MOOSE-VEGETATION-SOIL INTERACTIONS: A DYNAMIC SYSTEM

Abstract

We review the processes by which moose (Alces alces) interact with vegetation at the module (leaf and shoot) and genet (individual plant) levels of organization, and show the consequences of these interactions for plant population, community, ecosystem, and landscape dynamics. Moose forage selectively on photosynthetic and meristematic tissues of a few preferred species. These species respond with compensatory growth and often tissues of higher forage quality, leading to a positive feedback at the module and genet level. However, height growth of browsed genets is often reduced or even curtailed by browsing, leading to higher levels of mortality and eventual replacement of browsed species by unbrowsed ones. These unbrowsed species (predominantly conifers) grow more slowly and have litter of low nutrient content that decomposes slowly. Consequently, even though moose browsing stimulates growth and browse availability at module and genet levels, ecosystem productivity and nitrogen cycling decline. Such feedbacks eventually lead to spatial patterns in the landscape. Genotypic and phenotypic differences within forage species modify these responses somewhat, and plant responses to moose browsing all differ somewhat along productivity gradients. Other herbivores, notably invertebrates, are also affected by these changes in vegetation. We conclude by suggesting some unanswered questions and new directions for future research.