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Mapping Oriental Bittersweet to Prioritize Management Decisions

Sara Gabrielson

Advisor: Professor Meg Ronsheim
Mentor: Keri VanCamp

My research during the summer of 2011 focused on oriental bittersweet on the Vassar Ecological Preserve. Oriental bittersweet is an invasive vine that is changing the structure of forests where it overtops canopy trees and smothers them. The project mapped bittersweet densities across the Preserve and looked at factors that might influence its distribution as well as fruiting patterns. I have come to three major conclusions focusing on the ability of bittersweet to produce fruit, where it is located on the Preserve in high densities, and the potential facilitation of oriental bittersweet by the emerald ash borer, an invasive insect. I found that bittersweet requires high amounts of light to fruit, which means it must either have reached the canopy of its host tree or must grow along an edge or in a large gap. This will help focus management efforts on large bittersweet plants, and edges and gaps because by reducing the seed source, the spread of bittersweet to other areas on the Preserve and in the surrounding area can be reduced. I found that the highest densities of bittersweet are located in the forested areas of the Preserve that were more recently cleared land, as opposed to areas that have been reforested for a longer time. This indicates that land use history and bittersweet prevalence may be closely linked which could help other people targeting bittersweet in northeastern forests pin point areas where bittersweet might be more prevalent. Lastly, the emerald ash borer is an invasive insect that bores into ash trees and kills them by feeding on their phloem. When the emerald ash borer invades, which will most likely happen within the next few years as it is currently directly across the Hudson River, all of the ash trees will all die and create gaps in the canopy. My research found that the areas where bittersweet is most dense are also the areas where ash trees are most dense. Bittersweet has an amazing capacity to monopolize on new light sources and grow very quickly up into the canopy when it has enough light. The gaps that will be created when the emerald ash borer invades will provide new light sources which bittersweet will likely have access to due to the overlap of high density ash areas and high density bittersweet areas. This has lead me to recommend focusing management strategies on large fruiting bittersweet plants, recently regenerated forests and the specific areas of overlap between ash and bittersweet densities.