Research of soil aggregate stability in different degradation stages of Songnen grassland

Due to the combined effects of overuse by humans and climate changes, the Songen grassland is rapidly degrading, and the influence on soil structure and function have become a serious issue. In this study, four grassland communities (Leymus chinensis, Chloris virgata, Puccinellia distans, and Suaeda glauca communities) were selected as representatives of different degradation stages. To reveal the effect of degradation on soil structure and anti-erodibility, samples of vegetation, soil profiles, and surface soil were taken to the laboratory, where community characteristics, soil properties, and soil aggregate stability were analysed. Vegetation biomass, diversity index, and vegetation coverage generally declined with succession of degradation. Soil moisture, organic matter, and total N decreased, while pH and soil bulk density increased; the soil pH value of every stage of degradation was above 8.0. The size classes of water-stable soil aggregates had a trend such that the proportion of micro-aggregates increased, while the proportions of macro-aggregates and soil aggregate stability decreased. Within one degradation stage, soil aggregate stability decreased with increased soil depth in layers 0-10 cm to 20-30 cm. The results revealed the effects of the Songen grassland degradation on soil aggregate stability and have implications for the restoration of degraded grasslands.