Plant Community Composition in Two Human-Modified Landscapes, a Powerline Corridor and an Old Field

Human landscape modification elicits changes in plant community composition due to altered microclimate conditions. We asked the question whether floristic composition, abundance, species richness, and diversity differ between habitat types in two human-modified landscapes, with contrasting management regimes. We measured species richness and cover of all vascular plants in forest, edge, and corridor habitats of a powerline easement, as well as in a nearby old field. Powerline corridor habitat had 21% more species than adjoining forest habitat and was dominated by shrub and herbaceous species. We also found that soil pH and litter depth are significant predictors of species richness along powerline corridor edges and in open old-field habitat. Particularly, we observed maximum species richness in plots with moderately high soil pH of between 5 and 5.5 along powerline corridor edges and in open old-field habitat. Powerline corridor plots with less surface litter also had higher species richness. Invasive species such as Microstegium vimineum and Rosa multiflora were more abundant in the open old-field habitat maintained annually by mowing than in powerline corridor habitat maintained usually every five years by herbicide spraying and selective removal of trees. Our findings indicate that the diverse floristic composition of powerline corridors support organisms at higher trophic levels and hence provide opportunity for conserving biodiversity within human-modified landscapes.