Study on the characteristics of plant communities in different ecological restoration stages of Hulun Buir sandy grassland

Artificial vegetation restoration is an important measure to slow down grassland desertification and ecological reconstruction. Understanding the succession characteristics and influencing factors of plant communities in different restoration stages is conducive to the sustainable restoration of vegetation in the sandy land. Taking the vegetation restoration of Ganzhuer sandy land in Hulun Buir as an example, the plant community structure characteristics and soil physical and chemical properties at different restoration stages in 9, 11, 13 and 15 years were investigated respectively, and the succession changes of artificial restoration plant communities and their responses to environmental factors were explored. It was found that 42 species of plants were found in the study area, belonging to 17 families and 35 genera, including 39 species of herbs, mainly Compositae, Gramineae, Rosaceae and Leguminosae. There were 3 kinds of shrubs, including Leguminosae and Compositae. The number of species in different recovery years varied from large to small, and the order was 28 species (15 a) > 25 species (13 a) > 19 species (9 a) > 16 species (11 a). Within each year, the number of perennial herbaceous species was significantly higher than that of annual and biennial plants. In different restoration stages, the dominant species, aboveground biomass and species diversity of herbaceous and shrub fluctuated. Specifically, among the herbaceous plants, Cynanchum thesioides, Corispermum hyssopifolium, Elymus dahuricus, Cleistogenes squarrosa, Leymus chinensis and Setaria viridis had higher dominance, and Cynanchum thesioides was the main dominant species of shrub. The aboveground biomass and total coverage of herbaceous plants did not change noticeably, but the overall trend was fluctuating and increasing. The total coverage of shrub in 15 a was significantly higher than that in 9 a, and the aboveground biomass showed a trend of gradual increase, which was significantly higher in 11, 13, 15 a than in 9 a. The species diversity index of the herbaceous had no significant difference in different restoration stages, and the species diversity of shrub layer was significantly higher in 15 a than in 9 a. The random forest model showed that the contribution of local climate and soil factors to the characteristics of plant community structure was different in the restoration process of desertification grassland. Soil total nitrogen, total potassium, organic matter, annual precipitation and average annual wind speed were the dominant factors affecting herbaceous diversity in Ganzhuer sandy land, and all of them were positively correlated except the average annual wind speed. Therefore, it was suggested to appropriately increase fertilizer containing nitrogen, potassium, organic matter and other nutrients in the sandy land vegetation restoration, so as to promote the plant community structure reconstruction and diversity restoration in the desertification ecosystem.