甘肃河东地区坡度对生态系统服务的影响及其阈值效应

Impact of the Slope on Ecosystem Services in Hedong District of Gansu Province,China

生态系统服务作为生态系统功能向人类福祉转化的有效中介工具,研究其对人类活动具有重要意义。坡度作为地形要素之一对生态系统服务价值的影响巨大,严重影响着区域产水服务、土壤保持量等生态系统服务功能。基于InVEST模型测算甘肃河东地区1995-2020年产水量、碳储量和土壤保持量3种典型生态系统服务,探讨了生态系统服务的坡度效应及其重要性分级,分析了坡度对生态系统服务的影响,并对其坡度影响阈值进行了定量识别,相较于以往基于地形梯度的生态系统服务研究,该文更为全面明确的反映了多种生态系统服务综合效应随坡度的变化特征。结果表明,1)1995-2020年甘肃河东地区产水量和土壤保持量均呈先增加-减少-增加的趋势,碳储量呈减少趋势。空间分布上,3种典型生态系统服务总体呈现出陇中和陇东高原较低,陇南山地和甘南高原较高的空间分布格局。2)产水量和碳储量随坡度的增大呈先增加后缓慢降低的趋势,在坡度达到第Ⅷ级(25°-35°)时最高,土壤保持量随坡度增大持续增加,在坡度到第Ⅸ级(>35°)时最高。3)低坡度等级上占主导地位的是一般区和一般重要区,中高坡度上则以中度和高度重要区为主。当坡度超过最高阈值后,坡度增大对生态系统服务的影响强度趋于减弱。4)一般区、一般重要区、中度重要区和高度重要区坡度对生态系统服务影响的阈值分别为17.2°、9.6°、11.9°、20.5°。研究坡度对生态系统服务的影响可为未来土地整治工程优化调控措施提供重要参考。

The ecosystem services,as an effective intermediary tool for transforming ecosystem functions into human wellbeing,are of great significance in studying their importance for human activities.As a major topographical feature of a given terrain,the slope has a substantial impact on the value of ecosystem services,and significantly influences ecosystem service functions,such as regional water production services and soil conservation.In this study,we used the InVEST model to measure three typical ecosystem services—the water yield,carbon storage,and soil conservation in Hedong District of Gansu Province,China from 1995 to 2020.We investigated the effects of the slope on these services and their hierarchy of importance,and quantitatively identified the impact threshold of the slope on ecosystem service functions.Compared with previous studies on ecosystem services based on topographical gradients,this study more comprehensively and clearly reflects the changing characteristics of various ecosystem services with slope.The results show that 1)water yield and soil conservation in Hedong District initially increased and then decreased,followed by a subsequent increase from 1995 to 2020,while carbon storage decreased during this period.All three typical ecosystem services generally had a lower concentration in the Longzhong Plateau and Longdong Plateau,and a higher concentration in the Longnan Mountainous and Gannan Plateau.2)Water yield and carbon storage in the study area initially increased with the slope,followed by a gradual decrease,and reached their peak values at slope level Ⅷ(25°-35°).By contrast,soil conservation in the study area continually increased with the slope,and reached its peak at slope level Ⅸ(>35°).3)General areas and areas of general importance were the dominant regions at low slope levels,while moderately and highly important areas were dominant at medium to high slope levels.Once the slope exceeded the maximum threshold,the impact of slope on ecosystem services weakened.4)The thresholds for the impact of the slope on ecosystem services in the general,generally important,moderately important,and highly important areas were 17.2°,9.6°,11.9°,and 20.5°,respectively.The study provides important references for optimizing and regulating land consolidation projects in the future.