18 - Impact of beaver (Castor canadensis kuhl) foraging on species composition of boreal forests

Abstract

Herbivores can greatly influence plant community composition through selective foraging. Local vegetation diversity is produced and maintained not only by what and how much herbivores eat but also by what they do not eat. The effects of herbivores on community composition are particularly acute in boreal forests, where limited light, temperature, and nutrient resources restrict the capacity of woody plants to replace tissues eaten by browsing animals. It is well established that herbivory by large mammals can significantly influence boreal forest ecosystem structure and dynamics. However, of all the large herbivores, the beaver (C. canadensis Kuhl) has a much greater potential to alter these ecosystems through herbivory because most of the biomass they harvest is composed of mature trees. In this chapter, a review on herbivory in boreal forests is presented and temporal dynamics of beaver populations in these forests is discussed. In addition, the current traditional understanding of beaver foraging impacts in boreal forests is summarized. The chapter offers an alternative approach to gain understanding of how beaver herbivory causes the ecological effects seen in the composition and structure of boreal forests. The chapter discusses both direct and indirect vegetation responses to beaver activity in boreal forests.