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A Summary of 20 Years of Forest Monitoring in Cinnamon Bay Watershed, St. John, U.S. Virgin Islands.Author(s): Peter L. Weaver
Source: United States Department of Agriculture, Forest Service, General Technical Report IITF–34
Publication Series: General Technical Report (GTR)
Station: International Institute of Tropical Forestry
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DescriptionSt. John, and probably the Cinnamon Bay watershed, has a history of human use dating to 1700 B.C. The most notable impacts, however, occurred from 1730 to 1780 when sugar cane and cotton production peaked on the island. As agriculture was abandoned, the island regenerated in secondary forest, and in 1956, the Virgin Islands National Park was created. From 1983 to 2003, the staff of the International Institute of Tropical Forestry monitored 16 plots, stratified by elevation and topography, in the Cinnamon Bay watershed. The period included Hurricanes Hugo in 1989 and Marilyn in 1995 and a severe drought in 1994-95. In all years, plot tallies showed that from 55 to 60 percent of the stems were in height classes between 4 and 8 m, and 75 percent of the stems were in diameter at breast height (1.4 m above the ground; d.b.h.) classes between 4 and 10 cm. Stem density was greatest on the summit, followed by ridges, then slopes, and lowest in valleys. After 20 years, 65 percent of the original stems survived, with an average d.b.h. growth rate of 0.07 cm year-1. Tree species abundances varied by topography and elevation within the watershed. In 1983, total aboveground biomass on all plots combined averaged 138.7 tha-1; by 2003, it had declined by nearly 7 percent. In 1983, biomass was greatest on the summit, intermediate on slopes and valleys, and least on ridges; by 2003, the quantities for all sites had converged except on the summit plot. In 1992, total aboveground productivity was estimated at 10.64 t ha-1 year -1. Standing herbivory for leaves was 4.5 percent, and the herbivory rate was 4.6 percent per year. The standing crop of litter was 9.33 t ha-1. Hurricanes had a major impact on forest structure and species composition. The trees impacted (snapped, uprooted, or standing dead) by Hurricane Hugo totaled 210 ha-1 after 10 months and 288 ha-1 after 19 months. The proportion of impacted stems differed by elevation, topography, aspect, and slope. Tree species with ≥ 20 individuals showed a difference in the proportion of impacted stems, ranging from as low as 0.6 percent for Pimenta racemosa (Mill.) J.W. Moore to as high as 22.8 percent for Nectandra coriaceae (Sw.) Griseb. In conclusion, the structure, species composition, and forest dynamics within the Cinnamon Bay watershed vary in time and space, and short-term observations characterize only a fragment of the watershed’s continuously changing vegetational history. Monitoring of forest structure and dynamics should continue.
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CitationWeaver, Peter L. 2006. A Summary of 20 Years of Forest Monitoring in Cinnamon Bay Watershed, St. John, U.S. Virgin Islands. United States Department of Agriculture, Forest Service, General Technical Report IITF–34
KeywordsBiomass, dry forest, monitoring, St. John, U.S. Virgin Islands, tree species.
- Long-term diameter growth for trees in the Cinnamon Bay Watershed
- Tertiary vegetation history
- Boletus durhamensis sp. nov. from North Carolina
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