Treesearch

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon1–3. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses4–9. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad...

While testing genetic sexing techniques in Ovenbirds (Seiurus aurocapilla),we found a genetic polymorphism in the ATP5A1 gene in 38% of individuals. The Z ' allele included changes in both intronic and exonic portions of the sequenced region, but there was no evidence that this changed the resulting ATP synthase product. Males that had one or more copies of this allele had higher relative bodymass (mass corrected for size) than other genotypes. This allele was unrelated to stable isotope signatures, and so was not a useful predictor of latitude within the eastern portion of the Ovenbird...

Four watersheds with differing geology and land cover in eastern Puerto Rico have been studied on a long-term basis by the U.S. Geological Survey to evaluate water, energy, and biogeochemical budgets. These watersheds are typical of tropical, island-arc settings found in many parts of the world. Two watersheds are located on coarse-grained granitic rocks that weather to quartz- and clay-rich, sandy soils, and two are located on fine-grained volcanic rocks and volcaniclastic sedimentary rocks that weather to quartz-poor, fine-grained soils. For each bedrock type, one watershed is covered...

Based on theoretical underpinnings and an empirical review of forest laws and regulations of selected countries throughout the Americas, we examine key components of natural forest management and how they are addressed in the legal frameworks of Argentina, Brazil, Chile, Costa Rica, Guatemala, Nicaragua, Paraguay, Uruguay, and the U.S. We consider forest policy directives in terms of legislative, planning, operational, environmental/ecological, social, and economic aspects and classify them by the type of policy obligation: (1) non-discretionary laws or rules; or (2) discretionary,...

Anthropogenic activity is altering the global disturbance regime through such processes as urbanization, deforestation, and climate change. These disturbance events alter the environmental conditions under which organisms live and adapt and trigger succession, thus setting the biota in otiion in both ecological and evolutionary space. The result is the mixing of species from different biogeographic regions and formation of novel communities of plants and animals. In this essay I present the point of view that this mixing and remixing of species is a natural response to the changing...

Global anthropogenic activities are responsible for the modification of landscapes, creation of novel environments and movement of species across biogeographic regions. A consequence of this activity is the mixing of native and introduced species and the formation of novel biotic communities. We review the ecological consequences of the mixing of native and introduced species in the Caribbean Islands especially in Puerto Rico and the US Virgin Islands. Here we found documented examples indicating that novel communities of native and naturalized organisms are ubiquitous. The coexistence of...

Rainfall interception (I) was measured in 20 m tall Puerto Rican tropical forest with complex topography for a 1-year period using totalizing throughfall (TF) and stemflow (SF) gauges that were measured every 2–3 days. Measured values were then compared to evaporation under saturated canopy conditions (E) determined with the Penman–Monteith (P–M) equation, using (i) measured (eddy covariance) and (ii) calculated (as a function of forest height and wind speed) values for the aerodynamic conductance to momentum flux (ga,M). E was also derived using the energy balance equation and the...

Because of human pressures, the need to understand and predict the long-term dynamics and development of subtropical dry forests is urgent. Through modifications to the ZELIG simulation model, including the development of species- and site-specific parameters and internal modifications, the capability to model and predict forest change within the 4500-ha Guanica State Forest in Puerto Rico can now be accomplished. Published datasets and additional data from the U.S. Forest Service Forest Inventory Analysis were used to parameterize the new gap model, ZELIG-TROP. We used data from permanent...