Comparative productivity of monocultures and mixed-species stands

Abstract

Ecological theory suggests that there is a potential productivity advantage to be gained by designing managed forest stands to contain more than one tree species. The basis for this advantage, as noted by Ewel (1986) and Vandermeer (1989) is rooted in fundamental niche theory—two or more species must use resources differently if they are to coexist on a site. Differential resource use among species suggests that the species in a mixture may utilize the resources of a site more completely than any single species would be able to do, leading to greater overall productivity. However, the link between differential resource use among species and greater total resource use does not necessarily exist in all cases. For example, it is possible that a mixture of species may simply subdivide the total resource base that one highly efficient species may completely use on its own. In addition to niche separation, which potentially applies to all species in mixture, certain specific combinations of species may exist in which one species may directly benefit from the presence of another.