2000－2010年中国退牧还草工程区生态系统宏观结构和质量及其动态变化

本研究以生态学理论为基础，以空间信息技术为支撑，基于遥感数据、气象数据和地面观测数据，通过多源数据融合、生态模型模拟和尺度转换手段，分析中国退牧还草综合治理工程区2000－2010年生态系统宏观结构和质量的时空分布及变化趋势，探讨生态系统变化的自然和人文驱动机制，为退牧还草工程的生态成效评估提供理论依据。研究结果表明，1）2000－2010年，草地生态系统面积保持平稳，生态系统宏观结构稳定，但局部区域仍存在草地与农田、湿地和荒漠间的相互转化；2）研究区草地退化趋势已得到初步遏制，植被覆盖度略有增长，叶面积指数略呈波动式增加，净初级生产力呈显著上升，草地植被呈现恢复转好态势，生态系统总体质量有所提高，生态环境向良性演变；3）研究区生态状况具有空间差异性，总体转好，局部变差，各亚区整体水平排序为内蒙古东部退化草原治理区＞青藏高原江河源退化草原治理区＞新疆退化草原治理区＞蒙甘宁西部退化草原治理区；4）退牧还草工程的实施有利于草地保护，气候暖湿化促进植被生长与恢复，人类活动干扰局部地区生态系统，三者共同影响研究区总体生态状况。

Ecosystem dynamics in the ‘Returning Rangeland to Grassland’programs,China

Grassland in arid,semi-arid and alpine areas has experienced severe degradation in recent decades.To enable restoration of grassland vegetation and sustainable development,the Returning Rangeland to Grassland (RRG)program was initiated in 2003.Based on remote sensing images,meteorological data and ground ob-served data,this study utilized data fusion,ecological model simulation and scaling transformation to construct the regional macro ecosystem structure,ecosystem quality and dynamics in regions hosting RRG programs. Fractional vegetation cover (FVC),leaf area index (LAI)and net primary production (NPP)were utilised to indicate ecosystem quality.We examined the spatiotemporal characteristics of ecological structure and ecosys-tem quality in regions where the RRG programs were implemented from 2000 to 2010.Additionally,we ana-lyzed ecosystem evolution characteristics and the driving mechanism of ecosystem change.Grassland ecosystems were dominant in the study area.The ecosystem structure was stable,but grassland experienced local change in farmland,wetland and desert.FVC showed a slight increasing trend for grassland;LAI tended to fluctuate but tended to also increase;NPP increased,ranging from 218.23 g C/(m2 · a)in 2000,to 226.30 g C/(m2 ·a)in 2010,a 3.7% increase.Ecological conditions differed spatially;overall there was improvement but with areas of localized deterioration.The integral level of the sub-region was:the degraded grassland region of eastern Inner Mongolia>the riverhead grassland region of the Qinghai-Tibetan Plateau>the degraded grass-land region of Xinjiang>the desert grassland region of western Inner Mongolia-Gansu-Ningxia.The spatio-temporal variation of ecosystems was mainly affected by ecological restoration projects,climate change and hu-man activities.The RRG programs restored degraded grassland and promoted natural grassland protection. The warming-wetting trend observed over this time promoted the restoration of vegetation.Human activities such as overexploitation resulted in conversion of grassland into farmland in some areas.