Impact of Land Use Conversion on Soil Structure and Hydropedological Functions in an Arid Region

Abstract

Land use conversion critically affects soil structure and associated functions. This study investigated variations in soil structure and hydropedological characteristics across different land use types, that is, uncultivated, cultivated, and abandoned land under an arid condition. Water-stable aggregates in the uncultivated land were 15.4%–37.1% of those in the cultivated and abandoned lands at depths of 0–60 cm. Reclamation of the uncultivated land enhanced soil aggregate stability, while prolonged tillage led to the loss of binding organic matter, breakdown of large aggregates and decrease in aggregate stability. The mean weight diameter of aggregates at 0–40 cm depth in the cultivated land was 39.0% lower than in the abandoned land. The volume fraction of micropores (< 100 μm) in the cultivated soils was 3.7%–39.7% of that in the uncultivated soils, whereas macropores (> 1000 μm) was 1.4–1.8 times greater. Following the abandonment, soil pore diversity recovered and a hierarchical structure developed. In the abandoned land, the volume fraction of micropores (< 100 μm) was 2.4–18.9 times that of the cultivated lands, while macropores (> 1000 μm) constituted 81.4%–93.9% of those in the cultivated lands. The permeability and longitudinal dispersivity of soils in the cultivated land were significantly lower than in the uncultivated and abandoned lands, particularly at deeper soil layers. The increase in large pores in the abandoned land, important for water movement and solute transport, resulted in an order-of-magnitude rise in both permeability and longitudinal dispersivity compared with the cultivated lands. Overall, the abandoned land showed potential for rehabilitation from the perspectives of soil aggregates and pore structure. The findings may provide reference for land reclamation and management in arid regions.