U.S. Forest Service to take inventory of V.I. forests

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ST. THOMAS - The Virgin Islands had more than 45,100 acres of forest five years ago.

This year, that measurement could change, as the U.S. Department of Agriculture's Forest Service has sent three people to take an inventory of the forests on St. Thomas, St. Croix and St. John during a period of between six and eight months, starting this month.

A crew already visited St. John last week to train three main researchers to study the plots designated by the forest service.

This year's study will be the first in which an entomologist, or someone who studies insects, will be part of the team. The goal is that the entomologist can tell the service more about how insects and bugs are affecting the trees and surrounding plant and soil.

The team will locate circular plots mapped out on a grid of the territory, and forested areas are not the only areas being surveyed.

If an area includes an acre that comprises 10 percent trees, it is designated a forested area. However, the randomly mapped out plots, which are 48 feet in diameter, are not necessarily in forested areas.

Plots also could fall under an assortment of other categories, including urban space or fielded space.

"Some of the plots can land in a back yard or in the middle of the road," said Humfredo Marcano, lead researching biologist of the survey team.

On St. Croix, the researchers will have to look into 54 plots; on St. John, 30; and on St. Thomas, 26, Marcano said.

The researchers will study private and public lands. About 76 percent of the Virgin Islands' forests are privately owned, 19 percent are administered by the federal government and 5 percent are administered by the local government.

The inventory is an attempt to determine how many forested areas remain on the islands, what the conditions of the areas are and what changes have occurred within them in the last five or more years.

"The trees are pretty healthy from what we've seen lately. There's not been a hurricane lately," Marcano said.

When they venture out to the plots, the researchers measure the diameter, height and coordinates for each tree within a plot. They check for disease, sample the surrounding soil and identify the tree species.

"There's a lot of diversity here, especially in St. John," said Marcano.

Forest area on the Virgin Islands decreased slightly from 2004, when it hosted 46,564 acres, to 2009, when it had 45,163 acres. There were 26,179 acres of forest on St. Croix, which is 49.6 percent forested; 10,343 acres of forest on St. John, which is 85.5 percent forested; and 8,641 acres of forest on St. Thomas, which is 50.1 percent forested.

"We estimate there to be 85.1 million trees in the U.S. Virgin Islands holding 1.2 million tons of above-ground woody biomass," stated the 2009 inventory report.

This year's inventory will be the third in the territory. Besides the 2009 survey, the first such audit was done in 2004.

On average, in 2009, an acre of subtropical moist forest held 17.2 tons per acre of carbon, and an acre of subtropical dry forest held 11.4 tons per acre.

The territory's trees grew by 1.1 million cubic feet each year between 2004 and 2009 but lost 155,221 cubic feet per year to natural mortality and another 40,564 cubic feet to removals, for a net annual gain of 935,651 cubic feet on average.

This means a net total gain of 4.7 million cubic feet of wood volume during the entire five-year period. A total of 202,820 cubic feet of wood were removed from the forests by cutting or land clearance over that same five-year time period.

A total of 118 species were encountered in 2009.

West Indian mahogany replaced black mampoo as the tree with the highest importance value.

The "importance" of a tree species relative to others is calculated based on the relative density of that species; the relative dominance, or area taken; and the relative frequency, or percent of plots in which that species appears, for all of the territory.

Other than the promotion of the West Indian mahogany, the most important species have not changed much since the previous inventory. Smaller white leadtrees, or tan-tan, in both the subtropical dry and moist forests are another "important" species.

"As the territory's forest inventory moves from the initial 2004 measurement to the now-recurring re-measurement of established permanent plots, resource managers and policy makers will have more information to base their decisions on," the 2009 report stated. "Changes can be detected earlier and interventions planned before situations grow too large or complex to easily affect."

Forest inventories are taken nationwide, Marcano said, but he said that the territory is an exciting region to study.

Trees play an integral role in keeping the islands healthy, he said, in both their retention of emissions and their retention of soil, which helps prevent erosion.

- Contact Jenny Kane at 714-9102 or email jkane@dailynews.vi.

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