Puerto Rico

The Ecological Consequences of Socioeconomic and Land-Use Changes in Postagriculture Puerto Rico

Grau, H. Ricardo; Aide, T. Mitchell; Zimmerman, Jess K.; Thomlinson, John R.; Helmer, Eileen; Zou, Xioming 2003. The ecological consequences of socioeconomic and land-use changes in post agriculture Puerto Rico. BioScience. Vol. 53, no. 12 (Dec. 2003): Pages 1159-1168.

Abstract: 
Contrary to the general trend in the tropics, forests have recovered in Puerto Rico from less than 10% of the landscape in the late 1940s to more than 40% in the present. The recent Puerto Rican history of forest recovery provides the opportunity to study the ecological consequences of economic globalization, reflected in a shift from agriculture to manufacturing and in human migration from rural to urban areas. Forest structure rapidly recovers through secondary succession, reaching mature forest levels of local biodiversity and biomass in approximately 40 years. Despite the rapid structural recovery, the legacy of pre-abandonment land use, including widespread abundance of exotic species and broadscale floristic homogenization, is likely to persist for centuries.

Trends and scenarios of the carbon budget in postagricultural Puerto Rico (1936–2060)

Grau, H. R., T. M. Aide, J. K. Zimmerman, and J. R.
Thomlinson. 2004. Trends and scenarios of the carbon
budget in post-agricultural Puerto Rico (1936–2060). Global
Change Biology 10:1163–1179.

Abstract: 
Contrary to the general trend in the tropics, Puerto Rico underwent a process of agriculture abandonment during the second half of the 20th century as a consequence of socioeconomic changes toward urbanization and industrialization. Using data on landuse change, biomass accumulation in secondary forests, and ratios between gross domestic product (GDP) and carbon emissions, we developed a model of the carbon budget for Puerto Rico between 1936 and 2060. As a consequence of land abandonment, forests have expanded rapidly since 1950, achieving the highest sequestration rates between 1980 and 1990. Regardless of future scenarios of demography and land use, sequestration rates will decrease in the future because biomass accumulation decreases with forest age and there is little agricultural land remaining to be abandoned. Due to high per-capita consumption and population density, carbon emissions of Puerto Rico have increased dramatically and exceeded carbon sequestration during the second half of the 20th century. Although Puerto Rico had the highest percent of reforestation for a tropical country, emissions during the period 1950–2000 were approximately 3.5 times higher than sequestration, and current annual emission is almost nine times the rate of sequestration. Additionally, while sequestration will decrease over the next six decades, current socioeconomic trends suggest increasing emissions unless there are significant changes in energy technology or consumption patterns. In conclusion, socioeconomic changes leading to urbanization and industrialization in tropical countries may promote high rates of carbon sequestration during the decades following land abandonment. Initial high rates of carbon sequestration can balance emissions of developing countries with low emission/GDP ratio. In Puerto Rico, the socioeconomic changes that promoted reforestation also promoted high-energy consumption, and resulted in a net increase in carbon emissions.

A new genus and species of ‘giant hutia’ (Tainotherium valei ) from the Quaternary of Puerto Rico: an extinct arboreal quadruped?

Turvey, S.T., Grady, F.V., Rye, P., 2006. A new genus and species of
‘giant hutia’ (Tainotherium valei) from the Quaternary of Puerto Rico: an extinct arboreal quadruped? Journal of Zoology 270 (4), 585–594.

Abstract: 
A large incomplete rodent femur from a Quaternary cave deposit near Barahona, Puerto Rico, is established as the holotype of Tainotherium valei, a new extinct genus and species. Although biogeographic and body size similarities suggest that it may be related to the Puerto Rican giant hutia Elasmodontomys, the Antillean large-bodied rodent family Heptaxodontidae is now interpreted as invalid, and it is impossible to assign Tainotherium to a particular caviomorph family in the absence of associated craniodental material. Tainotherium differs from other West Indian species in possessing a large femoral head, a proximally angled femoral neck, a short greater trochanter and a medially positioned lesser trochanter unconnected by an intertrochanteric crest, and a transversely flattened, anteroposteriorly bowed shaft lacking well-defined ridges. These characters are all associated with arboreal life habits in other mammal groups. The Puerto Rican land mammal fauna was dominated by a rodent radiation occupying a wide variety of niches before human arrival in the West Indies, but although arboreality is correlated with increased likelihood of survival in Quaternary mammalian extinction events, all of this fauna is now extinct. It is unlikely that decreasing aridity and the reduction of Puerto Rican savanna-type environments at the end of the Pleistocene contributed to the extinction of the arboreal Tainotherium, and habitat destruction by pre-Columbian Amerindians may instead have been responsible.

Variation in Susceptibility to Hurricane Damage as a Function of Storm Intensity in Puerto Rican Tree Species

Canham, Charles D.; Thompson, Jill; Zimmerman, Jess K.; Uriarte, Maria. 2010 Variation in Susceptibility to Hurricane Damage as a Function of Storm Intensity in Puerto Rican Tree Species. Biotropica, 42 (1). 87-94. 10.1111/j.1744-7429.2009.00545.x

Abstract: 
One of the most significant challenges in developing a predictive understanding of the long-term effects of hurricanes on tropical forests is the development of quantitative models of the relationships between variation in storm intensity and the resulting severity of tree damage and mortality. There have been many comparative studies of interspecific variation in resistance of trees to wind damage based on aggregate responses to individual storms. We use a new approach, based on ordinal logistic regression, to fit quantitative models of the susceptibility of a tree species to different levels of damage across an explicit range of hurricane intensity. Our approach simultaneously estimates both the local intensity of the storm within a plot and the susceptibility to storm damage of different tree species within plots. Using the spatial variation of storm intensity embedded in two hurricanes (Hugo in 1989 and Georges in 1998) that struck the 16 ha Luquillo Forest Dynamics Plot in eastern Puerto Rico, we show that variation in susceptibility to storm damage is an important aspect of life history differentiation. Pioneers such as Cecropia schreberiana are highly susceptible to stem damage, while the late successional species Dacryodes excelsa suffered very little stem damage but significant crown damage. There was a surprisingly weak relationship between tree diameter and the susceptibility to damage for most of the 12 species examined. This may be due to the effects of repeated storms and trade winds on the architecture of trees and forest stands in this Puerto Rican subtropical wet forest.

POTENTIAL CAUSES FOR AMPHIBIAN DECLINES IN PUERTO RICO

P. A. Burrowes, R. L. Joglar and D. E. Green, Potential causes for
amphibian declines in Puerto Rico, Herpetologica, 2004, 60, 141–154.

Abstract: 
We monitored 11 populations of eight species of Eleutherodactylus in Puerto Rico from 1989 through 2001. We determined relative abundance of active frogs along transects established in the Caribbean National Forest (El Yunque), Carite Forest, San Lorenzo, and in the vicinity of San Juan. Three species (Eleutherodactylus karlschmidti, E. jasperi, and E. eneidae) are presumed to be extinct and eight populations of six different species of endemic Eleutherodactylus are significantly declining at elevations above 400 m. Of the many suspected causes of amphibian declines around the world, we focused on climate change and disease. Temperature and precipitation data from 1970–2000 were analyzed to determine the general pattern of oscillations and deviations that could be correlated with amphibian declines. We examined a total of 106 tissues taken from museum specimens collected from 1961–1978 and from live frogs in 2000. We found chytrid fungi in two species collected at El Yunque as early as 1976, this is the first report of chytrid fungus in the Caribbean. Analysis of weather data indicates a significant warming trend and an association between years with extended periods of drought and the decline of amphibians in Puerto Rico. The 1970’s and 1990’s, which represent the periods of amphibian extirpations and declines, were significantly drier than average. We suggest a possible synergistic interaction between drought and the pathological effect of the chytrid fungus on amphibian populations.

Acclimation of tropical tree species to hurricane disturbance: ontogenetic differences

Wen, S.Y., Fetcher, N. & Zimmerman, J.K. (2008) Acclimation of tropical tree
species to hurricane disturbance: ontogenetic differences. Tree Physiology,
28, 935–946.

Abstract: 
We investigated acclimation responses of seedlings and saplings of the pioneer species Cecropia schreberiana Miq. and three non-pioneer species, Dacryodes excelsa Vahl, Prestoea acuminata (Willdenow) H.E. Moore var. montana (Graham) Henderson and Galeano, and Sloanea berteriana Choisy ex DC, following a hurricane disturbance in a lower montane wet forest in Puerto Rico. Measurements were made, shortly after passage of the hurricane, on leaves expanded before the hurricane (pre-hurricane leaves) and, at a later time, on recently matured leaves that developed after the hurricane (post-hurricane leaves) from both seedlings and saplings at sites that were severely damaged by the hurricane (disturbed sites) and at sites with little disturbance (undisturbed sites). Pre-hurricane leaves of the non-pioneer species had relatively low light-saturated photosynthetic rates (Amax) and stomatal conductance (gs); neither Amax nor gs responded greatly to the increase in irradiance that resulted from the disturbance, and there were few significant differences between seedlings and saplings. Pre-hurricane leaves of plants at undisturbed sites had low dark respiration rates per unit area (Rd) and light compensation points (LCP), whereas pre-hurricane leaves of plants at disturbed sites had significantly higher Rd and LCP. Post-hurricane leaves of plants at disturbed sites had significantly higher Amax and Rd than plants at undisturbed sites. Compared with seedlings, saplings had higher Amax and Rd and showed greater acclimation to the increase in irradiance that followed the disturbance. Post-hurricane leaves of the non-pioneer species had significantly lower Amax and were less responsive to changes in irradiance than the pioneer species C. schreberiana. Variation in Amax across light environments and stages was strongly related to differences in leaf mass per unit area (LMA), especially in the non-pioneer species. As indicated by Vcmax or Jmax per unit nitrogen, light acclimation of Amax was determined by leaf morphology (LMA) for the nonpioneer species and by both leaf morphology and leaf biochemistry for C. schreberiana. Ontogenetic changes in Amax were attributable to changes in leaf morphology. The ontogenetic component of variation in Amax across light environments and stages differed among species, ranging from 36 to 59% for the non-pioneer species (D. excelsa, 59.3%; P. acuminata var. montana, 44.7%; and S. berteriana, 36.3%) compared with only 17% in the pioneer species C. schreberiana.

Ecosystem Development and Plant Succession on Landslides in the Caribbean

Ecosystem Development and Plant Succession on Landslides in the Caribbean
Lawrence R. Walker, Daniel J. Zarin, Ned Fetcher, Randall W. Myster and Arthur H. Johnson
Biotropica
Vol. 28, No. 4, Part A. Special Issue: Long Term Responses of Caribbean Ecosystems to Disturbances (Dec., 1996), pp. 566-576

Abstract: 
Landslides are common in mountainous regions of the Caribbean and are triggered by heavy rains and earthquakes, and often occur in association with human disturbances (e.g., roads). Spatially heterogeneous removal of both substrate and vegetation is responsible for a variety of patterns of ecosystem development and plant successional trajectories within Caribbean landslides. Soil nutrient pools in exposed mineral soils reach levels comparable to mature forest soils within 55 yr but soil organic matter recovers more slowly. Plant colonization of landslides depends on the availability of propagules and suitable sites for germination, soil stability, and the presence of residual or newly deposited soil organic matter and associated nutrients. Once initial colonization occurs, the rate and trajectory of plant succession on landslides is strongly affected by plant/plant interactions. We present two conceptual models of landslide succession that summarize the major processes and pathways of ecosystem development and plant succession on landslides. Additional work is needed to characterize interactions between spatially heterogeneous zones, controls over soil development, impacts of key plant species, and the role of animals on Caribbean landslides.

Land Use History, Environment, and Tree Composition in a Tropical Forest

Thompson, Jill; Brokaw, Nicholas; Zimmerman, Jess K.; Waide, Robert B.; Everham, Edwin M. III; Lodge, D. Jean; Taylor, Charlotte M.; Garcia-Montiel, Diana; Fluet, Marcheterre 2002. Land use history, environment, and tree composition in a tropical forest. Ecological applications. Vol. 12, no. 5 (2002): pages 1344-1363.

Abstract: 
The effects of historical land use on tropical forest must be examined to understand present forest characteristics and to plan conservation strategies. We compared the effects of past land use, topography, soil type, and other environmental variables on tree species composition in a subtropical wet forest in the Luquillo Mountains, Puerto Rico. The study involved stems > 10 cm diameter measured at 130 cm above the ground, within the 16-ha Luquillo Forest Dynamics Plot (LFDP), and represents the forest at the time Hurricane Hugo struck in 1989. Topography in the plot is rugged, and soils are variable. Historical documents and local residents described past land uses such as clear-felling and selective logging followed by farming, fruit and coffee production, and timber stand improvement in the forest area that now includes the LFDP. These uses ceased 40-60 yr before the study, but their impacts could be differentiated by percent canopy cover seen in aerial photographs from 1936. Using these photographs, we defined four historic cover classes within the LFDP. These ranged from cover class 1, the least tree-covered area in 1936, to cover class 4, with the least intensive historic land use (selective logging and timber stand improvement). In 1989, cover class 1 had the lowest stem density and proportion of large stems, whereas cover class 4 had the highest basal area, species richness, and number of rare and endemic species. Ordination of tree species composition (89 species, 13 167 stems) produced arrays that primarily corresponded to the four cover classes (i.e., historic land uses). The ordination arrays corresponded secondarily to soil characteristics and topography. Natural disturbances (hurricanes, landslides, and local treefalls) affected tree composition, but these effects did not correlate with the major patterns of species distributions on the plot. Thus, it appears that forest development and natural disturbance have not masked the effects of historical land use in this tropical forest, and that past land use was the major influence on the patterns of tree composition in the plot in 1989. The least disturbed stand harbors more rare and endemic species, and such stands should be protected.

RIPARIAN VEGETATION AND STREAM CONDITION IN A TROPICAL AGRICULTURE–SECONDARY FOREST MOSAIC

Heartsill-Scalley T, Aide TM. 2003. Riparian vegetation and stream condition
in a tropical agriculture–secondary forest mosaic. Ecological
Applications 13: 225–234.

Abstract: 
Changes in land cover from forest to agriculture often alter riparian vegetation, which modifies the physical conditions of streams. To understand the impacts of different categories of land cover on riparian and stream habitats, we sampled riparian vegetation and stream conditions in three adjacent watersheds in southeastern Puerto Rico. Land cover categories (pasture, mixed, and forest) were determined using aerial photographs. Vegetation structure and composition and characteristics of streams were assessed for 35 riparian sites. Sites were located along first-order streams, at 400–600 m elevation in the wet-forest life zone. Understory vegetation in the forest sites was mainly shrubs, herbs, and ferns, whereas the mixed and pasture sites were dominated by grasses, vines, and bare soil. Syzygium jambos and Spathodea campanulata, nonnatives, and Guarea guidonia, a native, were the most common tree species in the riparian areas. Surrounding land cover explained .60% of the variation among stream sites. There was a positive relationship between tree cover and percentage of dissolved oxygen, and a negative relationship between tree cover and percentage of substrata covered by sediments from eroded soil. The amount of woody debris in the streams tended to increase with forest cover. Overall, land cover is a landscape feature that effectively characterized riparian understory cover, tree species composition, and stream condition

The Bromeliad Microcosm and the Assessment of Faunal Diversity in a Neotropical Forest

The Bromeliad Microcosm and the Assessment of Faunal Diversity in a Neotropical Forest
Barbara A. Richardson
Biotropica
Vol. 31, No. 2 (Jun., 1999), pp. 321-336

Abstract: 
The faunas of tank bromeliads were sampled over two years in three forest types at different elevations in the Luquillo Experimental Forest, Puerto Rico, and the diversity of their animal communities compared. Bromeliad plants behaved as islands in that, within forests, the species richness and abundance of their animal communities were significantly and positively correlated with increase in plant size. The amount of canopy debris they accumulated was similarly correlated with increase in plant size. Overall diversity was lowest in the dwarf forest, where plants were uniformly small. Animal communities were stable from year to year, and could be characterised for each forest type and for compartments within the plant. They showed a pattern of high dominance, which increased with elevation (McNaughton index 37, 54, and 73, respectively, for the tabonuco, palo colorado, and dwarf forest). Alpha-diversity for sites sampled in each year reflected net primary productivity (NPP) of the forest, declining with increasing elevation when animal abundance measures were used (jackknife estimates of Simpson's diversity index 6.54 & 11.04 [tabonuco], 3.53 & 6.22 [palo colorado], and 2.75 & 2.17 [dwarf forest]). Species richness over the two years, however, was highest in the intermediate palo colorado forest (187 species), compared to 146 and 88 in the tabonuco and dwarf forests, respectively. These figures were close to jackknife estimates of maximum species richness. The difference in species richness between tabonuco and palo colorado forests was significant in one year only. In addition to NPP, other factors, such as litter quality and the structural complexity of the habitat in the palo colorado forest, may have influenced species richness. The most abundant species in individual plants were also the most widely occurring, confirming known patterns of abundance and distribution in other functional groups. Diversity within bromeliad microcosms at different elevations supported known relationships between diversity, productivity, and habitat complexity along gradients and was not related to differences in the total bromeliad habitat available for colonization.
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