One of the most contentious debates during the recent climate talks centered on the possible use of forests as credit towards reducing atmospheric carbon dioxide. Although it has long been assumed that these areas will act as sinks for excess carbon, the effects of species composition on the process of carbon sequestration is still largely unknown. A team of researchers working on eucalyptus plantations in Hawaii has discovered an important aspect of how carbon sequestration processes work in tropical tree plantations. The researchers, who have published their findings in the December edition of Ecology (Vol. 81, No. 12), discovered that carbon sequestration was significantly boosted when the composition of tree stands included nitrogen-fixing trees.

Jason Kaye and his colleagues from Colorado State University researched carbon storage on a former sugar cane farm which had been turned into a plantation for Eucalyptus trees (Eucalyptus saligna) in Hawaii. The team discovered that the acres which were interplanted with albizia trees (Albizia falcataria) were able to sequester more carbon than areas where eucalyptus trees were planted alone.

The researchers believe that this is due to the nitrogen-fixing qualities of the albizia trees. Albizias, which are sometimes also referred to as mimosa trees, are not a cash crop like eucalyptus. Although many tree plantations employ monoculture planting schemes, planting one tree species over hundreds of acres, the albizia trees' effect on soil quality has prompted some farmers to test the potential benefits of interplanting the two species. This kind of practice is increasingly common in tropical areas, where the nutrient level of soil is often limited.

Kaye and his colleagues studied carbon storage in forest stands planted 17 years ago with differing species composition. Some stands were planted as pure eucalyptus, some as pure albizia, and some with the two trees planted together. The researchers
'"/>

Contact: Alison Gillespie
alison@esa.org
202-833-8773 ext 211
Ecological Society of America
18-Dec-2000