Variation in soil saturated hydraulic conductivity along the hillslope of collapsing granite gullies.

Saturated hydraulic conductivity (<italic>K_s</italic>) affects the soil hydrological process and is influenced by many factors that exhibit strong spatial variations. To accurately measure <italic>K_s</italic> and its scale, spatial variability and relationship with collapsing gullies, we analysed four double-ring infiltrometer diameters in three soil layers during <italic>in situ</italic> experiments designed to measure <italic>K_s</italic> in two typical collapsing gullies (three slope sites) in Tongcheng County of China. The results showed that <italic>K_s</italic> increased with increasing inner ring diameter, but no significant difference existed between inner diameters of 30 and 40 cm. The <italic>K_s</italic> in red soil layers was higher than that in sandy soil layers, the transition layers had the lowest values. <italic>K_s</italic> also varied with slope position, gradually decreasing with distance from the gully head. The suggestion is that the spatial variation in <italic>K_s</italic> is affected not only by the intrinsic soil properties but also by the interaction with the collapsing gully. [ABSTRACT FROM AUTHOR]