Crescimento de Vochysia thyrsoidea Pohl (Vochysiaceae) em resposta às condições ambientais do cerrado rupestre

Abstract

Seasonal dry areas have limiting conditions, especially the water availability which may cause alterations in the growth pattern of plants. Tree species, since they have a longer life cycle, tend to show different strategies in the resource allocation, growth investment, and the capacity of losing modules in front of environmental conditions, indicating the success of individuals and populations along the time. Considering that, is important to monitorate the growth of these plants under natural conditions in order to understand the stability in relation to environmental fluctuations. Among the tree species that occupy rocky cerrado in the Alto do Rio Grande Basin, south of Minas Gerais, Vochysia thyrsoidea Pohl (Vochysiaceae) is an evergreen species which is a subject of research of the Plant Ecophysiology Laboratory at Federal University of Lavras, in two areas since 2013. Studies in these rocky cerrado areas show a continuous growth pattern even during periods of restricted water availability. However, to evaluate the success of these individuals under field conditions, a long-term monitoring is needed. Thus, this research is able to fill some gaps about environmental factors responsible for control of V. thyrsoidea in rocky cerrado areas. The growth was assessed using evaluations of radial increase, height, leaf demography, expansion and mortality of branches, water potential, chlorophyll index, and activity of antioxidant enzymes in two subpopulations of V. thyrsoidea, placed at Parque Ecológico Quedas do Rio Bonito (PEQRB), Lavras, MG and at Reserva Biológica Unilavras-Boqueirão, Ingaí, MG. In this scenario, we tested the hypothesis that V. thyrsoidea is an isohydric species and there are environmental differences between the two studied areas, as incident radiation, that may influence the growth of this species. Individuals maximize their growth by maintaining the water potential. Besides the difference in the orientation of the side of the relief slopes between the two areas, growth trend was similar between the subpopulations. However, individuals at PEQRB showed the highest increment at the end of the experimental period that was favored by the orientation to the east side, allowing the use of the best incident radiation in the carbon assimilation, during the morning. Furthermore, the two subpopulations optimized the radial increase during warmer and sunnier periods. On the other hand, the maximum of leaf production occurred during the cold months, with less radiation. Thus, this strategic aptitude in the resource allocation associated with the maintenance of the water potential is determinant of the success of V. thyrsoidea in rocky cerrado.