Land-space ecological restoration zoning of karst rocky desertification areas in Guangxi from multi-dimensional perspectives

Ecological restoration zoning has been one of the most important prerequisites for the efficient ecological restoration in recent years. An accurate identification can be determined the key ecological restoration areas and developing engineering projects. Taking the Hechi areas of Guangxi Province in China as an example, this study aims to build a zoning framework of "natural conditions-dominant ecological functions-ecological stress problems" using the concept of mountains-rivers-forests-farmlands-lakes-grasses-deserts. The quantitative evaluation and qualitative zoning were combined to delineate the ecological restoration zones. Firstly, the natural regions were the basic components for the ecological restoration, the integrity of the natural elements, and the continuity of geographic pattern. The natural regions were divided according to natural conditions such as watershed distribution, geomorphological classification, fractional vegetation cover, and vegetation type distribution. Secondly, the ecological evaluation was carried out on the ecosystem in the study area, in order to determine the objectives and tasks of ecological restoration. Both ecological functions and ecological stress problems were considered during evaluation. According to the restoration needs, five indicators were selected from the ecosystem service function, including the habitat quality, water conservation, carbon storage and oxygen release, soil and water conservation, food production. Six indicators were set as the ecological stress problems, including the stony desertification, soil erosion, mine geological hazards, ecological degradation, restoration potential of water environment, and potential of comprehensive land consolidation. After that, 11 indicators were evaluated and graded to obtain the distribution pattern of dominant ecological functions and ecological stress problems using the K-means cluster analysis and ArcGIS visualization function. Finally, the comprehensive analysis was weighed via the dominant ecological functions and ecological stress problems of the natural regions. Six natural regions were divided into 15 ecological restoration subregions using sub-watershed boundaries and township administrative boundaries. The results showed that: 1) The strong functions of ecological service were observed in the mountainous and hilly ecological restoration subregions in the northwest and northeast. Ecological stress problems were mainly geological disasters, such as historical mines, soil erosion, as well as stony desertification. One suggestion was proposed that these subregions can be expected to focus on the protection and mine restoration for the disaster prevention in small watershed. 2) The weak functions of ecological service were found in the ecological restoration subregions in the Longjiang Plain and hilly region or the Panyang River mesa region. The comprehensive and relatively serious problems were posed the ecological stress on the heavy task of ecological restoration. One suggestion was addressed to carry out the comprehensive regulation of multiple ecological systems in these subregions. 3) An important karst area was found in the Duyang Mountain mountainous and hilly region in the south, with the serious problems of soil erosion and stony desertification. Correspondingly, the special ecological restoration should be carried out for the ecological restoration subregions. Quantitative ecological evaluation can provide a scientific and objective basis to delimitate the restoration zoning. By dividing and adjusting the ecological restoration zones with the boundaries of sub-watersheds and townships, the problems of separate protection and individual restoration of each element can be solved, ensuring the feasibility of restoration implementation. The finding can provide a strong reference for the comprehensive, systematic and holistic implementation unit delineation of mountains-rivers-forests-farmlands-lakes-grasses-deserts, together with the scientific basis for the delineation and implementation of key areas and key projects for the ecological restoration in Hechi of China.