青藏高原冻土区土壤温度的时空变化及影响因素的识别和模拟

全球气候变暖驱动了大范围冻土区土壤温度的升高，但土壤温度变化与气温变化呈现复杂、非线性的关系，具有巨大空间异质性。什么原因导致了不同区域和环境下冻土温度对气温变化响应的差异性，仍不清楚。过去关于冻土温度变化机制的研究大量集中在土壤水-热动力耦合作用上，然而越来越多观测显示冻土区植被特征和土壤有机质含量显著影响了土壤温度的动态变化，但目前在植被和土壤性质如何改变冻土温度对气温变化敏感性方面的认识有限。为此，本项目以青藏高原冻土区为研究对象，基于站点观测和遥感数据解析土壤温度对气温响应关系的关键影响因素；并在此基础上评估陆面过程模型能否准确刻画不同植被和土壤条件下的土壤温度对气温变化的敏感性，据此优化模型关键过程参数；利用改进的模型预估未来青藏高原冻土区土壤温度的时空变化格局。本项目的实施有利于加深对冻土区土壤温度变化的过程和机理的认识，进而为评估青藏高原生态系统功能的动态变化提供重要基础。

Global warming drives the observed widespread increase in soil temperature in permafrost regions, while changes in soil temperature display a complex, non-linear relationship with changes in air temperature, which is highly spatially heterogeneous. It remains unclear what environmental factors have caused the different sensitivities of soil temperature to air temperature changes. Previous studies have mostly focused on the coupling of soil thermal and hydraulic processes, while recent observations have shown that the vegetation characteristics and soil organic matter content significantly affect the permafrost soil temperature dynamics. However, our current knowledge regarding how vegetation and soil properties influence the sensitivity of soil temperature to air temperature changes is limited. Here, this project focuses on the permafrost regions in the Tibetan Plateau, which are characterized by diverse plant and soil properties and high spatial heterogeneity. The project aims to reveal the key influential factors that drive the response of soil temperature to air temperature changes based on site observations and remote sensing data. The project will then evaluate whether the process-based land surface model can reproduce the diverse sensitivities of soil temperature to air temperature under different vegetation and soil conditions, the result of which will be used to improve the structure/processes and parameters of the model. The improved model will then be used to project the future spatiotemporal dynamics of soil temperature on the Tibet Plateau. The implementation of this project is conducive to deepening the understanding of the processes and mechanism of permafrost soil temperature dynamics, and thus provides an important basis for evaluating the dynamic changes of ecosystem functions on the Tibet Plateau.