Abstract: 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.

Key words: Loess Plateau, gully, soil bulk density, soil saturated hydraulic conductivity, soil water content