Treesearch

Nitrogen (N) deposition is projected to increase significantly in tropical regions in the coming decades, where changes in climate are also expected. Additional N and warming each have the potential to alter soil carbon (C) storage via changes in microbial activity and decomposition, but little is known about the combined effects of these global change factors in tropical ecosystems. In this study, we used controlled laboratory incubations of soils from a long-term N fertilization experiment to explore the sensitivity of soil C to increased N in two N-rich tropical forests. We found that...

We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500–5000 mm/yr) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 3 109 cells per...

Big-leaf mahogany (Swietenia macrophylla) trees are often retained in agricultural fields and pastures for seed and timber production after selective logging and forest clearing in the Brazilian Amazon. At a forest management site in southeast Para´, we censused trees growing scattered across a large open clearing after forest removal and in heavily disturbed forest after selective logging and canopy thinning for survival, stem diameter growth, fruit production, and date of dry season flowering initiation annually during 1997–2003. Trees in the open clearing died at faster rates, grew more...

The structure and dynamics of the cloud foreston Mombacho Volcano were evaluated 11 years after the establishment of six permanent plots (PPMs). The data collected during this period showed the following trends: stem density per hectare had been decreasing, basal area increasing, recruitment staying constant, and mortality diminishing on the most of the PPMs. Although the mortality rate on all of the PPMs was greater than the recruitment rate, both tended to equalize over time. During the 11 years evaluated in this study, the importance of a small group of species that constitute the major...

To characterize the nonbreeding habitat of Kirtland’s Warbler (Dendroica kirtlandii) on Eleuthera, The Bahamas, we quantified the habitat at sites where we captured the warblers and compared these traits with those of random sites and sites of tall coppice. On the basis of a chronosequence of satellite imagery, 153 capture sites ranged in age from 3 to 28 years after human disturbance, mean 14.6 years ± 6.3 (SD). Capture sites had been abandoned after clearing (65%), converted to goat pasture (26%), burned (2%), or were young second growth following unknown disturbance (7%). Canopies in...

Food abundance, time of year, and stage of the reproductive cycle are important factors affecting home range size in birds. Between 23 January and 28 November 2003, we determined the home range and core area sizes for 10 radio-tagged male Pearly-eyed Thrashers (Margarops fuscatus; Mimidae) within the Luquillo Experimental Forest, northeastern Puerto Rico. We found significant differences among the breeding stages in home range and core area sizes. Egg and nestling stages showed the largest and smallest home range sizes (medians = 2.0 and 0.5 ha, respectively) and core area sizes (median =...

European scientists initiated lichenology in Puerto Rico in the 19th century. Activity of the discipline increased notably on the island during the first three decades of the 20th century, primarily by the field explorations and publications of the New York Botanical Garden scientists and associates (A. A. Heller, N. L. and E. G. Britton, L. W. Riddle), and by the work of Bruce Fink of Miami University in Ohio and collaborators (E. A. Vainio, A. Zahlbruckner). Another period of research activity began in the late 1950s and was initiated by Henry Imshaug of Michigan State University. By the...