Enhancing the restoration of wet prairie following the removal of Frangula alnus (Glossy Buckthorn)

Background/Question/Methods Frangula alnus (Glossy Buckthorn) is an invasive species that dominates many former wet prairie habitats, which currently cover less than 1% of its original extent..  Restoration of wet prairie often involves removal of large monoculture buckthorn stands followed by the application of herbicide and natural regrowth from the seed bank. Buckthorn seeds have also been found to be sensitive to extended periods of water inundation. The goal of this study is to determine if the existing seed bank contains the appropriate native seeds and to examine the effect of hydrologic conditions on seed bank emergence.  52 georeferenced, randomly selected 10x10 m plots were established across three sites at different stages of restoration: an established restored wet prairie, an area that had been cleared of buckthorn and sprayed the previous summer, and a pre-restoration buckthorn monoculture. Five soil cores were collected at 10 and 20 cm depths from each plot, pooled within depths, and spread in shallow pans over x cm sand in a greenhouse for seed germination.  Soil samples were randomly distributed between two replicate benches maintained at either flooded or saturated water levels to examine the distribution, abundance, and diversity of emerging forb and graminoid seedlings.

Results/Conclusions The number of morpho-taxa of graminoids did not differ among sites, while forb diversity was significantly different among sites with the highest number of morpho-taxa found in the recently cleared site. Significantly more forbs were found at inundated water levels while no difference was found in graminoids between hydrologic treatments. Fewer buckthorn seedlings were found where soil was inundated compared to saturated, but sample size was too small for statistical analysis. Significantly fewer numbers of individuals were found in cores taken from 10-20 cm below the surface compared to those taken from the surface-10 cm at all sites. These data indicate that the greatest number of viable seeds for restoration are located in the upper levels of the soil and that restoring appropriate hydrologic levels is important for restoration.