Vesicular–arbuscular mycorrhizal ecology of little bluestem across a prairie–forest gradient

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Abstract
Changes in little bluestem (Schizachyrium scoparium) plant cover and vesicular–arbuscular mycorrhizae (VAM) root colonization, VAM spore density, and mycorrhizal inoculum potential were examined across a gradient from open sand prairie to closed oak–hickory forest in central Illinois. Soil samples were collected randomly and from the rhizosphere of little bluestem. Significant negative rank correlations were found between tree basal area and percent aerial cover of little bluestem, VAM colonization of little bluestem roots, mycorrhizal inoculum potential, and VAM spore abundance. However, spore abundances for randomly collected and rhizosphere soil samples, VAM colonization, and mycorrhizal inoculum potential had significant positive rank correlations with little bluestem cover. Highest spore densities were associated with the open sand prairie dominated end of the gradient, with lower spore numbers being found within the closed forest. Rhizosphere and randomly collected soil samples had a decrease in VAM fungal species richness as the vegetation types approached that of a closed forest community; however, dominant VAM fungal species were present throughout the gradient. Observed relationships between colonization, mycorrhizal inoculum potential, spore abundances, and little bluestem cover suggest interdependencies between host plant and associated mycobionts and (or) similar responses to environmental factors.