How does tree species composition vary in relation to geographical and environmental gradients in a globally rare tropical/subtropical broadleaf dry forest community in the Caribbean? We analyzed ...data from 153 Forest Inventory and Analysis (FIA) plots from Puerto Rico and the U.S. Virgin Islands (USVI), along with 42 plots that we sampled in the Bahamian Archipelago (on Abaco and Eleuthera Islands). FIA data were collected using published protocols. In the Bahamian Archipelago, we recorded terrain and landscape variables, and identified to species and measured the diameter of all stems ≥5 cm at 1.3 m height in 10 m radius plots. All data were analyzed using clustering, ordination, and indicator species analysis at regional and local scales. Regionally, the largest cluster group included over half of all plots and comprised plots from all three island groups. Indicator species were native Bursera simaruba (Burseraceae) and Metopium toxiferum (Anacardiaceae). Species composition was similar to dry forests throughout the region based on published studies. Other groups we identified at the regional scale consisted of many Puerto Rico and USVI plots that were dominated by non-native species, documenting the widespread nature of novel ecosystems. At the local scale the Bahamian data clustered into two main groups corresponding largely to the two islands sampled, a pattern consistent with the latitudinal aridity gradient. Bahamian dry forests share previously undocumented compositional similarity with native-dominated dry forests found throughout the Caribbean, but they lack extensive post-disturbance novel dry forests dominated by non-native trees found in the Greater Antilles.
Forest loss is occurring at alarming rates across the globe. The pine rockland forests of Andros, The Bahamas, likely represent some of the largest stands of Bahamian subspecies of Caribbean pine in ...the world. Given the unique species that inhabit these pine forests, such as the endemic and critically endangered Bahama Oriole, monitoring habitats on Andros is crucial to inform conservation planning. We developed a 2019 land classification map to assess the status of nine terrestrial habitats on Andros. Our Random Forest classification model predicted habitat classes with high overall accuracy. Caribbean pine was the dominant land class making up roughly one-third of the total terrestrial area. Whereas much of the pine forest area was found as small patches, most were close to other patches of pine suggesting isolation of forest patches is low. We compared our known intact forest areas to recent forest loss identified by the Hansen et al. Global Forest Change product and assessed areas of habitat disturbance in high-resolution imagery. Our results suggest that this global map overpredicted forest loss on Andros. The small degree of true forest loss on Andros was driven mostly by anthropogenic activity. A cross-tabulation of the Hansen forest loss with fire data showed that understory fires were frequently associated with falsely classified deforestation. Given the threats of climate change to this open forest type—intensifying fire regimes, strengthening hurricanes, and sea level rise—monitoring changes in open forest extent is a critical task across the Caribbean region and the world.
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