Interior Alaska is one of the last, great intact ecosystems in the world, with a rich abundance of wildlife species. Many of these species are of profound economic and cultural importance for rural and urban residents of Interior Alaska.

Credit: Marie Thoms

Mammalian herbivory, particularly by moose and snowshoe hares, has been studied at the Bonanza Creek LTER for more than two decades. Winter browsing by moose results in the consumption of up to 50% of preferred forage annual twig production and a delay in spring green-up. Moose prefer to browse on willow instead of alder, and as a consequence contribute to alder dominance, potentially accelerating successional change. Moose browsing also opens up the canopy, resulting in warmer and drier soils.

Credit: Knut Kielland

Whereas moose concentrate on deciduous species in early succession, seedlings of all tree species in Alaska's boreal forest may be subject to herbivory. For example, regenerating spruce seedlings are typically browsed heavily by snowshoe hares, resulting in curtailed height growth and high rates of mortality. When hares are abundant there is high spruce seedling mortality. This suggests that if masting in white spruce (typically occurs every 10 years) coincides with the peak of the hare’s cycle (also a period of about 10 years) a large proportion of the current spruce cohort may die, resulting in a delay of the establishment and dominance of spruce in succession.

Credit: Knut Kielland

Since 2008 we have been monitoring seasonal patterns of hare mortality and causes using radio telemetry. Survival of hares may be nearly 100% during the summer, but declines sharply during late fall when hares molt, food sources change, and the population faces a new world with the onset of winter. Sources of mortality appear to be related to the density of vegetation. Hares in spruce stands are mostly killed by lynx whereas those in riparian stands are more often killed by avian predators such as goshawks.