尕海湿地区沼泽草甸退化对土壤氮转化酶活性的影响

为探讨高寒湿地退化对土壤氮转化酶活性的影响，以青藏高原东缘尕海湿地未退化（ND）、轻度退化（LD）、中度退化（MD）和重度退化（HD）4种不同退化程度0~40 cm土层沼泽草甸为研究对象，研究不同退化与土层中土壤氮转化酶（蛋白酶、脲酶、硝酸还原酶和亚硝酸还原酶）活性的变化特征及其与土壤理化性质之间的关系。结果表明：1）随沼泽草甸退化程度加剧，土壤含水量、全氮、铵态氮和微生物生物量氮含量均显著降低，土壤温度与硝态氮含量却显著增加。2）随退化程度加剧，各土层土壤脲酶活性增加、蛋白酶活性降低，且仅在20~40 cm土层存在显著差异；硝酸还原酶活性增加、亚硝酸还原酶活性降低，在0~20 cm土层存在显著差异。3）各退化程度中，土壤脲酶、蛋白酶、亚硝酸还原酶活性均随土层深度的增加而显著下降，硝酸还原酶活性仅在HD显著下降。4）退化程度和土层对4种土壤氮转化酶活性均存在显著影响，且对土壤硝酸酶和亚硝酸还原酶活性存在显著交互作用。5）冗余分析表明土壤含水量对土壤氮转化酶活性变化的贡献率高达67.1%，其是驱动尕海沼泽草甸退化演替过程中土壤氮转化酶活性变化的主导因素。研究结果可为高寒湿地生态系统退化中的土壤酶活性变化规律提供理论依据。

Effects of swamp meadow degradation on soil nitrogen invertase activity in wet areas of Gahai

This study explored the effects of degradation of alpine wetlands on soil nitrogen invertase activities. Four swamp meadows exhibiting different degrees of degradation ［non-degraded （ND）， lightly degraded （LD）， moderately degraded （MD） and heavily degraded （HD）］ in the wet areas of the Eastern Qinghai-Tibetan Plateau were selected for study and data on the distribution characteristics of soil nitrogen invertase （protease， urease， nitrate reductase and nitrite reductase） in 0-40 cm soil horizon were collected and their relationship with soil physicochemical properties was ascertained. It was found that： 1） With increasing swamp meadow degradation， the soil moisture content， total nitrogen， ammonium nitrogen and microbial biomass nitrogen content were significantly reduced， but the soil temperature and nitrate nitrogen content were significantly increased. 2） As the degree of degradation increased， the soil urease activity increased and the protease activity decreased in each soil layer， but the changes were statistically significant only in the 20-40 cm soil horizon. The nitrate reductase activity increased and the nitrite reductase activity decreased， and there were significant differences in the 0-20 cm soil horizons. 3） The activities of soil urease， protease， and nitrite reductase for each meadow degradation status category all decreased significantly with increasing soil depth， while the nitrate reductase activity decreased significantly only in HD. 4） The activities of all four soil nitrogen converting enzymes varied with degradation status and soil depth， and a there was a significant interaction between degradation status and soil depth for soil nitrate and nitrite reductase activities. 5） Redundancy analysis showed that soil water content accounted for 67.1% to the change in soil nitrogen invertase activity， and was thus the dominant factor driving changes in soil nitrogen invertase activity across the degradation succession of Gahai. The results of this study provide a theoretical basis for defining the pattern of change in soil enzyme activity at different stages in the degradation of alpine wetland ecosystems.