COLOMBIAN CENTRAL MASSIF
The transect of La Plata Valley (Map 65) is between the crater of the volcano Puracé and the Serranía de las Minas, which is north of the Upper Magdalena River Valley - where the Central and Eastern cordilleras diverge northward from the Colombian Central Massif (Gran Macizo Colombiano). The transect includes part of Puracé Natural National Park, which extends from c. 2600-5000 m with the Serranía de Los Coconucos and covers c. 830 km² between latitudes 1°50'-2°24'N and longitudes 76°07'-76°37'W in the departments Huila and Cauca. Diverse life zones are present in this mountainous gradient; the high Andes and the páramo are biologically better known.
The regional geology presents a sequence: rocks from the Triassic-Jurassic, intrusive Jurassic rocks, marine sedimentary rocks of the Cretaceous, Tertiary molasse deposits and Quaternary deposits, which are related to orogenic volcanism or post-orogenic events in the rise of the Central and the Eastern cordilleras (Kroonenberg and Diederix 1985). Among the orogenic events, ignimbritic deposits characterize the landscape of the high plains, which are associated with lava flows of small volcanoes such as Merenberg and El Pensil. West of Puracé Volcano (4780 m) in the upper elevations of the massif is the Popayán formation of lavas, ashes, conglomerates, tufa and fluvial deposits.
Along the altitudinal transect of these mountain systems are different types of soil, as well as a wide variety of annual average temperatures and precipitation (Botero 1985; Rangel-Ch. and Espejo-B. 1989). From 500-1100 m in the tropical or equatorial region, in the alluvial plain of the Magdalena River and the foothills of Tesalia and Paicol, the prevailing soils are haplustalfs; the annual average temperature is 30°C, the precipitation varies between 1702-2108 mm. From 1150-2500 m in the higher tropical fringe and the sub-Andean region on recent colluvium, dystropept and haplustalf soils prevail; the temperature averages 18°C, the precipitation 1974 mm. From 2500-3300 m in the Andean montane region, in landscapes of ignimbritic high plains of old colluvium and ash mantles, dystropepts and dystrandepts prevail; the temperature is 15.2°C, the precipitation 1975 mm. From 3300-4400 m in the páramo region are moraines, deposits of pyroclasts, mud-flows and colluvium, with troposaprists, tropofluvents, hydrandepts and dystrandepts prevailing; the average temperature varies from 8°C to 5°C, the precipitation averages 2263 mm.
Although most often the rainiest month is May and the driest is January, and the mean monthly temperature may be lowest in about July to August and highest in about February or March, there is extreme diversity and even contrast from one part of the transect to another. Data on the seasonal variations with altitude through the year are presented in Rangel-Ch. and Espejo-B. (1989).
In the páramo different types of vegetation occur, principally bunchgrass fields ("pajonales") particularly on the slopes dominated by Calamagrostis species, "frailejones" of Espeletia hartwegiana subsp. centroandina (Asteraceae) on sites with well-watered soils, and peat bogs of Distichia muscoides. In the mid-elevations, the high-Andean forests (with trees to 10 m high) are dominated by Weinmannia and Miconia, whereas farther down slope are higher forests (over 25 m) of two strata in which Quercus humboldtii (Fagaceae) prevails. In adjacent zones following the gradient are forests of Lauraceae. In the tropical fringe prevail forests of deciduous foliage with Guarea guidonia (Meliaceae) and Leguminosae, and in semi-arid sites columnar cacti.
The syntaxonomic arrangement for part of the transect vegetation is as follows (Duque-N. and Rangel-Ch. 1989; Rangel-Ch. and Lozano-C. 1989; Rangel-Ch. and Franco-R. 1985):
1. Páramo region (4600-3500 m), with superpáramo fringe (4350-3800 m)
1.1. Azonal vegetation
1.2. Zonal vegetation
2. Andean montane region (3400-2400 m)
There are enclaves of páramo vegetation at low altitudes, in marshy or boggy sites originating from the damming of streambeds by volcanic flows (Kroonenberg and Diederix 1985). A typical example is at 2380 m with the peat bog of La Candelaria, close to the Merenberg Nature Reserve, where in a short stretch are different stages of the sequential vegetation process - from marshy sites with a few water holes where Guzmania gracilior, Blechnum columbiense and Oreobolus venezuelensis prevail, to frailejones physiognomically and floristically similar to those of the páramo zone at 3400 m, with Espeletia hartwegiana and Hypericum lancioides. In the ecotone with forest vegetation, Hedyosmum huilense and Lauraceae prevail, and thickets are established of Diplostephium floribundum, Weinmannia sp. and Miconia floribunda (Rangel-Ch. and Lozano-C. 1986).
4. Tropical region
The eastern slope of the Puracé Volcano and the Magdalena Valley are better known and these data refer mainly to them. The western slope facing the city Popayán is less known and the environmental impact in the surrounding area has been greater. The estimate of 1200 species of seed plants and ferns in the transect between 1000-4450 m corresponds to 431 genera of 167 families. Table 62 presents data on the dominant families and genera and those families' distributions in the four life zones of the gradient (Rangel-Ch. 1991; Lozano-C. and Rangel-Ch. 1989).
On the higher elevations of the massif, there is endemism or restricted distribution for Gunnera caucana (Gunneraceae); Miconia puracensis (Melastomataceae); Aphelandra grangeri (Acanthaceae); and Aequatorium latibracteolatum, Ageratina paezensis, Lasiocephalus puracensis, Pentacalia arbutifolia (Asteraceae). Between 3100-2000 m, endemics include Peperomia aguabonitensis, Piper subflavum var. longipedunculatum (Piperaceae); Ficus guntheri (Moraceae); Saurauia pulchra (Actinidiaceae); Begonia killipiana, B. tiliaefolia (Begoniaceae); Cavendishia divaricata, C. vinacea (Ericaceae); Salvia rufula var. paezorum (Lamiaceae); Aphelandra huilensis; and species of Meliosma (Sabiaceae), Alfaroa (Juglandaceae), Myrcia (Myrtaceae) and Solanum (Solanaceae).
In the high zones or páramo, bunches of Calamagrostis macrophylla and C. effusa are used to roof huts and for fodder. Species used to spice meats include Hypochoeris sessiliflora (Asteraceae) and Azorella spp. (Apiaceae). In the treeline open woods, the woody species are used for fuelwood. In the mid-Andean montane region, reforestation programmes use the native Quercus humboldtii, Billia columbiana ("cariseco"), Alnus acuminata ("aliso" - Betulaceae) and Beilschmiedia cf. sulcata (Lauraceae). Living hedges are made with Sapium cuatrecasasii ("lechero" - Euphorbiaceae), Cedrela montana (Meliaceae), Guazuma ulmifolia (Ulmaceae), Spondias mombin (Anacardiaceae) and Styrax leptactinosus (Styracaceae).
For folk medicinals, species include Oreopanax floribundus (Araliaceae); Baccharis genistelloides, B. nitida, Barnadesia spinosa, Bidens pilosa, Gnaphalium antennarioides, Mikania antioquensis (Asteraceae); Befaria aestuans, Gaultheria anastomosans (Ericaceae); Gentiana corymbosa, G. sedifolia, Gentianella dasyantha, G. diffusa (Gentianaceae); Dendrophthora clavata, Gaiadendron punctatum, Oryctanthus botryostachys (Loranthaceae); Oxalis latoides (Oxalidaceae); Passiflora cumbalensis (Passifloraceae); Peperomia cf. macrostachya (Piperaceae); Lachemilla galeioides, L. hispidula, L. nivalis, L. pectinata, Rubus glabratus, R. guyanensis (Rosaceae); Cinchona officinalis, Ladenbergia macrocarpa, Nertera granadensis (N. depressa), Relbunium hypocarpium (Rubiaceae); Solanum lepidotum, S. lycioides, S. nigrum, S. quitoense (Solanaceae); and Viola stipularis (Violaceae) (García-B. 1974-1975).
Social and environmental values
In localities of La Argentina and Serranía de las Minas are archaeological remains of houses and tombs of pre-Columbian settlements. The earliest known complex societies of the northern Andean highlands are in the Alto Magdalena region, which was densely populated by indigenous communities well before the arrival of the Spanish. The early cultures like those of San Agustín and Saladoblanco are of great archaeological and historical value, showing year-round settlements in the Upper Magdalena region for 2500 years (Drennan 1985a; Herrera, Drennan and Uribe 1989).
On the eastern slopes in the region of La Plata Valley, the inhabitants were Yalcones, Moscopanes and Quinchinas. The western slopes were inhabited by Paeces, Guambianos, Puracés, Coconucos and Popayanes. Most of these groups are extinct. A community of the Paece now lives in the neighbourhood of Puracé Volcano and Guambianos dwell in localities near Silvia (INDERENA 1984). Their homelands must be protected.
The páramo region close to Puracé Volcano is an important landscape resource. In the mid-elevation Andean region, the oak groves and other vegetation with Quercus humboldtii are the last remnants of the original vegetation; the associated fauna, especially birds and small mammals, find food there. Reforestation programmes with native species obtain necessary germplasm in these sites. The peat-bog zone of La Candelaria is a biological heritage that must be protected and studied in detail. There are over 50 lakes in the park. In localities of the transect several rivers flow - some originating on the mountaintops of the central massif. Conservation of these watersheds is vital to the surrounding municipalities. Several sites have thermal waters; their careful exploitation could bring in resources for conservation.
Threatened fauna in the region include mountain tapir (Tapirus pinchaque), rabbit deer (Pudu mephistophiles), spectacled bear (Tremarctos ornatus), Andean condor (Vultur gryphus) and black-and-chestnut eagle (Oroaetus isidori). Regional endemics include a bicolored antpitta (Grallaria rufocinerea romeroana). The Central Andean páramo Endemic Bird Area (EBA B60) and Subtropical inter-Andean Colombia EBA (B12) embrace the entire Central Andean cordillera from the páramo down to the subtropical (mid-Andean) forest. Twenty-seven restricted-range bird species occur in these two EBAs, 14 of which are entirely confined to the region. Due to increasing disturbance of the specialized vegetation, 15 bird species are considered threatened. In the drier low-lying zones of the adjacent Cauca and Magdalena valleys, this area overlaps with the Dry inter-Andean valleys EBA (B13), where four restricted-range birds occur.
In the páramo region close to the Puracé Volcano, sulphur is extracted by mining. Indigenous people make use of the bunchgrasses for extensive cattle-ranching, and on drier slopes, cultivate potatoes and barley. In the mid-part of the transect in the Andean montane region, a clay is utilized in arts and crafts. In this same region, coffee plantations exist, sometimes combined with grazing of cattle. In forested areas there is timbering; the forests of mid-elevations and those of the altitudinal ecotone between dense and open vegetation could be managed silviculturally, so that wood for the local populations would be a permanent resource. In the last few years an illegal crop (Papaver somniferum, opium poppy) has become a problem. Tourism is another resource - to visit the thermal spas of San Juan and Pilimbalá, the scenic páramo landscape and the areas of pre-Columbian settlement.
All areas suffer pressure from one or more factors of human origin. In the páramo, the mining causes access roads to be constructed without concern for biology or conservation, uncontrolled release of gases and solid residues into the atmosphere and disposal of untreated wastes into creeks and gullies. Although on the slopes that face Popayán there are indications of use as long as 2500 years ago (Drennan 1985b), the present cultivation of potatoes has transformed large areas.
Also responsible for modifying the landscape is disorderly construction of roads to the Puracé crater, and extensive cattle-ranching - which entails periodic burning of bunchgrass fields and frailejones. This produces soil erosion. The drying-out of páramo marshes and peat bogs constitutes irreparable damage, since it is in the highlands that the rivers originate. In the mid-part of the region, deforestation and excessive felling of trees have produced extensive cleared sectors, where soil erosion is worrisome.
Cinturón Andino Biosphere Reserve (declared in 1979) encompasses 8550 km² from Nevado del Huila Natural National Park (1580 km²) southward as far as Cueva de Los Guácharos NNP (90 km²) (Olaya-Amaya c. 1984), thus including Puracé NNP (830 km²), which was first protected in 1961 and established in 1968 - it should be extended to protect Paletará Valley (in Cauca), where areas of great biodiversity exist. A Forest Reserve should be strongly supported to supply seeds and seedlings necessary for reforestation of sites particularly in the mid-zone. The private Merenberg Nature Reserve (c. 3 km²), which began in 1932, conserves remnants of oak forest from 2300-2800 m; while protecting the reserve, in 1975 Mrs Mechthild Buch was murdered. Near the oak groves at 2300-2400 m, a buffer zone should be created to include peat bogs with enclaves of páramo vegetation and a representative portion of the zonal forest.In the vicinity of the Serranía de las Minas localities with very humid atmosphere exist, due to orographic precipitation; oak groves occur together with species of Alfaroa and Clusia in a unique situation (Rangel-Ch. and Lozano-C. 1989).
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