Worldwide Movement of Exotic Forest Fungi, Especially in the Tropics and the Southern Hemisphere

Plantations of forest trees have been established throughout the world, primarily to provide structural timber and fiber for pulp. In the Northern Hemisphere, plantations tend to be of native species generated from seedlings in nurseries. Over the last century, however, extensive plantations of exotic species have been established in many parts of the tropics and the Southern Hemisphere. In these areas, trees were initially established in provenance trials to identify superior seed sources and genetic material. Subsequent selection of desirable trees from the best performing provenances led to the establishment of seed orchards and sophisticated breeding programs. In some cases, these breeding programs have included hybridization of species and large-scale vegetative propagation of desirable genotypes. In both the tropics and the Southern Hemisphere, the most widely established tree species in plantations are Pinus Linnaeus, Eucalyptus L'Heritier, and Acacia Miller. Local land races—many of them natural hybrids resulting from early progeny tests, others the result of artificial hybridization between species (and land races) in all three genera—have emerged in countries with long histories of exotic plantation forestry. This hybridization, both natural and artificial, coupled with vegetative propagation, has made it possible to produce highly productive clones with a wide range of desirable traits. Based on the development of these species hybrids, large international companies have emerged and become important contributors to world timber and pulp production. Most of these companies also contribute to international efforts to reduce the logging of old-growth native forests.