Altitude e solos determinam variações abruptas da vegetação em gradiente altitudinal de Mata Atlântica.

The variation of vegetation in altitudinal gradients is usually conditioned by the thermal gradient. We hypothesized that the vegetation structure varies abruptly as a result of very distinct environments whose formation is not only related to altitude and climate. We selected three areas in the Morro do Baú, in Ilhota municipality, Southern Brazil. In each, we allocated 50 plots of 100 m2 (Area 1 - 340 m a.s.l., Area 2 - 540 m a.s.l. and Area 3 - 810 m a.s.l.). We measured all individuals with DBH = 4,77 cm. We elaborated a Venn diagram and compare areas using rarefaction curves. We applied DCA and NMDS ordination to identify the degree of vegetation variation. Because of its strong distinction, we compared Area 3 with part of the data from IFFSC. The vegetation structure varies abruptly between Areas 1/2 and 3, the latter being a true cloud forest determined by the joint effects of altitude, climate, soils and geomorphology. Regionally, however, the similarities are not greater with other cloud forests, but with areas near and of approximately the same altitude. [ABSTRACT FROM AUTHOR]