PATTERNS AND MECHANISMS OF PLANT DIVERSITY IN FORESTED ECOSYSTEMS - IMPLICATIONS FOR FOREST MANAGEMENT

The objectives of this paper are to (1) review existing diversity mode ls, (2) identify principles that explain patterns of plant species div ersity, (3) discuss implications for forest management, and (4) identi fy research needs. Many current theories cast disturbance as the key p layer in maintaining species diversity by preventing competitive domin ance of one or a few species. Equilibrium and nonequilibrium theories alike agree that maximum diversity should occur at intermediate size, frequency, and intensity of disturbance. These models do not adequatel y predict patterns at all spatial scales or across community types. A mechanistic theory is needed to explain diversity patterns at the patc h, stand, and landscape scales, as well as across site quality and suc cessional gradients. Such a theory should be based upon the interactio n between species' life-history characteristics and the nature of dist urbance. New research is needed in the following areas: identifying di sturbance-life-history interactions, particularly with respect to the short-term and longterm effects of disturbance; quantifying patch dive rsity and determining its relationship with species diversity; determi ning relationships between species diversity and structural and functi onal diversity; and identifying appropriate standards of comparison fo r managed stands. Comparative studies in different ecosystem types, su ch as boreal and tropical forests, should be encouraged to help clarif y the relative importance of processes that influence diversity.