热融湖塘对青藏高原土壤饱和导水率的影响及因素分析

Effect of thermokarst lake on soil saturated hydraulic conductivity and analysis of its influenced factors

为研究多年冻土区热融湖塘对湖岸生态水文过程的影响,该文基于湖岸不同迹地植被发育、导水性及土壤理化性质的分析,并结合土壤转换函数(pedo-transfer functions,PTFs),对土壤导水性及其影响因素进行研究。结果表明:热融湖塘的形成使土壤环境发生了重要演变,其中湖岸死根区土壤饱和导水率相比于未影响区域(110.88 cm/d)增加了70.1%之多,而其在盐渍化区域相比于未影响区域减少了33.8%,同时土壤饱和导水率随着坡度的增加而增强;通过比较ROSETTA、CAMPBELL和VAUCLIN 3种土壤转换函数的预测能力,发现VAUCLIN模型更适合于模拟青藏高原高寒草甸土壤饱和导水率。热融湖塘影响迹地对土壤饱和导水率的变化,是植被盖度、有机质含量、颗粒组成等因素耦合影响作用的结果,运用土壤转换函数对其进行预测时,须综合考虑以上因子。对热融湖塘不同迹地土壤水力参数的研究可为区域土壤侵蚀,产流模式及水文过程的研究提供理论基础。

Thermkarst lakes as a typical landform unit are widely distributed in permafrost areas of the source region of the Yangtze River. The thermokarst lakes can have huge impact on soil properties, permafrost distribution, eco-hydrological processes, etc. on the lakeshore area with its development process. In this study, we analyzed the influence factors on physical and chemical properties of soil and made comparative analysis of the spatial difference of soil saturated hydraulic conductivity in the undisturbed lakeshore area, the dead root area of lakeshore, saline soil area of lakeshore and different slope areas around a typical thermokarst lake in permafrost areas of the source region of Yangtze River. Our results showed that soil saturated hydraulic conductivity differed among soils from different areas. The soil saturated hydraulic conductivity was in an order of dead root area of lakeshore 〉 undisturbed lakeshore area 〉 saline soil area of lakeshore. Compared with the soil of undisturbed lakeshore area, the soil saturated hydraulic conductivity of the dead root area of lakeshore increased by 70.1%, while the saline soil area decreased by 33.8%. The results showed soil environment had a great change with the formation of thermkarst lakes. The results suggested that the formation of the dead root area of lakeshore led to an increase in soil saturated hydraulic conductivity and a decrease of runoff capacity. Opposite results were found with the saline soil. At different slope areas of lakeshore, the greater the slope was, the greater the soil saturated hydraulic conductivity. Furthermore the maximum difference appeared at the middle position of the slope while soil saturated hydraulic conductivity of slope bottom did not obviously changed. The results also showed that with the different effects of thermkarst lakes, the cause of the variation of soil saturated hydraulic conductivity at the different areas was coupled with the influences of vegetation coverage, soil organic matter content, and particle size distribution. When soil Pedo-transfer functions （PTFs） were used to predict soil saturated hydraulic conductivity, above factors must be considered. We used three models, ROSETTA, CAMPBELL and VAUCLIN to evaluate their predictive ability by comparing the simulated results with the measured values and found that VAUCLIN model was the most reliable one to predict soil saturated hydraulic conductivity of the alpine meadow in permafrost areas of the source region of Yangtze River. The study of soil hydraulic parameters in different affected area of thermokarst lakes can provide valuable information for the study of regional soil erosion, runoff models and hydrologic processes.