual change trend and vegetation coverage changes in Yiliang County in the past 10 years. The coupling changes of NDVI and influencing factors were analyzed using the correlation coefficient method, and the hysteresis effect of temperature and precipitation on NDVI was explored by cross-correlation analysis. The annual mean NDVI value of Yiliang County from 2014 to 2024 was 0.5949. The seasonal mean NDVI was highest in autumn and lowest in spring, reaching a peak in August and a minimum in March. The area of vegetation increase in Yiliang County was greater than the area of vegetation decrease, and vegetation growth generally improved. The vegetation coverage rate at an altitude of 1,900-2,000 m was the highest, at 17.23%, and the largest NDVI proportion occurred at slopes of 10°-15°, at 19.42%. The area of positive correlation was larger than the area of negative correlation. Increased precipitation and a moderate increase in temperature both promote vegetation growth, and there is a lag in the effects of precipitation and temperature on NDVI.