不同土地利用方式对岩溶作用的影响——以广西弄拉峰丛洼地岩溶系统为例

土地利用可使土壤理化性质产生一系列的变化。从而影响到岩溶作刚的方向和强度。以广西马山县弄拉典型峰丛洼地区为例．通过野外溶蚀试片法探讨丁不同土地利用方式对岩溶作朋的影响。结果表明不同土地利用类型土下溶蚀量存在显著差异。林地与同地土下溶蚀量极大部分大于20mg／a．明显高于灌丛地及（休）耕地（多小于20mg／a）。总体上，溶蚀量从大到小依次为同地、林地、耕地、休耕地与灌丛。其中至少有两个主要控制因素：土壤有机质和土壤CO2；林地和园地土下溶蚀作用主要受前者控制．土壤有机质含量越高、pH越低，土下溶蚀量越大。在耕地与灌丛条件下由于土壤有机质含量较低．土下溶蚀量主要受土壤CO2控制．

Impact of Land-use Patterns upon Karst Processes: Taking Nongla Fengcong Depression Area in Guangxi as an Example

Previous study on karst processes was always focused on karstification intensity and its variation under different geological settings, climatic and hydrologic conditions in view of macroscale, or on contribution of carbonate rock weathering to the atmospheric CO2 sink. Lesser attention was paid to impact of land-use types on karst processes. The direction and intensity of karst processes could be deeply affected by soil physical and chemical variations which were resulted from land cover. Taking Nongla Fengcong depression area, Mashan County, Guangxi as an example, the authors discussed the impact of landuse cover on karst processes based on the data of field standard limestone tablet. Almost all the land-use types occurred in a small study area, so the present study is also typical and representative. The results showed that the corrosional ratio at varied soil depth is quite different. Corrosional ratio in woodland and orchard is mostly bigger than 20mg/a, which is much higher than that in cultivated land and shrubs. Generally, corrosional ratio decreased from orchard, woodland, tilled land, fallow and shrubs successively, in which soil organism and soil CO2 are two major controlling factors: corrosion process is controlled remarkably by soil organism in woodland and orchard, the higher the organism content is and the less the pH value is, the higher the corrosional ratio is. Owing to lower organism content, the corrosional ratio affected mainly by soil CO2 in tilled land and shrubs. The impacts of land-use types on karst processes could be active to improve corrosional rate, for example organic fertilization in orchard resulted in soil organic matter increase; or negative to retard corrosional rate, for example surface disturbance in tilled land resulted in soil porosity increase and CO2 emission. Moreover, organism activities and their offspring could be the most active factor, vegetation succession can improve the three-phase condition of karst dynamics system, and thus accelerate the karst processes. Accordingly, the results of this paper have significance of protecting karst fragile soil resources and readjusting land-use structure in Fengcong mountainous area.