Tree species distribution and forest structure along environmental gradients in the dwarf forest of the Luquillo Mountains of Puerto Rico

摘要

Eleven groups of three plots stratified by aspect (windward vs. leeward) and topography (ridge, slope, and ravine) and varying in elevation from 880 to about 1,000 metres were used to sample forest structure and species composition within the dwarf forest of the Luquillo Mountains of Puerto Rico. Stem density to windward was significantly greater on slopes, and for all topographies combined, than to leeward. The leeward canopy height was significantly greater on slopes, and for all topographies combined, than to windward. In addition, combined mean density declined from ridge through slope to ravine for all sites whereas the opposite was true of the combined mean canopy height. Biomass was greater on ridges and slopes than in ravines for both aspects combined. Also, biomass to leeward was greater than to windward for all topographies combined; however, none of the biomass relationships was significant. Tabebuia rigida Urban was the most abundant species, accounting for > 23 % of the 3,619 stems counted, whereas Eugenia borinquensis Britton was the most widespread, occurring on 90 % of the plots. One-half of the 42 recorded species accounted for < 2 % all stems. Climatic, edaphic, and physiological factors account for dwarf forest, which is adaptedfor survival under rigorous conditions. Dwarf forest provides numerous benefits, including critical habitat for many endemic flora and fauna, valuable water supplies, panoramic vistas, and recreational opportunities.