Land use dependent variation of soil water infiltration characteristics and their scale-specific controls

Land use change has remarkable impact on hydrological processes. However, little is known on the land use dependent variation of soil water infiltration characteristics. This study aims to investigate the effects of land use type on the spatial variation of infiltration characteristics and to identify their scale-specific controls. A total of 132 in-situ infiltration measurements were conducted using a disc infiltrometer along four 96-m transects under different land use types (forestland, shrubland, cropland with tillage, and cropland without tillage) in a typical agricultural region in north China. Classical statistics and multivariate empirical mode decomposition (MEMD) were used to explore the features of the overall and scale-specific spatial variation of four infiltration characteristics, i.e., cumulative infiltration over 30 min (I30), sorptivity (S), unsaturated hydraulic conductivity (K0, h0 = -2 cm) and saturated hydraulic conductivity (Ks). Besides, the scale-specific correlations between the infiltration characteristics and selected environmental factors, i.e., bulk density (BD), soil organic matter (SOM), initial soil water content (IWC) and water temperature (T) were investigated. The results indicated that land use type significantly affected not only the values of the infiltration characteristics but also their overall and scale-specific spatial variability. Tillage was found to have great impact on these infiltration characteristics. Generally, cropland with tillage revealed significantly higher values and weaker overall spatial variation of I30 and S; while its K0 and Ks were significantly lower. Four major common spatial scales, i.e., 8-9 m, 13-16 m, 28-34 m and 47-94 m, were identified for the infiltration characteristics under different land use types using MEMD. The spatial variation of infiltration characteristics in forestland and shrubland were decomposed into larger common scales than that in croplands. Furthermore, the dominating factors of infiltration characteristics were scale-specific and also varied with land use type. Generally, SOM and BD were considered as important controls in smaller scales in croplands and the impacts of IWC and T were more effective in larger scales in forestland and shrubland.