Abstract: The Three River Headwater Region is the source of the Yangtze,Yellow,and Lantsang rivers.The objectives of this study were to analyze the dynamic changes of grassland productivity and explore the natural and human driven mechanisms causing the grassland ecosystem changes.Findings in this study would be applied to the development of scientific strategies and programs for grassland restoration,management,and utilization and assess the effectiveness of the ecological engineering project.Dynamic changes of grassland yield of the region from 1988 to 2005 were analyzed using the GLOPEM model.The results indicate that grassland productivity in the region fluctuated periodically with a 3 to 5 year cycle.The variation coefficient of annual productivity increased from the east to the west of the region and from marsh,alpine meadow,alpine steppe,to temperate steppe grasslands.In general,grassland yield in the region showed an increasing trend during the studied 18-year period,especially a remarkable increase in alpine steppe and grasslands in the west of the region.The analysis indicates that the increased grassland productivity during the 18 years was influenced by climatic change.These findings indicate that we should keep clear-headed understanding to the contingent increase of ecosystem supply function which probably covers up the long-term negative impact of climatic change on the holistic functions of ecosystem.

Key words: Three River Headwater Region, Grassland yield, Dynamic change

摘要： 三江源地区是我国长江、黄河、澜沧江的发源地,分析该地区草地生产力的变化动态,探讨导致草地生态系统变化的自然和人文驱动机制,对于制定科学的草地恢复、管理和利用战略,以及开展有效的生态工程成效评估具有重要意义。利用GLOPEM模型对三江源地区1988-2005年的草地产草量变化动态进行分析,结果表明:三江源地区草地生产力呈现出3-5年的周期性波动规律,其产草量的年际变幅表现出从东部地区到西部地区依次增高;从沼泽草地、高寒草甸、高寒草原到温性草原依次增高的特征。同时,18年来三江源地区草地产草量总体呈增加趋势,特别以高寒草原或西部地区草地的提高幅度较大。尽管如此,它仍受到气候变化的强烈驱动。因此,应该对由于全球气候变化造成的生态系统牧草供给功能的短期增加保持清醒的认识,这种增加有可能掩盖了气候变化对生态系统整体功能的长期负面影响。

关键词: 三江源, 草地产草量, 变化动态