中文摘要：

以桂林丫吉村岩溶试验场为考察基地，研究了不同地貌部位（洼地、坡地和垭口）土壤酶活性（转化酶、蛋白酶、脲酶、碱性磷酸酶和过氧化氢酶）的时空变化特征，结果表明，不同地貌部位土壤酶活性存在明显差异，洼地和垭口土壤水解酶类活性较高，与这两个地貌部位微生物数量较多的结果相对应。试验场不同地貌部位土壤水解酶类活性随土壤深度的增加而逐渐降低，但对于不同的酶和不同的地貌部位。酶活性降低的幅度有所差异。各地貌部位各层次土壤过氧化氢酶活性差别不大。4种水解酶活性的季节变化规律一般是春季上升，夏季或秋季为最高。此外，土壤水解酶类活性与不同地貌部位的土壤养分水平密切相关，一般与土壤有机质、全N、有效N、速效P之间呈显著或极显著正相关，这既说明土壤酶活性在一定程度上反映了岩溶土壤肥力水平的高低，可作为评价岩溶土壤肥力水平的重要指标之一，而且也为评价西南岩溶生态系统脆弱程度提供了新的生物学方面的指标，为不同地貌部位的土地利用方式和植被重建模式提供了一定的理论依据。

英文摘要：

The seasonal and spatial variation of soil enzyme activities （invertase, protease, urease, alkaline phosphatase and catalase） at different geomorphological positions （Depression, Slope and Saddle） were investigated in Guilin Yaji Karst Experimental Site, China. There were obvious differences in enzyme activities among different geomorphological positions. Activities of soil hydrolytic enzymes were higher at Depression and Saddle, which was consistent with the higher amount of soil microbes in these two geomorphological positions. The hydrolytic enzyme activities fell gradually with the increase of soil depth, which varied with different enzymes and with different geomorphological posi- tions. There was slight difference in soil catalase activities for every geomorphological position and every soil layer. Generally, the activities of four hydrolytic enzymes rose in spring and reached the highest level in summer or autumn. The enzyme activities correlated significantly with soil nutrients such as soil organic matter, total nitrogen, available nitrogen and available phosphorus in different geomorphological positions. These results illuminated that the soil enzyme activities could not only be used as one of the important indicators in evaluating karst soil fertility level, but also provide a new biological index for evaluating the fragility of karst ecosystem in Southwest China, and provide a certain theoretical basis for land use mode at different geomorphological positions.