Location and General Description
The Rio Negro Campinarana ecoregion occur in isolated patches along the Rio Negro and Rio Branco basins in northern Brazil. These isolated patches of oligotrophic, or low nutrient, soils host a range of vegetation types from herbaceous savannas to closed-canopy forests. Patches of similar vegetation occur in northern Peru, southwestern Venezuela, and eastern Colombia as well. Some patches of campinarana cover thousands of square kilometers. Variably called 'Rio Negro caatinga,’ 'campinarana' or 'heath forest,’ these areas of distinct vegetation are edaphic formations within the same climatic zone as the surrounding dense tropical forest. The type of soil, rather than rainfall or temperature, determines the vegetation type. Campinarana vegetation develops around circular swampy depressions of nutrient-poor hydromorphic or non-hydromorphic (depends on situation of the water table) podzols – usually highly leached white sands – in a matrix of lowland tropical moist forest.
One of two factors limits the establishment and growth of plants in the campinarana. The first is nutrient-poor soil with black and very acid humus. The second is seasonal physiological drought, caused either by flooding where the water table is near the surface, or extreme drought where the water table is deep and the porous sand does not permit ascent of water. Thus, the vegetation tends to be xerophytic but with persistent foliage. The Curicuriari, Uaupés, Negro, and Issana rivers influence these areas. These areas have a climate of high temperature. The annual average is 24° C slightly higher than the surrounding humid forests because of the open canopy. Annual rainfall ranges from 2,500 to 3,000 mm and is well distributed throughout the year.
Campinarana represents a series of variable formations of structural differences (high and low forest) found in transitional patterns, but each has similar floristic composition . The vegetation types range from herbaceous savannas dominated by lichens and grasses through scrub forest with bare sand and herbaceous plants intermixed with shrubs and small trees less than 7 m tall. Woodlands of shrubs and trees and forests as high as 20 to 30 meters round out the continuum of structural phases of the campinarana. Low biomass, high-light penetration, and absence of vines, tree buttresses, and lianas are characteristics of all phases. Epiphytic orchids and bromeliads are abundant. The tree stems are generally slender (less than 200 mm diameter) and often twisted.
The plant communities are characterized by dominance of one or two species, giving individual patches lower plant richness than the neighboring species-rich forest. However, beta (regional) diversity is high because many stands across the region as a whole host distinct floras. Some are rich in grasses and sedges such as Lagenocarpus whilst others are lacking in these plant forms. The majority of species occurring on the campinarana are exclusive to this vegetation type. Ducke and Black cite the following taxa as limited to these areas in the Upper Rio Negro Basin: Virola parvifolia, Compsoneura debilis, Pithecelobium leucophyllum, many Macrolobium, Dicymbopsis froesii, Eperua leucantha, Peltogyne catingae, Tachigalia rigida, Aldina discolor, Monopteryx angustifolia, Panurea longifolia, Hymenolobium nitidum, Sacoglottis heterocarpa, Vochysia catingae, Hevea rigidifolia, Pleurisanthes simpliciflora, Scleronema spruceana, Anthodiscus obovatus, Froesia tricarpa, Loricalepis duckei, Couma catingae, Neocouma ternstroemiacea, Platycarpum negrense, Calycophyllum obovatum, and Gleasonia uaupensis. The tree families typical of the neighboring humid rain forest, such as Moraceae, Lecythidaceae, and Loganiaceae, are absent here.
Some indicator species of Amazonian campinarana are Gaylussacia amazonica, Glycoxylon inophyllum, Mauritia carana, and Lissocarpa benthamii. Some species occur in both high and low forests such as Aldina discolor, Eperua purpurea, and Lissocarpa benthamii. The low woodlands are rich in Aldina discolor, Lissocarpus benthamii, Bactris cuspidata, Sphaeradenia amazonica, and Zamia ulei. Another association includes Eperua leucantha, E. rubiginosa, E. purpurea, Aldina discolor, Pouteria sp., and Tachigali sp. A characteristic high campinarana forest association includes the tree species Eperua leucantha, E. purpurea, Micrandra sprucei, Catostemma sclerophyllum, Hevea viridis, and Macrolobium unijugum.
These are areas with high numbers of endemic plants and some very primitive species, such as the cycad Zamia. As with plants, animal diversity is lower in the campinarana than in the surrounding tropical moist forest. Here, a total of 153 mammals are reported. Mammals that have a restricted distribution include various primates such as white-faced sakis (Pithecia pithecia), black uakari monkeys (Cacajao melanocephalus), black spider monkeys (Ateles paniscus), tamarins (Saguinus inustus), bats (Diclidurus isabellus, Lonchorhina marinkellei, Micronycteris pusilla, Scleronycteris ega, Vampyressa brocki), and rodents, such as Brazilian squirrels (Sciurus gilvigularis), rats (Akodon urichi), porcupines (Coendou melanurus), and spiney rats (Proechimys semispinosus). Larger and widespread mammals include peccaries (Tayassu tajacu and Tayassu pecari), tapir (Tapirus terrestris), jaguars (Panthera onca), and deer (Mazama americana).
Bird richness is low for Amazonia ecoregions with 368 species. Endemic species found here include Rio Branco antbirds (Cercomacra carbonaria), spot-backed antwrens (Herpsilochmus dorsimaculatus), chestnut-crested antbirds (Rhegmatorhina cristata), and Orinoco piculets (Picumnus pumilus). Birds with a restricted distribution found here include russet-backed oropendolas (Psarocolius angustifrons), white-bellied dacnis (Dacnis albiventris), dotted tanagers (Tangara varia), Serra do Mar tyrant-manakins (Neopelma chrysolophum), yellow-crested manakins (Heterocercus flavivertex), and crestless curassows (Mitu tomentosa).
The ecoregion as a whole, comprising large, isolated patches, is fairly intact. None however, falls within a protected area. Because of the low productivity of these areas, there is little intensive land use on them, in general although some cattle grazing and burning has degraded portions of them.
Types and Severity of Threats
The most severe threats are burning for pasture maintenance and cattle grazing.
Justification of Ecoregion Delineation
These distinctive patches of forest are distinct from the surrounding moist forest due to extremely poor white-sand soils which characterize them. The resulting vegetation is often stunted and sparse, with some open areas and a woody-grass in interface. The delineation for this ecoregion are according to the IBGE (1993) and da Silva (1998), and the linework follows the IBGE classification of "oligotrophic woody swamp vegetation and of sand accumulation", and of three types: "dense trees", "open trees", and "woody-grass" (graminoid). Because of the unique soil characteristics, these patches of campinarana host unique floral and faunal assemblages and some endemic species.
Anderson, A. B. 1981. White-sand vegetation of Brazilian Amazonia. Biotropica 13: 199-210.
Ducke, A., and G. A. Black. 1953. Phytogeographical notes on the Brazilian Amazon. Anais da Academia Brasileira de Ciências 25: 1-46.
Fundação Instituto Brasilero de Geografia Estatástica-IBGE. 1993. Mapa de vegetação do Brasil. Map 1:5,000,000. Rio de Janeiro, Brazil.
Richards, P. W. 1996. The Tropical Rain Forest. Cambridge New York: University Press.
Veloso, H. P., and L. Góes-Filho. 1982. Fitogeográfica Brasileira: Classificação fisionômico-ecológica da vegetação Neotropical. Salvador, Brasil: Ministério das Minas e Energia.
Silva, J.M. C. 1998. Um método para o estabelecimento de áreas prioritárias para a conservação na Amazônia Legal. Report prepared for WWF-Brazil. 17 pp.
Prepared by: Robin Sears
Reviewed by: In process