Objective To study the characteristics of understory plant communities of plantations and their relationship with stand factors, which is of great significance for evaluating the effectiveness of vegetation restoration in sandy areas and managing plantations.

Methods In this study, based on the poplar plantation in Mu Us sandy land the understory plant community was investigated. The effects of stand factors such as canopy density and density on understory vegetation were studied.

Results The results showed that a total of 32 species of herbaceous plants belonging to 28 genera of 12 families were found in the herbaceous layer under the poplar plantation in the study area,. Among them, Leguminosae, Gramineae and Compositae plants were the most species, accounting for 62.51% of the total plant species. The life forms of understory herbaceous plants were mainly perennial herbaceous plants, accounting for 78.13% of the total species. The plant water ecotypes were mainly xerophytes and mesoxerophytes, accounting for 75.00% of the total species, followed by xeromesophytes and mesophytes. The Margalef richness index, Simpson dominance index, Shannon-Wiener diversity index and Pielou evenness index of understory herb layer ranged from 1.20 to 3.17, 0.48 to 0.88, 0.95 to 2.34 and 0.16 to 0.48, respectively. The species diversity was the highest when the forest age was 32 years. The results of the structural equation model showed that canopy density and stand density were negatively correlated with the coverage of the understory shrub layer. When the plantation canopy density was high, no shrub layer was found under the forest. The increase of canopy density was beneficial to the development of herbaceous layer, and there was a negative effect relationship between stand density and herbaceous layer, which affects the growth of herbaceous plants under the forest. The effect of shrub layer on herbaceous layer was similar to that of tree layer.

Conclusion The diversity of understory herbaceous plants in poplar plantations in Mu Us Sandy Land is high, and there are fewer shrub species. The size is obviously affected by stand factors such as canopy density and stand density. Appropriate regulation of stand density and structure will be conducive to the maintenance of understory species diversity and close-to-nature management of poplar plantations in Mu Us Sandy Land.