Glossy Buckthron (Rhamnus frangula L.) invasion in Pleasantview Swamp in Michigan's northern lower peninsula with regard to distance from Robinson Road and the Maple River.

Abstract

Rhamnus frangula Linnaeus, originally native to Europe, western Asia, and North Africa, was introduced into North America as a horticultural species (Barnes and Wagner 1981). Since its introduction, Glossy Buckthorn has become naturalized and locally aggressive in a variety of sites, but has become a serious pest in wetlands such as fens and swamps (Voss 1985). In a Canadian survey it was rated as second only to Purple Loosestrife, Lythrum salicaria, in both its spread in natural habitats and its impact (Catling and Porebski 1994). R. frangula is particularly disruptive in its ability to shade out shrubs and herbaceous understory vegetation (Voss 1985). First collected in Michigan in 1934, R.frangula has been dispersed across the Upper and Lower Peninsulas by birds and mammals that feed upon its drupes. As with many invasive species, R. frangula tends to be more densely distributed along disturbed areas, like roadsides, and natural edges. To evaluate this trend, we chose a site that bordered a road as well as a natural edge provided by a river. It was our belief that R. frangula would be located in greater density closer to the roadside and riverbank, because birds are the main dispersal vector and have a great affinity for edges (Catling and Porebski 1994).