Initial Inventory of Three Permanent Forest Plots in the Virgin Islands National Park

Earhart, John; Reilly, Anne; Davis, Matt

A quantitative forest inventory was conducted in three permanent study plots within the boundaries of the Virgin Islands National Park on the island of St. John, U.S.V .I. Plot One, on Bordeaux Mountain, is located in the Reef Bay watershed and is 1 hectare (ha) (100m x 100m). Plot Two is found in the L'Esperance area of St. John in the Fish Bay watershed and measures .5 ha (50m x 50m) in area. Plot Three is located on the north coast of the island in the Hawksnest Bay watershed and is also .5 ha (50m x 50x). All stems with a diameter at breast height (DBH, at 1.3 meters) greater than or equal to 5cm were sampled. Information gathered included taxonomic identification, DBH measurements in centimeters, tree heights in meters and spatial distribution within the study plot. With these data, basal area, relative density, relative dominance and relative frequency values were calculated by species. Plot One (Bordeaux) is located in upland moist forest. A total of 62 species were identified representing 33 families with a basal area of 31.08 square meters from the 2348 stems sampled. The five most important species based on calculation of ecological importance value or I.V. (sum of relative density, relative dominance and relative frequency values) included: Guapira fragrans (I.V.=34.79); Pimenta racemosa (I.V.=32.37); Inga fagifolia (I.V.=31.61); Acacia mur icata (I.V .=29.20); and Byrsonima coriacea (I.V.=25.66). Together these five species make up 51.19% of the total importance value. Plot Two (L'Esperance) is also located in upland moist forest. A total of 39 species were identified representing 26 families with a basal area of 15.82 square meters from the 1199 stems sampled. The five most ecologically important species included: Ardisia obovata (I.V.=67.35); Guapira fragrans (I.V.=38.08); Inga fagifolia (I.V.=21.00); Andira inerrnis (I.V.=19.09); and Ocotea coriacea (I.V.=l3.74). These five trees make up 53.09% of the total importance value. Plot Three (Hawksnest) is located in the dry evergreen woodland vegetation type. A total of 54 species representing 26 families were identified. The total basal area for the plot was 13.269 square meters from the 1327 sampled stems. The five most ecologically important species included: Melicoccus bijugatus (I.V.=l02.67); Guapira fragrans (I.V.=28.46); Bursera simaruba (I.V.=l6.23); Ocotea coriacea (I.V.=l5.38); and Krugiodendron ferreum (I.V.=l2.80). Melicoccus bijugatus an introduced species, makes up 34.22% of the importance value and the five combined total 58.51% of the importance value. Each study plot has been located in a critical study watershed as determined by VIRMC. The study will be long-term (20 years) and will generate information on the dynamics of secondary forests including growth rates, basic ecology, phytosociology, impact of previous land use practices, and the role of exotic plant species. Information gathered from this study will provide information to develop strategies for forest management, ecosystem restoration and rare species conservation. It is hoped that this initial inventory will also facilitate additional ancillary studies both in the permanent plots as well as in the watersheds where they are located.