The Vitex tree is one of the most troublesome invasive alien trees for Guam. It is native in Indonesia, Malaysia, and Philippines. This is an unusual species in that it is considered vulnerable to threats in its native range, but a detrimental weed in other locations like Guam.
The attractive purples flowers and tree canopy are traits that make the species popular in the landscape trade, which is one way the tree gets introduced to regions like Guam where it escapes cultivation and becomes a threat to native forests.
Elemental composition of Vitex leaf litter from two locations throughout the Mariana Islands.
| Nitrogen | 2.07% |
| Sulfur | 0.36% |
| Phosphorus | 0.22% |
| Potassium | 0.66% |
| Magnesium | 0.58% |
| Calcium | 2.74% |
| Iron | 670.00 ppm |
| Aluminum | 215.50 ppm |
| Managese | 124.50 ppm |
| Boron | 62.00 ppm |
| Copper | 12.50 ppm |
| Zinc | 128.17 ppm |
Chemical and physical traits of Vitex leaf litter that may influence speed of litter decomposition.
| Carbon/Nitrogen | 24 |
| Carbon/Phosphorus | 256 |
| Carbon/Potassium | 104 |
| Lignin | 13.65% |
| Cellulose | 20.42% |
| Specific leaf area | 11.5 mm2 / mg |
| Total phenolics | 4,228 Gallic acid equivalents |
Vitex leaf litter decomposed rapidly compared to the other tree species. About 85% of the litter had decomposed by four months. Both Guam farm sites exhibited complete decomposition by 12 months.
