中文摘要：

在陕西合阳黄河湿地,通过野外采样和室内分析相结合的方法,研究该湿地退化过程中不同土地利用方式（湿地、天然草地、开荒耕地和盐碱地）对土壤养分（有机质和N,P,K）和酶活性（脲酶、蔗糖酶、过氧化氢酶、碱性磷酸酶）的影响及其变化规律。结果表明：土地利用方式对土壤养分和酶活性的影响极显著（P〈0.01）,其排列顺序为：天然草地〉开荒耕地〉湿地〉盐碱地。开荒耕地的土壤有机质和土壤养分介于天然草地和湿地之间,盐碱地土壤有机质仅为天然草地和湿地的3.4%和6.9%,土地资源的过渡开发利用会严重影响土壤肥力导致土壤退化。酶活性与土壤有机质及各养分成显著和极显著相关,且不同土壤酶活性间也存在显著相关性。不同土地利用方式下,脲酶、蔗糖酶、过氧化氢酶和碱性磷酸酶差异极显著（P〈0.01）,其活性高低与土壤养分变化顺序基本一致。土壤酶活性反映出土壤肥力水平的高低,可以作为评价黄河湿地土壤肥力的指标。

英文摘要：

The effects of different land use patterns（wetland,natural meadow,cultivated land,saline-alkali land） on soil nutrient（organic matter,N,P,K） and enzyme activities（urease,invertase,catalase,alkaline phosphatase） in wetland degradation were studied for the Yellow River wetland of Shaanxi using field sampling and indoor analysis.Results indicated that soil nutrient and soil enzyme activities had significant differences among different land use patterns（P0.01）.The order was natural meadowcultivated landwetlandsaline-alkali land.Soil organic matter and soil nutrients of cultivated land fell between that of natural meadow and wetland,but saline-alkali land was far below that of natural meadow and wetland by 3.4% and 6.9%,indicating that over-exploitation of land resources will seriously affect soil fertility and lead to soil degradation.Enzyme activities were significantly correlated with soil organic matter and soil nutrient,and between soil enzyme activities themselves.The activities of urease,invertase,catalase,alkaline phosphatase were significantly different under diverse land use patterns（P0.01）,varied in the same order as that of soil nutrient.Soil enzyme activities could indicate the level of soil fertility,and could be used as an index for soil fertility evaluation of wetlands.