Venezuelan Andes Research Articles

Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma

A carbon-rich black layer encrusted on a sandy pebbly bed of outwash in the northern Venezuelan Andes, previously considered the result of an alpine grass fire, is now recognized as a ‘black mat’ candidate correlative with Clovis Age sites in North America, falling within the range of ‘black mat’ dated sites (~ 12.9 ka cal BP). As such, the bed at site MUM7B, which dates to < 11.8 ka 14C years BP (raw dates) and appears to be contemporaneous with the Younger Dryas (YD) cooling event, marks a possibly much more extensive occurrence than previously identified. No fossils (megafauna) or tool assemblages were observed at this newly identified candidate site (3800 a.m.s.l.), as in the case of the North American sites. Here, evidence is presented for an extraterrestrial impact event at ~ 12.9 ka. The impact-related Andean bed, located ~ 20 cm above 13.7–13.3 ka cal BP alluvial and glaciolacustrine deposits, falls within the sediment characteristics and age range of ‘black mat’ dated sites (~ 12.9 ka cal BP) in North America. Site sediment characteristics include: carbon, glassy spherules, magnetic microspherules, carbon mat ‘welded’ onto coarse granular material, occasional presence of platinum group metals (Rh and Ru), planar deformation features (pdfs) in fine silt-size fragmental grains of quartz, as well as orthoclase, and monazite (with an abundance of Rare Earth Elements—REEs). If the candidate site is ‘black mat’, correlative with the ‘black mat’ sites of North America, such an extensive occurrence may support the hypothesized airburst/impact over the Laurentide Glacier, which led to a reversal of Allerød warming and the onset of YD cooling and readvance of glaciers. While this finding does not confirm such, it merits further investigation, which includes the reconnaissance for additional sites in South America. Furthermore, if confirmed, such an extensive occurrence may corroborate an impact origin.

Chemical Composition and Antibacterial Activity of the Essential Oil of Cordia verbenacea from the Venezuelan Andes

The essential oil of Cordia verbenacea D.C. (Boraginaceae) that grows in Mérida-Venezuela was obtained by hydrodistillation from the aerial parts of the plant, yielding 0.21%. The oil was analyzed by GC-FID and GC-MS. Thirty one components which made up 94.3% of the oil were identified. The most abundant constituents found were: tricyclene (23.9%), bicyclogermacrene (11.7%), germacrene D (9.9%) and beta-caryophyllene (8.2%). Antibacterial activity determination was carried out according to the disc diffusion assay. Activity against Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212, at a minimal inhibitory concentration (MIC) of 170 microg/mL and 200 microg/mL, was found.

Inner-tropical ozone measurements at the Mérida Atmospheric Research Station (MARS) using ground-based microwave radiometry

Since March 2004 the ground-based 268–280 GHz radiometer MIRA 2 has been in quasi-continuous operation at the inner-tropical Mérida Atmospheric Research Station (MARS) on Pico Espejo (8.58°N, 71.15°W, 4765 m above sea level) in the Venezuelan Andes. Using the optimal estimation method concentration profiles of ozone have been retrieved in the stratosphere and mesosphere. In the middle stratosphere variations of ozone on a time scale of several months were revealed in the resulting time series that probably result from the turnaround of the Brewer–Dobson circulation. In the mesosphere photochemistry plays the most important role for the ozone concentration. Therefore a diurnal cycle is observed in the upper part of the retrieved ozone profiles. The measurements are used to verify model results of ozone in the mesosphere obtained by a photochemistry model, which reproduces the diurnal variation of ozone very well. Also an inter-annual variation of mesospheric ozone during the month of November in 2004–2007 was observed, primarily during the night. As the time series is still too short to clearly distinguish solar or QBO signals, the cause of this inter-annual variation cannot yet be related to one or the other. In November 2006 an unusual decrease of the ozone partial columns above 60 km was measured; the cause of this decrease is also not identified so far.

Gas exchange of juvenile and mature trees of Alnus jorullensis (Betulaceae) at sites with contrasting humidity in the Venezuelan Andes

AbstractThe reduction of photosynthetic rates with tree age has been proposed as a major driver of the productivity declination along ontogeny. It is not clear, however, how environmental humidity affects stomatal conductance and biochemical potential of photosynthesis in trees belonging to different age‐classes. We assessed daily cycles of gas exchange on leaves of juvenile and mature individuals of the tropical high‐elevation tree Alnus jorullensis Kunth (Betulaceae), at two sites with contrasting precipitation in the Venezuelan Andes. Photosynthesis and stomatal conductance were higher in juvenile trees during the morning and at noon in the mesic site, and were in general similar between age‐classes in the wet site. Under light‐saturating conditions, the net photosynthetic rate was similar between the age‐classes at the wet site and higher for juvenile trees at the mesic site, whereas stomatal conductance did not differ between age‐classes and was higher at the wet site. Daily cycles of gas exchange and a type II regression model between photosynthesis and intercellular CO2 concentration indicated that the better performance of juvenile trees at the mesic site was due to lower non‐stomatal limitations. These results support the proposal that non‐stomatal limitations—rather than stomatal ones—are involved in the decay of photosynthesis in mature trees, and suggest that such limitations may be evident only under drier conditions.

Chemical Composition and in Vitro Antibacterial Activity of the Essential Oil of Minthostachys Mollis (Kunth) Griseb Vaught from the Venezuelan Andes

Chemical constituents of the essential oil from the leaves of Minthostachys mollis (Kunth) Griseb Vaught var. mollis collected in January 2008 at Tuñame, Trujillo State, Venezuela, were separated and identified by GC-MS analysis. The essential oil was obtained by hydrodistillation and thirteen components (98.5% of the sample) were identified by comparison with the Wiley GC-MS library data base. The two major components were pulegone (55.2%) and trans-menthone (31.5%). The essential oil showed a significant inhibitory effect against Gram-positive and Gram-negative bacteria, especially Bacillus subtilis and Salmonella typhi (4 microg/mL).

Low temperature resistance in saplings and ramets of Polylepis sericea in the Venezuelan Andes

The frequent occurrence of all year-round below zero temperatures in tropical high mountains constitutes a most stressful climatic factor that plants have to confront. Polylepis forests are found well above the continuous forest line and are distributed throughout the Andean range. These trees require particular traits to overcome functional limitations imposed on them at such altitudes. Considering seedling and sapling stages as filter phases in stressful environments, some functional aspects of the regeneration of Polylepis sericea, a species associated to rock outcrops in the Venezuelan Andes, were studied. We characterized microclimatic conditions within a forest, in a forest gap and surrounding open páramo and determined low temperature resistance mechanisms in seedlings, saplings and ramets. Conditions in the forest understory were more stable compared to the forest gaps and open surrounding páramo. Minimum temperatures close to the ground were 3.6 °C lower in the open páramo compared to the forest understory. Maximum temperatures were 9.0 °C higher in the open páramo. Ice nucleation and injury temperatures occurred between −6 and −8 °C for both ramets and saplings, an evidence of frost avoidance to low nighttime temperatures. In this particular forest, this resistance ability is determinant in their island-like distribution in very specific less severe temperature habitats.

Migratory songbird use of shade coffee in the Venezuelan Andes with implications for conservation of cerulean warbler

Although previous studies have demonstrated high use of shade coffee plantations by Neotropical migratory birds, we still have a poor understanding of the suitability of shade coffee plantations as habitat on the wintering grounds. We studied density, body condition, and survivorship of Neotropical migrants, with emphasis on cerulean warbler ( Dendroica cerulea), in primary forest and shade coffee plantations in Venezuela. We worked in three primary forest sites and three shade coffee plantations on the western slope of the Cordillera de Mérida of the Andes Mountains. At each site, we surveyed migrants with distance-based line transects and mist-netted and banded migrants during November–February 2005/06 and 2006/07. In addition, we estimated apparent monthly survival for cerulean warbler based on 29 color-banded individuals. Densities of migrants were 3–14× higher in shade coffee plantations than primary forest sites, even after accounting for differences in detectability. Apparent monthly survival of cerulean warblers was estimated at 97% and overwinter persistence was similarly high. In addition, cerulean warblers demonstrated high between-season fidelity, with 65% of the birds banded the first year being resighted during the second year. Interestingly, immature birds returned at nearly half the rate as did adults. Banding data indicated that body condition increased significantly as the season progressed for cerulean warblers, Tennessee warblers ( Vermivora peregrina), and American redstarts ( Setophaga ruticilla). Collectively, these data provide evidence that shade coffee plantations offer high quality wintering habitat for Neotropical migrants, including cerulean warblers.

Interception of water by pastures of Pennisetum clandestinum Hochst. ex Chiov. and Melinis minutiflora Beauv.

The conversion of montane cloud forests into pastures for grazing cattle is the main cause of important impacts on rivers and streams in most of the Andes. In order to evaluate the effects of vegetation changes we need to understand water fluxes, particularly canopy interception. We measured net precipitation responses by the canopies of Pennisetum clandestinum Hochst. ex Chiov. and Melinis minutiflora Beauv. under simulated rainfall. The samples were taken from grazed pastures during 1 year, digging out round mats of grass, placing them on wire-mesh devices after eliminating soil and underground biomass, and irrigating with different water amounts. The resulting data allow us to present a validated model for each species that predicts percentage of interception at different precipitation intensities taking into account previous canopy wetness within determined biomass ranges. We use these models to estimate 2 years of interception values for pastures of both species in the upper watershed of El Cañadón, Capaz River, Venezuelan Andes. Mean annual precipitation of El Cañadón is 1244 mm and the estimate of pasture interception was 36.5% and 31.8% for P. clandestinum and M. minutiflora, respectively. Interception models, such as the ones derived in this study, provide a basis for quantifying interception rates as a function of previous wetness of canopies and grass species.

The forest vegetation of Ramal de Guaramacal in the Venezuelan Andes

Montane forest community composition of Ranial de Guaramacal, Venezuelan Andes, was studied along the altitudinal gradient on both sides of the range with different slope expositions. Thirty five 0.1 ha plots were Surveyed, with variable intervals of 30 to 150 meters between 1350 in and 2890 in and mile plots of variable size (50 m(2) to 400 m(2)) Were surveyed in dwarf forests located between 2800-3050 m. A total of 388 morphospecies with dbh >= 2.5 cm, corresponding to 189 genera and 78 families of vascular plants, were recorded from a total of 45 forest plots. The TWINSPAN phytosociological classification, based on both floristic composition and species relative abundance, revealed seven forest communities,it association level, grouped in three alliances and one montane forest order group. Three subandean forest (LMRF) communities and four Andean - high Andean forest (UMRF-SARF) communities are distinguished and described according to the Zurich-Montpellier method. The Geonomo undatae-Posoquerion coriaceae alliance contains two subandean forest communities (Simiro erythroxyli-Quararibeetum magnificae and Conchocarpo larensis-Coussarectum moritzianae); the Farameo killipii-Prunion moritzianae alliance contains one subandean forest community, (Croizatio brevipetiolatae-Wettinietum praemorsae) and one Andean forest community (Schefflero ferrugineae-Cybianthetum laurifolii) and the Ruilopezio paltonioides-Cybianthion marginatii alliance includes one Andean (Geissantho andini-Miconietum jahnii) and two high Andean forest communities (Gaultherio anastomosantis-Hesperomeletum obtusifoliae and the Libanothamnetum griffinii). Altitudinal zonation, forest floristic diversity, composition and forest structure is discussed between slopes and along the altitudinal gradient and compared, where possible, to other montane forests. In LMRF, Rubiaceae, Lauraceae and Melastomataceae are the most speciose of woody families. In UMRF, the Lauraceae family is still the most diverse, followed by Melastomataceae and Myrtaceae, while in SARF the Asteraceae and Ericaceae are the most species rich families. The structure of the montane forests of Ramal de Guaramacal becomes more compressed towards higher elevations. LMRF are dense and of medium height, with canopies up to 25 in tall, while UMRF canopies can reach up to IS in, and those of SARF are only 6-8 (10) m tall. Basal area was slightly increased on the North than on the South slopes and shows different patterns against altitude between slopes. More diversity and density of palms, lianas and climbers is clearly observed in LMRF, but richness of liana species is also important in SARF forests. Forest altitudinal zonation is variable between the North and South slopes of Guaramacal, with the forest zones of UMRF on the windward South slope, tending toward reaching lower elevations than on the opposite and drier North slope. There is a low altitudinal limit of the upper forest (Upper Forest Line or UFL) apparently caused by the top effect

A soil chronosequence in Late Glacial and Neoglacial moraines, Humboldt Glacier, northwestern Venezuelan Andes

Late Glacial and Neoglacial (Little Ice Age) deposits on the Humboldt Massif were analyzed for relative-age dating parameters, including geomorphic and weathering characteristics, geochemical and soil properties. The soil chronosequence, formed in chemically uniform parent materials, provides an important database to study soil evolution in a tropical alpine environment. Extractable and total Fe and Al concentrations, examined to assess their use in relative-age determination, and as paleoenvironmental indicators, provide an important measure of the accumulation and downward profile movement over time of organically-bound Al, ferrihydrite and other crystalline forms (hematite and goethite) of extractable Fe. Ferrihydrite is particularly useful in determining former perched water levels in soils with relation to paleoclimate. The ratios of most Fe extracts are time dependent. The Fe d/Fe t ratio, within statistical limits, shows a slow increase from LIA (Little Ice Age) to Late Glacial soils, which closely correlates with other alpine soil studies in the middle latitudes and other tropical alpine locales. Values of Al d (dithionite) and Al o (oxalate extractable) generally do not correlate with time; however, Al p (pyrophosphate extractable) measured against Al t (total) provides insight on the downward translocation over time of organically-bound Al. Low leaching rates in this chronosequence are further supported by clay mineralogy trends and the geochemical data.

POLLEN WITH VISCIN THREADS FROM THE LATE CRETACEOUS AND PALEOCENE, MERIDA ANDES, WESTERN VENEZUELA

Abstract Fossil pollen exhibiting viscin threads are reported from Upper Cretaceous and Paleocene deposits in western Venezuela. The sediments were deposited in a marginal marine environment in an area presently occupied by the northern flank of the Venezuelan Andes. The palynofloras are well preserved and diverse and provide insight into the ancient vegetation of Venezuela. Pollen-bearing viscin threads from the Upper Cretaceous Mito Juan Formation are assigned to the genus Colombipollis Sarmiento Perez 1994. The pollen grains are tri(col)porate, normally quite smooth, and most often viewed in an oblate (flattened) state. The viscin threads are on the proximal and distal sides of the pollen and vary in length; they appear to have a simple morphology unlike the complex, ropelike threads seen on pollen of the Onagraceae and some other angiosperm families. All observations to date are made using a standard light microscope but more morphological detail could be revealed using scanning electron microscopy. T...

Upper mantle structure beneath the Caribbean‐South American plate boundary from surface wave tomography

We have measured shear wave velocity structure of the crust and upper mantle of the Caribbean‐South American boundary region by analysis of fundamental mode Rayleigh waves in the 20‐ to 100‐s period band recorded at the BOLIVAR/GEODINOS stations from 2003 to 2005. The model shows lateral variations that primarily correspond to tectonic provinces and boundaries. A clear linear velocity change parallels the plate bounding dextral strike‐slip fault system along the northern coast of Venezuela, illustrating the differences between the South American continental lithosphere, the Venezuelan archipelago, and the Caribbean oceanic lithosphere. At depths up to 120 km beneath the Venezuelan Andes and the Maracaibo block, there is evidence of underthrusting of the Caribbean plate, but there is no other evidence of subduction of the Caribbean plate beneath the South American plate. In eastern Venezuela, linear crustal low velocities are associated with the fold and thrust belts whereas as higher crustal velocities are imaged in the Guayana shield lithosphere. The subducting oceanic part of the South American plate is imaged beneath the Antilles arc. The surface wave images combined with seismicity data suggest shear tearing of the oceanic lithosphere away from the buoyant continental South American plate offshore of northeastern Venezuela. The continental lithosphere south of the slab tear is bent down toward the plate boundary in response to the propagating tear in the lithosphere. We interpret a nearly vertical low‐velocity “column” west of the tear centered beneath the Cariaco Basin, with three‐dimensional asthenospheric flow around the southern edge of the subducting oceanic lithosphere, with the asthenosphere escaping from beneath continental South America and rising into the plate boundary zone. The complex plate boundary structure is best examined in three dimensions. We discuss the new surface wave tomographic inversion in the context of results from other researchers including local seismicity, teleseismic shear wave splits, and interpretations from active source profiling.

Viable technologies for Sustainability and Local Integrated Development, Tech/SUDIL

This paper is aimed at presenting the project of the creation of a Virtual Group made up of highly-qualified technology specialists of different national and foreign universities. The task to be performed by the group would be the creation of the framework necessary for the university to perform its new role within the knowledge society. The creation of technologies applicable in a framework of sustainability and local integrated development will pave the way for the participation of the Venezuelan university in the solving of problematic situations at the local level with a global perspective and the implementation of the following strategy: Interaction among universities, local governments and communities aimed at fostering competitiveness and higher life-quality standards. Interaction among the different universities, as a group, which should in turn interact with the local government and the communities, in order to achieve sustainable development. Generation new appropriate technologies and adapted to the increment of the local productivity and the economic diversification of the areas of the Venezuelan Andean Highlands and Northeastern Coast of the Caribbean, respecting the ecological balance and the local cultural identity.

Widespread occurrence of an emerging pathogen in amphibian communities of the Venezuelan Andes

Many recent amphibian declines have been associated with chytridiomycosis, a cutaneous disease caused by the chytrid fungus Batrachochytrium dendrobatidis, but increasing evidence suggests that this pathogen may coexist with some species without causing declines. In the Venezuelan Andes, the disappearance of three anuran species during the late eighties was attributed to B. dendrobatidis. Recently, this pathogen was found to be prevalent in this region on the introduced American bullfrog, Lithobates catesbeianus. As a first step toward assessing the risk of amphibian communities to B. dendrobatidis in this region, we conducted a broad survey across multiple habitat types and an altitudinal gradient spanning over 2000 m. We diagnosed 649 frogs from 17 species using real time and conventional PCR assays, and recorded relevant abiotic characteristics of host habitats. Infection was detected in 10 native species of pond, stream and terrestrial habitats from 80–2600 m, representing nine new host records. L. catesbeianus was the most important reservoir with 79.9% of individuals infected and an average of 2299 zoospores. Among native frogs, Dendropsophus meridensis, an endangered species sympatric with L. catesbeianus, showed the highest infection prevalence and mean zoospore load (26.7%; 2749 zoospores). We did not detect clinical signs of disease in infected hosts; however, species such as D. meridensis may be at risk if environmental stress exacerbates vulnerability or pathogen loads. While surveillance is an effective strategy to identify highly exposed species and habitats, we need to understand species-specific responses to B. dendrobatidis to stratify risk in amphibian communities.

Ilex guaramacalensis (Aquifoliaceae), a New Species from the Ramal de Guaramacal in the Venezuelan Andes

Ilex guaramacalensis Cuello & Aymard (Aquifoliaceae), a new species from the Andean forests and páramos of Guaramacal massif in Venezuela, is described and illustrated, and its morphological relationships with allied species are discussed. Ilex guaramacalensis is morphologically similar to I. kunthiana Triana from the high mountains of Costa Rica and Panama, the Coastal Cordillera, and the Andes of Venezuela to Peru, but the new species differs by the shape of its young branchlets, leaves, pedicels, and petals; the higher number of secondary veins; the shorter inflorescences; and the 4-merous flowers. Information about the floristic composition and habitat characteristics for the new species is also provided.

How do two Lupinus species respond to temperature along an altitudinal gradient in the Venezuelan Andes?

La temperatura determina las formaciones vegetales y la distribucion de especies a lo largo de gradientes altitudinales. Las plantas en los altos Andes tropicales, a traves de diferentes caracteristicas morfologicas y fisiologicas, responden a temperaturas congelantes nocturnas y altas entradas energeticas durante el dia en cualquier momento del ano. El objetivo principal de este estudio fue caracterizar las respuestas relacionadas con temperaturas diurnas y nocturnas en dos especies de Lupinus con diferente distribucion altitudinal (L. meridanus, 1.800-3.600 y L. eromonomos, 3.700-4.300 m de altitud). ?Existen diferencias en los mecanismos de resistencia a bajas temperaturas entre las especies a lo largo del gradiente? ?Como responden estas especies, en terminos de temperatura optima para fotosintesis, a incrementos en altitud? Lupinus meridanus evade el congelamiento, en contraste a L. eromonomos, que tolera el congelamiento a mayores altitudes. La temperatura optima para fotosintesis disminuye a lo largo del gradiente para ambas especies. Las maximas tasas de asimilacion de C02 se obtuvieron en L. meridanus, mientras que L. eromonomos mostro una disminucion en sus tasas de asimilacion de C02 a mayor altitud. En la mayoria de los casos, la temperatura foliar medida siempre estuvo dentro del 80 % del optimo fotosintetico. El limite superior de distribucion de L. meridanus parece estar restringido por mecanismos de resistencia a la temperatura, mientras que en L. eromonomos por una combinacion de ambas resistencia al frio y respuestas en asimilacion de C02 a mayores altitudes.

Avifauna of Dinira National Park, Venezuela

This is a preliminary inventory of the avifauna of Dinira National Park (DNP), northeastern of Venezuelan Andes, a region that is poorly known ornithologically. In the field work (30 days), 127 bird species (10 orders, 41 families) were recorded, ca. 9 % of the total birds known to Venezuela. From them, just three corresponding to endemic species (2.4 %) whereas 14 (11.0 %) were migrants. Also, new important range extensions were documented, especially for some birds previously reported in Táchira and Mérida states (Merganetta armata and Dendrocincla tyrannina). From recorded species 33 are threatened in different levels, but only five of them are protected by Venezuelan laws.

Sesquiterpene lactones isolated from a medicinal plant of the Venezuelan Andes

Sesquiterpene lactones isolated from a medicinal plant of the Venezuelan Andes

Guiding Principles for Small-Scale Forestry in a Watershed of the Venezuelan Andes: Constraints and Opportunities

In the Venezuelan Andes, some small-scale forest plantations have become an important resource basis for forest management. In this paper, the forestry management progress in the Mucujun river watershed is analyzed. Constraints and opportunities for sustainable management within national policies, local regulations, environmental features and social benefits are also examined. Plantation assessment, and biophysical, legal and socioeconomics information, are used for guiding small-scale forestry practices in this watershed, with emphasis on the main principles of landscape management. These plantations have become an important part of the socio-ecological landscapes with potential for wood production—in the context of low intensity and low environmental impact environmental services and amenity—because of the two protected areas within the watershed. Current forest stand conditions, however, reflect that management requires improvement. Furthermore, the analysis suggests that improvement of local livelihoods may be achieved with a small-scale forestry approach, taking properly into account the basic criteria of social involvement and management of planted forests, while maintaining ecosystem services including biodiversity and water supply.

Dinosaur remains from the La Quinta Formation (Lower or Middle Jurassic) of the Venezuelan Andes

Dinosaur remains are exceptionally scarce in northern South America and Jurassic faunas from this area are particularly poorly known. We provide descriptions of new dinosaur specimens from a bonebed in the La Quinta Formation (Early or Middle Jurassic) of western Venezuela. The specimens are disarticulated and associations of elements are rare, but at least two distinct taxa appear to be present. Ornithischian dinosaurs are identified on the basis of isolated teeth and a distal tibia. The teeth represent a non-cerapodan basal ornithischian and possess a unique combination of character states, suggesting that they pertain to a new and unnamed taxon. Other remains represent an indeterminate basal saurischian (based on an ilium) and indeterminate dinosaurs (caudal vertebrae and a femur). The apparently plesiomorphic morphology of many of the dinosaurian remains is consistent with suggestions of an Early or Middle Jurassic age for the La Quinta Formation. Previous reports of the basal ornithischianLesothosaurus sp. from the La Quinta Formation cannot be substantiated on the basis of available data.