Arctic Ecology

The Arctic ecosystem is characterized by its cold climate and annual cycle of mid summer sun and mid winter night. In summer, there is a short period of production, while in winter everything is stored in the freezer. The study of arctic breeding geese has unraveled some of the ecological relationships in this ecosystem. The geese time their annual cycle, so that their peak requirements coincide with the peak in plant production. As the goslings are born and the adults renew their flight feathers, the growing plants have their peak in protein. Protein content of plants is much lower than protein content of animal tissue and the geese need to forage on the plants with highest protein to enable growth.

Plant production is limited by temperature and nitrogen. Nitrogen can be assimilated by nitrogen fixing bacteria, which play an important role. The activity of these bacteria is highest when nitrogen is limited. Goose droppings are also a source for nitrogen. Every food item, eaten by the goose is leaving its body in two hours. Celloluse digestion by bacteria (which is the most important source of energy for large herbivores like cattle) is not possible in this short period. Every 5 minutes a goose produces a goose dropping, which can fertilize the vegetation but is also a nice bite for reindeer.

In our study area reindeer are feeding on goose droppings regularly. They are even very selective for those droppings that have the higest quality.
Predation plays an important role in determining productivity of geese. The most important predator is the arctic fox. This animal can occur in extreme high numbers in some years. This depends on the lemming cycle (for Siberia) or the winter mortality of reindeer (Spitsbergen). On Spitsbergen there are no rodents and the arctic fox will follow polar bears on the pack ice when there are only very few cascasses of reindeer on land. Most animals living in the arctic have large fluctuations in population number. Sometimes these fluctuations even seem to become population cycles. And some of these cycles have been even linked to parasites, which have also an ecological relation with their host.

more information: Maarten Loonen