Abstract:

Northern China’s farming-pastoral ecotone is an ecologically fragile and sensitive transitional zone that serves an important role in China’s environmental protection strategies. This paper aims to evaluate the trends and driving factors of changes in vegetation ecological function throughout the agro-pastoral ecotone of northern China from 2000 to 2020 using satellite remote sensing and meteorological observation data. Vegetation net primary productivity (NPP), water conservation, and soil-water conservation values were used as indicators to quantify vegetation ecological function in this period. The long-term trends in vegetation ecological function were assessed through spatial overlay analysis, trend analysis, and correlation analysis. The driving effects of climate and human activities on vegetation ecological function were also analyzed. The results indicate that more than 95% of the vegetation ecological functions in the northern agro-pastoral ecotone showed significant improvement from 2000 to 2020. The values of vegetation NPP, soil-water conservation function, and water conservation function improved by 57.1%, 57.3% and 86.7% respectively. Specifically, vegetation NPP increased from 502.6 g∙m^-2∙a^-1 (by C, the same below) in 2000 to 789.6 g∙m^-2∙a^-1 in 2020, soil-water conservation function increased from 473.5 t∙hm^-2∙a^-1 in 2000 to 744.9 t∙hm^-2∙a^-1 in 2020, and water conservation service capacity index increased from 42.7 in 2000 to 79.7 in 2020. The significant trends in vegetation NPP, soil-water conservation function, and water conservation function indicate favorable improvement in the regional ecosystem. Among the many driving factors that have contributed to these trends, increased annual precipitation is the key climatic factor that has led to changes in vegetation ecological function. Likewise, environmental protection measures have greatly increased the area of conserved forests and grasslands, and have thus promoted the improvement of ecological function in this region.

Key words: ecological function, net primary productivity of vegetation (NPP), water and soil conservation, water conservation, driving factors

摘要：

中国北方农牧交错区是种植业和草地畜牧业交错的生态过渡区,也是生态脆弱和生态敏感带,在中国生态环境保护中具有重要战略地位。为探讨2000—2020年中国北方农牧交错区植被生态功能变化趋势及其驱动因子,以北方农牧交错区的植被生态功能为研究对象,利用卫星遥感和气象观测数据,选择植被净初级生产力（NPP）、水源涵养能力和水土保持等指标来量化植被生态功能,采用空间叠加分析、趋势分析和相关分析等方法探索了植被生态功能长期变化趋势,分析气候和人为活动对植被生态功能变化的驱动作用。结果显示,2000—2020年北方农牧交错区95%以上区域的植被生态功能呈现变好趋势。其中,NPP、水土保持和水源涵养能力的提升幅度分别为57.1%、57.3%和86.7%。植被NPP由2000年的502.6 g∙m^-2∙a^-1（以C计,下同）增加到2020年的789.6 g∙m^-2∙a^-1;水土保持量由2000年的473.5 t∙hm^-2∙a^-1增加到2020年的744.9 t∙hm^-2∙a^-1;水源涵养能力指数由2000年的42.7增加到2020年的79.7。NPP、水土保持功能和水源涵养能力指数明显提高预示该区域生态系统向良性发展。其中,年降水量增加是驱动植被生态功能变化的关键气候因素。人类的生态保护措施使林地和草地等生态用地面积大幅度上升是促进生态功能提高的主要人为因素。

关键词: 生态功能, 植被净初级生产力, 水土保持, 水源涵养, 驱动因子