Included here is a small area of the Chaco or Gran Chaco. It covers the vast plains of north-central Argentina, western Paraguay, southeast Bolivia and extends into Brazil along the a narrow strip parallel to the River Paraquay in Mato Grosso do Sul. The climate varies, being much dryer in the west. However, it is one of the few areas in the World where the transition zone between tropic and temperate regions supports semi-arid vegetation rather than complete desert.

Chacoan Cactus Scrub

Cactus scrub dominated by the monotypic genus Stetsonia (Cactaceae) endemic to the Chaco is common in the western Chaco, but moving east it becomes increasingly rare. Stetsonia coryne is a large candelabra-like species that can become particularly dominant in strongly saline soils where much of the ground is either bare or covered in mosses and the clubmoss Selaginella sellowii.

References

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 and B. H. Walker. Springer-Verlag.

Fernandez, O. A. & Busso, C. A. (undated). Arid and semi-arid rangelands: two thirds of Argentina. RALA Report No. 200.

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.

Hilgert, N. I., Pensiero, J. F., Marino, G., Lewis, J. P. & D’Angelo, C. 2003. Vegetation of the Saladillo area (Province of Santa Fe), in the south of the Chaco, Argentina. Interciencia, 28: 512-520.

Lewis, J. P., Pire, E. F., Prado, D. E., Stofella, S. L., Franceschi, E. A. & Nélida, J. 1990. Plant communities and phytogeographical position of a large depression in the Great Chaco, Argentina. Vegetatio, 86: 25-38.

Prado, D. E. 1993. What is Gran Chaco vegetation in South America? I. A review. Contribution to the study of flora and vegetation of Chaco. V. Candollea, 48: 145-172.

Ragonese, A. E. & Castiglioni, J. C. 1970. La vegetacion del Parque Chaqueno. Boletin de la Sociedad Argentina de Botánica, 11: 133-160.