黄土区坡面尺度不同植被类型土壤饱和导水率剖面分布及影响因素

Profile Distribution of Soil Saturated Hydraulic Conductivity and Controlling Factors Under Different Vegetations on Slope in Loess Region

土壤饱和导水率(K_s)是影响水、溶质运移过程和水文模型模拟精度的重要参数,了解坡面尺度下不同植被类型K_s的剖面分布与影响因素有助于更好地理解土壤水文过程及其调控机制。本研究通过测定典型黄土区坡面尺度不同植被类型下12个土壤剖面(0～200 cm)的K_s及土壤基本性质,分析了不同坡向间及同一坡向内随植被类型变化土壤K_s的剖面分布特征及其影响因素。结果表明:不同植被类型下土壤K_s首先随着土壤深度的增加而减小,而后呈增大趋势。东北坡林地、西坡草地和林地剖面上层(0～20 cm)的平均土壤K_s(K_(s-average))均显著高于剖面下层(20～200 cm)(P<0.05)。同一坡向内不同植被类型及不同坡向间相同植被类型0～20 cm土层的K_(s-average)没有显著差异(P>0.05);而由于土壤质地和有机质含量的差异,20～200 cm土层的K_(s-average)表现为同一坡向内东北坡草地显著高于林地(P<0.05),不同坡向间东北坡草地和林地分别显著高于西坡草地和林地(P<0.05)。六道沟小流域不同植被类型下土壤K_s与容重、黏粒含量、粉粒含量呈极显著负相关(P<0.001),与毛管孔隙度、饱和含水量、砂粒以及有机质含量(西坡草地除外)呈显著正相关(P<0.05)。影响六道沟小流域K_s剖面分布的因素可由土壤持水特性(49.36%)、质地(24.98%)和养分含量(13.92%) 3个主成分贡献。本研究利用多元逐步回归分析获得了以容重、土壤质地和有机质为输入因子的土壤K_s传递函数(R^2=0.60～0.86,P<0.001),可为典型黄土区坡面尺度土壤K_s的模拟和预测提供参考。

Soil saturated hydraulic conductivity (Ks) is an important parameter influencing hydrological processes and the accuracy of hydrological model simulation. Understanding the profile distribution of Ks and their controlling factors under different vegetations at the slope scale are conductive to better understand the hydrological process and its regulation mechanism. In this study, the Ks and soil basic properties were measured of 12 profiles (0-200cm) under different vegetations on slopes. These profiles were chosen according to different vegetations (grassland and forestland) and different slope aspects (northeast orientation and west orientation). The objective of this study is to examine the changes in the vertical distribution of Ks and to identify the main controlling factors for the variations of Ks at the slope scale in a relative small region. The results showed that Ks under different vegetations decreased initially with depth and then tended to increase downward, and the average values of Ks (Ks-average) in 0-20cm soil layer were significantly higher than that in 20-200cm soil layer (P < 0.05). There were no significant differences of the Ks-average in 0-20cm soil layer among different vegetation types in the same slope as well as between different slopes for the same vegetation type (P > 0.05). However, due to the differences of soil texture and organic matter, the Ks-average in 20-200cm soil layer under grassland was higher than that under forestland in the northeast organization slope, and the Ks-average in 20-200cm soil layer in northeast orientation slope was higher than that in west orientation slope whether under grassland or forestland (P< 0.05). Ks under different vegetations were positively correlated with capillary porosity, saturated water content, sand and organic matter (except grassland in the west orientation slope)(P < 0.05), but were negatively correlated with bulk density, clay and silt content (P< 0.05). The factors influencing Ks can be attributed to three principal components: soil water retention capacity (49.36%), soil texture (24.98%) and soil fertility characteristic (13.92%). Based on the effects of soil properties, the pedotransfer functions (PTFs) of Ks under different vegetations were proposed by using multiple stepwise regression analysis. The PTFs with inputs of bulk density, soil texture and organic matter had a better fitting ability of Ks (R^2 = 0.60 ~ 0.86,P < 0.001), which could be used as a reference for the simulation and prediction of Ks at the slope scale in Liudaogou watershed.