Edwin C. Liebig will give a lecture about his masters thesis in Biology. The thesis is titled The Impacts of Sheep Grazing on Bryophyte Communities.
Abstract
Plant communities are sensitive to trampling and grazing by large herbivores. Depending on grazing intensity and the growing conditions, these disturbances may therefore have strong effects on bryophyte communities. However, it is not well known how sheep grazing affects bryophyte communities in tundra ecosystems. This study aimed at assessing the impacts of sheep grazing on the structure and composition of bryophyte communities. Bryophyte communities were compared in three grazed and three ungrazed valleys, in two regions in Northwest and North Iceland. Sampling was stratified to allow for an investigation of different growing conditions with respect to exposure, elevation, and landform. Bryophyte layer depth, species diversity and abundance were measured, and species were grouped by growth form and life-history. The depth of the bryophyte layer was significantly deeper in ungrazed than grazed valleys, which indicates that sheep grazing may have consequences at the ecosystem level. Within west-facing slopes, species diversity was greater in grazed than in ungrazed valleys. Pleurocarpous mosses, the most abundant growth form in general, were more abundant in grazed than ungrazed valleys, suggesting this growth form tolerates herbivore disturbance relatively well. Early successional species were less abundant in grazed than ungrazed valleys. Competitive and stress tolerate species were more abundant in grazed valleys, suggesting they cope with disturbance and other impacts caused by sheep grazing. Sheep grazing impacts bryophyte communities in Iceland, and this can have ramifications to other ecosystem functions.
Advisors: Ingibjörg Svala Jónsdóttir and Þóra Ellen Þórhallsdóttir, professors at the Faculty of Life and Environmental Sciences at the Universisty of Iceland.
Examiner: Dr. Borgþór Magnússon, Plant Ecologist at The Icelandic Institute of Natural History