Mon, Aug 02, 2021:On Demand
Background/Question/Methods:
Within the field of plant invasion ecology there has historically been a strong emphasis on disturbance-mediated invasions and early-successional traits. Our understanding of forest invasions, especially with regard to invasive plants that do not rely on canopy gaps and other disturbances, is limited. The rapid spread of a shade-tolerant perennial grass species (wavyleaf basketgrass (Oplismenus undulatifolius (Ard.) Roem. & Schult.) (WLBG) within the Mid-Atlantic region of the United States has caused concern for its potential negative effects. However, little is known regarding the degree to which this species is having an effect on forested communities. Here we investigated the effect of WLBG on the diversity, composition, and cover of functional groups within resident plant communities using a removal experiment at six sites. We monitored plots over a three-year period, applying either hand-weeding or chemical removal treatments in all three years and fenced half of all blocks to test the interactive effect of white-tailed deer. We also planted tulip tree and red oak seedlings within plots to directly measure WLBG’s effect on seedlings survival and growth.
Results/Conclusions: We found strong evidence that WLBG suppresses resident plant diversity and the cover of nearly all plant functional groups, lending support to WLBG being a driver of community change. However, we did not find compelling evidence that WLBG affects plant community composition across all sites, indicating that the resident community plays an important role in the eventual response to invasion. We also found that the presence of WLBG did not have a measurable effect on the growth or survival of planted red oak and tulip tree seedlings. We hypothesize that the initial height of these planted seedlings allowed them to escape strong competitive effects of WLBG. Besides newly established tulip tree seedlings, violets (Viola spp.) were the only other native taxa within our plots to consistently show a strong response to WLBG removal. We also found strong evidence that WLBG competes with other invasive plants, notably Japanese stilt grass (Microstegium vimineum), and it is likely that these two species interact to suppress native plants. Last, we were not able to conclude with our results that WLBG interacts with white-tailed deer to suppress native plants as we did not find consistent evidence that diversity, composition, or functional group cover was highest when both WLBG and deer were removed.
Results/Conclusions: We found strong evidence that WLBG suppresses resident plant diversity and the cover of nearly all plant functional groups, lending support to WLBG being a driver of community change. However, we did not find compelling evidence that WLBG affects plant community composition across all sites, indicating that the resident community plays an important role in the eventual response to invasion. We also found that the presence of WLBG did not have a measurable effect on the growth or survival of planted red oak and tulip tree seedlings. We hypothesize that the initial height of these planted seedlings allowed them to escape strong competitive effects of WLBG. Besides newly established tulip tree seedlings, violets (Viola spp.) were the only other native taxa within our plots to consistently show a strong response to WLBG removal. We also found strong evidence that WLBG competes with other invasive plants, notably Japanese stilt grass (Microstegium vimineum), and it is likely that these two species interact to suppress native plants. Last, we were not able to conclude with our results that WLBG interacts with white-tailed deer to suppress native plants as we did not find consistent evidence that diversity, composition, or functional group cover was highest when both WLBG and deer were removed.