Incidence of Invasive Plant Species in Water Level Managed and Unmanaged Wetlands in Northern Ohio

Abstract

Fluctuating water levels may facilitate non-native plant invasion of wetlands by providing suitable establishment conditions or inhibiting competition from native species not adapted to the new hydraulic regime. This study investigated compositional differences of plant communities in two water level-managed and two unmanaged wetlands in northern Ohio. Comparing native and non-native species responses can help determine whether different management techniques effectively control the incidence of non-native species and affect native plant diversity. The objective was to correlate native and non-native species cover and diversity among natural and anthropogenically altered hydrologic regimes. Within each wetland, species richness and percent cover of native and non-native species were measured in two 20x25m Whittaker plots containing two 25m2 and six 1m2 plots. Using the Daubenmire method, we found invasive plant species cover in managed wetlands was 34.6% higher than in reference wetlands, with a mean non-native species cover of 30%. Reference wetlands had a mean 9.5% of invasive species cover. Major invasive species found in the water flow managed wetlands were Butomus umbellatus, Sagittaria latifolia, Typha angustifolia and Hydrocharis morsus-ranae. Findings from this study suggest anthropogenically altered hydrologic regimes may facilitate the establishment of non-native species, and that the length and time of year of inundation should be carefully considered to promote native species vegetation.