关键词: 生态环境质量, 演变机制, 趋势分析, 最优参数地理探测器, 喀斯特

Abstract:

The ecological environment is the cornerstone of the survival and development of human society. In recent years, due to the excessive exploitation of resources and the impact of extreme meteorological disasters, the global ecological environment has been facing great threats, especially in ecologically sensitive and fragile areas. However, in ecologically sensitive and fragile areas, the intertwining of poverty and fragile ecological environments can lead to mutual effects. The rocky desertification area in Southwest China is one of the three major karst distribution areas in the world, and the Yunnan-Guangxi-Guizhou rocky desertification area is the main area where the ecological fragility of karst desertification is intertwined with the population poverty. This not only affects the social and economic development of the region but also poses a major challenge to its ecological environment protection and restoration. Therefore, studying the spatial and temporal evolutionary patterns of the ecological environment and its driving mechanisms in this region is crucial for formulating ecological environmental protection and restoration measures, and guiding regional planning and development. Based on natural geography and spatial theory perspectives, this study used multi-source remote sensing data as an application, spatiotemporal analysis using ArcGIS software, combined with Theil-Sen trend analysis, the Mann-Kendall test, the coefficient of variation, the Hurst index, and other methods to analyze the ecological environment quality of the Yunnan-Guangxi-Guizhou rocky desertification area from 2001 to 2021 and to assess the ecological environmental quality of the Yunnan-Guangxi-Guizhou rocky desertification area. We analyzed the spatio-temporal evolution of ecological environment quality and its driving mechanism from 2001 to 2021.This study analyzed the spatiotemporal evolution of the ecological environment from two levels: past evolution trends and future evolution trends. In addition, the factor detection, interaction detection, risk detection, and spatial data discrete optimization functions of the Optimal Parameter Geo-Detector model are also utilized to explore the driving mechanisms affecting spatial and temporal changes in the ecological environment at the optimal spatial effect scale at three levels (surface environment level, climate condition level, and economic and social level) from two perspectives: natural geographic conditions and anthropogenic disturbances. We obtained the following results: 1) Characteristics of the temporal and spatial changes in the ecological environment. The temporal and spatial changes in the ecological environment were remarkable. The mean value of the ecological environment quality increased from 0.52 in 2001 to 0.61 in 2021, showing a decreasing and then increasing trend. The mean value of the ecological environment quality dropped to its lowest in 2005 and continued to rise after 2013, indicating that the recovery of the ecological environment is long-term and sustainable. The spatial distribution of ecological quality generally shows a pattern of “high in the east and low in the west”, which is typical of a karst landscape in which the quality of the ecological environment decreases with an increase in altitude. 2) The evolution of the ecological environment and its spatial characteristics showed clear trends. Between 2001 and 2021, 57.23% of the ecological environment quality in the region showed a clear improvement trend, mainly concentrated in the central Guangxi area, the junction of the three provinces (autonomous regions), and other areas at a lower altitude. In addition, 11.79% of the regions showed a decreasing trend, and these regions were mainly distributed in the Guizhou and Yunnan areas, again indicating that the spatial distribution of the ecological environment decreased with increasing altitude. The maximum value of the coefficient of variation of changes in ecological quality in the study area was 0.4, and the mean value was 0.07, indicating that the fluctuation of changes in ecological quality over the past 21 years was low, with 33.82% of the area having a low fluctuation rating of ecological quality. In the analysis of future trends, the percentage of areas showing an improving trend of development was higher than the percentage of areas showing a decreasing trend of development, with 53.91% of the areas showing an improving trend; however, the degradation trend still reached 40.64%, which calls for strengthening the monitoring of these areas. 3) Factors that influence the evolution of ecosystem quality and the establishment of optimal risk thresholds were also considered. From 2001 to 2021, the evolution of ecological environment quality in the Yunnan-Guizhou-Guizhou rocky desertification area is affected by both natural geographic conditions (elevation, slope, slope direction, precipitation, actual evapotranspiration, surface temperature, air temperature) and anthropogenic disturbances (land cover type, degree of land development and utilization, population density, GDP, nighttime light), and the co-interaction between them is a much stronger driver of ecological environment quality. The driving force for ecological environment quality was stronger under the joint interaction of the two. The strongest and weakest influences on the spatial and temporal evolution of ecosystem quality, respectively, were the degree of land development and utilization, daytime surface temperature, land cover type, actual evapotranspiration, population density, elevation, mean annual temperature, mean annual precipitation, GDP, nighttime lighting, slope, and slope orientation. This finding suggests that human activities have a more significant impact on the quality of the ecological environment. We subdivided the physical geographic and anthropogenic perspectives into three dimensions and explored the optimal risk thresholds for each driver based on these three dimensions. Among the surface environmental factors, the highest ecological quality values were reached when the land cover type was forest or shrub, the elevation was above 442 m and below 673 m, the slope was between 27.5° and 33.3°, and the slope direction was between 1.09° and 3.36° (northern slope). Among the climatic conditions, the ecological quality was best when the annual precipitation was 2850-3000 mm, annual mean temperature was 26.1-27.3 ℃, surface temperature was 25.3-28.7 ℃, and actual evapotranspiration was 1440-1980 mm. Among the economic and social factors, the ecological environment quality is best when the GDP is in the range of 0-789 yuan·km⁻², the population density is in the range of 39.8-71.3 people·km⁻², the light at night is in the range of 0-0.46, and the degree of land development and utilization is in the range of 204-212. This study provides beneficial theoretical references for solving the problems of resource utilization and environmental protection in ecologically fragile and poorly overlapping areas.

Key words: ecological quality, evolutionary mechanisms, trend analysis, optimal parameter geo-detector, karst