青藏高原风火山流域多年冻土活动层土壤水分入渗特征及变化分析

Analysis of infiltration characteristics and variations of soil moisturein the active layer of permafrost in Fenghuoshan basin,Qinghai-Tibet Plateau

坡向和坡位是影响坡面活动层土壤水分入渗的重要因素,然而当前对多年冻土区活动层土壤冻融循环影响下不同坡向、坡位土壤水分入渗特征的研究甚少。本文设置了不同时空条件的野外试验点,更加系统地分析了青藏高原多年冻土区活动层土壤水分入渗过程的时空差异性。选取青藏高原腹地风火山流域高寒草甸坡面活动层土壤为试验地,分别在不同的坡向(阳坡、阴坡)和坡位(坡顶、坡中)设置观测点,分析活动层土壤在完全融化期(7—8月)和开始冻结期(9—10月)坡面水分的入渗特征及其时空差异性,评估不同入渗模型在研究区的适用性。结果表明,多年冻土区坡面活动层土壤水分入渗特征具有较强的时空差异性。土壤水分入渗过程可以分为入渗瞬变阶段(0~30 min)、入渗渐变阶段(30~100 min)、入渗稳定阶段(>100 min)三个阶段,入渗速率的大小整体表现为阳坡>阴坡,坡顶>坡中,完全融化期>开始冻结期,瞬变阶段>渐变阶段>稳定阶段。五种模型对入渗过程的模拟结果显示,Horton模型对青藏高原多年冻土区土壤水分入渗过程的模拟效果最佳,而通用经验模型和蒋定生公式对入渗的拟合曲线和统计参数几乎完全相同,但模型表达式不同。本文研究结果可为不同时空条件下的陆地水文过程模型参数化提供数据支持。

Slope aspect and position are important factors influencing the infiltration of soil moisture in slope ac-tive layer,but there is currently limited research on the infiltration characteristics of soil moisture in different slope aspect and position under the influence of freeze-thaw cycles in the active layer of permafrost region.This study establishes field experimental sites with different spatiotemporal conditions,enabling a more comprehen-sive analysis of the spatiotemporal variations in the soil moisture infiltration process within the active layer of per-mafrost region on the Qinghai-Tibet(Xizang)Plateau.We select the active layer soil on the slope surface of the alpine meadow in the Fenghuoshan basin,located in the hinterland of the Qinghai-Tibet Plateau,and set observa-tion points at different slope aspects(sunny and shady slopes)and positions(top and middle of slopes)to ana-lyze the infiltration characteristics and spatiotemporal differences of soil moisture on the slope surface during complete thawing period(July to August)and initial freezing period(September to October)of the active layer soil,and evaluate the applicability of different infiltration models in the study area.The results indicate that the infiltration characteristics of soil moisture in slope active layer in permafrost region exhibit significant spatiotem-poral variations.The infiltration process of soil water can be divided into three stages:infiltration transient stage(0~30 min),infiltration gradual stage(30~100 min),and infiltration steady stage(>100 min).The infiltration rate shows as follows:sunny slope>shady slope,top of slope>middle of slope,complete thawing period>ini-tial freezing period,infiltration transient stage>infiltration gradual stage>infiltration steady stage.By using five models to simulate the infiltration process,the results show that the Horton model has the best simulation ef-fect for the infiltration process of soil water in permafrost regions of the Qinghai-Tibet Plateau.However,the general empirical model and Jiang Dingsheng’s formula has almost identical fitting curves and statistical parame-ters for infiltration,but the model expressions are different.The simulation and analysis of soil moisture infiltra-tion in permafrost region of Qinghai-Tibet Plateau in this study will provide data support for parameterization of land hydrological model under different spatiotemporal conditions.