Abstract: Selecting a typical karst peak cluster-depression system in northwest Guangxi Autonomous region, we have evaluated the effects of land-uses and topographic factors on soil nutrients. The results indicated that: with a long-term of tillage, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN) and available potassium (AK) in depression are significantly lower than slope land. Yet the available phosphorus (AP) is significantly higher than that of slope land，and it may be implied that fertilizer input was very important for AP in soil; SOC, TN, TP, TK, AN and AP were highly affected by Land-uses in slope-line scale. Topographic factors have a significant effect on SOC, TN, TP, AN, AP, AK and PH, but its variance ratio is lesser than land-use type; In the depression, different cropping systems have a significant effect on SOC, TP, TK and AK, though its variance ratio is low, it reflected the difference of fertilization and crop character among cropping systems; In research area, SOC, TN and AN decrease significantly with land-use intensity increases. Nature field and abandoned field have a higher accumulation of SOC, and it’s SOC contents is 3.35 times and 1.91 times of the tillage field. As a result of erosion and leaching, witch are induced by cultivation (or past cultivation), tillage field have a lower accumulation of SOC, TN and AN. SOC, TN, TK, AN and AK is significantly higher in rehabilitated field than in tillage field on research area scale, converting cropland to forest-land has a positive effect on soil organic matter accumulation. But on slope-line scale, SOC, TN, TP, AN and AK in rehabilitated field is significantly lower than in Nature field and abandoned field, suggesting that physical and chemical property changes within the degradation soil may take a longer periods to the nature level.

Key words: karst peak-cluster depression, soil nutrient, land-use type, topography indices, soil organic carbon