金沙江干热河谷不同区段土壤碳氮磷化学计量和酶活性研究

探明金沙江干热河谷土壤C、N、P化学计量和土壤酶活性特征，是该区域生态恢复的重要决策依据. 2021年1月通过野外调查、土样采集及室内分析，对金沙江干热河谷上、中、下游共32个样地表层土壤的C、N、P化学计量和酶活性特征及其相互关系进行研究. 结果表明:①金沙江干热河谷土壤C、N、P元素含量受气候、土壤和植被等环境因子影响，其含量均表现为上游>下游>中游的特征，而土壤C/N值(含量比)从上游向下游逐渐降低，土壤C/P值(含量比)和N/P值(含量比)均呈从上游向下游逐渐增加的趋势. ②土壤脲酶(Ure)、β-葡萄糖苷酶(BG)和酸性磷酸酶(AP)的酶活性受金沙江干热河谷上、中、下游气候以及土壤、植被等环境因子的影响，其活性均表现为上游>下游>中游的特征. ③金沙江干热河谷不同植被类型土壤C、N、P含量和酶活性均表现为天然林>人工林>稀树灌草丛的特征. 研究显示:金沙江干热河谷上、中、下游土壤C、N、P元素含量及其化学计量比和土壤酶活性存在空间差异，可能与不同区段的气候、土壤、植被等因素有关；适宜的气候、土壤和植被能增加土壤C、N、P元素含量，提高土壤Ure、BG和AP酶活性. 

Stoichiometry of Soil Carbon,Nitrogen and Phosphorus and Soil Enzyme Activity at Various Reaches of the Dry-Hot Valley of Jinsha River

Identifying soil C, N, P stoichiometry and enzyme activity in the Dry-Hot Valley of Jinsha River is the decision-making basis for regional ecological restoration. The relationships between soil C, N, P stoichiometry and enzyme activities were studied from 32 soil samples in the upper, middle and lower reaches of the Dry-Hot Valley of Jinsha River. The results showed that: (1) The contents of soil C, N and P were affected by climate, soil and vegetation, and the highest contents of soil C, N and P were in the upper reaches and the lowest were in the middle reaches, and soil C/N ratios were decreased down the Jinsha River, and C/P and N/P ratios were increased down the Jinsha River. (2) The activities of soil urease (Ure), β -glucosidase (BG) and acid phosphatase (AP) were affected by climate, soil, vegetation and other environmental factor, and the activities were showed as upper reaches> lower reaches> middle reaches. (3) Soil C, N, P contents and enzyme activities from plots of different vegetation types were as follows: natural forest >plantation forest > savannah. The results showed that the spatial differences of soil C, N, P contents and soil enzyme activities at various reaches of the Dry-Hot Valley of Jinsha River may be related to climate, soil, vegetation and other factors in the region. Suitable climate, soil and vegetation can increase soil C, N and P contents, and improve the soil enzyme activities.