El legado científico de Juan A. Torres-Negrón

Juan A. Torres-Negron (Juan Torres) studied ants, wasps, termites and other insect groups. I reviewed 34 of his publications and grouped them into six subjects: ecological theory, taxonomy, chemistry, ecology, synthesis, and commentaries. Juan Torres used empirical fieldwork, keen observations, and experimentation to advance the understanding of ant taxonomy and ecology in Puerto Rico. His taxonomic work involved the description of new species and genera of various insect groups, as well as revisions of taxonomic groups, and other observations of the ecology and behavior of rare taxa. Juan Torres also published several taxonomic keys in English and Spanish for various insect groups and localities. His work with ant communities advanced ecological niche theory and island biogeography highlighting the non-equilibrium and stochastic nature of ant community dynamics in Puerto Rico and adjacent islands. He also published synthesis summaries of the ants of Puerto Rico, Mona Island, and the Luquillo Mountains. His ecological studies of ants ranged from descriptions of biotic interactions among ants and with other animal species, to the quantification of the role of insects in wood decomposition and nutrient cycling. The research spanned from dry to wet forest and non-forest conditions in Puerto Rico and adjacent islands and cays.Juan A. Torres Negrón (Juan Torres) estudió hormigas, avispas, comejenes y otros grupos de insectos. Revisé 34 de sus publicaciones y las agrupé en seis temas: teoría ecológica, taxonomía, química, ecología, síntesis y comentarios. Juan Torres utilizó trabajo empírico de campo, sagaces observaciones y experimentación para avanzar el campo de la taxonomía y ecología de las hormigas en Puerto Rico. Su trabajo taxonómico resultó en la descripción de nuevas especies y géneros de insectos, revisiones taxonómicas, reportes de presencia de especies en la Isla y la documentación de nuevos aspectos ecológicos y del comportamiento de varios grupos taxonómicos. Además, publicó claves taxonómicas en inglés y español para varios grupos de insectos y distintas localidades. Sus trabajos con comunidades de hormigas ampliaron las teorías de ecología de nicho y la de biogeografía de islas enfatizando el estado de desequilibrio y la naturaleza estocástica de las comunidades de hormigas en Puerto Rico e islas adyacentes. Publicó resúmenes sobre la ecología y taxonomía de hormigas e insectos en Puerto Rico, Isla de Mona y las Montañas de Luquillo. Sus estudios ecológicos cubrieron una amplia gama de tópicos desde las interacciones bióticas entre grupos de hormigas y con otros grupos de plantas y animales, hasta la función de los insectos en la descomposición de la madera y el reciclaje de nutrientes en los bosques. Las investigaciones de Juan Torres incluyeron desde bosques secos a bosques muy húmedos, pastizales y sistemas agrícolas en el archipiélago de Puerto Rico

Structural response of Caribbean dry forests to hurricane winds: a case study from Guanica Forest, Puerto Rico

Aim Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple-stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance. Location Guánica Forest, Puerto Rico. Methods Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics. Results Direct effects of the hurricane were minimal, with stem mortality at \u3c 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high – over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (\u3e 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species. Main conclusions Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi-stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short-term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds

Regional Forest Types - Tropical Dry Forests

Tropical dry forests occur in nearly every tropical country. This forest type provides critical habitat for large mammals and migratory birds, and patches of dry forest can support a high proportion of endemic plant and animal species, as well as being highly valued for agricultural and production forestry uses. Consequently, conservation and understanding of these forests need emphasis, yet conservationists and scientists still frequently overlook this ecosystem

A link between hurricane-induced tree sprouting, high stem density and short canopy in tropical dry forest

The physiognomy of Caribbean dry forest is shorter, denser and contains a greater proportion of multi-stemmed trees than other neotropical dry forests. Our previous research, conducted after Hurricane Georges in 1998, has shown that dry forest trees sprout near the base following hurricane disturbance, even if the trees have not incurred structural damage. However, for these hurricane-induced sprouts to contribute to the physiognomy of the forest, they must grow and survive. We followed sprout dynamics and stem mortality on 1,407 stems from 1998, after Hurricane Georges, until 2005. The number of surviving sprouts and the proportion of sprouting stems decreased during the 7-year period, but the sprouting rate was still 3-fold higher and the proportion of sprouting stems 5-fold higher than before the hurricane. Mortality of non-sprouting stems (15.4%) was about the same as for sprouting stems (13.9%) after 7 years. The mean length of the dominant sprout surpassed 1.6 m by 2005, with over 13% of the dominant sprouts reaching subcanopy height. Sprout growth and survival varied among species. These results demonstrate that, despite some thinning, hurricane-induced sprouts survive and grow and that the unique physiognomic characteristic of Caribbean dry forests is related to hurricane disturbance

Hurricane Hugo: Damage to a Tropical Rain Forest in Puerto Rico

Hurricane Hugo of September 1989 caused severe damage to the rain forest in the north-east corner of Puerto Rico. We assessed the severity of damage distributed in space, species, and size-classes of trees in the Bisley Watersheds of the Luquillo Experimental Forest. We analyzed pre- and post-hurricane data for vegetation from transects established in 1987 and 1988. The severity of damage was significantly greater in valleys than on ridges and slopes. All the species except Dacryodes excelsa, Sloanea berteriana, and Guarea guidonia showed 100% severe damage. Large trees (\u3e 70 cm DBH) were highly susceptible to hurricane damage, but there was no clear pattern in the small size-classes. D. excelsa (tabonuco) was the most resistant to damage by the hurricane. Tabonuco which has extensive root-grafts and root anchorage to bedrock and subsurficial rocks, apparently can survive frequent hurricanes and continue as a dominant species in this montane tropical rain forest. The high frequency of hurricanes, which can override other ecological and topographic factors, may largely determine the overall spatial pattern of species in this rain forest

Landform type mediates compositional change in a hurricane-disturbed sub-tropical forest

Background Categorization of topographical features into landform type is a long-standing method for understanding physiographic patterns in the environment. Differences in forest composition between landform types are driven primarily by concurrent differences in soil composition and moisture, but also disturbance regime. Many studies have focused on the interaction between fire disturbance, succession, and landforms, but the effects of hurricane disturbance on compositional differences between landforms are poorly understood. In the study presented here, we assess compositional and structural differences between landform types in the tree community of a young sub-tropical forest that is frequently subjected to hurricanes. Specifically, we ask whether the tree community (1) changed structurally over the study period, (2) experienced compositional change over the study period, (3) is compositionally different between landform types, and (4) exhibits compositional change mediated by landform type. Results The tree community experienced significant structural change over the course of our study, but compositional change was only significant for some landforms. Conclusion Despite large-scale, intense, and frequent hurricane disturbance to our study system, compositional change in the tree community was localized and only significant for some landform types

Forecasting effects of sea-level rise and windstorms on coastal and inland ecosystems

Author Posting. © Ecological Society of America, 2008. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Frontiers in Ecology and the Environment 6 (2008): 255–263, doi:10.1890/070153.We identify a continental-scale network of sites to evaluate how two aspects of climate change – sea-level rise and intensification of windstorms – will influence the structure, function, and capacity of coastal and inland forest ecosystems to deliver ecosystem services (eg carbon sequestration, storm protection, pollution control, habitat support, food). The network consists of coastal wetland and inland forest sites across the US and is representative of continental-level gradients of precipitation, temperature, vegetation, frequency of occurrence of major windstorms, value of insured properties, tidal range, watershed land use, and sediment availability. The network would provide real-time measurements of the characteristics of sea-level rise and windstorm events and would allow an assessment of the responses of wetlands, streams, and inland forests at spatial and temporal scales associated with sustainability of ecosystem services. We illustrate the potential of this approach with examples of hypotheses that could be tested across the network.The research that led to this paper was supported in part by grants to CSH (NSF BCS-0709685, DEB-0614282, OCE-0423565, GA Sea Grant NA080AR4170724), AEL (NSF BIR-8811902, DEB-9411973, DEB-9705814, DEB-0080538, DEB- 0218039), MA (NSF OCE-0620959, GA Sea Grant NA08OAR4170724, GA Coastal Management Program NA07NOS4190182), APC (NSF DEB-0218039), and SJVB (USDA CSREES PR00NRI001, McIntire Stennis PR014)

The Influence of Hurricane Winds on Caribbean Dry Forest Structure and Nutrient Pools

In 1998, we measured the effects of Hurricane Georges after it passed over long‐term research sites in Puerto Rican dry forest. Our primary objectives were to quantify hurricane effects on forest structure, to compare effects in a large tract of forest versus a series of nearby forest fragments, to evaluate short‐term response to hurricane disturbance in terms of mortality and sprouting, and to assess the ability of hurricanes to maintain forest structure. We sampled damage from 33 plots (1.3 ha) across a 3000‐ha tract of forest as well as in 19 fragments. For stems with 2.5‐cm minimum diameter, 1004 stems/ha (12.4%) suffered structural damage, while 69 percent of the undamaged stems were at least 50 percent defoliated. Basal area lost to structural damage equaled 4.0 m2/ha (22%) in south‐facing native forests. Structural damage and defoliation increased with stem diameter and were more common in certain dry forest species. South‐facing forests and those on ridgetops incurred more damage than north‐facing forests or those comprised primarily of introduced species. Stem mortality was only 2 percent of all stems after 9 mo. Structural damage did not necessarily result in stem mortality. Hurricane‐induced mortality was not associated with stem height or diameter, but was ten times greater than background mortality. Basal sprouting was proportional to the amount of structural damage incurred in a stand. Forest fragments experienced the same patterns of hurricane effects as the reference forest. The low, dense structure of Caribbean dry forest can be maintained by hurricane damage to larger stems and induction of basal sprouting to generate multistemmed trees