Crescimento radial e resposta ecofisiológica de Vochysia thyrsoidea (Pohl.) às condições ambientais do cerrado rupestre

Abstract

The Alto do Rio Grande is a region of the Rio Grande Basin, located in southern Minas Gerais, Southeast Brazil. In this area the vegetation is composed by remnants of the Cerrado and Atlantic Forest formations. The landscape is highly fragmented due to the large concentration of agrosilvopastoral properties. Among the Cerrado vegetation remaining in this region, the rocky formations have important floristic diversity besides the environmental limiting conditions that includes the low availability of water associated with high solar radiation, the high aluminum concentration in the soil and wildfires. Among the species living in those areas the Vochysia thyrsoidea is highlighted for its high capacity for adjustment in this adverse habitat. Our objective was to observe the growth patterns of the V. thyrsoidea in two different areas of rocky Cerrado situated in two conservation units: Parque Ecológico Quedas do Rio Bonito and Reserva Biológica Unilavras-Boqueirão. In 2013 we evaluated the radial growth by dendrometric bands, the growth in height and of the lateral branches, the phenology and the physiological characteristics of 60 plants from each area, divided into 30 small individuals (< 1.70 m and DSH < 3 cm) and 30 tall individuals (> 2.50 m and DBH ≥ 5 cm). The environmental characterization of the areas was evaluated and the relative content of water in the soil was determined in order to understand the relations between growth and water availability. It was observed that the radial growth decreases in situations of intense water deficit, with the reduction of stomatal conductance rates and, consequently, of net photosynthesis. However, this decrease is recovered shortly after, when the soil water availability increases. These morphophysiological strategies reinforce the idea that the Vochysia thyrsoidea is an excellent model for eco-physiological studies aiming at verifying plant plasticity in adverse environmental conditions for woody species of the Cerrado, over time, by means of growth patterns.