| The karst ecosystem in southwestern china has experienced a serious deterioration since the past 20 years due to unreasonable human activities. The land use and land cover changes have a dramatic impact on karst hydrosystem after a long-term unwise exploitation in karst regions. It is a new field to study the interaction between the ecological environment and human activities through land use and land cover changes. So the issue has both theoretical and practical significance.We choose three karst sites, named ShuiCheng Basin, GuiLin East District and CongLin Ridge-Trough Region with different land use features, as typical karst regions to analyze the karst water quality changes on temporal and spatial scale. The main methods involve field investigations and survey, water parameters measurement in situ, and water and soil samplings analysis.The karst water quality, not only bared and covered karst regions but also buried karst region, is readily damaged by the improperly human activities because of its extremely fragile characters. Results from the three study regions indicated that land use has great influence on the temporal and spatial change of karst groundwater quality. According to the previous analysis data in the three study regions, there was high quality groundwater in the early of 1980s. But the karst water quality tends to be polluted gradually during the past 20 years because of the expanding of land use on the function, the intensity and the area. Furthermore, the local pollution centers of karst groundwater quality are consistence with the intensity centers of land use. So we think that land use is the primary cause of karst groundwater pollution or deterioration.The change in the parameters or indicators of karst groundwater quality also reflects the modification of land use types and intensity in the three study regions. Generally speaking, distinguished from other land use types, most of the ions or elements content in karst springs are the lowest under the area covered with forests, due to the powerfulpurification capability of forests. The high concentrations of SO42-and NO3- in karstsprings is associated with the agriculture land use, especially with the domestic wastewater, rural rubbish and excessive use of fertilization. So the nonpoint sourcepollution is a significant character in agricultural areas. With the development of urbanization ?the agricultural land transformed to suburb land -more and morehuman-derived solutes, such as Ca2+ Mg2+ Cl- SO42-, are bring about pollution tothese karst springs. However, many of the nutrition elements of karst springs, such as K + Na+ Cl- NO3-and NH4+, were significantly higher in suburb land use than that of urban. And the high content of Pb2+ Cu2+ Cd2+ Mn2+and COD appear to be an important response to human disturbance from infrastructure, vehicles, industrial and commercial establishments. Factor analysis identified consistent relationship between industrial activity and trace elements besides common elements. In view of above analysis, complex and unreasonable land use is always associated with worse of karst water quality.The spatial difference of several of trace elements in soil - Cu Pb Zn Cr Mn - fits in with the land use distribution and spatial variation of karst water quality. It can be seen that land use has also great influence on elemental migration of soil. And spatial variation of trace elements in soil also responses to the negative environment effect of land use. It is well known that soil has eminent capability of adsorption and filtrating and can prevent trace elements migration. So thick soil plays an important role in protecting karst groundwater quality.Unwise land use make negative functions on karst groundwater quality by offering pollution source, erosion and transportation of soil and debris, causing environmental acidity, reducing the thinness of soil and lowering adsorption capability, forming surface collapses and sinkhole. One of the most important results is element immigration duri...
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