Spatial variation of soil physical properties and its relationship with plant biomass in degraded slopes in dry-hot valley region of Southwest China

Abstract

Soil properties are one of the most important factors affecting the distribution and growth of plants in arid and semi-arid regions, especially in the dry-hot valley of southwest China, where desertification is a serious environmental problem deteriorating the dryland ecosystems. However, the spatial variation of soil physical properties and its relationship with plant productivity in degraded slopes is not yet fully understood. In this study, three parallel downslope transects were built on a typical degraded slope in the dry-hot valley of Jinsha River, and soil physical properties (including soil particle size, bulk density (BD), total porosity (TP), capillary porosity (CP), noncapillary porosity (NP), saturated water capacity (SWC), capillary water capacity (CWC), field water capacity (FWC), and hydraulic conductivity (Ks)) at two soil depths (0–10 cm and 10–20 cm) and plant biomass (reflected by aboveground biomass) were measured. The results indicated that the sand content, TP, NP, SWC, CWC, and Ks increased firstly and then decreased, while the silt content and BD decreased firstly and then increased from upper slope to lower slope. Plant biomass was only observed in middle and lower slopes, and that in the lower slope was decreased significantly to slope foot. Slope position and soil depth had significant effects (P < 0.05) on soil physical properties, indicating that topography and soil depth play a key role in driving the spatial variation in soil physical properties. Simple linear regression analysis showed that Ks, sand, and silt content are the key soil indicators affecting plant growth, and the soil layer differences in BD, CWC, and FWC are also the important factors affecting plant productivity. Our findings highlight the spatial variation of soil physical properties, and plant biomass is attributed to the interactions of topography-soil-plant, which is critical for the healthy function of degraded slopes. Such findings provide an important basis for ecological restoration and management in degraded regions.