L’etagement Altitudinal de la Vegetation au Chili Central: Les Profils Phytogeographiques

Abstract

Central Chile extends under a mediterranean type of climatic influence between the 30^th and 38^th grades of southern latitude. Due to a great concentration of population and the agricultural activity this part of the national territory practically is lacking in natural vegetation in the interiors valleys and coastal sectors of the precordillera.

Therefore, a descriptive analisis of the vegetation is more realistic if we do it in the Andes and in the coast ranges, following the criteria of altitudinal zonalization.

The northern sector of the region shows in its vegetation levels a certain similarity in its composition and physionomy with the natural formations of lowlands and plain regions which belong basically to latitudinal grou** typical of the region.

However, south of the 33 latitude, this similarity begins to disappear mainly due to high humidity registered in the mountains. The sclerophytal woods are replaced by mixted formations where the predominant species are the Fagaceae, Lauraceae and conifer.

Between the 37 and 38 grades of southern latitude, in both mountains ranges an almost pure formation of Araucaria araucana woods, an endemic conifer of South America is developed. In the coastal range, this formation reachs its optimun ecology between 800 and 1300 meters aproximately while in the Andes this one is achieved only at 1.600 meters of altitude.

The altitudinal descent of both ranges is almost parallely with the latitudinal development to the south and this is one of the reasons why some trees have a wide distribution in some attitudinal levels. (Nothofagus obliqua, Nothofagus alpina, Nothofagus dombeyi).

It is worth noting that at present, the anthropologycal action and the reforestation with foreign species are seriously affecting the preservation of the natural woods on this mountain ranges.