植被不同退化状态下尕海湿地土壤氮含量及酶活性特征

土壤中氮素的吸收、转化及含量的变化是影响植被生长的关键因素。为探讨湿地植被不同退化状态对土壤氮组分含量和相关酶活性的影响,以及土壤氮组分含量与相关酶活性之间的关系,以甘南尕海湿地不同植被退化状态样地(未退化CK、轻度退化SD、中度退化MD和重度退化HD)为研究对象,采用野外采样与室内实验相结合的方法,分析了植被不同退化状态下不同形态氮组分(全氮、铵态氮、硝态氮和微生物量氮)含量的变化特征,以及土壤氮转化酶(蛋白酶、脲酶、硝酸还原酶和亚硝酸还原酶)活性之间的相关关系。结果表明:(1)在植被退化状态下,土壤含水量逐渐减小,土壤温度呈先减小后增大的趋势;(2)随着植被退化程度的加剧,硝态氮含量呈增加趋势,而全氮、铵态氮和微生物量氮含量均随退化程度加剧呈减小趋势;土壤蛋白酶活性随退化程度的加剧而减小,脲酶活性呈先减小后增大的趋势,重度退化活性最高,轻度退化最低;硝酸还原酶活性随退化程度的加剧而增加,亚硝酸还原酶活性表现为"升-降-升"的变化趋势,即轻度退化活性最高,未退化和中度退化较低;(3)土壤蛋白酶活性与全氮、铵态氮和微生物量氮呈极显著正相关关系(P<0.01),与硝态氮含量呈显著负...

Characteristics of soil nitrogen content and enzyme activity in Gahai wetland under different vegetation degradation conditions

The absorption, transformation and content of nitrogen in soil are the key factors affecting the growth of vegetation. In order to explore the effects of various degradation conditions of wetland vegetation on the content of soil nitrogen components and related enzyme activities, as well as their relationship, research was conducted in sample areas with the following vegetation conditions (non-degraded CK, slightly degraded SD, moderately degraded MD and severely degraded HD) in Gahai wetland, Gannan.We combined field sampling and laboratory experiments, and analysed the variation characteristics of the content of various nitrogen components (total nitrogen, ammonium nitrogen, nitrate nitrogen and microbial biomass nitrogen) under different vegetation conditions, as well as the correlation between soil nitrogen invertase activities (protease, urease, nitrate reductase and nitrite reductase). The results show that: (1) Under the condition of vegetation degradation, the soil moisture content decreased gradually, and the soil temperature first decreased and then increased with the aggravation of the degree of degradation; (2) With the aggravation of vegetation degradation, the content of soil nitrate nitrogen showed an increasing trend, while the contents of total nitrogen, ammonium nitrogen and microbial biomass nitrogen showed a decreasing trend. Soil protease activity decreased with the degree of degradation, and the unease activity first decreased and then increased; the activity of heavily degraded was the highest, and the activity of slightly degraded was the lowest. The nitrate reductase activity increased with the aggravation of the degree of degradation, and the nitrite reductase activity showed a trend of "up-down-up", that is, the slightly degraded activity was the highest, while that of the non-degraded and moderately degraded was lower; (3) Soil protease activity has a very significant positive correlation with total nitrogen, ammonium nitrogen and microbial nitrogen content (P < 0.01), and a significant negative correlation with nitrate nitrogen content (P < 0.05). The activity of nitrate reductase was opposite to that of protease, and has a significant negative correlation with total nitrogen, ammonium nitrogen and microbial nitrogen. Urease activity has a very significant positive correlation with microbial nitrogen content (P < 0.01) and a significant positive correlation with total nitrogen content (P < 0.05). Nitrite reductase activity has a very significant positive correlation with total nitrogen and ammonium nitrogen content (P < 0.01), and a significant negative correlation with nitrate nitrogen content (P < 0.05). In summary, under the various degraded conditions of vegetation in Gahai wetland, the increase in soil nitrogen content can effectively increase the activity of related enzymes.