Resposta de duas fitofisionomias de cerrado stricto sensu (cerrado típico e ralo) ao distúrbio recorrente provocado por fogo, ao longo de três anos

Abstract

The Cerrado, Brazilian Savannah Biome, has been suffering for years with the high recurrence of fire, raising questions about the effects that this can cause for its flora. The state of Tocantins, which has most of its territory covered by the Cerrado, records a high number of fires every year. Our objective was to investigate the response of two phytophysiognomies of Cerrado Stricto Sensu (Cerrado Typical and Cerrado Ralo) to annual fires in three successive years (2010, 2011, 2012). The study was carried out at Fazenda São Judas Tadeu, in the municipalities of Porto Nacional and Brejinho de Nazaré, Tocantins - Brazil. In each physiognomy we sampled the vegetation of 15 plots (10x5m) burned annually and 5 plots without records of burnings in the last 3 years. We evaluated the annual changes in the abundance of individuals and the richness and composition of species. We showed, using a rarefaction technique, that the species richness was higher in the burned plots, both in the Cerrado Typical and in the Cerrado Ralo. In the Typical Cerrado we noticed a trend towards greater floristic similarities between the control plots (MNDS), but this was not evidenced for the Cerrado Ralo. In dominance, the species with the greatest number in the control plots differed from those found in the fire groups, for the two Cerrado areas. We conclude that, even in conditions of high frequency of fire, the typical Cerrado retains the richness and composition of species, but in Cerrado Ralo this high frequency led to changes in these parameters.