Diferenças de brotamento foliar entre plantas juvenis e adultas em espécies de caatinga com madeiras de densidades contrastantes.

Abstract

In seasonal temperate forests early budding juvenile plants have been documented in species that have adaptive benefits of the shading escape and herbivory currents this behavior. In tropical seasonal forests, the same was not observed, but the intense herbivory and shading in the rainy season are limiting factors that could be overcome with early budding. Due to water restriction to early budding, this behavior is expected in species that have forms of reserve water. Thus, it was assumed that young plants would be subject to shading comparable to other regions where light is limiting, and those species that have the capacity to store water sprout in advance, responding to different phenological triggers of adult plants. To check these ideas, we studied the light environment, leaf phenology and its relationship with meteorological variables of twenty adults and twenty juvenile Cochlospermun vitifolium (low wood density) and Poincianella bracteosa (high wood density) in a seasonal tropical forest. Hemispherical photos were taken at the level of juvenile plants and canopy opening average was compared to other types of vegetation. The budding and leaf expansion were followed for ten weeks in the transition between the dry and rainy season, the differences in average dates on which each individual presented each phenophase were tested and correlation tests were performed with meteorological variables. The opening canopy varied widely during the dry and rainy season and the rainy season shading is comparable to other areas where light is limiting. Both species sprouted during the dry season, with individuals of C. vitifolium sprouting before and asynchrony in the leaf budding between classes was identified only in juvenile individuals of P. bracteosa. There were no differences in the average date of leaf expansion between adults and juveniles of both species, and C. vitifolium took longer to expand its leaves. Juvenile P. bracteosa demonstrate possible shading escape, which does not occur for C. vitifolium because both classes are early. The mechanisms that make it possible to dry the budding by P. bracteosa are unclear and need to be investigated.