Brazilian Paramos I. An introduction to the physical environment and vegetation of the campos de altitude

Aim The campos de altitude are a series of cool-humid, grass-dominated form ations restricted to the highest summits of the southeastern Brazilian High lands. Relatively little is known of the ecology, biogeography, or developm ental history of this archipelago of mountaintop formations. This contribut ion presents an overview of our present state of knowledge with respect to the past and present physical environment and vegetation of the campos de a ltitude. The aim is (1) to introduce an international audience to the natur al history of these diminutive yet important ecosystems, and (2) to provide the background for a series of forthcoming contributions that will treat t he ecology of the campos de altitude and explore physical and biotic relati onships between these 'Brazilian paramos' and similar formations in the hig h mountains of equatorial South and Central America. Location Beginning at altitudes of 1800-2000 m, the campos de altitude are found atop the highest summits of the main ranges of the southeastern Brazi lian Highlands, between the states of Santa Catarina and Minas Gerais/Espir ito Santo. Methods Drawing upon both original data and previously published results, t his contribution reviews what we presently know about the physical environm ent and vegetation of the campos de altitude, in the context of geographic setting, geology, palaeoclimatology and palaeobotany, modern climate, moder n vegetation, and conservation. Results and main conclusions Uplift of the southeastern Brazilian ranges to altitudes high enough to support orographic grasslands may have occurred a s early as the middle- to late-Tertiary; pollen records show that campos de altitude have been extant on southeastern summits at least since the Late Pleistocene. The present-day climate of the campos de altitude is cool and (per)humid, but patterns of rainfall, temperature, and frost are distinctly seasonal. Although the flora of the campos de altitude is highly diverse a nd characterized by a high degree of endemism, the campos de altitude maint ain strong floristic similarities to equatorial alpine formations of the An dean and Central American Cordillera; these similarities also extend to cli mate, soils, and vegetation physiognomy. Anthropogenic fires and grazing ar e widespread in the campos de altitude and probably contribute significantl y to the modern structure of vegetation communities.