西藏高原生态系统服务时空格局及其变化特征

西藏高原是我国国家生态安全格局中至关重要的区域,维护提升其生态屏障功能是该区生态保护的核心目标。论文分析了1990—2010年西藏高原生态系统类型及其服务能力的时空变化格局,开展近20 a生态屏障功能的综合评估。结果表明:1)近20 a,西藏高原生态系统宏观格局稳定少动,森林、水体与湿地面积略有增加,草地、荒漠面积减少;2)森林、草地、湿地生态系统水源涵养量为895.19×10~8m~3,平均单位面积水源涵养量为744.48 m~3/hm~2,近20 a水源涵养服务在波动中有所提升;3)水蚀区土壤水蚀模数为3 876 t/km~2,土壤水蚀量为10.31×10~8t,生态系统土壤保持服务保有率为66.3%,近20 a土壤侵蚀量下降,而土壤保持服务保有率呈持续上升趋势;4)土壤风蚀模数为1 581.2 t/km~2,土壤风蚀量为18.99×10~8t,防风固沙服务保有率为66.5%,近20 a由于风场强度减弱与植被覆盖度增加,土壤风蚀量下降,而生态系统防风固沙服务保有率持续提升;5)森林、草地、湿地碳固定服务量为1.95 Pg C,从前10 a略有下降态势转变为后10 a轻微上升趋势。

The Temporal and Spatial Variations of Ecological Services in the Tibet Plateau

The Tibet Plateau is one of the vital zones to the national ecological security pattern, and the maintenance and enhancement of its ecological barrier function is the core objective of ecological protection in this area. This paper analyzed the variations of macrostructure and services of ecosystems in Tibet Plateau from 1990 to 2010, and integratedly assessed its ecological barrier function. The results showed that: 1) In recent 20 years, the ecosystem pattern in Tibet Plateau is stable, and the change of ecosystems is relatively slow. The grassland area increased in the northern and western Tibet Plateau, glaciers and permanent snow covered area retreated, and lake and swamp wetland area expanded. 2) The average annual water conservation quantity of forest, grassland and wetland ecosystems in Tibet Plateau was 89.52 billion m³, water conservation amount per unit area being 744.48 m³/hm². The carbon sequestration capacity of forest, grassland and wetland ecosystem reached 1.95 Pg C, presenting the pattern of gradually decreasing from southeast to northwest. 3) The annual average soil water erosion modulus is 3 876 t/km², and annual soil erosion quantity is 1.02 billion tons in the Tibet Plateau. The retention rate of ecological soil conservation service was 66%. The annual average soil wind erosion modulus is 1 581.2 t/km² and soil wind erosion quantity was 1.899 billion tons in the Tibet Plateau. The average sand fixation service quantity was 2.83 billion tons, and the retention rate of the average annual wind prevention and sand fixation service was 66.5%. 4) The water conservation capacity has improved in the past 20 years. The carbon sequestration amount reduced by 0.87% in the former 10 years and increased by 3.71% in the latter 10 years. In water erosion zones of the Tibet Plateau, the soil erosion amount and the soil conservation amount decreased, while the retention of soil conservation services continued to rise. The overall trends of wind erosion amount, ecosystem wind prevention and sand fixation service went downward due to weakened wind strength and increased vegetation coverage, while the retention rate of ecosystem wind prevention and sand fixation service continued to increase.