农牧交错区生态工程建设对生态系统服务的影响

Effects of ecological engineering construction on ecosystem services in the agro-pastoral transitional zone:A case study of Zhangbei County,Hebei Province of China

查明农牧交错区生态工程建设对区域生态系统服务的影响可为生态环境建设和优化管理提供有益参考。该研究以农牧交错区典型县域张北县为例,综合利用光谱混合分解模型、InVEST模型和回归分析方法,基于原始影像的端元分解、土地利用/覆被制图和生态系统服务评估,从生态用地数量和质量变化两个角度探析生态工程建设对区域生态系统服务的影响。结果表明:1)2000—2020年间,生态工程建设影响下张北县林地分布范围迅速扩张,耕地和草地面积持续收缩,林地扩张与耕地和草地缩减存在一定的空间重合现象。张北县土壤保持、水源涵养和防风固沙3种服务整体表现为强化趋势,但具体分布存在明显的空间异质性;2)在生态用地数量变化方面,生态用地总面积不断增长,20 a间增加了687.67 km^(2)。其中,林地面积、草地面积及其总面积增加对土壤保持和水源涵养服务的提升效果明显,而仅有林地面积增加对防风固沙服务具有积极作用。在生态用地质量变化方面,20 a间林地端元要素丰度值平均含量下降了0.108,其质量整体呈衰退趋势。20 a间草地端元要素丰度值平均含量增加了0.099,其质量整体表现为微弱上升的态势。林地和草地质量改善均增强了土壤保持、水源涵养和防风固沙服务,但防风固沙服务对林地和草地质量变化最为敏感。研究结果为生态工程建设对生态系统服务的影响研究提供了新的认知视角,未来应从生态用地精细分类对生态系统服务的影响差异方面深化研究,也应重视气候要素对区域生态系统服务的相对贡献。

Ecological engineering can dominate the structure and function of ecosystems.The quantity and quality of ecological land can be directly related to the pattern and dynamics of regional ecosystem services.It is very necessary to identify the impacts of ecological engineering construction on regional ecosystem services,especially in agro-pastoral transitional zones.This study aims to explore the impact of the quantity and quality of ecological land on ecosystem services under ecological projects.A case study was taken in Zhangbei County,a typical county in an agro-pastoral transitional zone.The map of land use was then classified using a random forest model,according to the Landsat remote sensing images in 2000,2010,and 2020.The linear spectral mixture model was also used to decompose the original image for the abundance values of typical endmembers.Three key ecosystem services were included soil conservation,water conservation as well as windbreak,and sand fixation.The evolutionary characteristics were quantitatively assessed using the InVEST model and ArcGIS.The correlation analysis was then applied to reveal the impact of the quantity and quality of ecological land on the key ecosystem services.The results showed that:1)The distribution of forestland in Zhangbei County was expanded rapidly,with a total increase of 986.10 km^(2) from 2000-2020.But the areas of arable land and grassland continued to shrink,thus decreasing by 802.86 and 307.43 km^(2),respectively.There was some spatial overlap between the expansion of forestland and the shrinkage of arable land and grassland.An overall strengthening trend was found for soil conservation,water conservation,windbreak,and sand fixation as a whole.However,there was outstanding spatial heterogeneity in the specific distribution.2)In the quantity of ecological land,the total area of ecological land has continuously increased by 687.67 km^(2) over the past 20 years.Among them,the increases in the area of forestland,grassland,and their total area posed a significant effect on the soil conservation and water conservation services,while only the increase in the area of forestland shared the positive impact on the windbreak and sand fixation.In the quality of ecological land,the average abundance values of endmember elements in forestland declined by 0.108 during the 20-year period,indicating an overall decreasing trend.The average abundance values of endmember elements in grassland increased by 0.099,with an overall weakly increasing trend.The quality of forestland and grassland was enhanced the soil conservation,water conservation,windbreak,and sand fixation,whereas the windbreak and sand fixation were the most sensitive to changes in the quality of forestland and grassland.The findings can offer a promising perspective to explore the impact of ecological engineering construction on ecosystem services.The region-specific decision-making insights can also be provided for ecological restoration in the agro-pastoral transitional zone.The impact of fine classification of ecological land on ecosystem services should be further examined in future research.Additionally,it is necessary to incorporate the time-series data of climatic factors into vegetation ecological process models,in order to reveal the feedback effects of ecosystem services on climatic factors.This approach can be expected to distinguish the relative contributions of climatic factors and ecological engineering in regional ecosystem services.