气候要素和土壤质地对青藏高原草地净初级生产力和降水利用率的影响

Response of climate and soil texture to net primary productivity and precipitation-use efficiency in the Tibetan Plateau

植被净初级生产力(net primary productivity,NPP)和降水利用率(precipitation-use efficiency,PUE)是直观反映群落生长状况以及植被对降水的利用效率的重要指标。以青藏高原为研究区,利用2000–2015年植被NPP遥感产品,结合同时期的气象和土壤质地数据,采用回归分析、相关性分析和构建结构方程模型分析降水、气温和土壤质地对青藏高原NPP和PUE变化的影响。结果表明,1)降水(|r|=0.71,P <0.001)和气温(|r|=0.67,P <0.001)与NPP呈极显著正相关关系,且降水对NPP影响大于温度;2)降水(|r|=0.4,P <0.001)和气温(|r|=0.56,P <0.001)与PUE呈极显著正相关关系,但降水对PUE变化的解释能力低于温度;3)土壤黏粒含量和PUE之间呈极显著正相关关系(|r|=0.41,P <0.001),土壤砂粒含量和PUE之间呈显著负相关关系(|r|=0.35,P <0.001)。综上可知,在青藏高原降水是NPP的第一限制因子,而温度是控制PUE的首要因子,土壤质地对PUE的影响应予以长期关注,这有利于为不同质地条件下的水资源分配方式提供参考。

Precipitation-use efficiency(PUE)can be used as an indicator of ecosystem function.This study collected remote sensing data of net primary productivity and meteorological and soil texture data for the Tibetan Plateau for the period from2000 to 2015.We used regression analysis,correlation analysis and structural equation modeling to characterize the relationships between productivity and precipitation across different soil texture types.NPP was positively correlated with precipitation,and precipitation(|r|=0.71,P<0.001)and temperature(|r|=0.67,P<0.001).PUE was positively correlated with precipitation(|r|=0.4,P<0.001)and temperature(|r|=0.56,P<0.001),but temperature had a larger effect on PUE than precipitation.Soil sand content and PUE were positively correlated(|r|=0.41,P<0.001),and soil clay content and PUE were negatively correlated(|r|=0.35,P<0.001).The results of the structural equation modelling showed that the influence of soil sand content on NPP and PUE was much greater than that of clay content.Therefore,precipitation is the main limiting factor affecting NPP,but the temperature is the main limiting factor affecting PUE.The soil clay content can inhibit the infiltration of precipitation,and improved the PUE of vegetation.We expect the findings of this study to draw attention to the influence of soil texture on PUE and provide scientific theoretical guidance for ecological restoration under different texture conditions.