Michael W. Cunningham and Bijay Tamang

ArborGen Inc., U. S.A.

9.1 Phylogeny, Growth, Yield and Chemical Composition

9.1.1 Introduction and Phylogeny

Eucalyptus belongs to the Myrtaceae family and is comprised of more than 700 species. Most Eucalyptus species are native to Australia but a few are also native to New Guinea, Indonesia and Philippines. Corymbia and Angophora are two closely related genera with Eucalyptus. These three genera are collectively known as eucalypts, but Corymbia and Angophora have been classified as subgenera of the Eucalyptus genus in the recent taxo­nomic classification [1].

Eucalyptus is one of the most widely planted genera in the world but large scale planta­tions are mostly limited to tropical areas. Eucalyptus plantations worldwide cover a total of

17.9 million ha [2]. About 11 million ha are located in Asia while South America has about 5 million ha [2]. Eucalyptus has been an attractive species to farmers in developing coun­tries because of its fast growth, straight form, coppicing ability and adaptation to various soil types.

Out of more than 700 species of Eucalyptus, only about 500 have the potential for commercial plantation [3]. E. grandis is one of the widely planted species because of its fast growth and higher productivity. Eighty percent of the Eucalyptus plantations worldwide are comprised of E. grandis, E. urophylla, E. camaldulensis, E. globulus, and their hybrids [4]. In the United States, there are approximately 50 000 ha of Eucalyptus planted in Florida, California and Hawaii [5]. Major species planted in the United States are E. grandis, E. urograndis (a hybrid between E. urophylla and E. grandis), E. benthamii, E. globulus, E. robusta and E. camaldulensis, but only the former three, as well as E. amplifolia, are commercially planted in the southeastern states.

Cellulosic Energy Cropping Systems, First Edition. Edited by Douglas L. Karlen. © 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

Eucalyptus species have various uses. It is a major source of wood for fuel and con­struction material in developing countries. Some species have been used in windbreaks in agricultural farms to modify microclimate and increase yields [6,7]. In South America, Australia and South Florida, U. S.A., Eucalyptus is a major windbreak species to manage citrus canker. Lately, Eucalyptus has received wide attention because of its potential to supply the increasing wood demand from emerging biomass power plants. The pulp and paper industry has been using Eucalyptus for decades for fiber. Because of its fast growth and early canopy closure, some Eucalyptus species also have the potential to suppress light — dependent invasive species such as cogongrass (Imperata cylindrica) and restore degraded mined sites [8].