Abstract:

Qujing City is located in the upper reaches of the Yangtze River and the source of the Pearl River holding an important ecological position. Exploring the dynamics and evolutionary process of rocky desertification over a long time series in this area is of great significance. In this study, using Landsat5, Landsat8, DEM, etc., we obtained the rocky desertification distribution from 1990 to 2020 through the Google Earth Engine(GEE) cloud platform and decision tree classification, and analyzed the spatial and temporal change characteristics and evolution process of the rocky desertification. The results show that: 1) the overall rocky desertification in Qujing City was primarily characterized potentially rocky and no rocky desertification; in 31 years, the rocky desertification area in Qujing City decreased by 1 728.38 km², while the no rocky desertification area increased by 1 936.61 km², and the overall rocky desertification was significantly improved.(2) From 1990 to 2020, the overall change rate of rocky desertification in Qujing City was -57.61 km²/a, and the change rate decreasd as the intensity of rocky desertification aggravated: extreme intensity > intensity > moderate > mild > no > potential desertification. (3)Over 31 years, the pattern of rocky desertification evolution in Qujing City remained mostly unchanged, covering an area of 7 967.67 km², accounting for 61.39%. Continuous and fluctuating transformations, reflecting improvements in rocky desertification, covered an area of 3 197.03 km², or 24.63%. The area of deterioration was 558.52 km², accounting for 4.3%. The results indicate a general improvement in rocky desertification in the study area.

Key words: karst rocky desertification, GEE, evolution track, Qujing City