三江源区草地生态系统质量及其动态变化

为探讨三江源区2000—2010年草地植被的时空演变特征，定量评价三江源区草地生态系统质量及其动态变化，采用植被覆盖度和NPP 2个生态参数，分析三江源区草地生态系统的时间变化特征和空间分布规律.结果表明:2000—2010年三江源区草地年均植被覆盖度为26.89%，年均NPP（以C计）为34.35 g/m2，11 a间二者均呈增加趋势.三江源区草地质量具有明显的季节性变化特征，呈南高北低、东高西低的空间分布格局.从11 a的平均结果来看，三江源区草地植被覆盖度在8月达到最大值，约为59.19%；而草地NPP在7月达到最大值，为98.53 g/m2.气温是三江源区草地植被覆盖度变化的主要影响因子，而雨热不同期则造成三江源区草地NPP的年际波动变化.植被覆盖变化是气候变化和人类活动共同作用的结果.研究显示，2000—2010年三江源区草地生态系统质量有所改善，特别是生态工程实施后，草地生态系统质量明显好转.三江源区需在促进农牧业产业升级和资源优化配置的基础上，继续采取积极的减压增效措施，真正实现草畜平衡，达到生态保护的目的. 

Quality and Dynamic Changes of Grassland Ecosystems in the Three-River Headwater Region

Vegetation coverage and net primary productivity (NPP) were used to analyze the temporal-spatial characteristics and evaluate the quality and dynamic changes of grassland ecosystems in the Three-River Headwater Region from 2000 to 2010. The results showed that:over the past 11 years, the vegetation coverage and the NPP tended to increase; the average annual value of vegetation coverage and NPP from 2000 to 2010 were 26.89% and 34.35 g/m2, respectively. The grassland quality in the Three-River Headwater Region showed significant seasonal variation and a spatial pattern which was high in the south and east while low in the north and west. From the average of the 11 years, the grassland vegetation coverage of the Three-River Headwater Region in August reached a maximum of about 59.19%, while the net primary productivity in July reached a maximum value of 98.53 g/m2. The main reason for vegetation coverage changes was temperature change, while the inter-annual variation of NPP was caused by the non-synchronous characteristics of precipitation and warmth. The results indicated that the quality of grassland ecosystem in the Three-River Headwater Region was improving from 2000 to 2010 and markedly improved especially after the implementation of ecological projects. We suggest taking remaining measures to reduce pressure and increase efficiency for the purpose of achieving forage-livestock balance and ecological protection, on the bases of the industrial upgrading of farming and animal husbandry and optimal allocation of resources.