青藏高原高寒草甸不同围栏年限土壤酶化学计量特征

为探究土壤酶活性和酶计量比的变化特征及影响机制，本试验以青藏高原若尔盖高寒草甸为对象，研究了围栏2，4，6，8和10年自然恢复条件下土壤理化性质和酶活性差异性规律。结果表明：随着恢复年限的增加，与碳（carbon，C）循环密切相关的β-葡萄糖苷酶、与氮（nitrogen，N）循环密切相关的N-乙酰-β-D-葡萄糖苷酶和亮氨酸氨基肽酶以及与磷（phosphorus，P）循环密切相关的碱性磷酸酶活性均呈现增加趋势；围栏8年时，土壤C：N酶活性比特征值下降，C：P酶活性比特征值上升，前者与土壤含水量和pH值呈显著负、正相关关系（P<0.05），后者与土壤有机碳显著负相关（P<0.05）。整体而言，严重沙化的高寒草甸，在围栏封育过程中受N养分限制，在围栏6~8年时，与养分循环相关的酶活性对植被特征和土壤属性的响应敏感。

Response of Soil Enzyme Stoichiometry to Different Enclosure Durations in Alpine Meadow,Tibetan Plateau

Soil enzymes play an important role in the process of community succession and nutrient conversion. With the implementation of fencing measures,it is vital to explore the driving mechanism of soil enzyme activity in the process of grassland restoration. We conducted a manipulative grazing exclusion experiment with fences lasting 2,4,6,8,and 10 years in alpine meadow,Tibetan Plateau. We investigated soil properties,soil enzyme activities and stoichiometry,and their drivers. The results showed that β-1,4-glucosidase closely related to C cycle,N-acetyl-β-D-glucosidase and leucine aminopeptidase related to N cycle and alkaline phosphatase related to P cycle,expressed an increasing trend with increasing the duration of fences. When the duration of fence reached 8 years,the ratio of soil C to N enzyme activities decreased,and was significantly negatively and positively correlated with soil water content and pH,respectively,while the ratio of soil C to P enzyme activities increased,which was significantly negative and positive correlated with soil organic carbon. In summary,soil enzyme activities and stoichiometry remarkablely varied with the different durations of fence,and the nutrients of alpine meadow was limited by the lack of nitrogen,and the sensitive responses of soil enzyme activity to the vegetation characteristics and soil properties were observed in the duration of 6 to 8 years fences.