Caatinga Tall Forest
These tall, dry, largely draught deciduous forests can reach heights of up to 30 m and have a least three distinct strata. They are mainly associated with eutrophic soils derived from basic rocks. Common tree species include Astronium urendeuva, Cavanillesia arborea, Pterogyne nitens, Schinopsis brasiliensis, Tabebuia avellandae and the endemic Cereus jamacuru (Cactaceae). Cavanillesia arborea with its huge bloated trunk is a conspicuous species that has a distribution extending in to Western Amazonia. Other characteristic species that may be encountered include Anadenanthera macrocarpa and the endemic Aspidosperma pyrifolium (Apocynaceae) and Bursera leptophloeos (Burseraceae).
Caatinga Medium to Low Forest of Crystalline Rocks
These forests show considerable variation and can be divided in to several community types. The trees rarely exceed about 15 m in height and commonly include Astronium urundeuva and Schinopsis brasiliensis. Smaller trees typically comprise Caesalpinia bracteosa and the endemic Caesalpinia pyramidalis (Fabaceae). Other relatively common species are Amburana cearensis, Anadenanthera macrocarpa, Cnidoscalus phyllacanthus and Piptadenia zehntneri. Among the endemic species are Aspidosperma pyrifolium (Apocynaceae) found in the hotter less humid areas; Spondias tuberosa (Anacardiaceae) found on lighter soils with good drainage, and Ziziphus joazeira (Rhamnaceae) found in some of the wetter areas. Cacti are also a fairly important but have scattered distributions. Typical species include the endemic Cereus jamacaru and Opuntia palmadora (Cactaceae). At ground level the vegetation is very sparse and virtually devoid of grasses. The main under shrubs and herbs include species of Bromelia, Cassa, Melochia, Portulaca and Sida. In places the endemic Auxemma oncocalyx (Boraginaceae) is one of the dominant species especially in the State of Rio Grande de Norte and Ceará.
Caatinga Low Forest of Sandstone
This distinctive form of Caatinga is confined to highly permeable sandy soils derived from sandstone, which severely limits the amount of water available. Some of the most characteristic trees include Acacia bahiensis, Anadenanthera macrocarpa, Piptadenia obliqua, Poeppigia procera and the endemic Bursera leptophloeos (Burseraceae) and Dalbergia cearensis (Fabaceae). These range in height from 5-7 m but often emerging above the canopy are the distinctive blackish branches of Pilosocereus piauhiensis. Characteristic shrubs include Cassia acuruensis, Mimosa verrucosa, Pilosocereus tuberculatus and the endemic Cratylia mollis (Fabaceae) and Waltheria ferruginea (Sterculiaceae). The ground layer is typically poor in both herbs and grasses but of interest is the endemic Hohenbergia caatingae (Bromeliaceae). It has an adaptation for storing water in its leaf-base, which provides a convenient water supply for the local fauna.
Caatinga Valley Palm Forest
Dominated by the endemic palm Copernicia prunifera (Areacaceae) these forests are confined to the margins of rivers (and their tributaries) generally flowing in a northerly direction in the states of Ceará, Piauí and Rio Grande do Norte. Many of these have humid valleys that flood during the wet season but these forests show their best development on heavy alluvial soil saturated for most of the year. Associated species typically include the tree Geoffroea spinosa and the endemic shrub Licania rigida (Chrysobalanaceae). The endemic Cereus jamacaru (Cactaceae) and Pilosocereus gounellei (Cactaceae) can be found here growing as epiphytes on Copernicia sheaths.
Caatinga Tall to Low Shrubland of Crystalline Rocks
This is another complex formation comprising several different plant communities. It typically develops on shallow soils derived from gneiss, granites or schists, but represents the most extensive form of Caatinga. On the other hand, it is often difficult to determine how natural this vegetation is and much may have been altered by human intervention. In a number of areas, such as the Borborema Highlands, the main species include the endemic Aspidosperma pyrifolium (Apocynaceae) and Caesalpinia pyramidalis (Fabaceae). The few associates include other highly draught adapted species such as Jatropha pohliana and the endemic Bursera leptophloeos (Burseraceae). In other places species of Mimosa such as M. limana and M. malacocentia dominate, but in some cases these may have colonized abandoned agricultural land. Other species that may be encountered include Angelonia arguta, Melochia tomentosa, Paspalum scutatum, Portulaceae halymoides, Sida cordifolia, Tragus berteronianus and the endemic Gaya aurea (Malvaceae) and Herrissantia crispa (Malvaceae). However, when deeper soils with better water storage capacity prevail the endemic bromeliad Neoglaziovia variegata can form dense stands - the long, thick leaves of this species have been used for fiber production. On more rocky terrain the endemic cactus Opuntia inamoena (Cactaceae) becomes one of the main species. In the Seridó region where the shallow soils are derived from metalogenic rocks the strong run-off has caused severe erosion. Here the main shrubs, Caesalpinia pyramidalis and Mimosa species, have a stunted, dwarf appearance. Growing between the shrubs are a few hardy species such as the grass Aristida adscensionis and the endemic Cereus jamacaru (Cactaceae) and Pilosocereus piauhiensis (Cactaceae).
Caatinga Low Shrubland of Metamorphic Rocks
Confined to gravelly or sandy soil mainly derived from metamorphic rocks this type of Caatinga is restricted to a few scattered areas. It is largely dominated by the endemic shrubs Calliandra depauperata (Fabaceae) and Pilosocereus gounellei (Cactaceae), which rarely exceed about 1.5 m in height. The few other associated species include herbs such as Portulaca halimoides and the cactus Melocactus bahiensis.
Caatinga Fixed Dunes
Dune vegetation is mainly confined to the paleodunes along the Sãn Francisco River between Ibiraba and Casa Nova (Bahia State) extending north to the Gurguéia Valley (Piauí State) and the Moxotó Valley (Pernambuco State). In the former area, which has been described as the little Sahara, the dunes can reach heights of up to 40 m above the adjacent river, and the vegetation is largely dominated by a patchy scattering of small trees and shrubs. Here plant species diversity can be considerably lower than other Caatinga formations. The most frequent species include trees such as Copaifera coriacea, Mouriri pusa, Ouratea glaucescens, Peltogyne pauciflora, Ruprechtia ramiflora, Simaba ferruginea and the endemic Bombacopsis retusa (Bombacaceae), Commiphora leptophloeos (Burseraceae), Maytenus rigida (Celastraceae) and Pterocarpus simplicifolius (Fabaceae), shrubs such as Bocoa mollis, Byrsonima gardnerana, Croton sonderianus, Harpochilus neesianus, Ximenia americanus and the endemic Chamaecrista belemii (Fabaceae), Cratylia mollis (Fabaceae), Jatropha mutabilis (Euphorbiaceae), Senna gardneri (Fabaceae), and the two endemic succulents Pilosocereus gounellei and P. tuberculatus (Cactaceae). Some trees, such as Bombacopsis retusa, Mouriri pusa and Pterocarpus monophyllus can grow to heights of 5 m or more but most woody species are less than 2 m. A number of these woody species provide an important food source, in the form of fruits and seeds, for various local endemic rodents. At ground level there is a distinct lack of herbaceous cover with much of the sandy soil exposed apart from occasional patches of the terrestrial bromeliad Bromelia antiacantha and the small cactus Tacinga inamoena. Epiphytes are absent but a few climbing plants (lianas and vines) occur such as Cardiospermum corindum, Centrosema brasilianum, Chaetocalyx scandens, Dalechampia scandens, Ipomoea setifera, Serjania comata and the endemic Dioclea marginata (Fabaceae) are present. There are also a few hemiparasitic species like Phoradendron linearifolium, Psittacanthus bicalyculatus and Strutanthus syringifolius. Other endemic plants found here include trees such as Callandra macrocalyx (Fabaceae), Godmania dardanoi (Bignonaceae), Hymenaea eriogyne (Fabaceae), Pterocarpus monophyllus (Fabaceae), Ziziphus joazeiro (Rhamnaceae) and shrubs such as Aeschynomene martii (Fabaceae), Allamanda puberula (Apocynaceae), Cordia globosa (Boraginaceae), Manihot heptophylla (Euphorbiaceae), Lantana caatingensis (Verbenaceae), Mimosa xiquexiquensis (Fabaceae), Pavonia varians (Malvaceae) and Sida galheirensis (Malvaceae).
Further information required.
References
Andrade-Lima, D. de. 1981. The caatinga dominium. Revista Brasileira De Botanica, 4: 149-153.
Andrade-Lima, D. de. 1982. Present-day forest refuges in northeastern Brazil. In: Biological Diversity in the Tropics. Ed. G. T. Prance. Columbia University Press.
Anon. 1996. Habitats of South America. Institute of Terrestrial Ecology and Intitut Royal Des Sciences Naturelles De Belgique.
Bucher, E. H. 1982. Chaca and Caatinga - South American Arid Savannas, Woodlands and THickets. In: Ecology of Tropical Savannas. Eds. B. J. Huntley & B. H. Walker. Springer-Verlag.
Daly, D. C. & Mitchell, J. D. 2000. Lowland vegetation of tropical South America – an overview. In: Imperfect Balance: Landscape Transformations in the pre-Columbian Amercas. Ed. D. Lentz. Columbia University Press, New York.
Fernandez, O. A., Bóo, R. M. & Sánchez, L. F. 1989. South American Shrublands. In: The Biology and Utilization of Shrubs. Ed. C. M. McKell. Academic Press, Inc.
Junk, W. J. 1993. Welands of tropical South America. In: Welands of the World: Inventory, ecology and management. Vol. 1. eds. D. Whigham, D. Dykyjova & S. Hejny. Kluwer Academic Press.
Leal, I. R., Da Silva, J. M. C., Tabarelli, M. & Lacher, T. E. 2005. Changing the course of biodiversity conservation in the Caatinga of northeastern Brazil. Conservation Biology, 19: 701-706.
Paganucci de Queiroz, L. 2006. The Brazilian Caatinga: Phytogeographical Patterns Inferred from the Data of the Leguminosae. In: Neotropical Savannas and Seasonally Dry Forests. Plant Diversity, Biogeography, and Conservation. Eds. R. T. Pennington, G. P. Lewis and J. A. Ratter. Taylor & Francis.
Reis, A. M. S., Araújo, E. L., Ferraz, E. M. N. & Moura, A. N. 2006. Inter-annual variations in the floristic and population structure of an herbaceous community of “caatinga” vegetation in Pernambuco, Brazil. Revista Brasileira De Botanica, 29: 497-508.
Rocha, P. L. B. da., Queiroz, L. P. de. & Pirani, J. R. 2004. Plant species and habitat structure in a sand dune field in the Brazilian Caatinga: a homogenous habitat harbouring an endemic biota. Revista Brasiliera de Botânica, 27: 1-19.
Sampaio, E. V. S. B. 1995. Overview of the Brazilian caatinga. In: Seasonally Dry Tropical Forests. Eds S. H. Bullock, H. A. Mooney & E. Medina. Cambridge University Press.