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VOLCANOES OF NARIÑENSE PLATEAU
Central-eastern Nariño is bounded by two mountain ranges with south-west -north-east axes (Map 66), and has major elevations as the four volcanoes Chiles (4761 m), Cumbal (4850 m), Azufral (4070 m) and Galeras (4276 m) (Cuellar-R. and Ramírez-L. 1986). The high Túquerres-Ipiales plateau of the inter-Andean depression is an inclined terrace starting with the mountainsides of Cumbal and Azufral and forms a series of low hills eastward down to the deep Guáitara River Valley (Luna-Z. and Carlhoum 1986). The area of these volcanoes is west and south-west of the city Pasto in Colombia's municipalities El Encano, Pasto, La Florida, Sandoná, Ancúya, Consacá, Yacuanquér, Tángua, Guaitarilla, Túquerres, Guachucal, Cumbal and Carlosama, with Chiles Volcano also in Ecuador's Province Carchi.
The landscape of the Nariño high plateau has resulted from a sequence of uplifts and sinkings during the Tertiary, processes of erosion and sedimentation due to orogenic movements, and volcanic activity of the Pleistocene continued during the Quaternary (cf. van der Hammen and Cleef 1986). The most important geomorphological factor relates to volcanic activity; the inter-Andean depression is filled with material from old eruptions. Quaternary (also volcanic) material is composed of andesitic tufa, agglomerite and gravel (pumice stone and sandy tufa). The tufic layers are of great extent and varied thickness (Grosse 1935). Toward the southern end of the region in the foothills of Azufral and Cumbal there are also pyroclastic deposits. The soils have originated from the volcanism of the Tertiary and the Quaternary.
Differences in soil types and annual mean temperature and precipitation are found along the gradients of these mountain systems (Luna-Z. and Carlhoum 1986). From 2000-3000 m, the soils are classified as andic humitropepts and typic dystrandepts; the mean temperature varies between 15°-10°C, the precipitation between 600-2000 mm. From 3000-3500 m, the soils belong to the umbric vitrandept and dystric cryandept groups; the mean temperature varies between 10°-6°C, the precipitation between 1000-2000 mm. From 3500-4200 m, the soils belong to the humitropept, dystropept and cryumbret groups; the mean temperature varies between 6°-0°C, and the thermal gradient changes 0.6°C per 100 m in elevation.
The high-Andean fringe and the páramo region are considered for these four volcanoes; they are best conserved along the gradients studied (Sturm and Rangel-Ch. 1985; Erazo-N. et al. 1991; Rangel-Ch. 1995).
1. High-Andean region (3100-3500 m)
There are also thickets of Diplostephium floribundum, Miconia salicifolia, Pentacalia sp. and Solanum bogotense. In the lower stratum, the dominants are Coriaria thymifolia, Vaccinium sp. and Siphocampylus giganteus.
2. Páramo region (3600-4400 m)
2.1. Páramo proper
Thickets of Loricaria thujoides and Arcytophyllum capitatum prevail in páramo above 3800 m, with Vaccinium floribundum, Hesperomeles heterophylla, Brachyotum strigosum and Gynoxys sancti-antoni. In the herbaceous stratum are Calamagrostis effusa, Halenia sp. (Gentianaceae), Rhynchospora macrochaeta and Hypericum lancioides (Clusiaceae). In the ground stratum are Gunnera magellanica, Geranium sibbaldioides and Nertera granadensis (Rubiaceae).
2.2. Superpáramo (over 4200 m)
1. High-Andean region (3200-3600 m)
On the hillsides (3540 m), shrub-like forests are dominated by Escallonia myrtilloides (Saxifragaceae) and Weinmannia microphylla. In the lower stratum are species of Diplostephium and Gynoxys. In the ground stratum is Lachemilla orbiculata together with bryophytes such as Pleurozium schreberi and Campylopus spp.
2. Páramo region (3600-4200 m)
In fields and peat bogs in marshy sites predominate Werneria humilis, Loricaria thujoides and Luzula racemosa (Juncaceae), associated with Oritrophium limnophyllum, Eryngium humile and the moss Rhacocarpus purpurascens. Above 4000 m, peat-bog vegetation is dominant. Occasionally there are patches of Oritrophium limnophyllum, mosses such as Rhacocarpus purpurascens and Racomitrium crispulum, and Disterigma empetrifolium, Lachemilla hispidula and Loricaria spp.
1. High-Andean region (3450-3600 m)
Forests of Polylepis cf. incana grow in protected sites with Diplostephium floribundum, Macleania rupestris, Myrsine dependens (Myrsinaceae) and Miconia salicifolia. In the lower stratum are Rhynchospora aristata, Carex bonplandii and other Miconia spp.
Shrub-like forest is dominated by Miconia salicifolia, Solanum bogotense and species of Asteraceae.
2. Páramo region (3600-4100 m)
Thickets are generally dominated by Pentacalia vernicosa. Thickets dominated by Loricaria thujoides continue above 3950 m.
Fields and peat-bog vegetation have Werneria humilis, Cotula minuta, Eryngium humile, Juncus effusus (Juncaceae) and Sphagnum sp. In marshy sites, Espeletia pycnophylla also occurs; where the water diminishes, the vegetation is dominated by J. effusus, Rhynchospora macrochaeta, Loricaria thujoides and Pleurozium schreberi.
In the superpáramo, patches of vegetation with Werneria spp., Draba and Azorella predominate (Rangel-Ch. 1995).
2. Páramo region
2.1. Páramo proper (3800-4200 m)
On very moist sites in gullies is frailepajonal scrub of Espeletia pycnophylla and Arcytophyllum capitatum, with Festuca cf. sublimis and Pernettya prostrata. In the ground stratum are Ourisia chamaedrifolia, Disterigma empetrifolium, Azorella aretioides and Plantago rigida (Plantaginaceae).
Peat-bog vegetation covers considerable surface from the middle páramo to superpáramo, with Plantago rigida, Oritrophium limnophyllum, Gentiana sedifolia, Distichia muscoides, Werneria humilis and Lachemilla hispidula.
Vegetation forming mats on firm (not marshy) ground in the zone between mid-páramo and superpáramo is characterized by Azorella pedunculata, A. diapensioides, Werneria humilis, Werneria sp., Hypochoeris sessiliflora and Plantago rigida.
This geographic region does not yet have a detailed floristic inventory. It is estimated to have 450 vascular plant species and 80 species of bryophytes (mosses and liverworts) (Erazo-N. et al. 1991). The topography and the spatial continuity from sub-Andean and Andean life zones up to the páramo with the upper limit in permanent snow (on Cumbal) give special characteristics to the volcanoes, resulting in diversification. These environments experience volcanic eruptions, which may have a stimulating effect on speciation or a controlling effect on local species - which may disappear.
There is small-scale landscape diversity on these volcanoes that yields close to 25 types of vegetation. Furthermore, these areas are the most northerly for some species of the Austral-Antarctic geographic region (van der Hammen and Cleef 1986). Outstanding characteristics of the Galeras and Chiles volcanoes are: (1) the diversity of the plants growing in mats; (2) extensive and vigorous thicket communities with prevalence of Loricaria spp. (Asteraceae); and (3) presence of elements unusual for páramo vegetation, i.e. species that in other geographic areas of Colombia belong to the montane Andean region - such as Fuchsia (Onagraceae), Siphocampylus (Campanulaceae) and Weinmannia (Cunoniaceae).
Most of the typically páramo species of Colombia are found on the Nariño volcanoes (Rangel-Ch. 1995). Comparison of the 11 families with seven or more genera in the biogeographic region of páramo with those taxa known on the páramos of the Nariño volcanoes shows at least the following representation (Sturm and Rangel-Ch. 1985; Luteyn, Cleef and Rangel-Ch. 1992; cf. van der Hammen and Cleef 1986):
The following species are restricted in distribution or endemic to this region (Rangel-Ch., in prep.): Ranunculus guzmanii (Ranunculaceae); Begonia pastoensis (Begoniaceae); Draba pycnophylla (Brassicaceae); Cavendishia oligantha, Disterigma dumontii (Ericaceae); Brunellia bullata (Brunelliaceae); Gunnera tajumbina (Gunneraceae); Ottoa oenanthoides (Apiaceae); Lepechinia vulcanicola, Salvia sagittata, Satureja jamesonii, S. tonella (Lamiaceae); Aphelandra mutisii (Acanthaceae); Arcytophyllum filiforme (Rubiaceae); Gynoxys sancti-antoni, Espeletia pycnophylla (Asteraceae); Anthurium carchiense (Araceae); Pitcairnia bakeri, Puya gigas, P. vestita, Guzmania wittmackii, Tillandsia pectinata (Bromeliaceae); and Epidendrum cernuum, E. scolptum (Orchidaceae).
The use of plants in folk medicine, crafts, etc. is related to indigenous traditions (García-B. 1974-1975; Correa-Q. and Bernal 1989-1991; Kathleen 1978):
Social and environmental values
The Pasto, indigenous people who have inhabited the region since before the Spanish, occupy the high and middle valley of the Guáitara River down to Ancúya. Their territory extended along the high plateau to the Colombia-Ecuador border, limited to the east and west by the summits of the cordilleras. The Quillacinga had land north of the Pasto along the eastern side of the Guáitara, in the valley of the Juanambú River and along the foothills to the middle and high parts of the Mayo River (Kathleen 1978; Cerón 1987). The Kwaiker presently also live in the region (Cerón 1987).
The major importance of this volcanic region is its biological and cultural legacy. The great diversity of the vegetation communities, the sites as zones that represent important biogeographic boundaries, the decisive role of the high zones in the ecological behaviour and the economy of the human populations in the lower zones, are reasons enough for the preservation of these highlands.
Although the diversity of the fauna is less than in other páramo regions of Colombia, it is important to highlight the presence of spectacled bear (Tremarctos ornatus), páramo deer (Odocoileus virginianus cf. goudotii) and diverse species of amphibians in Eleutherodactylus, Centrolenella and Phrynopus (Sánchez-P. et al. 1990).
The Central Andean páramo Endemic Bird Area (EBA B60) includes the highest peaks of the Central Andes in Colombia and Ecuador. Ten bird species of restricted range occur in this EBA (nine are confined to it); six of them probably occur on the Nariño volcanoes. All these restricted-range species are confined to páramo grassland and Polylepis scrub, and the elfin forestpáramo ecotone. Due to the extensive destruction or disturbance of these habitats, five of the species are considered threatened.
Along the high-Andean fringe and lower páramo (3000-3400 m), potatoes and to a lesser extent broad beans (Vicia faba) are cultivated and extensive cattle-ranching is practised. The woody vegetation of the ecotone between the montane Andean and páramo regions has been much depleted for domestic fuelwood. In Cumbal Volcano there are reserves of sulphur estimated at three million tons; 20% of Colombia's production comes from Cumbal (IGAC 1967). The ice from Cumbal's glacier is extracted under rudimentary conditions by nearby farmers for the manufacture of ice cream and cool drinks.
The most relevant environmental values are the scenic landscapes and their floristic diversity. Galeras Volcano is readily accessible, with roads that lead close to the crater; it is a natural laboratory for understanding the ecologic gradation in mountainous Colombia, and should be used more frequently for environmental education. Other environmental values include watercourses that originate in the high elevations and supply water to the aqueducts of the communities in the foothills; ecotourism; and in a similar fashion, controlled use of the lakes for water sports. An alternative use in the region can be attained by means of equipment for electronic data transmission (radio, television).
Natural threats are related to volcanic eruptions, particularly from Galeras. The extension of the agricultural frontier into páramo (cattle-ranching and farming potatoes) has greatly modified some areas of Azufral Volcano and to a lesser extent the other volcanic areas. Exploitation of the lower páramo fringes (e.g. for fuelwood) has resulted in plantations of exotic pine (Pinus), but in areas that for climatic reasons do not make this cultivation economically viable. In several localities, lakes and marshes have been drained to make agricultural land.
The Galeras Fauna and Flora Sanctuary (176 km²) was established in 1985 and is under administration of the Instituto Nacional de los Recursos Naturales Renovables y del Medio Ambiente (INDERENA). Protected areas are needed in the remaining locales. In Túquerres, there is interest and concern by the community to preserve the Azufral volcanic area. On Cumbal and Chiles, protected zones should be established for the areas that have not already been greatly transformed. In Ecuador, the highlands above 4500 m are legally considered to be national public property.
Map 66. Volcanoes of Nariñense Plateau, Colombia and Ecuador (CPD Site SA30)
Cerón, B. (1987). Kwaiker. Introducción a la Colombia Amerindia. Instituto Colombiano de Antropología, Bogotá. Pp. 203-216.
Correa-Q., J.E. and Bernal, H.Y. (1989-1991). Especies vegetales promisorias de los países del Convenio Andrés Bello, Vols. 2, 3, 6. Junta del Acuerdo de Cartagena (JUNAC). Ministerio de Educación y Ciencia, Spain & Secretaría Ejecutiva del Convenio Andrés Bello (SECAB), Bogotá. 462 pp., 485 pp., 507 pp.
Cuellar-R., J. and Ramírez-L., C. (1986). Descripción de los volcanes colombianos. Postgrado en geofísica. Publicación interna, Universidad Nacional de Colombia, Bogotá. Pp. 2-12.
Erazo-N., G., de la Cruz-G., A., Delgado-M., A. and Montenegro-P., L. (1991). Caracterización de la vegetación paramuna de los volcanes Azufral y Galeras. Trabajo de grado presentado como requisito parcial para optar al título de Especialista en Ecología. Escuela de Postgrado, Universidad de Nariño, Pasto. 242 pp.
García-B., H. (1974-1975). Flora medicinal de Colombia, Vols. 1-3. Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogotá. 561 pp., 538 pp., 495 pp.
Grosse, E. (1935). Acerca de la geología del sur de Colombia. Informe rendido al Ministerio de Minas, sobre un viaje al departamento de Nariño. Compilación de Estudios Geológicos Oficiales en Colombia (Bogotá), Vol. 3. Pp. 139-231.
IGAC (1967). Atlas de Colombia. Instituto Geográfico Agustín Codazzi (IGAC), Bogotá. 204 pp.
Kathleen, R. (1978). Las tribus de la antigua jurisdicción de Pasto en el siglo XVI. Rev. Col. Antropol. (Bogotá) 21: 11-14.
Luna-Z., C. and Carlhoum, F. (1986). Suelos derivados de cenizas volcánicas del departamento de Nariño. IGAC, Dirección Agrológica 9(2): 1-131.
Luteyn, J.L., Cleef, A.M. and Rangel-Ch., J.O. (1992). Plant diversity in páramo: towards a checklist of páramo plants and generic flora. In Balslev, H. and Luteyn, J.L. (eds), Páramo: an Andean ecosystem under human influence. Academic Press, London. Pp. 71-84.
Rangel-Ch., J.O. (ed.) (1995). Colombia: diversidad biótica I.. INDERENA - Universidad Nacional de Colombia, Santafé de Bogotá. 442 pp.
Rangel-Ch., J.O. (in prep.). Vegetación y flora en los volcanes del sur de Colombia. Caldasia.
Sánchez-P., H., Hernández-C., J.I., Rodríguez-M., J.V. and Castaño-U., C. (1990). Nuevos parques nacionales Colombia. Instituto Nacional de los Recursos Naturales Renovables y del Medio Ambiente (INDERENA), Bogotá. 213 pp.
Sturm, H. and Rangel-Ch., J.O. (1985). Ecología de los páramos andinos: una visión preliminar integrada. Biblioteca J.J. Triana No. 9. Instituto de Ciencias Naturales, Museo de Historia Natural, Universidad Nacional de Colombia, Bogotá. 292 pp.
van der Hammen, T. and Cleef, A.M. (1986). Development of the high Andean páramo flora and vegetation. In Vuilleumier, F. and Monasterio, M. (eds), High altitude tropical biogeography. Oxford University Press, New York. Pp. 153-201.
This Data Sheet was written by Dr J. Orlando Rangel-Ch. and Aída Garzón-C.,
Universidad Nacional de Colombia, Instituto de Ciencias Naturales, Museo de Historia
Natural, Apartado Aéreo 7495, Santafé de Bogotá, Colombia).
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