Vertical partition patterns of infiltration within soil profile and its control factors at large-scale arid mountainous areas

Abstract

Infiltration process controls how rainfall is stored in soil and subsequently used by plants, thus, plays a critical role in eco-hydrological processes. However, the vertical pattern of infiltration partitioning within a soil profile and the factors that control it remain poorly understood, especially in data-scarce mountainous areas. Based on a large-scale long-term soil moisture (SM) network in the Qilian Mountains, Northwest China, we explored infiltration partitioning and its control factors using a new metric, percentage of soil water storage increment in each layer to the soil profile during a rainfall infiltration event (PSTI). We found that both vegetations with deep roots and wet SM conditions facilitated infiltration into the deeper soil, although meadow favored infiltration within the surface layer. Hillslope stations showed a higher degree of infiltration partitioning in subsurface layers than the flatland stations due to the influence of topography on soil properties. Meanwhile, the increasing slope gradient will reduce the partition of infiltration at the subsurface layers. Among the soil properties, sand content, soil organic carbon, α (parameter of soil retention curve), and soil saturated hydraulic conductivity promoted infiltration into greater depth, while clay content and bulk density had the opposite effect. The major factors controlling the pattern of infiltration partitioning were n (parameter of soil retention curve) for 0–10 cm depth, α for 10–20 cm and 20–30 cm depths, and SM for PSTI below 30 cm. This quantitative analysis method for the infiltration partitioning improves our understanding of infiltration regimes, and supports water resources management in dryland mountains.