UNDERGROWTH DIVERSITY AND SOLAR RADIATION IN A Pinus hartwegii Lindl. FOREST WITH PRESCRIBED BURNING

Abstract

Pinus hartwegii forests are favored when they have the right fire regimes, but when this does not happen, the use of prescribed burnings is an option to correct them, which makes the study of fire ecology a relevant matter in this context. In the particular case of Distrito Federal, forests provide environmental services to the people who live at the southern part. Therefore, over a hillside of Ajusco volcano, three plots with prescribed burnings of low intensity (flame length <1 m, propagation speed 3 m min-1), and three plots without burning as control were established at a completely random experimental design (3.6 ha per plot in average). A year later, data from the undergrowth were taken to determine species richness, Shannon-Wiener and Simpson diversity indexes as well as the importance values. The multivariate and univariate analyses of variance revealed an increment in the richness and diversity of species in the burned plots. Muhlenbergia quadridentata increased its density and dominance below greater radiation, but Penstemon gentianoides reduced the latter when radiation was higher, which might be related to a greater moisture in partially shadowed sites. Diversity becomes more important when competition with grasses gets lower, as they dominate the not-burned locations.