Rock fragments and soil hydrological processes: Significance and progress

In this review, we explore the significance of rock fragments in studies of soil hydrological processes, because according to research, the effects of rock fragments on soil hydrological processes are inconsistent (positive/negative). Rock fragments play a critical role in the biosphere as the primary filter for water and solutions containing contaminants and heavy metals. Rock fragments have a complex influence on soil hydrological processes (e.g. soil erosion, runoff generation, water infiltration, solute transport and water flow) and are highly relevant in a typical system in the soil-plant-atmosphere continuum. Cracks related to rock fragments provide preferential flow paths through which pollutants are transported into groundwater. In this paper, the published literature is reviewed concentrating on rock fragments and their effects on soil hydrological processes. Systematic studies and examples illustrate the effects of rock fragments architecture (i.e. coverage, content, size, position, spatial heterogeneity, morphology, weathering and topography) on soil hydrological processes. Methods and models applied to evaluate the effects of rock fragments on soil hydrological processes are examined in detail. We conclude that the relationship between rock fragments and soil hydrological processes is complicated and requires more international research efforts. This review concludes with a discussion of perspectives on areas of research that can improve understanding of the effects of rock fragments on soil hydrological processes, with insights and suggestions also being provided regarding potential research trends, requirements and solutions. (C) 2016 Elsevier B.V. All rights reserved.