Restoring native plant and arthropod communities in gulf coastal prairies following plant invasion and drought

Abstract

Plant invasions are a threat to biodiversity, as changes in plant community characteristics resulting from invasion can affect other organisms, such as arthropods. The effects of invasions may interact with other disturbances and alter the efficacy of restoration strategies. We sought to understand the effects of Old World bluestem grasses (OWBs, Bothriochloa, Dichanthium spp.), which have become dominant in prairie ecosystems and reduce the quality of habitat for wildlife. In an attempt to reduce OWBs, we applied treatments to modify soil conditions to a state which favors native plants and arthropods. We conducted our research in 2011, which coincided with extreme drought and provided us with the opportunity to test the efficacy of soil modification under varying conditions. First, we explored the effects of plant invasion and drought on native plant and arthropod communities by comparing characteristics of plots dominated by native plants to plots dominated by OWBs. As drought subsided, we observed a shift from an arthropod community driven by detritivores to one driven by herbivores associated with plant invasion. Arthropod communities were dominated by invasive species. Second, we explored the efficacy of soil modification and seeding treatments to reduce OWBs in the presence and absence of drought based on a field experiment and a more controlled microcosm experiment. Although changes in soil chemistry from soil treatments were short-lived, we observed reduced dominance of OWBs in areas treated with soil disturbance and seeding in both experiments and we observed no differences between experiments when we alleviated the effects of drought. Finally, we examined the concomitant effects of our soil modification and seeding treatments on arthropod communities in the field experiment. We observed fewer arthropods in treated plots than undisturbed OWB monocultures, but soil and seeding treatments increased arthropod diversity and reduced dominance of invasive arthropods relative to undisturbed OWB monocultures. Based on our findings, simple soil disturbance in combination with seeding of native plants may increase diversity of native plants and arthropods where invasive plants are dominant in the short term, but monitoring over longer time frames may reveal additional benefits from soil modification.