Spatial and Temporal Variation Characteristics of Vegetation Greenness in Rocky Desertification and Non-rocky Desertification Areas of Chongqing

Abstract

[Objective] The investigation of temporal and spatial variations in vegetation greenness and its response to different land use types in karst rocky desertification and non-rocky desertification areas in Chongqing is crucial for guiding ecological restoration efforts in karst regions. [Methods] This study utilized vegetation leaf area index (LAI) data and land use type information to conduct a trend analysis and Hurst index calculations, aimed at analyzing the temporal and spatial evolution characteristics of vegetation greenness in both rocky desertification and non-rocky desertification areas. Additionally, a land use transfer matrix was employed to quantitatively assess the impact of land use changes on vegetation greenness. [Results] (1) Vegetation greenness exhibited an increasing trend in both rocky desertification and non-rocky desertification areas, reaching maximum values of 1.36 and 1.69 respectively, with average annual growth rates of 0.014 and 0.012. (2) The dynamic changes observed in vegetation greenness within these areas demonstrated positive trends, with improvement trends accounting for 86.84% (rocky desertification) and 87.04% (non-rocky desertification). Furthermore, anti-continuous improvement trends were observed at rates of 52.82% (rocky desertification) and 80.29% (non-rocky desertification), indicating the primary change trajectory for future vegetation greenness. (3) The main land use types in both rocky and non-rocky desertification areas were woodland and cropland, and cropland converted from woodland was the main occurrence of degradation of vegetation greenness, while woodland converted from cropland, shrubs and grassland was the main occurrence of improvement of vegetation greenness. (4) The conversion of land use types with high leaf area index (LAI) to those with low LAI resulted in a decrease in LAI and vegetation greenness, while the conversion from low LAI land use types to high LAI land use types led to an increase in LAI. In areas affected by stony desertification and non-stony desertification, the maximum reduction in total LAI transfer was 11 902.04 and 4 442.18 respectively, whereas the maximum increase was 14 983.78 and 17 109.46 respectively. The impact on total LAI from construction land, water area, and bare land area was minimal and not significant. [Conclusion] These research findings contribute to understanding the change characteristics of vegetation greenness and its response mechanism towards land use changes in ecologically fragile areas. Furthermore, they provide a scientific basis for controlling rock desertification, ensuring ecological security, and promoting sustainable economic development in karst areas of Chongqing.

Keywords

• rocky desertification and non-rocky desertification
• vegetation greenness
• leaf area index
• the temporal and spatial variation trend
• land use types