Research guides management decisions to protect Guam’s native forests

Guam’s limestone forests are being overtaken by an invasive overstory tree called Vitex parviflora, known commonly as the molave tree. Native to the Philippines, Vitex is now the most common invasive tree species in Guam. Because this tree tends to form a monoculture, it competes with the native species that are needed to balance and sustain Guam’s ecosystems.

Clearing the forests of this invasive tree, especially where it has formed a monoculture, can adversely open the canopy and allow for other invasive weeds to flourish in the understory. Other methods, such as girdling the trees or removing a ring of bark to slowly starve the tree of nutrients, provides an alternative that minimizes flooding the understory with light as the undesirable tree dies.

Researchers at the University of Guam Western Pacific Tropical Research Center compared whole tree removal to both girdling and no treatment. They found in areas where native trees were more prevalent, the canopy could recover before allowing too much light to reach the forest floor. Their results provide land managers with important information that can guide management decisions and help to sustain the native ecosystem.

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Photo courtesy of University of Guam Western Pacific Tropical Research Center.