While ecologists have studied succession for well over 100 y, there has been little characterization of diversity patterns in nonplant organisms or their interactions across successional gradients. In this study we examined herbaceous vertical vegetation structure and diversity in plants, arthropods, and arbuscular mycorrhizal fungi (AMF) in three Great Lakes sand dune chronosequences. Plant species richness increased linearly across the primary successional gradients at the three sampling sites, while plant vertical structure remained constant. Total arthropod abundance and species richness were positively associated with plant vertical cover, while AMF spore abundance and morpho-type richness were positively associated with plant species richness. Carnivore and herbivore functional groups of arthropods responded differently to plant vertical cover and species richness. Diversity across early primary successional gradients does not consistently increase among different trophic levels, and the vertical structure of vegetation can be important in explaining richness and abundance in other trophic levels across a successional gradient.