Herbivory-mediated responses of selected boreal forests to climatic change

Recent efforts to project vegetation responses to climatic warming have emp hasized the tight linkages between climate and vegetation distribution. Her e we provide several examples indicating that the direct effects of climati c warming on boreal vegetation can be qualitatively different than the indi rect effects mediated by climatic responses of herbivores. These herbivore- mediated vegetation responses to climatic warming will likely vary regional ly. In southern Fennoscandia, we project that the climatically induced chan ges in animal populations should enhance the density of spruce at the expen se of pine and broadleafed trees. In northern Fennoscandia we project reduc ed herbivory on broadleafed trees and increased herbivory on pine, leading to an increase in broadleafed trees and spruce and a reduction in pine. Cli matic warming in interior Alaska may reduce herbivory on broadleafed trees and increase herbivory on evergreen spruce, thus reinforcing the impact of increased fire frequency.