Ecologia e clima na formação do lenho de Myrocarpus frondosus Allemão em formações secundárias da floresta estacional decidual

Abstract

With the increasing spread of secondary forests around the world, the development of management strategies aiming at the enhancement of these formations and their species is a way to contribute to their conservation, thereby ensuring the maintenance and progress of the numerous ecosystemic and economic benefits they offer. Additionally, secondary forests are potentially more vulnerable to environmental shifts, especially climate changes, impacting their ability to recover and thrive. This underscores the critical need to deeply understand the interplay of dynamics and ecology within these communities. In light of this, the aim of the present study was to investigate the ecological and climatic factors associated with wood formation in Myrocarpus frondosus, a notable species found in secondary habitats of the Seasonal Deciduous Forest (FED) in the southern region of Brazil. This research is structured into four comprehensive chapters: In Chapter I, we sought to investigate the dendrochronological potential of M. frondosus and to characterize the growth pattern of the species in two FED fragments under varying status of secondary forest recovery. For this purpose, wood samples were collected from 110 trees of the species (using a non-destructive method), allowing for the retrieval of tree-ring widths. In this study, we applied traditional dendrochronological methods to standardize the increment series and generate an average chronology, which reflected common signals shared among trees at each site. In Chapter II, based on a generalized additive model (GAM) constructed as a distributed lag model, we were able to jointly consider inter-annual and inter-tree variations to assess climate-sensitivity in tree-ring width time series of M. frondosus. Parsimoniously considering current and time-lagged climate variables, our results demonstrate that, for a subtropical region, both precipitation and temperature are strong drivers of the species’ radial growth, and raise concerns about its sensibility: An interaction effect between the regressor variables revealed a likely water stress scenario arising from warm and dry summer conditions. Additionally, lack of winter chilling, during the trees’ dormancy period, also proved detrimental to the development, with legacy effects on growth for up to two subsequent years. In Chapter III, we shifted our focus to an intra-annual scale, to assess xylem developmen and species' phenological patterns. By setting up dendrometers and conducting monthly observations of both vegetative and reproductive phenophases for 24 months, we were able to confirm the seasonality of M. frondosus growth throughout the year in the region, with pronounced peaks of intensity in March and April, closely align with the foliage patterns of its canopy (vegetative phenophases). Finally, in Chapter 4, variations in the heartwood and sapwood content of M. frondosus trees were studied, based on color differentiation. Size, growth, competition, and vigor variables were assessed to investigate whether and how these conditions might influence heartwood-sapwood patterns in the wood. The diameter at breast height (dbh) was identified as an important predictor for heartwood content, however, this variable falls short in stratifying additional variations between the two secondary forest sites assessed. In this regard, evaluations of crown vigor, reflecting the tree's activity over recent years, provided further insights into this dynamic.