粤北岩溶山地土壤地下漏失程度评价指标构建探讨

为了弥补岩溶区地下土壤漏失程度评价指标体系空白，基于在粤北岩溶区连南县多个岩溶山地采矿断面、公路修建断面实地调查获得的56条裂隙、40个漏斗和多个孔穴的调查数据，以及粤北岩溶丘陵、峰林区英德市岩背镇、九龙镇等40多个样方的地表景观实地调查资料，探讨构建岩溶地下土壤漏失程度评价指标与标准。首先，充分考虑了土壤漏失途径、阶段、各指标的关联性、断面调查数据及数据采集的可操作性等，将定性指标与量化指标结合，采用裂隙、洞穴、漏斗3个一级指标和与溶洞连通度、断面比、密度，洞穴类型、数量、位置，漏斗深宽比、形状、周边裂隙发育情况9个二级指标，构建了岩溶区地下漏失无漏失、轻度漏失、中度漏失、重度漏失分级标准；其次，将基岩、地貌、地形、岩石裸露率、植被结构、类型、盖度和土壤深度等地表景观特征作为地下漏失程度的辅助参考指标，使地下漏失评价与地表石漠化程度评价能够有机结合，共同形成岩溶环境评价的整体系统。

Grading Standard for Determining Underground Soil Leakage in a Mountain with Karst Topography in the North of Guangdong Province

Soil transfer and loss on the surface of terrain with karst topography due to fissures or caves in carbonate rocks, together with rainwater infiltration is a universal phenomenon. The degree of soil loss increases with increases in combined geological conformation movement, physical and chemical weathering, and corrosion. The combined action of underground soil leakage and surface erosion can lead to changes in the karst ecosystem and degeneration of soil and vegetation. Establishment of a grading standard for underground soil leakage is essential for assessing and analyzing degradation of karst ecosystems. For this purpose, a field study was conducted in Karst Mountain located in Liannan County, covering eight surfaces fractured by mining and road building, over 40 quadrats in Karst Hill, and the needle area of Yanbei town, Jiulong town, and Yingde city, north of Guangdong province. Based on field survey, we had got basic data, including data on 56 fissures, 40 doline funnels, and some karst caves in fractured surfaces, in addition,together with research results and survey data collected over 10 years in the Karst Mountains, hill, and needle Karst landscape, a grading standard for underground soil leakage, and a reference index for landscape characteristics of Karst mountain surfaces were set and discussed. (1) Three primary indices (fissure, karst cave, and doline funnel) and nine secondary indicators (connecting fissures between Karst caves, area ratio of fissures to fracture surfaces, fissure density, type of Karst cave, quantity of Karst caves, Karst cave location, doline funnel depth to width ratio, doline funnel shape, and fissure development surrounding a doline funnel) were selected. Underground leakage was stratified into four levels: no soil leakage, light soil leakage, moderate soil leakage, and serious soil leakage. The pathway of soil leakage, stage, relevance among all indicators, survey data from all fracture surfaces, and easily obtained index data were fully considered before selecting indices and standard data. Indicators were quantized to the extent possible, but were also combined with some qualitative indices to ensure practical grading of underground leakage. (2) Key features of karst landscape and data, including rock type, geomorphic features, landform, extent of uncovered rock, vegetation form, vegetation structure, vegetation coverage, and soil depth were selected to construct a reference index for determining landscape characteristics of the Karst mountain surface as an auxiliary index to the grading standard for underground leakage. A combination of these two sets of evaluation criteria will contribute to the development of an intact karst ecosystem evaluation method that is fully integrated with the assessment systems for rocky desertification. (3) This new evaluation criterion system for underground soil leakage will contribute to the overall assessment of karst ecosystems, especially for assessments of water and soil loss in road building, mining, and ecological environment construction, and can help us to draft a scientifically sound environmental governance policy for karst ecosystem resource utilization. These results will support further studies on karst ecosystems and more comprehensive evaluation of degraded karst environments.