藏东-川西生态维护水源涵养区产水量驱动机制

Driving mechanism of water yield in the ecological and water conservation zone of east Tibet and west Sichuan province

藏东-川西生态维护水源涵养区位于西南高山峡谷区北部,是中国典型的生态脆弱区,生态系统抗干扰能力差,对气候变化的反应敏感。产水量是生态系统服务中的一项重要功能,研究产水量空间分布特征及其影响因子对该地区水资源保护、涵养,开发和利用有重要意义。基于2000—2020年地表覆盖产品、气候、基岩深度、土壤和地形等数据,运用InVEST模型Annual Water Yield模块模拟了藏东-川西地区产水量;结合地理探测器(GDM)分析了造成产水量空间分异的各因子的解释能力;对q>0.1的因子引入多尺度地理加权回归(MGWR)分析它们对研究区不同地理位置产水量的影响程度,并运用Theil-Sen趋势分析、Mann-Kendall显著性检验得到了产水量及其主导因素时空变化特征;同时利用Hurst指数预测了未来短期内产水量上升或下降趋势和评估了研究时段内产水量在不同空间位置的波动水平。结果表明:1)降水量和产水量空间分布在研究区内呈现“东西高,中部低”的分布格局,岷江流域降水量为最大,金沙江流域蒸散水平最高,怒江流域产水量领先其余三个流域;2)除降水量和蒸散发外,藏东-川西地区产水量主要影响因子有气候因子(年均湿度和年均风速)、地形因子(高程)、土壤类型、植被因子(归一化植被指数和净初级生产力)与社会因子(地表覆盖类型和人类活动强度指数);其中降水量、蒸散发、高程、归一化植被指数、净初级生产力和地表覆盖类型是产水量的主导影响因素。3)降水、高程与人类活动强度指数对产水服务的影响有较强的正向作用,而蒸散发、归一化植被指数和净初级生产力展现出较强的负向作用。4)研究区南部区域产水量波动水平高。在未来短期内,研究区95.30%的区域有下降趋势。5)藏东-川西地区不应将盲目提升人工植被覆盖度作为提高产水量首要方案,应注意对天然林的保护和预防石漠化。

The east Tibet and west Sichuan ecological and water conservation zone,a notable ecological vulnerable area with low anti-disturbance capability and climate sensitivity,is located in the northern part of Southwest Alpine Canyon Region of China.It is important to study the spatio-temporal distribution characteristics and influencing factors of water yield for the water resources protection,conservation,development and utilization.We simulated the water yield by using the Annual Water Yield module of the InVEST model,mainly based on the data set of surface cover products,climate,bedrock depth,soil,and topography from 2000 to 2020,and analyzed the explanatory power of the factors contributing to the spatial variability of water yield by combining with GeoDetector(GDM),and for the factors with q>0.1 were introduced into the multiscale geographically weighted regression(MGWR)to analyze their influence on water yield in different geographic locations of the region,and the spatio-temporal variation characteristics and dominant factors of water yield were obtained by using the Theil-Sen trend analysis and the Mann-Kendall significance test,and in the meantime.Hurst index was used to predict the upward or downward trend of water yield in the future for a short period of time and the fluctuation level of water yield during the study period at different spatial locations was assessed.The results showed that:1)the spatial distribution of precipitation and water yield presented a distribution pattern of“higher in the east and west,lower in the middle”,the greatest amount of precipitation in the Minjiang River basin,the greatest amount of evapotranspiration in the Jinsha River basin,and the amount of water yield in the Nujiang River basin was more than other three basins.2)except for precipitation and evapotranspiration,the main factors affecting water yield were climate factors(annual mean humidity and annual mean wind speed),topographic factors(DEM),soil type,vegetation factors(NDVI and NPP),and social factors(LULC and HAI),especially precipitation,evapotranspiration,DEM,NDVI,NPP and surface cover type were the dominant influencing factors on water yield.3)There were strong synergies between precipitation,DEM and HAI,and strong trade-offs between evapotranspiration,NDVI and NPP to water yield services.4)The water yield fluctuation level was higher in the southern part of the region and in the short-term future,the water yield showed a decreasing trend in the 95.30%of the study area.5)Increasing the artificial vegetation coverage blindly should not be the primary solution to increase water yield in the region,and the priority was to pay attention to of natural forest protection and rocky desertification prevention.