Abstract: Due to the complexity and diversity of ecosystems, it is difficult to quantify the impacts of habitat conditions on the formation and succession of plant community. Here, we collected samples from 55 patches of wet meadow and from 278 patches of sand dune from Horqin Sandy Land located in the southeast of the West Liaohe River Basin. The relationships between plant communities and habitat conditions at different scales (wet meadowsand combination patches and individual sand dune patches) were evaluated by a mixed structural equation model, with the structural equation being analyzed by the partial least square method. In the wet meadowsand combination patches, the direct factors with significant effects on plant communities were soil structure, soil water content, and groundwater depth sorted by effect size, with the path coefficients of 0.607, 0.230, and -0.224, respectively. In the individual sand dune patches, thedirect factors with significant effects on plant communities were soil structure, soil water content, and soil organic matter (SOM) content sorted by effect size, with the path coefficients of 0.399, 0.224, and 0.206, respectively. When the direct effect of groundwater depth on plant community was significant, the direct effect of SOM content on plant community was insignificant, but with indirect effects on plant community indirectly by affecting soil structure. The direct effects of slope and elevation on soil quality were opposite at both scales, and the effect of slope direction was not significant. By constructing a latent variable of vegetation pattern in the structural equationmodel, we can infer the dynamics of community succession in the study area.

Key words: karst, beech, ecological group, soil mites, community diversity