O f all ecosystems in tropical America, seasonally dry forests, patchily distributed where relatively fertile soils, annual rainfall 1,600 mm, and strong seasonal drought coincide, are perhaps the least understood and most endangered (1, 2). Mesoamerican dry forest diversity peaks in southwest Mexico, where up to 16% of tree species are local endemics (3). Judith Becerra, in this issue of PNAS ...

1 We hypothesized that severe drought affects the structure of tropical forests by favouring seedlings of some species or groups at the expense of others. To test this hypothesis, we irrigated naturally occurring woody seedlings during an El Niño-related drought in seasonal moist tropical forest on Barro Colorado Island, Panama. We predicted that irrigated plots would retain greater species ric...

Tropical and subtropical dry forest life zones support forests with lower stature and species richness than do tropical and subtropical life zones with greater water availability. The number of naturalized species that can thrive and mix with native species to form novel forests in dry forest conditions in Puerto Rico and the US Virgin Islands is lower than in other insular life zones. These no...

Daytime xylem sap flow was measured by the compensation heat pulse velocity technique in dipterocarp forest trees growing on sandy loam (haplic acrisol) and in heath forest trees growing on bleached sand (albic arenosol) in Brunei during wet and dry periods. In dipterocarp forest trees, daily sap flow was stable during the dry period but declined on rainy days presumably as a result of reduced ...

The Oaxacan Spiny-tailed Iguana Ctenosaura oaxacana is a restricted species to the Isthmus of Tehuantepec in Southern Oaxaca, Mexico. This reptile is one of the less known iguanid species. We census-tracked a population in the South ofNiltepec, Oaxaca, Mexico from May 2010 to April 2011. Throughout one year, a total of 10 line transects were situated and recorded in the study area to determine ...

Dead wood is a substantial carbon stock in terrestrial forest ecosystems and hence a critical component of global carbon cycles. Given the limited amounts of dead wood biomass and carbon stock information for Caribbean forests, our objectives were to: (1) describe the relative contribution of down woody materials (DWM) to carbon stocks on the island of St. John; (2) compare these contributions ...

The Hawaiian Islands are an ideal location to study the response of tropical forests to climate variability because of their extreme isolation in the middle of the Pacific, which makes them especially sensitive to El Niño-Southern Oscillation (ENSO). Most research examining the response of tropical forests to drought or El Niño have focused on rainforests, however, tropical dry forests cover a ...

Deforestation and changes in land use have reduced the tropical dry forest to isolated forest patches in northwestern Costa Rica. We examined the effect of patch area and length of the dry season on nestedness of the entire avian community, forest fragment assemblages, and species occupancy across fragments for the entire native avifauna, and for a subset of forest dependent species. Species ri...

Carbon accounting, forest health monitoring and sustainable management of the subtropical dry forests of Puerto Rico and other Caribbean Islands require an accurate assessment of forest aboveground biomass (AGB) and stem volume. One means of improving assessment accuracy is the development of predictive equations derived from locally collected data. Forest inventory and analysis (FIA) measured ...

Culturable methanotrophic bacteria (CMB) were studied in the soils of forest and savanna of tropical dry deciduous forest ecosystems employing most probable number (MPN) technique. The spatiotemporal study was conducted at the six sites differing in the soil physicochemical properties and vegetational cover. CMB population was high in the moist sites compared to the dry sites and in sub soil be...