EFFECTS OF FIRES ON THE STRUCTURE OF THE UNDERGROWTH IN A TEMPERATE ECOSYSTEM

Abstract

Fire is a natural factor that exerts a significant influence on the composition of the vegetation that grows under the canopy. There are few studies characterizing the structure and assessing the consequences of the modification in the undergrowth as a consequence of fires in the mixed ecosystems of northeast Mexico. The purpose of this research was to analyze the density, canopy coverage, wealth, and α and β diversity of this stratum in areas with different succession stages in a pine-holm oak forest in the northeast of the country. Three areas were selected; two, according to the year in which the disturbance occurred, and third one, by way of reference: 1 (2006), 2 (1998) and 3 (mature forest, control). And in 2009, forty 1 m2 sampling sites were established in each location; the results show that the canopy coverage (F= 7.593, P= 0.001), the specific wealth (F= 2.818, P= 0.064) and diversity (F= 2.516, P= 0.085) of the assessed vegetation are significantly larger in the first stages of the succession and that they decrease with time; there is a statistical equality regarding their density ; furthermore, the different stages show significant differences in the composition (β diversity), since in every case there was less than 50% similarity.