Effects of supplementary sowing on plant community and soil physical and chemical properties in Ningxia desert steppe

Studying the effects of supplementary sowing on grassland vegetation and soil provides a basis for restoration of degraded grasslands. In the Ningxia desert steppe, grassland protected from grazing and grassland after three years of restoration (by supplementary sowing of native species) were sampled for plant composition and community characteristics, diversity and stability. In addition, soil moisture and physicochemical properties of the 0 – 40 cm soil layer were determined. The relationship between vegetation changes and soil properties was analyzed. The results showed that: 1) The number of plant species in the restoration grassland increased; however, whereas the proportion of legumes and annual plants increased, the proportion of perennials and semi-shrubs decreased. 2) Supplementary sowing increased grass plant richness, coverage, height, and aboveground biomass, and the community stability improved significantly (P < 0.05); however, grassland species diversity, uniformity and dominance were unchanged. 3) The moisture content of the restoration grassland soil was higher than that of the enclosed grassland, as were the soil water holding capacity, capillary porosity, total porosity, and organic matter content. The available potassium content at 30 – 40 cm was higher in the restoration than in the enclosed grassland, but there was no significant difference in soil total nitrogen and alkaline hydrolysis nitrogen between the two grasslands (P > 0.05). 4) Soil organic carbon content and field water holding capacity were the most significant factors affecting the vegetation characteristics. It was concluded that supplementary sowing of degraded desert grasslands, according to local conditions, can improve grassland productivity, plant communities, soil nutrients, and the soil-water balance.