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 meters (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. The geological constitution consists mainly of quartzite schists, gneisses, limestones, and isolated granitic and diabasic intrusions. Soils are predominantly inceptisols, but entisols are also common in the slopes and areas exposed to erosion.
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 800–2,500 meters (m) altitude, and micrometric conditions with average annual temperatures of less than 12°C above 2,500 m.
Annual rainfall is about 2,000-3,000 millimeters (mm), but can be strongly variable. On the slopes that face the Llanos, high rainfall averages begin at 2,400 m, changing gradually with elevation, whereas on the Maracaibo Lake facing slopes, the high rainfall averages begin at 1,200 m. The internal slopes are driest, with some very dry xeric areas common in the Andean valleys.
Vegetation of this ecoregion is characterized by evergreen transition forests and evergreen montane cloud forests. Located between 800–1,800/2,000 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.
The regional flora of the Andes represents explosive adaptive radiation and extraordinary diversification. Steyermark recognized the Venezuelan Andes as a dispersal center and plant refuge, due to its great species richeness and plant endemism. According to Steyermark, specific differentiation in the Andean center takes place in the montane forests, situated below and removed from the páramo hábitat, at altitudinal levels between 1,500 meters to nearly 2,900 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 are 155 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. 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. 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. 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.
Tamá Center, included in the Endemic Bird Area (EBA) 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, 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 known 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 1,000–3,000 meters. Both species are considered endangered because of hunting. 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.
The Venezuelan Andean montane forests have a great number of endemic frogs. In the Cordillera de Mérida alone, there are 62 frog species; 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.
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. 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. 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. Declines may also be associated with the declines in other species of Atelopus in the Andes.
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. Kattan et al, 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.
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. 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 [[horticulture|horticulturally[[ prized orchids and bromeliads, may be endangered, by people, especially in forests near large cities. Massive tourism, fires, and proposed road and pipe construction represent potential threats to several National Parks.
Mining concessions for zinc, copper, 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 exploitation. Coal mining in the Táchira depression is another potential threat to adjacent areas, such as the Tamá National Park.
Justification of Ecoregion Delineation
These montane forests occur between approximately 800-3,000 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 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.
Additional Information on this Ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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- Gentry, A. 1982. Neotropical Floristic Diversity: Phytogeographical Connections Between Central and South America, Pleistocene Climatic Fluctuations, or an accident of the Andean Orogeny? Annals of the Missouri Botanical Garden, 69:557-593.
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