Pretorius, Andrew2015-06-152015-06-152015-04https://hdl.handle.net/11299/172621University of Minnesota Master of Science thesis. April 2015. Major: Natural Resources Science and Management. Advisor: Rebecca Montgomery. 1 computer file (PDF); vi, 53 pages.Buckthorn breaks bud earlier in the spring and holds leaves later in the fall compared to co-occurring native understory species and the forest canopy. This phenology may allow buckthorn to take advantage of high light levels prior to canopy closure in spring and after leaf drop in fall. We hypothesized that this unique phenology is one mechanism that facilitates invasion of the forest interior by buckthorn. To test our hypothesis, we experimentally shaded buckthorn seedlings, reducing high light levels in the spring and fall to simulate intact canopy conditions. We measured spring and fall leafing phenology, light availability and seedling survival and growth. After a year and half of shading little mortality was observed but individuals receiving shading treatments had significantly decreased growth. Supporting our hypothesis that access to phenology-induced high light levels in the spring and autumn is one mechanism for buckthorn success in closed canopy forests.enEcologyForestInvasive speciesPhenologyRhamnus catharticaNatural resources science and managementThesis or Dissertation