Closing Canopies and Changing Trophic Energy Pathways in Western Conifer Forests: Where Do We Go from Here?

The persuasive evidence of closing forest canopies across the western United States during the last century suggests that primary energy production in forest ecosystems is shifting from herbaceous and shrubby vegetation to trees. This conclusion is supported by established inverse relationships between tree crown density and forage in the form of shrubs and herbaceous plants. Shrub and herbaceous layers in forest ecosystems are essential habitat elements for many species providing critical trophic pathways to numerous primary consumers. Essential to understanding and conserving ecological function should be the maintenance of energy transfer through diverse food webs. The relationships between producer plants and consumer animals, between predator and prey, and kinds of organisms in a given environment, are all controlled by the basic concepts of energy, ultimately limited by light. Yet in spite of this fundamental principle, much of the focus in contemporary forest management has been on a few secondary consumers thought to have reproductive habitat requirements associated with dense, late seral forest conditions, with relatively little attention given to the habitat requirements of prey for these species. Shifts in vegetation composition and the decline of critical ecological elements, argues for an approach to forest management that focuses more on fundamental processes and the promotion of vegetative diversity rather than featured species, especially secondary consumers.