摘要:为深入了解高寒草甸退化对草原生态系统中土壤微生物碳氮量、土壤氮矿化及土壤微生物相关酶的变化特征，以祁连山东缘4个不同退化程度（未退化、轻度退化、中度退化和极度退化）的高寒草甸为研究对象，采集了深度为0-10 cm的土壤样品，并对不同退化程度高寒草甸中植物因子、土壤理化性质、土壤氨化速率、土壤硝化速率、土壤净氮矿化速率以及转化氮素的相关酶和微生物进行了相关研究。结果表明：（1）随退化程度的加剧，高寒草甸土壤中氨化速率和净氮矿化速率逐渐降低，硝化速率逐渐升高；（2）高寒草甸的退化降低了有关氮素转化相关酶，如土壤蛋白酶、脲酶、亮氨酸氨基肽酶的活性，而β-乙酰葡糖胺糖苷酶的活性呈先下降后上升趋势，且在极度退化草地活性最高；（3）随退化程度的加剧，高寒草甸土壤中微生物生物量碳和氮的含量逐渐降低，同时土壤基础呼吸、土壤微生物熵和代谢熵的指数也呈下降趋势。RDA分析表明，高寒草甸中氨化速率和净氮矿化速率与微生物生物量碳、微生物生物量氮、土壤基础呼吸、植物高度、植被盖度、地上生物量、蛋白酶、脲酶以及亮氨酸氨基肽酶呈显著正相关，而硝化速率则表现为负相关性。因此，高寒草甸退化对土壤微生物特性以及氮素转化和循环具有重要影响。



Abstract:Soil microbial nitrogen and carbon content, soil nitrogen mineralization, and enzymes related to soil microbes were studied in order to better understand the variation characteristics of degrading alpine meadows. At the Qilian Mountains, alpine meadows with four different degradation degrees (no degradation, ND; light degradation, LD; moderate degradation, MD; and severe degradation, SD) were selected and soil samples from the uppermost layer (0-10 cm in depth) were used to study several plant factors, soil physicochemical properties, soil ammoniation, nitrification, and soil net nitrogen mineralization rates, as well as nitrogen-related enzymes and microorganisms. Results showed that (1) degradation of alpine meadows reduced both the ammoniation and the net nitrogen mineralization rates in soils while increased their nitrification rate; (2) degradation of alpine meadows also reduced the activity of nitrogen-related enzymes such as soil protease, urease, and leucine aminopeptidase (LAP), while the activity of β-1,4-N-acetylglucosaminidase (NAG) decreased first and then increased, showing its highest activity under SD conditions; (3) along with the increase in degradation, the amount of microbial biomass carbon (MBC) and nitrogen (MBN) in the soil was reduced. At the same time, soil basic respiration (SBR), soil microbial entropy, and metabolic entropy indices were reduced as well. Results of an RDA analysis showed that both the ammoniation rate and the soil net nitrogen mineralization rate significantly positively correlated with MBC, MBN, SBR, plant coverage, plant height, aboveground biomass, and protease, urease, and LAP activities, while the nitrification rate showed a negative correlation. The degradation of alpine meadows showed an important impact on soil microbial properties and nitrogen transformation and cycling.





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