Preferential water flow through decayed root channels enhances soil water infiltration: Evaluation in distinct vegetation types under semi-arid conditions

Abstract. Topsoil desiccation alters soil physical characteristics and seriously limits plant growth in semi-arid and arid areas. The phenomenon of dried soil layer has generated increasing attention, but the process of preferential flow through decayed root channels – when the plants decompose after death – and its benefits on soil water supply in the soil dry layers are rarely evaluated. This study examines the effects of root channels on soil infiltrability in three contrasted vegetation types developed in a loessial soil, namely: Scrubland (Caragana korshinskii), fruit tree plantation (Armeniaca vulgaris) and grassland (Medicago sativa; using data from a previous study); setting bare land as control. The infiltration rates of the alive and decayed specimens were measured using a double-ring infiltrometer, and methylene blue allowed us to trace the pathways of water flow. Results indicated that scrubland species had the highest steady infiltration rates, which were about 23 % and 83 % higher than those rates measured in the fruit tree plantation and grasslands, respectively. Regarding root geometry, the steady infiltration rates were significantly and positively correlated with the average root channel diameter (ARCD) and area (RCA). Under the same root diameter conditions, soil water infiltrability significantly improved in the decayed root plots and compared with the alive root plots. Our findings contribute to a better understanding of the effects of root channels of different degraded vegetation types on soil moisture and infiltrability, which are conductive to provide knowledge base in the research of hydrological processes in degraded soils in water-scarce regions.