Response of preferential flow to soil − root − rock fragment system in karst rocky desertification areas

Abstract

The response of preferential flow to the soil − root − rock fragment systems is essential for understanding the eco-hydrological processes in karst rocky desertification (KRD) areas. In this study, we investigated the soil properties, root, and rock fragment distribution characteristics and preferential flow in this system. Results show that there are differences in the development of preferential flow under five grades of rocky desertification: light rocky desertification (LRD) > potential rocky desertification (PRD) > non-rocky desertification (NRD) > moderate rocky desertification (MRD) > severe rocky desertification (SRD). Different degrees of rocky desertification have facilitating or inhibiting effects on preferential flow. LRD and PRD promote preferential flow with ratio of 6.6 %–9.6 %, while MRD and SRD inhibit preferential flow with ratio of 4.2 %–6.7 %. The preferential flow is simultaneously influenced by the components of soil − root − rock fragment systems. Root system indicators (i.e., root biomass, root bulk density, and root length density) generally decrease as grades of rocky desertification increase. The surface outcrops density, rock fragment density, and volume fraction tend to increase with grades of rocky desertification. A principal components analysis found that preferential flow of MRD and SRD is highly influenced by rock fragments, while LRD is more driven by root systems and soil properties. PRD is averagely influenced by the combination. These findings suggest that appropriate plant and rock fragment ratios can effectively avoid water loss in the form of preferential flow and more attention should be paid to the ecological problems of LRD and PRD areas.