State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, CAS, Lanzhou 730000, China; Centre for Northern Studies and Geography Department, University of Montreal, Montreal, Quebec, H2B 2V8, Canada.
State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong University, Chongqing, 400074, China; State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, CAS, Lanzhou 730000, China; School of Civil Engineering, Chongqing Jiaotong University, Chongqing, 400074, China.
J Environ Manage. 2020 May 15;262:110302. doi: 10.1016/j.jenvman.2020.110302. Epub 2020 Feb 27.
Soil thermal state exerts an important role in soil physicochemical properties, nutrient content, soil carbon losses, and hydrological processes in cold regions. In the Qinghai-Tibet Plateau, desertification and aeolian sand accumulation greatly change the surface cover types and simultaneously alter the surface energy budget. However, the quantification of their impacts on the soil thermal state hasn't been studied methodically. Here, a laboratory experiment was conducted to investigate the impact of surface cover types, including bare surface, grass-coved surface, dry and wet (3%) aeolian sand-covered surface, on underlying soil thermal state. Our results demonstrate that there is a reciprocal relationship between environment change and permafrost degradation. The amount of heat entering the active layer was determined by the surface cover types and soil water content. Using the bare surface case as a reference, vegetation layer acted as a buffer to reduce the amount of heat propagation downwards the ground by 20% and to lower the near surface temperature by 0.7 °C. In contrast, dry aeolian sand acted as an insulation layer and warmed the ground by about 2 °C. Also, wet aeolian sand with high thermal conductivity facilitated the heat exchange with the atmosphere and warmed the ground about 1.5 °C. Our results have implications for thermal and hydrological processes in the atmosphere-ground-permafrost system and thermal stability of infrastructure under the effect of the desertification and aeolian sand accumulation. The hydrothermal interaction of desertification and permafrost needs to be quantified in the further study through long-term field observations and a fully-coupled water flow and heat transport model under a changing climate.
土壤热状况对寒冷地区土壤理化性质、养分含量、土壤碳损失和水文过程起着重要作用。在青藏高原，沙漠化和风沙堆积极大地改变了地表覆盖类型，同时改变了地表能量平衡。然而，它们对土壤热状况的影响还没有被系统地量化。在这里，进行了一项实验室实验，研究了不同地表覆盖类型（裸地、草地、干沙和湿沙（3%））对下垫面土壤热状况的影响。我们的结果表明，环境变化和多年冻土退化之间存在相互关系。进入活动层的热量取决于地表覆盖类型和土壤含水量。与裸地情况相比，植被层起到了缓冲作用，减少了约 20%的热量向下传播，并使近地表温度降低了 0.7°C。相比之下，干燥的风沙层起到了隔热层的作用，使地面升温约 2°C。此外，具有高导热系数的湿风沙促进了与大气的热交换，使地面升温约 1.5°C。我们的研究结果对大气-地面-多年冻土系统中的热和水文过程以及沙漠化和风沙堆积作用下基础设施的热稳定性有一定的启示。在气候变化的影响下，需要通过长期的现场观测和一个水-热完全耦合的水流和热传输模型来量化沙漠化和多年冻土的水热相互作用。
