Fungi associated with Rhamnus cathartica in Southwestern Ontario

Common buckthorn (Rhamnus cathartica) is a competitive Eurasian woody shrub currently invading North America. Buckthorn thickets reduce native diversity and may reduce mycorrhizal diversity through the release of allelochemicals. Two aspects of buckthorn’s invasional biology are explored: 1) determining buckthorn’s allelochemical impacts on arbuscular mycorrhizae in mature sugar maple (Acer saccharum) stands, and 2) assessing possible changes in mycorrhizal communities in sugar maple soils in an open-greenhouse experiment. Data from invaded and uninvaded sugar maple soils revealed that arbuscular mycorrhizal fungi (AMF) diversity fluctuated as a function of season, sampling site or potting disturbance, but the presence of buckthorn had little effect on AMF development in maple roots. Buckthorn may be a mycorrhizal generalist, and changes in AMF abundance may be more influenced by underlying stochastic soil processes and aboveground plant composition than by buckthorn and its allelochemicals.