中国北方草地生态系统服务评估

北方草地是我国天然草地主体部分，其生态功能对提升生态系统稳定性、保障国家生态安全具有重要的作用。在北方草地生态功能分区基础上，开展2011-2015年不同功能区内防风固沙、土壤保持、水源涵养等生态功能评估，探明其现状和空间格局，为北方草地生态功能分区研究提供评估数据，也为推进草地生态系统保护与修复工作提供科技支撑。结果表明：（1）北方草地防风固沙能力为32.44 t hm^-2 a^-1，防风固沙量为89.22亿t/a。半干旱草原区防风固沙能力和固沙量最大，分别为68.76 t hm^-2 a^-1和29.16亿t/a，其固沙量占北方草地固沙总量的32.68%。（2）北方草地土壤保持能力为124.5 t hm^-2 a^-1，土壤保持量为243.59亿t/a。土壤保持功能的空间异质性较大，暖性灌草丛区土壤保持能力最大，为431.52 t hm^-2 a^-1；高寒草甸区土壤保持量最多，为105.36亿t/a，占北方草地土壤保持总量的43.19%。（3）北方草地水源涵养能力为93.03 m³ hm^-2 a^-1，水源涵养量为288.98亿m³/a。高寒草甸区和高寒草原区水源涵养能力较大，分别为211.09 m³ hm^-2 a^-1和118.04 m³ hm^-2 a^-1。两个区域的水源涵养量也较多，分别为125.36亿m³/a和72.13亿m³/a，合占北方草地水源涵养总量的68.34%。整体上，北方半干旱草原区、暖性灌草丛区、高寒草甸区和高寒草原区对发挥我国草地防风固沙、土壤保持、水源涵养等生态多功能效益、提升生态系统服务和稳定性具有极其重要的作用。

Evaluation of grassland ecosystem services in northern China

Northern grassland is the main part of natural grassland in China. Its multiple ecological functions play extremely important role in promoting ecosystem stability and ensuring ecological security in northern China. In this study, based on the grassland ecological function area, we used the revised wind erosion equation (RWEQ), revised universal soil loss equation (RUSLE), and water balance method to evaluate the soil conservation function, sand fixation function, and water conservation function in different grassland ecological function areas of northern China during 2011-2015. The results will provide the assessment data for studying grassland ecological function area, and provide the scientific policies for grassland ecosystem protection and restoration. The results showed that:(1) the values of sand fixation capacity and sand fixation amount in northern grassland ecosystem, were 32.44 t hm^-2 a^-1 and 8.922 billion t/a, respectively. The highest values, both observed in semi-arid grassland areas, were 68.76 t hm^-2 a^-1 and 2.916 billion t/a, respectively. The total sand fixation amount in this area contributed 32.68% of the northern China. (2) The values of soil conservation capacity and soil conservation amount in northern grassland ecosystem, were 124.5 t hm^-2 a^-1 and 24.359 billion t/a, respectively. Soil conservation function presented a great spatial heterogeneity in northern grassland ecosystem. The highest value of soil conservation capacity was 431.52 t hm^-2 a^-1, that was observed in warm shrub-grassland area. Moreover, the highest value of soil conservation amount was 10.536 billion t/a, that was observed in alpine meadow area. The total soil conservation amount in this area contributed 43.19% of the northern China. (3) The values of water conservation capacity and water conservation amount in northern grassland ecosystem, were 93.03 m³ hm^-2 a^-1 and 28.898 billion m³/a, respectively. Compare to other areas, the areas of alpine meadow and alpine grassland had higher water conservation capacity, with values of 211.09 m³ hm^-2 a^-1 and 118.04 m³ hm^-2 a^-1, respectively. Simultaneously, the areas of alpine meadow and alpine grassland had greater water conservation amount than other areas, with values of 12.536 billion m³/a and 7.213 billion m³/a, respectively, and accounting for 68.34% of the total water conservation amount in northern China. Overall, compare to other areas, the areas of semi-arid grassland, warm shrub-grassland, alpine meadow, and alpine grassland in northern China, which play extremely important role in exerting the multiple ecological functions of soil conservation, sand fixation, and water conservation, and improving the services and stability of northern grassland ecosystem.