高原鼠兔扰动对高寒草甸土壤水热条件的影响研究

The plateau pika (Ochotona curzoniae) is a keystone species for biodiversity on the Tibetan plateau, and its disturbance has significant effect on the soil hydrothermal conditions and ecological functions of alpine meadow. Based on the field investigation of aboveground mounds and the geophysical scanning of belowground burrows in Qinghai Lake watershed, this study analyzes the spatial pattern of plateau pika in the whole watershed, builds a 3-D image of plateau pika's disturbance, and reveals its characteristic at the landscape scale by linking aboveground and belowground together. The horizontal distribution of soil moisture under plateau pika's disturbance is studied by the electromagnetic induction, and then the source-sink relationship of precipitation redistribution between the mound and the surrounding grassland is evaluated. By the measurement of land surface reflectance, soil thermal conductivity, and soil heat flux, this study investigates the variation of the energy redistribution above the ground and the heat conduction below the ground, and further shows the influence of plateau pika's disturbance on the heterogeneity of soil-heat processes. By considering the water balance and energy balance, a water-heat coupled model is used to simulate the soil moisture and soil temperature, and to reveal the interaction mechanism between soil moisture and soil temperature under plateau pika's disturbance. This study would provide scientific base for the protection and management of alpine meadow.

高原鼠兔是维护青藏高原生物多样性的关键物种，其扰动对高寒草甸的土壤水热条件和生态系统功能具有重要影响。本项目通过对青海湖流域高原鼠兔扰动形成的地表鼠丘的调查测量和地下鼠洞的地球物理探测，分析高原鼠兔在流域尺度的分布格局及其关键影响要素，构建高原鼠兔扰动的地下三维结构图，将地上和地下作为整体阐明高原鼠兔在景观尺度的扰动特征。利用大地电导仪研究高原鼠兔扰动下土壤水分的水平分布，探究鼠丘与周围草地之间降水再分配的源-汇关系，通过对地表反射率、土壤导热率和土壤热通量的观测，分析不同扰动情景下地表能量分配和地下热量传输的变化，揭示高原鼠兔扰动对土壤水热过程异质性的影响规律。综合考虑水量平衡和能量平衡，利用土壤水热耦合模型对土壤水分和土壤温度进行模拟，揭示高原鼠兔扰动下土壤水分与土壤温度的相互作用机制，为高寒草甸生态系统的保护和管理提供依据。

项目以青海湖流域为研究区，通过野外调查、实验观测和模型模拟方法，研究了高原鼠兔等鼠类扰动对高寒草甸土壤结构、土壤水分和土壤温度的影响，取得以下主要进展：（1）明确了青海湖流域适宜高原鼠兔生存的面积约为3982km2，主要位于青海湖西岸、布哈河上游和沙柳河中游地区，确定了影响其分布的主要因素包括与道路之间距离、土壤类型等，量化了人类活动的可能影响。（2）阐明了高原鼠类洞道分布的深度、直径、走向等结构特征，发现地下洞道所处位置与地表鼠丘分布具有良好的对应关系，新鼠丘下方洞道较连续，旧鼠丘下方洞道较破碎。（3）发现不同地表类型10cm和20cm土壤温度变化分别比净辐射变化延迟约6h和9h，高原鼠类扰动之后土壤吸热有所减少而地表能量净输出有所增加。（4）明确了高原鼠兔扰动能在短时间内增加土壤微生物碳、氮含量并使其垂向分布更加均匀，主要通过改变土壤容重、土壤粉粒含量、地上生物量和土壤重量含水量对土壤营养成分产生影响。（5）确定了Brutsaert公式是青海湖地区晴天条件下最适用的大气比辐射率参数化方案，定量评估了云对大气向下长波辐射的影响。（6）利用SHAW模型对青海湖地区土壤水热特征进行了模拟，发现进气势和孔径指数是影响土壤温度变化模拟的主要因素。以上研究可为高寒地区生态系统的管理与退化植被的恢复提供科学依据。