Abstract: We investigated the mechanisms underlying the spatial point patterns of sand-fixing shrubs, including Artemisia ordosica and the coexisting shrubs Corethrodendron fruticosum var. mongolicum, Caragana korshinskii, and Corethrodendron scoparium in the Mu Us Sandy Land. The pair correlation functions g(r) and null models were used to analyze the spatial distribution patterns and correlations of A. ordosica at different growth stages, as well as the spatial dynamics of the three coexisting shrubs. The results showed that under the influence of seed dispersal limitation, A. ordosica and the three coexisting shrubs, predominantly exhibited a spatial pattern of small-scale aggregated and large-scale random distribution. Intraspecific associations of A. ordosica were largely positive or non-significant, primarily influenced by seed dispersal limitations. After excluding habitat heterogeneity, interspecific associations between A. ordosica and C. mongolicum, as well as between A. ordosica and C. korshinskii, displayed positive correlations at small scales (0-4 and 0-2 m) but no significant correlations at medium and large scales (3-20 and 2-11, 13-20 m). There was no significant correlation between A. ordosica and C. scoparium at small and medium scales (0-13 m), but negative correlation at large scales (13-20 m). The spatial associations between young A. ordosica and the three coexisting shrubs were weakest across different growth stages. In contrast, vegetative and reproductive individuals showed similar trends, with both displaying positive associations at small scales.

Key words: Mu Us Sandy Land, Artemisia ordosica, sand-fixing shrub, spatial point pattern, spatial correlation, null model