Evolution of rocky desertification and its response to land use changes in the karst areas of Guangxi

ZHU Degen; YANG Hui; ZHAO Hu; SHI Shaoliang; WU Xiuqin; Mitja Prelovšek; Nataša Ravbar

doi:10.11932/karst2024y042

Abstract：This study focuses on the karst areas of Guangxi,Southwest China,which cover an area of 9.87× 104 km2(accounting for 41％of Guangxi's total land area)and feature a subtropical monsoon climate,complete karst landforms(dominated by peak cluster depressions,peak forests,and peak cluster valleys),and a fragile ecological environment with thin soil layers(mostly less than 30 cm)and severe rocky desertification.The study aims to quantitatively analyze the impact of land use change on rocky desertification in the Guangxi karst area,resolve the lack of quantitative assessment of such impacts in previous studies,and provide a scientific basis for rocky desertification control and ecological restoration. Based on Landsat data and land use data of Guangxi from 2001,2006,2011,2016,and 2020,GIS methods were used to construct a rocky desertification transfer matrix,a land use transfer matrix,and their interaction matrix.Additionally,the Habitat Quality Change Index(CI)and Habitat Quality Contribution Index(HQCI)were introduced to evaluate the effect of land use conversion on rocky desertification.Rocky desertification was classified into five grades using the NDVI-based vegetation coverage method,and the accuracy verification was conducted with 92 field survey points.The results showed that:(1)Both rocky desertification and land use in the study area showed a dynamic improvement trend.Spatially,rocky desertification presented the characteristics of"severe in the west and mild in the east,severe in the south and mild in the north",which was correlated with the spatial distribution of cropland("increase in the east-west and decrease in the north-south")and forestland("decrease in the east-west and increase in the north-south").(2)Different land use conversions had distinct effects on different rocky desertification grades:grassland conversion to forestland had the most significant improvement effect on severe rocky desertification,cropland conversion to forestland was effective for moderate and mild rocky desertification,and shrubland conversion to forestland worked best for potential rocky desertification.(3)Vegetation restoration was the main driving force for rocky desertification control.According to HQCI,cropland conversion to forestland contributed the most(HQCI=1.196),followed by shrubland to forestland(HQCI=0.328)and forestland to shrubland(HQCI=0.095);conversions of other land use types to grassland had negative contributions. In conclusion,land use change has a significant impact on rocky desertification evolution in the Guangxi karst area.Targeted land use adjustment(e.g.,converting cropland,grassland,and shrubland to forestland based on rocky desertification grades)can effectively promote rocky desertification improvement.Future study should further explore the application effects of different ecological restoration technologies to optimize rocky desertification control strategies.