人为干扰对藏北高寒草原群落生物量及其碳氮磷含量特征的影响

Effect of Human Disturbance on Plant Biomass and CNP Contents of the Alpine Steppe in Northern Tibet

退牧还草工程是国家为改善草原生态环境和促进牧区经济持续发展而实行的一项战略性工程,禁牧和休牧措施是其主要措施。以藏北高寒草原申扎区域的退牧还草工程为研究对象,分别选取禁牧围栏样地、休牧围栏样地和围栏外的一块自由放牧样地,比较分析这三种人为干扰下的放牧样地的生物量及其碳氮磷含量的特征。结果表明:休牧样地地上和地下生物量分别为35.69 g/m2和237.11 g/m2,均显著高于禁牧样地(22.48 g/m2和151.22 g/m2)和自由放牧样地(25.27g/m2和96.37 g/m2)。植物中碳氮磷含量,地上部分禁牧样地含碳量最高,植物氮、磷含量自由放牧样地最高;地下部分碳、氮含量差异不明显,P含量自由放牧最高。说明植物生物量大小与植物体内碳氮磷元素含量大小无相关关系。对于禁牧样地,在长期围栏封育的同时,应适当的添加P元素或N、P元素;而休牧样地,在短期围栏封育时,可添加适当的N元素。

The ＂grazing withdrawal project＂is a key national undertaking projectwith aims to develop the western re- gion, which is one of the major ecological construction project suported by the government. Protective measuresin the project, such as grazing bans and intermittent grazing, are usedto rehabilitate grassland vegetation and to improve grassland productivity. Those methods were for the benefit of pastoral development andachieving a sustainable cycle of ecological development. In order to investigate the effects of the project on plant biomass and carbon （C） ,nitro- gen（N） and phosphorous （P） content, three plots were selectedat Xainza Alpine Steppe and Wetland Ecosystem EG , the content of N and P in aboveground part are the highest in FG. The C and N content of the underground part have no significant differenceamong three plots. There are also no significant correlationship between aboveground biomass and the C, N, P content. Those results suggest that it should add P element for the long term enclosed grassland and add N element for the short term enclosed grassland, which is benefit for the plant growth.