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区域尺度喀斯特区石漠化强度对土壤流失的影响

Influence of rocky desertification intensity of karst areas on soil loss at a regional scale

  • 摘要: 石漠化和水土流失是西南喀斯特区突出的生态问题,制约着社会经济的发展。目前,石漠化与土壤流失的耦合关系尚未系统探明,石漠化强度评价因子植被盖度、土层厚度和基岩裸露率的交互作用如何影响土壤流失知之甚少。基于石漠化现状的调查,采用RUSLE模型、Getis?OrdGi*、地理探测器等方法,测算了贵州喀斯特区土壤侵蚀状况并识别了冷热区分布,量化了石漠化强度评价因子与土壤侵蚀之间的关系,解析了因子组合对土壤流失的交互影响。结果表明:1)贵州喀斯特区土壤侵蚀以中度和微度侵蚀为主,平均土壤流失率17.69 t/(hm2·a),侵蚀热区(重点防治区)主要集中在贵州西部经济相对欠发达区,侵蚀冷区(轻微区)则主要集中在黔北遵义市和黔中贵阳市等经济相对发达区。2)土壤流失随石漠化强度评价指标植被盖度、土层厚度的增加呈降低趋势,随基岩裸露率的增加则呈增加趋势;石漠化与土壤流失之间并非简单的线性关系,而呈复杂的非线性关系,3个评价因子分别以三次曲线函数、指数函数和反正弦函数拟合优度最高。3)石漠化强度评价因子对土壤流失空间分异的解释力依次为植被盖度、基岩裸露率和土层厚度,且因子组合对土壤流失的交互影响均呈非线性增强,其中基岩裸露率与植被盖度的交互作用起主导作用,其次是土层厚度与植被盖度,基岩裸露率与土层厚度的解释力最小。研究结果可为喀斯特区水土流失、石漠化的协同防治提供理论参考。

     

    Abstract: Rocky desertification and water and soil loss are prominent ecological problems in karst area of Southwest China, which restrict the development of social economy. At present, the coupling relationship between rocky desertification and soil loss has not yet systematically proven, and how the interaction of rocky desertification intensity evaluation factors-vegetation coverage, soil layer thickness and bedrock exposure rate affects soil loss is ill-informed. Based on the investigation of the current situation of rocky desertification, the RUSLE model, spatial association index Getis-Ord Gi* analysis, Spearman correlation analysis, geographic detector and other methods were used to calculate the soil loss status in karst area of Guizhou Province(103°36′-109°35′E、24°37′-29°13′N), identify the distribution of cold and hot zones, quantify the relationships between rocky desertification intensity evaluation factors and soil loss, and analyze the interactive effects of factor combination on soil loss. The results showed that: 1) The soil erosion in karst area of Guizhou was dominated by moderate and micro erosion, with a total of 65 469.32 km2, accounting for 58.71% of the total study area, and with an average soil loss rate of 17.69 t/(hm2·a). Erosion hot zones (major prevention and control area) were mainly in the relatively underdeveloped areas in western Guizhou, such as the eastern part of Bijie City, the western part of Anshun City, the central part of Liupanshui City and the junction of Bijie and Liupanshui, and the total area of erosion hot zones was 31 617.18 km2, accounting for 28.35% of the total study area; while erosion cold zones (slight area) were mainly in relatively economically developed areas such as Zunyi in northern Guizhou and Guiyang in central Guizhou, with a total area of 22 533.26 km2, accounting for 20.21%. 2) Soil loss had a significant negative correlation with vegetation coverage and soil layer thickness, and had a significant positive correlation with the exposure rate of bedrock. The correlation coefficients were -0.067, -0.022 and 0.025, respectively. The relationship between rocky desertification and soil loss was a complex nonlinear relationship. Among them, the relationship between vegetation coverage and soil loss was optimal by a cubic curve function. The relationship between soil layer thickness and soil loss could be described by an exponential function. And the arcsine function had the highest goodness of fit between the exposed rate of bedrock and soil loss. 3) The explanatory power of the evaluation factors of rocky desertification intensity on the spatial differentiation of soil loss was the highest by vegetation coverage, followed by bedrock exposure rate and soil layer thickness. The interaction effects of the factor combination on soil loss were all non-linear enhancement, among which the interaction between the exposed rate of bedrock and vegetation coverage had the strongest explanatory power for the spatial difference of soil erosion, playing a leading role in the spatial differentiation of soil erosion. It was followed by the thickness of soil layer and vegetation coverage, with the least explanatory power for exposed rate of bedrock and soil layer thickness. The results provide valuable information for the coordinated prevention and control of water and soil erosion and rocky desertification in karst area.

     

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