Xiong Xiaofeng, Li Jianhong, Zhang Tao, Wang Sainan, Huo Weijie
Key Laboratory of Karst Dynamics, MNR & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, No. 50, Qixing Ave, Qixing District, Guilin, 541004, China.
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China.
Environ Sci Pollut Res Int. 2021 Jan;28(4):4716-4730. doi: 10.1007/s11356-020-10784-2. Epub 2020 Sep 19.
Understanding the transport processes of soil moisture and heat is critical for vegetation restoration in karst rocky desertification areas where serious soil erosion and extensive exposure of carbonate rocks occur. Numerical simulation can provide an important approach to explore the transport processes of soil moisture and heat, but few studies employing this technique have been carried out in karst rocky desertification areas of southwest China. In this study, a model of coupled soil moisture and heat transport was established using HYDRUS-1D based on the high-resolution data of soil moisture, soil temperature, and meteorological parameters obtained throughout a year in a typical karst rocky desertification area in Yunnan province, southwest China. The modeling results reflect the rainfall-infiltration-evaporation processes in rocky desertification areas well. The frequently rainfall events in small intensity in the study site often induced great variations of soil moisture in the near-surface soil layer (< 1-cm depth). However, soil moisture in deep soil layer (> 10-cm depth) kept stable during light rainfall events, implying that the deep soil was only influenced by heavy rainfall events. The variations of soil temperature showed a high sinusoidal fitting trend. At the annual scale, variations of soil temperature were distinct apparent evident below the depth of 40 cm, but no evident daily variations were observed. The simulated fluxes of soil water showed that the vapor fluxes were lower than the liquid water fluxes by 3-6 orders of magnitude, suggesting the control of soil thermal gradients. Our results also indicate that the vapor flux has great significance for plant water utilization in the drought periods. The simulation errors are small for soil temperature but slightly more significant for the soil moisture in deep soil layer. This primary failure may result from the occurrence of preferential flows at the rock-soil interface, which needed to be further investigated in the future.
了解土壤水分和热量的传输过程对于岩溶石漠化地区的植被恢复至关重要，这些地区存在严重的土壤侵蚀和大面积的碳酸盐岩裸露。数值模拟可以提供一种重要的方法来探索土壤水分和热量的传输过程，但在中国西南岩溶石漠化地区，很少有研究采用这种技术。在本研究中，基于中国西南部云南省一个典型岩溶石漠化地区全年获得的土壤水分、土壤温度和气象参数的高分辨率数据，利用HYDRUS-1D建立了土壤水分和热量传输耦合模型。模拟结果很好地反映了石漠化地区的降雨-入渗-蒸发过程。研究地点频繁出现的小强度降雨事件常常导致近地表土壤层（<1厘米深度）土壤水分的巨大变化。然而，在小雨事件期间，深层土壤（>10厘米深度）的土壤水分保持稳定，这意味着深层土壤仅受大雨事件的影响。土壤温度的变化呈现出较高的正弦拟合趋势。在年尺度上，40厘米深度以下土壤温度的变化明显，但未观察到明显的日变化。模拟的土壤水通量表明，水汽通量比液态水通量低3-6个数量级，这表明土壤热梯度起控制作用。我们的结果还表明，水汽通量在干旱时期对植物水分利用具有重要意义。土壤温度的模拟误差较小，但深层土壤水分的模拟误差略大。这种初步的误差可能是由于岩土界面处出现优先流所致，未来需要进一步研究。
