Biocrusts and subshrub development and soil water through a slope-gully system in a vegetation-restored site on the Loess Plateau of China

Abstract

The landscape position (LP) of slope-gully system (SGS) greatly influences the variations in soil water content, and development of biocrusts and vegetation. It is unclear the relationships between biocrusts, natural successional vegetation, and soil water content in the SGS with different LPs and habitats in semiarid regions. Therefore, this study aimed to clarify the relationships between moss-dominated biocrusts and natural successional A. sacrorum in the utilization of soil water; and investigate their spatial variation characteristics in a typical SGS. Soil water content in the 0–1 m soil layer, and biocrust and vegetation characteristics were measured at the summit, ridge slope, gully slope, and gully floor of an SGS in five habitats (i.e., bare areas (BA), moss-dominated biocrusts (BC), A. sacrorum (AS), A. sacrorum with biocrusts (ASB), and dead A. sacrorum with biocrusts (DASB)). The results showed that plant aboveground biomass and soil water content in the 0–1 m soil layer followed the pattern of DASB < ASB < AS and BC < DASBC≈ASB < BA ≤ AS for the summit, and ridge and gully slopes, respectively. While, those followed the pattern of DASB < ASB≈AS and BC < DASBC≈ASB≈BA≈AS for the gully floor, respectively. Compared to bare lands, soil water content and aboveground biomass were lower in habitats covered by biocrusts, which was likely related to reduced infiltration of biocrusts. This phenomenon was insignificant at the gully floor, which was attributed to the decreasing effect of biocrusts on soil water content with the improvement of water conditions. Soil water content of subshrub covered habitats were slightly higher than those of bare lands, which probably related to the reduced soil evaporation under shading conditions. This study showed that the relationships between biocrusts, subshrubs, and soil water were complex under natural succession conditions, and further observations are needed in the future in semiarid regions.