黄土区坡沟系统容重、饱和导水率和土壤含水量变化分析

切沟是黄土高原侵蚀沟的重要类型之一,对流域水文、植被、地貌和生态等地表过程具有深刻影响。为明确土壤物理参数对切沟地形、坡位和深度的响应,在陕北黄土高原选择典型切沟,根据其走向设置沟道、沟缘及坡面3条样线,对40个样点按照10 cm深度间隔采集0~30 cm各土层原状土样,利用定水头法和烘干法对土壤容重、饱和导水率和土壤含水量进行测定并分析。结果表明:(1)地形对容重、饱和导水率和土壤含水量具有显著或极显著影响,3个参数随坡位自下而上均呈波浪式变化趋势;沟缘和坡面位置容重随坡位上升总体呈微弱减小趋势,沟缘表层坡下土壤含水量较其他坡位明显偏低;(2)沟缘和坡面位置不同土层深度饱和导水率及容重的大小变化规律与沟道恰好相反;(3)对于各土层深度而言,沟缘和坡面土壤含水量均与沟道内差异显著,且沟缘土壤含水量总是低于坡面。以上结果表明,切沟分布改变了土壤容重、饱和导水率和土壤含水量在坡面的空间格局,在黄土区坡沟系统内不同地形条件对相关土壤物理参数的影响不应忽视。

Spatial Variation of Soil Bulk Density,Saturated Hydraulic Conductivity and Soil Water Content in a Slope-gully unit of the Northern Loess Plateau

Gully is an important kind of erosional landform in the watershed of northern Loess Plateau and has a profound effect on the surface processes such as hydrological, vegetational, geomorphologic and ecological et al. To clarify the response of three soil physical parameters (soil bulk density, BD; saturated hydraulic conductivity, Ks; soil water content, SWC) to gully topography, slope position and soil depth, we layouted three sampling transects in the bottom, edge and nearby bank of an erosional gully, with the sampling site numbers set as 40. At every site, undisturbed soil cores were sampled at three soil depth layers: 0~10 cm, 10~20 cm and 20~30 cm, they were regarded as surface, sub-surface and shallow layers, respectively. Based on the constant water-head method and drying method, we obtained the data of BD, Ks and SWC. The results showed: (1) three topography condition had significant or highly significant effect on BD, Ks and SWC, and the three parameters showed wave-like trend along the slope length. The BD on the gully edge and bank slightly decreased with the increase of slope length. With exception to soil surface on the gully edge, SWC on down slope was significantly higher than middle and upper slope; (2) On the gully edge and bank, the variation trend of Ks and BD with the depth layer was different from that on the gully bottom; (3) At every depth layer, SWCs on the gully edge and bank were significantly different from those on the gully bottom; and SWC on the gully edge was always lower than that on the gully bank. The results above mentioned indicated that the spatial pattern of BD, Ks and SWC on the slope was changed by the distribution of gully, the influence of different topography conditions of the slope-gully unit on the soil physical parameters could not be neglected.