Aggregate Characteristics During Natural Revegetation on the Loess Plateau*1

Field investigations and laboratory analysis were conducted to study the characteristics of soil water-stable aggregates during vegetation rehabilitation in typical grassland soils of the hilly-gullied loess area. The relationship between water-stable aggregates and other soil properties was analyzed using canonical correlation analysis and principal component analysis. The results show that during the natural revegetation, the aggregates > 5 mm dominated and constituted between 50% and 80% of the total soil water-stable aggregates in most of the soil layers. The 2–5 mm aggregate class was the second main component. The mean value of water-stable aggregates > 5 mm within the 0–2 m soil profile under different plant communities decreased in the following order: Stipa grandis > Stipa bungeana Trin. > Artemisia sacrorum Ledeb. > Thymus mongolicus Ronn. > Hierochloe odorata (L.) Beauv. Clay, organic matter, and total N were the key factors that influenced the water stability of the aggregates. Total N and organic matter were the main factors that affected the water stability of the aggregates > 5 mm and 0.5–1 mm in size. The contents of Fe2O3, Al2O3, and physical clay (< 0.01 mm) were the main factors which affected the water stability of the 1–2 and 0.25–0.5 mm aggregates.