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Venezuela´s Eco Regions

 

Los Andes Venezuelan Andes montane forests

The geological history, glacial movements, and a great variety of physical and geographical
factors give shape to this moist forest ecoregion’s particularly complex and dense transitional and montane evergreen cloud forests. Surrounded by inter-Andean xeric valleys and páramo, the high richness of plant
and animal species, and large number of endemic species make this ecoregion one of the most interesting areas of Venezuela in terms of biodiversity. 

Location and General Description 

This moist forest ecoregion encompasses the high altitude cloud forests of the Andean Venezuelan Cordillera, representing an ecological barrier that separates the great basins of Maracaibo Lake and the Llanos of Venezuela. This ecoregion occupies montane forests at middle elevations of the Venezuelan Andes or
Venezuelan Andean Cordillera, a northeastern branch of the Andes. They are separated form the eastern Andes of Colombia by the Tachira depression at the border between Colombia and Venezuela. The end of the ecoregion lies roughly at 450 m northeast in the depression of Barquisimeto. These mountains reach altitudes
between 4,000 and 5, 007 m, and separate the Maracaibo lake basin from the plains of the Llanos. The Venezuelan Andes montane forest also includes those forests located around Tamá Massif , a relatively isolated montane area located between the Eastern Andes of Colombia and the Táchira depression. 

Politically, the Venezuelan Andes montane forests include almost all the Mérida and Trujillo
states, a large part of the Táchira state, and the adjacent highlands of Lara and Barinas states.
Many of the rivers born in the summits created great valleys that separate the Cordillera
montane ranges. One of the most important rivers, the Chama, crosses the Cordillera at its
middle portion, along its northeast- southwest axis. This breaks the Cordillera in to two main
sections: the Cordillera de Mérida in the south and the Sierra de la Culata in the north. Other
important rivers are the Santo Domingo, the Boconó and Motatán. These rivers also indicate
physiographical barriers along the Cordillera. 

The Venezuelan Andes were formed from surrounding areas during the Paleocene, and they
continued developing until the end of the Pliocene, at which time they attained their greatest
height (Steyermark 1979). The geological constitution consists mainly of quartzite schists,
gneisses, limestones and isolated granitic and diabasic intrusions (Huber and Frame 1989). Soils
are predominantly inceptisols, but entisols are also common in the slopes and areas exposed to
erosion (Vivas 1992).

The climate is strongly influenced by the north eastern trade winds, especially during the dry
season, from December to April. From April to November, the inter-tropical convergence zone
brings the highest rainfall of the year. In general, this ecoregion has mesothermic conditions
with average annual temperatures of 24–12°C between 800–2500 m altitude, and micrometric
conditions with average annual temperatures of less than 12°C above 2500 m. 

Annual rainfall is about 2000-3000 mm, but can be strongly variable. On the slopes that face the
Llanos, high rainfall averages begin at 2400 m, changing gradually with elevation, whereas on
the Maracaibo Lake facing slopes, the high rainfall averages begin at 1200 m. The internal
slopes are dryest, with some very dry xeric areas common in the Andean valleys (Vivas 1992).

Vegetation of this ecoregion is characterized by evergreen transition forests and evergreen
montane cloud forests (Huber and Alarcon 1988). Located between 800–1800/2000 m altitude,
evergreen transition forests are dense middle-high forests structured in two or three layers, in
which Lauraceae, Moraceae, Myrtaceae, Bignomiaceae, Euphorbiaciae and Araliaceae are the
most common families.

Very dense evergreen montane cloud forests occur in higher elevations between 2,000 and 3,000
meters. These are high forests with two or three structural layers, and a well-developed
understory with abundant epiphytes. The most common species are Decussocarpus
(Podocarpus) rospingliosii, Prumnopytis (Podocarpus) montana, Podocarpus oleifolius, Alnus
jorullensis, Oreopanax moritzii, Brunellia integrifolia, Hedyosmum glabratum, Weinmannia
jahnii, W. microphylla, Tetrorchidium rubrivenium, Beilschemieda sulcata, Ruagea glabra
and R. pubescens.

Biodiversity Features

The regional flora of the Andes represents explosive adaptive radiation and
extraordinary diversification (Gentry 1982). Steyermark (1979) recognized the
Venezuelan Andes as a dispersal center and plant refuge, due to its great species
richeness and plant endemism. According to Steyermark (1979), specific
differentiation in the Andean center takes place in the montane forests, situated
below and removed from the páramo hábitat, at altitudinal levels between 1500
meters to nearly 2900 meters. 

The highest concentration of endemic plants are found in the montane forests of this ecoregion
and páramos of the state of Mérida, where there are155 endemic plants. This area alone
represents 30% of the endemic flora for the ecoregion. Eighty-two additional plant species are
known to be endemic to the Tamá paramos and forests, where the depression of Táchira acts as
an effective barrier to plant dispersion (Steyermark 1979). Some of the most common plant
endemics of these montane forests are represented by Podocarpus pedulifolius, Oreopanax
veillonii, Psychotria aristeguiateae, Lagenanthus princeps, Delostoma integrifolium, and
many species of bromeliads, ferns and orchids. 

There are twenty-five restricted-range endemic bird species in this ecoregion. The Tamá Center
itself is part of the Cordillera de Mérida Endemic Bird Area designated by BirdLife International
(Stattersfield et al. 1998). Of the twenty-five endemic bird species, four are confined to this
montane forest ecoregion, and two are also found in the Cordillera de Mérida Páramo ecoregion.
In general, richness is high in the montane forests but decreases with altitude, resulting in a low
number of species in the páramos (Kattan et al. in prep). Some endemic birds are the Mérida
sunangel (Heliangelus spencei), the grey-capped hemispingus (Hemispingus reyi) and the
white-fronted whitestart (Myoborus albifrons), which live in the montane evergreen transitional
elfin forest and scrub. The gray-naped antpitta (Grallaria griseonucha) lives in the montane
evergreen forest. The rose-headed parakeet (Pyrrhura rhodocephala) and the Mérida
flower-piercer (Diglossa gloriosa) live in the montane evergreen, elfin and secondary forests as
well as in the páramos (Stattersfield et al. 1998).

Tamá Center, included in the Endemic Bird Area of the Colombian East Andes, has
restricted-ranges species like the Táchira antpitta (Grallaria chthonia) and hooded antpitta
(Grallaricula cucullata) that are also present in the Colombian East Andes EBA. Also, the
Venezuelan wood quail (Odontophorus columbianus), an endemic of Venezuela, is only present
in this ecoregion in an isolated area and in the western Cordillera de la Costa. 

According to Linares (1998), four endemic mammals are present in the Venezuelan Andean
montane forests ecoregion: a marsupial (Gracilinanus dryas), a bat (Anoura luismanueli), a rat
(Thomasomys vestitus), and a poorly know fish eating rat, (Neusticomys mussoi). The marsupial
and bat are distributed in the Andean Cordillera and the Tamá Center. T. vestitus is restricted to
the Andean Cordillera, and N. mussoi has been reported for only one locality of the Andean
Cordillera. 

Some subspecies of mammals are also restricted to this ecoregion, and the Cordillera de Mérida
Páramo ecoregion. The Andean white-tailed deer (Odoncoileus virginianus goudotii) a
Venezuelan endemic subspecies, is restricted to the ecotone between the high mountain forests
and the páramos. The rufous brocket deer (Mazama rufina bricenii), an endemic from Colombia
and Venezuela, inhabits areas of evergreen forest and paramos between 1000–3000 meters. Both
species are considered endangered because of hunting (Rodriguez and Rojas-Suarez 1997).
Other species such as the fish eating rat (Ichthyosomis hidrobates), restricted to Andean
Venezuela and Colombia, and the pacarana (Dinomys branickii), broadly distributed in the
Andes, live in adjacent areas to the páramos, and are considered threatened due to habitat
modification, and hunting, respectively (Rodriguez and Rojas-Suarez 1997).

The Venezuelan Andean montane forests have a great number of endemic frogs. In the
Cordillera de Mérida alone, there are 62 frog species (Kattan et al. in prep.); many of them are
endemic to the cloud forests. As in other ecoregions of the Andes, Eleutherodactylus and
Centrolenidae are the most common families. Frog richness also decreases with altitude. This
ecoregion also has two endemic species of salamander, Botiglosa orestes and the recently
described B. spongai (Barrio-Amoroz and Fuentes-Ramos 1999).

Some endemics frog species are the little striped or little yellow frogs, such as Atelopus
mucubajensis, A. Oxyrhinchus, A. pinangoi, A. sorianoi and A. tamaence. They are confined to
the Venezuelan Tamá center but may be present in the Colombian portion of this area (La Marca
and Lotters 1997). These anurans present altitudinal distributions between 2,000 and 3,400 m,
and inhabit cloud forests and very humid páramos where, in general, they are associated with
little streams (Rodriguez and Rojas-Suarez 1997). All species are considered endangered
because of their fast population decline. The massive reduction in frog populations worldwide
and here, has been related to the global decline of amphibians (Rodriguez and Rojas-Suarez,
1997). Declines may also be associated with the declines in other species of Atelopus in the
Andes (L. Coloma pers. com.). 

A species of special concern is the spectacled Bear (Tremarctos ornatus), an endangered
mammal with wide distribution in the Andes, from Colombia and Venezuela, to Ecuador, Peru
and Bolivia. In the Venezuelan Andes and Perijá Mountains, the spectacled bear occurs
between 380 to 4,700 meters elevation, but is more frequent in cloud forests from 1,000 to 3,000
m (Rodriguez and Rojas-Suarez 1997). Kattan et al (in prep.), proposed the bear as a potential
focal species for all of the Northern Andes Bioregion, based upon its range, low reproductive
rates, low population size, and the threats associated with it as a result of hunting and habitat
destruction.

Current Status 

Venezuelan national parks included in this ecoregion are: the Sierra Nevada, Sierra
de la Culata, General Pablo Peñalosa (Batallón and La Negra páramos), General
Cruz Carrillo (at Guaracamal), Dimira (Sierra de Barbacoa), Yacambú, El Tamá,
and the Tamá National Park in Colombia. Protected areas constitute only 20.78 %
of the total area of this ecoregion (Kattan et al. in prep.). Almost all montane forests
(which would include both semi-evergreen and the evergreen forests of low to mid
altitudes) are being invaded with varying intensity. Most of the slopes are, or have
been worked by shifting cultivators. This has given the slopes a mosaic appearance
and fragmented habitat.

Venezuelan national parks included in this ecoregion are: the Sierra Nevada, Sierra de la Culata,
General Pablo Peñalosa (Batallón and La Negra páramos), General Cruz Carrillo (at Guaracamal),
Dimira (Sierra de Barbacoa), Yacambú, El Tamá, and the Tamá National Park in Colombia.
Protected areas constitute only 20.78 % of the total area of this ecoregion (Kattan et al. in prep.).
Almost all montane forests (which would include both semi-evergreen and the evergreen
forests of low to mid altitudes) are being invaded with varying intensity. Most of the slopes are,
or have been worked by shifting cultivators. This has given the slopes a mosaic appearance
and fragmented habitat.

Types and Severity of Threats 

Agricultural colonization for subsistence represents the most significant threat to this
fragile ecosystem. However, other kinds of threats are also important including
predation of some populations of horticulturally prized orchids and bromeliads, may
be endangered, by people, especially in forests near large cities (Huber and Frame,
1989). Massive tourism, fires, and proposed road and pipe construction represent
potential threats to several National Parks (Kattan et al. in prep.).

Mining concessions for zinc, cooper, lead and silver are being requested in the
Bailadores-Guaraque sector, including General Pablo Peñalosa National Park. Until now,
permission for this kind of activity has been rejected by the official environmental agency
(Ministerio del Ambiente), due to the impacts associated with mineral explotation (Vivas 1992).
Coal mining in theTáchira depression is another potential threat to adjacent areas, such as the
Tamá National Park.

Justification of Ecoregion Delineation

These montane forests occur between approximately 800-3000 meters elevation
along the slopes of easternmost finger of the northern Andes, the Cordillera de
Mérida. They are interspersed at higher elevation with high altitude páramo
grasslands, and at lower elevations occur in a transitional gradient with lowland moist
forests to the north and dry forests to the south. Linework follows the Huber and
Alarcon (1988) map classifications of "Cordillera de los Andes" subregion (D.2) and
included "premontane ombrophilous forests", "submontane ombrophilous forests",
"montane ombrophilous forests", and all human modified habitats within this greater
classification.                     


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