Ptarmigan as Engineers of Change in Arctic Shrub Ecosystems
Overview
I am interested in plant–animal interactions in the arctic. My research focuses on how ptarmigan and other browsers affect the architecture, demography, and productivity of shrubs. I am also interested in quantifying spatio-temporal patterns of ptarmigan distribution across the arctic landscape using occupancy models. This information will help us to understand how ptarmigan influence, and are in turn influenced by shrub expansion in the arctic.
Background
Arctic ecosystems are currently undergoing rapid change, and one of the most dramatic changes has been the expansion of woody shrubs into tundra regions. Herbivory is a critical process to consider when predicting ecological change over time because herbivores have the capability to strongly influence the physical structure, nutrient pathways, and competitive relationships within plant communities. Ptarmigan are ubiquitous but often overlooked herbivores in arctic ecosystems. Their tendency to specialize on willow buds, their abundance on the arctic landscape, and their occurrence in flocks near the range limits of shrubs likely result in a large cumulative impact on arctic shrub communities.
Little is known about the timing of migration and distribution of willow and rock ptarmigan (Lagopus lagopus, L. muta) in northern Alaska. Many arctic-breeding ptarmigan spend their winters south of the Brooks Range, and migrate to the arctic in the early spring to congregate in tall shrub patches. Here, ptarmigan feed almost exclusively on willow buds as they prepare for the breeding season. Arctic river valleys dominated by tall shrubs therefore provide a critical source of food and shelter for ptarmigan, while also providing food for moose, hares, and other wildlife. One shrub species, feltleaf willow (S. alaxensis), appears to be extremely important for ptarmigan and other herbivores during this time, because it is often the only willow tall enough to exceed snow depth.
Research focus
A major focus of my research is to investigate the role that ptarmigan play in shaping arctic shrub communities. By measuring how willows respond to different types and intensities of natural and simulated browsing, I hope to determine how browsing influences their architecture and productivity. I am also interested in whether ptarmigan, through moderately browsing willows, create a patchwork of “browsing lawns”, that have higher palatability, abundance, and accessibility of willow buds compared with un-browsed willows. To address whether browsing increases the palatability of willow buds, I will use cafeteria trials to test whether wild ptarmigan prefer browsed over un-browsed willows. In addition, I will determine whether browsing causes willows to increase their bud population growth rates using stage-based matrix population models.
To complement the browsing study, extensive aerial surveys over a mosaic of riparian and upland habitat types will indicate ptarmigan habitat associations and spring distribution in north-eastern Alaska. These surveys can also be used to infer the geographical extent of ptarmigan browsing and subsequent influence on shrub communities. Furthermore, surveys will be conducted from March to May over a two year period, and will thus provide novel information on the timing of ptarmigan spring migration.
Co-Advisors
Mark Lindberg and Roger Ruess, Institute of Arctic Biology, University of Alaska Fairbanks
Funding for this project
The Natural Sciences and Engineering Research Council of Canada
Alaska EPSCoR
University of Alaska Fairbanks Institute of Arctic Biology
The National Park Service Murie Science and Learning Center
