Abstract:

With the population growth, more and more land use types concentrate into ecological fragile area in China. The structure, processing and function aspects of ecosystem are changed resulted from the land use, which changes the soil quality and productivity. These phenomena are obvious especially in karst area due to the typical characteristics of harsh habitat and ecological vulnerability. Nowadays, most investigations mainly focused on karst desertification in cause-effect, controlling, etc. However, the study of the soil quality under different land use types is scarce. The soil is very important for plant growing, especially in the ecological fragile area. In order to explore the effects of land use on soil quality, field experiment combined with laboratory analyses were conducted in the forest, grassland, fruit forest and farmland of karst area in Guizhou. At the same time, the comprehensive index of soil nutrition was adopted to evaluate the sequence of 4 land use types. The results showed that there was no difference in soil bulk density, porosity and capillary moisture capacity among 4 land use types. However, the soil pH value of fruit forest significantly decreased comparing with other 3 land use types. The soil organic matter and available N content of forest were significantly higher than other 3 land use types, and the available P content of cropland and the available K content of grassland were the lowest in the counterpart chemical parameters. Land use significantly changed the characteristics of soil trace elements, and some kinds of trace elements such as the available Zn and B contents in the whole study area, the available Cu content in forest and cropland, the available Mo content in cropland were lower than the demand of plant growing. The comprehensive indices of soil nutrition in 4 land use types were ordered as grassland > forest land > fruit forest > farmland. The projects of returning farmland to forest or grassland are suggested in order to accomplish the sustainable development of soil. The findings will provide references for developing the scientific strategies of land use in fragile ecological area.

Key words: Karst, Soil use, Ecosystem, Soil quality, Availability

摘要：

为探明生态脆弱区土地利用方式对土壤性质的影响，以喀斯特山区林地、草地、经果林和农田为研究对象，对比分析了中国西南山区4种典型土地利用方式下的土壤性质。结果表明：研究区不同土地利用方式对土壤容重、孔隙度、毛管持水力等物理性质影响不显著，经果林与其他3种土地利用方式相比显著降低了土壤pH。林地土壤有机质和有效氮含量显著高于其他3种土地利用方式，农田中有效磷、草地中有效钾含量在4种土地利用方式中均为最低。不同土地利用方式改变了研究区土壤微量元素特征，整个研究区土壤有效锌及硼、林地中的有效铜、农田中的有效铜及钼的丰度处于低水平，不能满足植物生长发育需要。通过土壤养分有效性综合评价指数得出，研究区4种土地利用方式下土壤质量顺序为草地>林地>经果林>农田，建议喀斯特山区大力开展退耕还草工程，以实现土地资源的可持续发展。

关键词: 喀斯特山区, 土地利用, 生态系统, 土壤质量, 有效性