Scale-dependent effects of Gypsophila paniculata invasion and management on plant and soil nematode community diversity and heterogeneity

Invasion by exotic plant species has led to concerns of homogenization of biotic communities. Where plant invasion occurs, heterogeneity in plant community composition can decrease, even when other diversity responses are minimal. Homogenization of soil communities may also result from exotic plant invasion, though responses of soil communities to plant invasion are relatively understudied. In a long-term study underway since 2007, we examined effects of invasion and subsequent management of Gypsophila paniculata, a large invasive forb on Lake Michigan sand dunes, on aboveground plant community diversity and heterogeneity and belowground nematode community diversity and heterogeneity using Bray-Curtis and Jaccard dissimilarity measures. While invasion and management had only minor effects on plant and nematode richness and Shannon diversity, we found that invasion reduced plant and nematode community heterogeneity while management of the invasive species increased heterogeneity at smaller spatial scales. However, at larger spatial scales, neither invasion nor management had any effect on plant or nematode community heterogeneity. Overall this indicates that this invasion had the effect of homogenizing local communities, while landscape-level heterogeneity was unaffected. Reduced heterogeneity, particularly belowground, could have effects on plant community dynamics, since plant-soil interactions can contribute to continued invasion. Including the study of the soil community will enhance our understanding of community responses during exotic plant invasion and management.