“Guam’s native psyllid is an insect that feeds on the increasingly rare Intsia bijuga tree. (Photo credit: Aubrey Moore)

 

UOG Research Published in Journal of Tropical Forest Science

Article discusses complications of conservation decisions on native tree and insect species.  

 

Research conducted by the University of Guam Western Pacific Tropical Research Center (WPTRC) on the native Intsia bijuga tree has been published in a recent issue of the Journal of Tropical Forest Science (JTFS). The research was designed to reveal how conservationists should keep an open mind when implementing management decisions, using the example of the relationship between a native tree and the native insect affecting the tree's population growth. Thomas Marler, an ecologist with WPTRC conducted the research and is the author of the journal article.

Intsia bijuga, known locally as ifit, is designated as the official territorial tree of Guam. As in other regions where it is native, ifit wood is renowned for its quality for construction, furniture, and artisan uses. The historical and current population of the species is exemplary of trends in tropical forest health in general. The species was widespread in Guam’s forests historically, but is represented today with isolated rare occurrences of very old trees showing no substantial recruitment. The lack of natural recruitment is a concern for contemporary ecologists because the ifit population will continue to dwindle unless conservation intervention is employed to reverse or manage the trend.

The native Guam insect that reduces ifit tree growth is called a psyllid. The relationship between the ifit and the psyllid is an example of a system that perplexes conservationists because the native tree may be more valuable economically, but may not be more valuable ecologically than the native insect. Indiscriminate control of the insect pest may benefit the native tree, but certainly does not benefit the native insect. This case study shows that appropriate balance between ecology and silviculture, which is the science and art of growing and caring for forest crops, is often difficult to achieve during rare species recovery efforts.

“Many decisions in silviculture are focused on the single objective of maximizing tree growth, and this article reveals that this one-sided approach to management decisions may compromise success,” said said Kunju Sarifah, editor for JTFS. The publication conveyed the trade-off between the positives of increasing tree growth by controlling insect damage and the negatives of reducing wood density as a consequence.

The article is available from the Journal of Tropical Forest Science website or can be directly downloaded in PDF format here.