Niche, Interspecific Association and Community Stability of Understory Vegetation in Artificial Sand-Fixing Forests of the Mu Us Sandy Land

Understanding the community assembly mechanisms and stability of artificial sand-fixing forests is critical for the management of desert ecosystems. This study investigated the understory vegetation of four artificial sand-fixing shrub forests in the Mu Us Sandy Land to understand community assembly mechanisms and stability by analyzing niche characteristics, interspecific associations, and community stability. The results showed the following: (1) Lc (<i>Leymus chinensis)</i>, Ee (<i>Euphorbia esula)</i>, Gd (<i>Grubovia dasyphylla)</i>, and Ch (<i>Corispermum hyssopifolium)</i> all have wide ecological niches and high importance values, serving as key species for maintaining community function. (2) The understory herbaceous plant communities of <i>S. psammophila</i>, <i>A. ordosica</i> and <i>C. fruticosum</i> exhibited low niche overlap, and the <i>A. fruticosa</i> understory herbaceous plant community showed high niche overlap. (3) The overall association of the understory herbaceous plant communities of <i>S. psammophila</i>, <i>A. ordosica</i>, and <i>C. fruticosum</i> is positive, while that of the understory herbaceous plant community of <i>A. fruticosa</i> is negative; the interspecific associations are weak, and the species show an independent distribution pattern. (4) Among the four understory herbaceous plant communities, the stability of the <i>S. psammophila</i> understory herbaceous plant community is relatively the highest, followed by <i>A. ordosica</i> and <i>C. fruticosum</i> understory herbaceous plant community, and the stability of <i>A. fruticosa</i> understory herbaceous plant community is the lowest. Furthermore, community stability was positively correlated with the variance ratio (VR) but negatively correlated with mean niche overlap. We recommend prioritizing <i>S. psammophila</i> and <i>C. fruticosum</i> for sand fixation and conserving key herbaceous species to optimize resource use and stabilize interspecific relationships. The novelty of this study lies in its integrated assessment of niche characteristics, interspecific associations, and community stability, and it primarily focused on the role of interspecific relationships. Future research should incorporate environmental drivers and shrub functional traits to disentangle the synergistic effects of biotic and abiotic factors, thereby providing a more robust scientific foundation for vegetation restoration in desert ecosystems.