黄河水源涵养区水碳变量的时空变化特征及其影响因素

Spatial and temporal variation characteristics of the water and carbon variables in the water conservation zone of the Yellow River and their influencing factors

明晰黄河水源涵养区水碳变量变化规律对于理解黄河流域水碳循环演变过程与机理、保障水资源和生态安全以及支撑水碳资源管理等具有重要意义。论文采用时空统计分析、地理探测器和偏相关分析等方法,在全区、分区和栅格尺度上对黄河水源涵养区的6个典型水碳变量(总初级生产力、净初级生产力、碳利用效率、蒸散发、径流和水分利用效率)2001—2018年的时空变化特征及其成因进行探析。结果表明:(1)黄河水源涵养区全区及3个分区的水碳变量主要呈现波动上升的变化趋势,空间分布具有明显的区域分异性。碳变量(总初级生产力、净初级生产力、碳利用效率)和水碳耦合变量(水分利用效率)多年均值大小次序为Ⅲ区(伊洛河区)>Ⅱ区(渭河南部山区)>Ⅰ区(黄河上游水源区),均呈现由东南向西北递减的空间变化格局,而水变量(蒸散发、径流)则大致呈现南部和西北部高、中部低的空间分布格局。(2)表征水热条件的气候因子和下垫面因子共同驱动黄河水源涵养区水碳变量的变化。全区探测的水碳变量影响因子的驱动力大小次序未发生根本改变,全区尺度主要受到叶面积指数、气温和降水因素的驱动;分区及栅格尺度的碳变量和水碳耦合变量的变化受叶面积指数驱动主导的范围最大,水变量的变化受净辐射和降水驱动主导的范围最大。

Clarifying the changes of water and carbon variables in the water conservation zone of the Yellow River is important for understanding the evolution processes of water and carbon cycles and mechanism in the Yellow River Basin,ensuring water resources and ecological security,and supporting water and carbon resources management.In this study,we investigated the spatial and temporal variation characteristics of the six typical water and carbon variables(gross primary production,net primary production,carbon use efficiency,evapotranspiration,runoff,and water use efficiency)in the water conservation zone of the Yellow River and their causes at different spatial scales,using spatiotemporal statistical analysis,Geodetector,and partial correlation analysis,based on annual water and carbon variable data,meteorological data,and vegetation leaf area index data during 2001-2018.The results show that:1)The water and carbon variables in the water conservation zone of the Yellow River and the three subregions mainly showed a fluctuating upward trend during the study period;the spatial distribution of water and carbon variables showed obvious regional heterogeneity.The interannual mean values of the carbon variables(gross primary production,net primary production,carbon use efficiency)and the water-carbon coupling variable(water use efficiency)were in the order of Zone III(Yiluo River Zone)>Zone II(Southern Weihe Mountainous Zone)>Zone I(Upper Yellow River Zone),which decreased spatially from southeast to northwest,while the water variables(evapotranspiration and runoff)generally showed a spatial distribution pattern of high in the south and northwest and low in the central area.2)Climatic factors,especially water-heat factors,and land surface factors jointly drove the variation of the water and carbon variables in the water conservation zone of the Yellow River.The ranking of the driving forces of the water and carbon variables detected at the regional scale did not change fundamentally,and they were mainly driven by the leaf area index,temperature,and precipitation factors;the changes of carbon and water-carbon coupling variables at the subregional and grid scales were mainly driven by the leaf area index and the changes of water variables were mainly driven by net radiation and precipitation.