Plant succession in the High Arctic : patterns & mechanisms

Succession is defined as species change over time, and investigations into its nature over the past century have shown that it is a highly variable process, dependent on local environmental conditions and species pools. The High Arctic is a landscape currently experiencing rapid change, and the response of ecosystems to certain changes can be better predicted by understanding succession. However, little research has been conducted about succession in High Arctic environments. Consequently, in this thesis we investigate the patterns of and mechanisms behind plant succession at and around Alexandra Fiord, Ellesmere Island, in the Canadian High Arctic. In Chapter 2 we resurvey three glacial forelands originally surveyed 21 years ago to investigate patterns of primary succession. We find that species advance predictably in a directional manner towards the retreating glacial margin, however the rates and patterns of change are unique to each species, and species do not behave as well define communities. However, distinctly different species dominated on successional areas compared to older mature areas. In Chapter 3 we survey a topographically heterogeneous foreland to investigate the mechanisms driving primary succession. We find that micro-environmental influences played the most important role. Variation in substrate grain size explained the largest amount of variation in vegetation patterns. Other important influences included facilitation from moss and other vascular plant species, time since deglaciation, intrinsic life history traits, and distance to a seed source. In Chapter 4 we visit a site of secondary succession that has been recovering for 31 years. We find that this site was far more advanced in its recovery than the glacial forelands, but it had not yet reached a community composition similar to that of the surrounding mature tundra. Many successional species were the same at both the site of secondary succession and the site of primary succession. This work has provided new insights into the patterns and mechanisms of succession in the High Arctic, emphasizing the importance of understanding succession at a local scale, and providing testable hypothesis for further research.Arts, Faculty ofGeography, Department ofGraduat