中文摘要：

放牧牲畜排泄物是青藏高原高寒草地生态系统的一种重要养分来源,对于维持草地土壤肥力和植被生产力具有重要意义.采用尼龙网袋法监测了两种主要放牧牲畜牦牛和藏绵羊粪便干物质量及主要养分含量在降解过程中随时间的动态变化特征.结果表明,牦牛和藏绵羊粪便在经过93 d的降解后,干物质量分别减少了30.9％和21.6％.到试验期末,牦牛粪便全碳和全氮含量显著降低,其值降至初始的81.8％和79.2％,而全磷和全钾的变化则不显著,表明碳氮减少量较磷和钾更为明显.藏绵羊粪便全碳和全钾含量在试验期末降至初始的87.7％和72.6％,差异具有极显著性,但全氮和全磷减少不显著.牲畜粪便在一个生长季内的降解和养分释放量较少可能使得其对土壤和植被产生的潜在生态环境效应具有滞后性.放牧过程中,牧民少量捡拾牲畜粪便用作生活资料将有利于维持高寒草地生态系统的养分平衡和可持续发展.

英文摘要：

Grazing livestock excretain natural grasslandis regarded as animportant source of nutrientsfor alpine grass- land ecosystem in Qinghai -Tibet Plateau, which may play a critical role in maintaining soil fertility and vegetation productivity of grazed grassland. This paper monitored the temporal variation of dry matter and main nutrients of yak and Tibetan sheep dung by using the nylon-mesh-bagmethod. The results indicated that dry matter of yak and Tibet- an sheep dung decreased by 30.9% and 21.6% after the decomposition of 93 days, respectively. Total carbon and total nitrogen contents of yak dung reduced to 81.8% and 79.2% of the initial values, respectively, while no sig- nificant differences were observed for the contents of total phosphorus and total potassiumbetween the initial and fi- nal sampling time, implying that the losses of total carbon and nitrogen of yak dung were more obvious than total phosphorus and potassium. Total carbon and total potassium contents of Tibetan sheep dung had dropped to 87.7% and 72.6%, respectively, but similar values were found for the initial and final contents of total phosphorus and to- tal potassium. It can be concluded thatthe little decomposition and nutrients returns of livestock dung in one growing season may lead to series of potential ecological environment effects on soil and vegetation act as prominent hysteresis quality. We suggest that herders use livestock excrement as necessities timely and small quantity are beneficial to assure the nutrients balance and sustainable development of alpine pasture ecosystem.