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The Chiribiquete-Araracuara-Cahuinarí region is in the north-western portion of the Amazon Basin. The largest of the three main rivers is the Caquetá, which originates in the Andes and is the region's only white-water river; together with the Apaporis, it drains into the Japurá River of Brazil. Farther north, the Vaupés River forms part of the catchment of Brazil's Rio Negro (CPD Site SA6).
The northern (Chiribiquete-Araracuara) portion of this region is dominated by north-south aligned outcrops of Palaeozoic sandstone formations in an extensive interrupted sandstone plateau at c. 400 m, rising locally to c. 700 m (confirmed by a recent Colombian-Spanish botanical expedition), with broad interior valleys which are partially filled with sandy colluvial sediments. The highest plateau outcrops or cerros (Cerro Azul, Cerro Quemado, Cerro Chiribiquete, Cerro Campana) appear as characteristic table mountains. Southward the overall plateau gradually descends: at Araracuara it has an elevation of c. 300 m, and beyond 1°40'S no sandstone outcrops are found.
The sandstone plateaux have a generally flat topography, dissected by numerous fissures of variable depth. Mostly along the plateau margins dissected portions occur with hilly to undulating topography. Dominant soils of the plateaux are moderately deep to shallow, greyish white and sandy in texture, poorly to somewhat excessively drained and with extremely poor nutrient chemical properties. The poorly drained soils might be called "groundwater podzols" or "wet white-sand" soils. At sites with hardrock outcrops, soil is virtually absent.
The southern and eastern (Araracuara-Cahuinarí) portion of the region consists mostly of slightly consolidated Tertiary sediments, which form a dissected sedimentary plain at c. 250 m (c. 60-80 m above the lowest riverwater levels). Most valleys are 30-60 m deep, with 20°-40° slopes. The drainage pattern is a tree-like branching of watercourses occurring in high density (3.1-4.7 km per km²). The soils of this hilly terrain are well drained, from loamy to clayey and chemically poor to very poor (Duivenvoorden and Lips 1993).
The alluvial plains of the larger rivers comprise less than 5% of the region (Duivenvoorden and Lips 1993), and have been built up by Pleistocene and Holocene deposits (van der Hammen et al. 1991a). They consist of flat to dissected terraces and floodplains c. 5-60 m above average riverwater levels. The soils of the Caquetá floodplain are relatively rich, whereas the soils of the floodplains of the black-water Amazonian rivers are chemically poor. Occasionally, particularly on flat sites of the higher fluvial terraces of the Caquetá River, small to extensive areas with podzolised soils are found, which are comparable to the groundwater podzols on top of the sandstone plateaux (Duivenvoorden and Lips 1993).
The tropical climate (Afi of Köppen 1936) has a mean daily temperature closely fluctuating around 26°C, to somewhat cooler at the more elevated sites in the Chiribiquete area. The annual precipitation is c. 3000 mm (the monthly mean exceeding 60 mm) and has a nearly unimodal distribution: most of the rainfall occurs in May-July, the least in December-February, which still averages well over 100 mm. The monthly average precipitation always exceeds the average potential evaporation. However, the sandy soils of the sandstone plateaux are likely to experience a water deficit almost every year for short intervals during the drier months (Duivenvoorden and Lips 1993, based on data from a meteorological station at Araracuara). In the Chiribiquete general area, rainfall might be somewhat lower due to the drier Llanos Orientales farther north, but on the high Chiribiquete cerros frequent low clouds and mist might increase the humidity and rainfall.
The evergreen moist tropical forests that cover most of the Tertiary sediments and Quaternary alluvial plains of the Chiribiquete area and Middle Caquetá River Basin represent one of the few remaining extensive, undisturbed rain-forest ecosystems in the Amazon Basin. Knowledge of the forests of the Middle Caquetá Basin has improved since 1986 from inventories due to the Tropenbos-Colombia Programme (Duivenvoorden and Lips 1993; Urrego 1990; Galeano 1991; Alvarez and Londoño, in prep.; and students' unpublished reports).
The forests on well-drained sites in the Middle Caquetá Basin generally are 25-30 m high; 0.1-ha samples have 65-85 trees (10 cm or more dbh) with a basal area of 3.0-3.5 m² and aerial biomass of 25-30 tonnes. On well-drained upland sites, at least two forest communities can be recognized; the more common trees are Clathrotropis macrocarpa, Iryanthera tricornis, Micropholis guyanensis, Eschweilera rufifolia, Micranda spruceana, Pouteria sp. and Swartzia schomburgkii. At well-drained sites on the floodplains, at least six different forest communities occur; the most common species are Cecropia membranacea, Annona hypoglauca, Iriartea deltoidea, Ficus spp., Astrocaryum jauari, Parkia multijuga, Oxandra mediocris, Mollia lepidota and Pouteria torta. Other common trees include Oenocarpus bataua, Euterpe precatoria, Eschweilera coriacea, Brosimum utile, Virola elongata and Hevea guianensis. The understorey of the forest is particularly rich in species belonging mostly to Melastomataceae, Rubiaceae, Arecaceae, Annonaceae, etc.
The forests on poorly drained sites generally are lower, have less tree aerial biomass, higher densities of palms and (much) higher treelet densities. At least six different forest communities have been recognized; often the palm Mauritia flexuosa (picture) is a frequent tree. In the higher floodplain and low terraces of the Caquetá River, peat forests are found, dominated by among others Clusia spathulifolia, Rhodognaphalopsis brevipes, Mauritiella aculeata and Euterpe catinga. At the sites with podzolised soils on the high terraces of the Caquetá River, a sclerophyllous low forest and scrub vegetation is found (Amazonian caatinga according to Anderson 1981), which has a number of species in common with the wet white-sand vegetation of the sandstone plateaux.
Species diversity of the rain forests of the Middle Caquetá Basin is very high, both the [alpha] type (species richness at small homogeneous sites) and the [beta] type (overall number of species related to degree of habitat differentiation), particularly on the alluvial plains and the sandstone outcrops. Tree species richness of the forest on well-drained uplands (Table 57) is comparably high with some Peruvian rain forests (Gentry 1988, 1990).
On the sandstone outcropped plateaux, vegetation patterns are complex mosaics. Most of the more elevated plateaux in the Chiribiquete area are covered by open low tree and shrub communities with the following taxa common: Graffenrieda fantastica, Clusia chiribiquetensis, C. schultesii, Tepuianthus savanensis, Pochota nitida, Ternstroemia campinicola, Miconia paradoxa, Hevea viridis var. toxicodendroides, Decagonocarpus cornutus and Ficus chiribiquetensis. On the sandier soils Vellozia phantasmagoria forms an open low vegetation, whereas on flat sites with hardrock outcrops Navia garcia-barrigae is a dominant. At small sites of stagnant rainwater on shallow sandy soils, Utricularia chiribiquetensis, Burmanniaceae, Drosera sp. and Abolboda macrostachya form herb communities. Utricularia neottioides occurs alone in running water on hardrock (Fuertes and Estrada, in prep.). On the sandy colluvial deposits, a low forest of Protium leptostachyum, Bonnetia martiana, Meriania urceolata, Matayba macrolepis, Oenocarpus bataua and Pagamea coriacea has been discerned.
At Araracuara, the top of the sandstone plateau is partially covered by low forest, generally with a high density of treelets (to 10 cm dbh); at least two floristic communities are found: a forest marked by Dimorphandra cuprea, D. vernicosa and Ocotea esmeraldana and a very distinct forest dominated by Bonnetia martiana (picture). There is also a closed scrub vegetation 2-3 m high with Bonnetia martiana dominant. Common species in wet white-sand vegetation are Ilex divaricata, Ternstroemia spp., Abolboda macrostachya, Macairea rufescens, Syngonanthus umbellatus, Lagenocarpus pendulus, various species of Clusia, Xyris and Utricularia, and Cladonia lichens (Duivenvoorden and Cleef 1994). A considerable part of this poorly drained plateau is covered by a closed, medium-tall graminoid vegetation with Axonopus schultesii and Schoenocephalium martianum co-dominant.
On sites with very thin, colluvial sandy soils there is an open low herb community with among others Xyris wurdackii var. caquetensis, X. savanensis, X. araracuare, Paspalum sp., Syngonanthus vaupesanus and Cladonia peltastica. These graminoid and herb communities are clearly related to the wet white-sand savannas of Surinam (Heyligers 1963; van Donselaar 1965), and may represent the southernmost, lowest extension of the wet white-sand table-mountain vegetation of the Guayana floristic region. At sites on the Araracuara plateau with hardrock outcrops, an open vegetation with Navia garcia-barrigae, Acanthella sprucei and Cladonia vareschii occurs.
Much of the flora has still to be studied; the region may harbour 12,000 species of vascular plants. The region is rich not only in vascular plant species: a preliminary inventory of epiphyllous lichens at Araracuara yielded 135 species - over one-third of such lichens known in the world (Sipman 1990). The floristic research of the Tropenbos-Colombia Programme in the Middle Caquetá River area by 1992 had inventoried some 24 ha (well distributed over all the physiographic units); c. 3000 species of vascular plants in 129 families have been recorded. Among the quantitatively most important families are Melastomataceae, Rubiaceae, Annonaceae, Moraceae, Arecaceae, Fabaceae, Mimosaceae and Euphorbiaceae.
The Chiribiquete-Araracuara-Cahuinarí region is the westernmost transition between the floristic regions of Guayana and the Amazon Basin. The vegetation of the Tertiary sedimentary plain and the younger alluvial valley systems contains dominantly Amazonian lowland elements. The outcropped sandstone plateaux have a high percentage of elements of the Guayana region, and apparently represent its most south-western habitats for a number of taxa in Xyris, Abolboda, Vellozia, Rapatea, Schoenocephalium, Brocchinia, Navia, Steyerbromelia, Duckeella, Decagonocarpus, Senefelderopsis, Gongylolepis, Retiniphyllum, Pagamea and Tepuianthus (the family Tepuianthaceae has been considered endemic to the Guayana floristic region).
The following 23 taxa presently are considered endemic to the sandstone plateaux of the Chiribiquete-Araracuara area: Asplundia ponderosa, Clusia chiribiquetensis, C. schultesii, Combretum karijonorum, Euplassa saxicola, Ficus ajajuensis, F. chiribiquetensis, Graffenrieda fantastica, Hibiscus sebastianii, Justicia cuatrecasasii, Macairea schultesii, Navia schultesiana, Paullinia splendida, Paepalanthus moldenkeanus, Senefelderopsis chiribiquetensis, Solanum apaporum, Styrax rigidifolius, Tragia new sp., Raddiella molliculma, Utricularia chiribiquetensis, Vellozia phantasmagoria, Xyris araracuare and X. trachysperma (Schultes 1944; Smith 1944; Fuertes 1992; Kral and Duivenvoorden 1993; Duivenvoorden and Cleef 1994).
The importance of the Chiribiquete-Araracuara-Cahuinarí region in botanical and phytogeographical research are illustrated by the recent discovery of 35 species new to science, including a new genus of the Dipterocarpaceae (only the second genus in the neotropics of this predominantly palaeotropical family), as well as the first records in Colombia for some 50 species; and the finding of several species in the alluvial plain of the Caquetá River that were hitherto known only from the Guayana Highlands (e.g. Oxandra asbeckii, Ocotea neblinae).
The indigenous peoples of the region extract products from the forest mostly for subsistence purposes. Nearly 90% of the trees (10 cm or more dbh) are used (Sánchez and Miraña 1991). Among the most important species and products are (1) fruits: Unonopsis spectabilis, Couma catingae, Mauritia flexuosa, Pourouma tomentosa; (2) palm hearts: Euterpe precatoria, Oenocarpus bataua; (3) woods: Iryanthera juruensis, I. laevis, Ocotea acyphylla, Calophyllum longifolium; (4) fibres: Astrocaryum aculeatum, Eschweilera tessmannii, Cariniana decandra; (5) medicines: Protium nodulosum, Crepidospermum cuneifolium, Iryanthera ulei, Vismia macrophylla; and (6) dyes: Genipa americana, Duroia spp.
Certain Hevea species have been commercially exploited and studied as genetic resources for rubber, particularly during the first three decades of the 1900s. The palm Bactris gasipaes, as well as Pourouma cecropiifolia and Theobroma bicolor, widely known as potentially valuable for commercial exploitation, are present in all the local home gardens. In the Amerindian peoples' shifting slash-and-burn agriculture, the most important species are Manihot esculenta, Zea mays, Dioscorea trifida, Xanthosoma violaceum, Nicotianum tabacum, Erythroxylum coca and Ananas comosus; often a large number of Amazonian selections can be distinguished, e.g. 18 kinds of hot peppers (Capsicum chinense) (Vélez 1991).
Social and environmental values
The several indigenous peoples in the region are very concerned to maintain their own Amazonian cultures, habits and ways of sustainable use of the forest. More than 90% of the area between Araracuara and the mouth of the Cahuinarí River has been declared Amerindian reserves. Northward, surrounding Chiribiquete Natural National Park, no Amerindian reserves exist. An intriguing aspect of the Chiribiquete area is impressive Amerindian wall paintings; their origin, exact age and meaning are not understood. Near Araracuara, archaeological research has detected one of the oldest dates (2700 BC) for the beginning of maize cultivation in the Amazon Basin (Mora et al. 1991). In the general region, several sites with anthropic soils occur.
The integral vastness of this rain forest provides important habitat for large Amazonian predators (e.g. jaguar, puma, harpy eagle). Without doubt attractive for tourists are the striking scenery of the cerros of Chiribiquete and the canyon of Araracuara, the petroglyphs on Precambrian rocks along the Caquetá River (Reichel de von Hildebrand 1975) and the beautiful, undisturbed wilderness of the basins of the Caquetá River and particularly the Cahuinarí River with its abundant animal diversity.
At present, the population density in this region is very low (less than 0.2 person per km² along the Middle Caquetá River, still lower in the Chiribiquete area). The several indigenous groups are small. Few settlements of colonists exist. Tourism to the National Parks and other attractions is strenuous. It is extremely difficult to estimate the potential economic value of the plant resources, including the traditionally cultivated strains. Currently, hardly any forest products from the region reach the national market. Nonetheless, sustainable economic benefits from products certainly can be expected by careful development using forest species (e.g. medicines, fruits, dyes, fibres, woods) and plateau species (e.g. ornamentals) due to the high floristic diversity of the vegetation.
Fortunately, the region's remoteness and inaccessibility because of rapids in all of the major rivers (Vaupés, Apaporis, Caquetá) and the absence of roads have been safeguarding the Chiribiquete-Araracuara-Cahuinarí rain forest from almost all disturbance. However, the large expanse of the region makes it vulnerable to colonization, and the government has tried to encourage people to move into the Llanos Orientales and Amazon regions (Forero 1989). The potential exists to construct roads into the region, especially from San José del Guaviare (north of the Vaupés River). The easy entrance of colonists would lead to large-scale deforestation (pastoral development and timbering) (cf. Gentry 1989) and uncontrolled burning of the fragile dry sandstone vegetation.
The most immediate threat to the region comes from the Andean headwater areas, particularly of the Caquetá River. Increasing deforestation and the development of mining and industry are likely to be altering the flood regime of the Caquetá River (van der Hammen et al. 1991b) and causing contamination of the water and sediments, thus affecting the floodplain forests. Commercial fishing along the Caquetá River is the only natural resource use with products reaching the national market (Rodríguez 1991).
Two Natural National Parks (totalling 18,550 km²) have been established in the region (Map 43): Chiribiquete NNP (12,800 km²) to the north-west - the largest park in the Colombian National Park system; and Cahuinarí NNP (5750 km²) in the south-east (Sánchez et al. 1990). The establishment of three Amerindian reserves (comprising c. 3470 km²) in the Araracuara-Cahuinarí area also favours protection and conservation of the forest: for the Muinane, Villa Azul (c. 598 km²); for the Andoke, Aduche (579 km²); and for the Wetoto, Monochoa (c. 2294 km²), and as well a small part of the sizeable Predio Putumayo (c. 57,992 km²) extends into the region. The environmental policy of the Colombian government for the Amazon Basin tries to combine conservation with development, looking for improvement of living conditions for the human population within an ecologically viable framework (DNP 1991). Presently, however, there is no land-use and management plan for integrated conservation of the Chiribiquete-Araracuara-Cahuinarí region.
Map 43. Chiribiquete-Araracuara-Cahuinarí Region, Colombia (CPD Site SA7)
Anderson, A.B. (1981). White-sand vegetation of Brazilian Amazonia. Biotropica 13: 199-210.
DNP (1991). Política para el desarollo y la conservación de la Amazonia. Doc. Dirección Nacional de Planeación (DNP) 2545UDT. Colombia Amazónica 5: 11-44.
Duivenvoorden, J.F. and Cleef, A.M. (1994). Amazonian savanna vegetation on the sandstone plateau near Araracuara, Colombia. Phytocoenologia 24: 197-232.
Duivenvoorden, J.F. and Lips, J.M. (1993). Landscape ecology of the Middle Caquetá Basin. Explanatory notes to the maps. Estudios en la Amazonia Colombiana, Vol. 3A. Tropenbos-Colombia, Bogotá. 301 pp.
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Fuertes, J. (1992). Estudios botánicos en la Guayana colombiana, 1. Una nueva especie de Hibiscus sección Furcaria (Malvaceae). Anales Jard. Bot. Madrid 50: 65-72.
Galeano, G. (1991). Las palmas de la región de Araracuara. Estudios en la Amazonia Colombiana, Vol. 1. Tropenbos-Colombia, Bogotá. 181 pp.
Gentry, A.H. (1988). Tree species richness of Upper Amazonian forests. Proc. Natl. Acad. Sci. 85: 156-159.
Gentry, A.H. (1989). Northwest South America (Colombia, Ecuador and Peru). In Campbell, D.G. and Hammond, H.D. (eds), Floristic inventory of tropical countries. New York Botanical Garden, Bronx. Pp. 391-400.
Gentry, A.H. (1990). Floristic similarities and differences between southern Central America and Upper and Central Amazonia. In Gentry, A.H. (ed.), Four neotropical rainforests. Yale University Press, New Haven. Pp. 141-157.
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Kral, R. and Duivenvoorden, J. (1993). A new species of nematopoid Xyris (Xyridaceae) from the Araracuara area of Colombia. Novon 3: 55-57.
Mora, D., Herrera, L.F., Cavelier, I. and Rodríguez, C. (1991). Cultivars, anthropic soils and stability. A preliminary report of archaeological research in Araracuara, Colombian Amazonia. Univ. Pittsburgh Latin Amer. Archeol. Reports No. 2. 87 pp.
Reichel de von Hildebrand, E. (1975). Levantamiento de los petroglifos del río Caquetá entre La Pedrera y Araracuara. Rev. Colombiana Antropol. 19: 303-370.
Rodríguez, C.A. (1991). Commercial fisheries in the Lower Caquetá River. Estudios en la Amazonia Colombiana, Vol. 2. Tropenbos-Colombia, Bogotá. 152 pp.
Sánchez, H., Hernández, J.I., Rodríguez, J.V. and Castaño, C. (1990). Nuevos parques nacionales, Colombia. Instituto Nacional de los Recursos Naturales y Renovables y del Ambiente (INDERENA), Bogotá. 213 (+ 25) pp.
Sánchez, M. and Miraña, P. (1991). Utilización de la vegetación arbórea en el Medio Caquetá, A. El árbol dentro de las unidades de la tierra, un recurso para la comunidad Miraña. Colombia Amazónica 5: 151-160.
Schultes, R.E. (1944). Plantae colombianae, IX. Caldasia 3: 121-130.
Sipman, H. (1990). Colección preliminar de líquenes sobre hojas en Araracuara, Colombia. Colombia Amazónica 4: 59-65.
Smith, L.B. (1944). A new bromeliad (Navia) from Colombia. Caldasia 3: 131.
Urrego, L.E. (1990). Apuntes preliminares sobre la composición y estructura de los bosques inundables en el Medio Caquetá, Amazonas, Colombia. Colombia Amazónica 4: 23-30.
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van der Hammen, T., Urrego, L.E., Espejo, N., Duivenvoorden, J.F. and Lips, J.M. (1991b). Fluctuaciones del nivel del agua del río y de la velocidad de sedimentación durante los últimos 13,000 años en el área del Medio Caquetá (Amazonia Colombiana). Colombia Amazónica 5: 91-130.
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Vélez, A.J. (1991). El ají (Capsicum chinense Jacq.), patrimonio cultural y fitogenético de las culturas amazónicas. Colombia Amazónica 5: 161-185.
This Data Sheet was written by M.
Sánchez-S., L.E. Urrego (Departamento de Ciencias Forestales, Universidad de Colombia,
Apartado Aéreo 568, Medellín, Colombia), Dr J.G. Saldarriaga (Fundación
Tropenbos-Colombia, A.A. 36062, Bogotá, D.E., Colombia), J. Fuertes, J. Estrada (Real
Jardín Botánico, Consejo Superior de Investigaciones Científicas, Plaza de Murillo 2,
28014 Madrid, Spain) and Dr J.F. Duivenvoorden (University of Amsterdam, Hugo de Vries
Laboratorium, Kruislaan 318, 1098 SM Amsterdam, The Netherlands).
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