Effects of Rhamnus frangula on nitrogen cycling in wetland ecosystems through competitive exclusion of the nitrogen fixing shrub Alnus rugosa.

Abstract

In this study we sought to quantify the effects of invasive species Rhamnus frangula on the surrounding plant communities that it invades. We proposed that through competitive exclusion of the nitrogen fixing species Alnus rugosa, R. frangula invasion would lead to a decrease in biologically available nitrogen in the systems, and a subsequently lower floristic quality of the sites would result. We sampled for abundance of N15 in both target shrubs and the surrounding vegetation in hopes of measuring the contribution of A. rugosa to the systems, as well as identifying plants for use in a Floristic Quality Analysis. Our results on the contribution of A. rugosa to the nitrogen were inconclusive, but we did find a decrease in the overall floristic quality of sites that were invaded by R. frangula.