Jamir Afonso do Prado Júnior

Mortality, recruitment and growth of the tree communities in three forest formations at the Panga Ecological Station over ten years (1997-2007)

ABSTRACT The area evaluated in this study was a continuous stretch comprising three vegetation formations: gallery forest, semi-deciduous seasonal forest and cerradao (woodland savanna). The aim of this study was to examine the tree community dynamics in a forest gradient—from gallery forest to cerradao —at Panga Ecological Station, in the city of Uberlandia, located in the state of Minas Gerais, Brazil. The study was based on data from a previous inventory of the continuous forest conducted in 211 permanent 10 × 10 m sample plots in eight parallel transect running perpendicular to Panga Creek. Trees with a diameter at breast height ≥ 4.77 cm were sampled in 1997, 2002 and 2007. With the exception of the cerradao , there was a net reduction in tree density over the studied period of ten years, because mortality rates were higher than the recruitment rates. The basal area in creased during the period of the study, especially at cerradao . The mean mortality rate in the studied area was 2.64%.yr

Plastic responses in tree architecture and specific leaf area of Xylopia aromatica (Annonaceae): adaptations to environments with different light intensities

The capacity of plants to occupy different environments is made possible by the plastic responses they present in heterogeneous environments. Light directly influences the plastic responses of plant functional traits, mainly involving leaf traits (specific leaf area and leaf dry matter content). Our objective was therefore to evaluate the phenotypic plasticity of Xylopia aromatica, a heliophilous species occurring in two physiognomies: cerrado sensu stricto (savanna—high light intensity environment) and Cerradão (woodland savanna—shaded environment). It is expected that trees growing in Cerradão will present adaptations that reduce self-shading and optimize their photosynthetic capacity. We sampled 40 trees (20 in each physiognomy) and collected seven parameters of tree architecture and specific leaf area (SLA) of these individuals. We found that in Cerradão, a closed and shaded physiognomy, X. aromatica showed significantly more cylindrical trunks, greater overall height, first branch height and SLA, and a lower crown length ratio. This differentiation can be defined as a plastic phenomenon, likely related to the higher efficiency of light interception and absorbance by trees and beyond to reduce self-shading in Cerradão. The plastic response of X. aromatica showed in this study is potentially a strong explanation for the adaptive success of cerrado plant species in different environments.

Water Availability Drives Gradients of Tree Diversity, Structure and Functional Traits in the Atlantic-Cerrado-Caatinga Transition, Brazil

Aims Climate and soil are among the most important factors determining variation in tree communities, but their effects have not been thoroughly elucidated to date for many vegetation features. In this study, we evaluate how climate and soil gradients affect gradients of vegetation composition, species diversity and dominance, structure and functional traits (seed mass and wood density) using over 327 000 trees in 158 sites distributed along environmental gradients in the transitions among the Atlantic forest, Cerrado and Caatinga in Minas Gerais State (MG), Brazil (nearly 600 000 km 2). Methods Gradients in species, genus and family abundance in addition to basal area, stem density, species diversity (Fishers alpha), dominance percentage, seed mass and wood density were correlated using multiple regressions with environmental variables, as summarized in four principal component analysis axes (two climatic - precipitation seasonality and temperature range - and two edaphic - soil fertility and soil moisture). Additionally, ordinary kriging maps were used to better illustrate the gradients. Important Findings Multiple regression models indicate that all variables but dominance percentage were affected by one or more of the environmental gradients, but the average R 2 was low (26.25%). Kriging maps reinforced the patterns observed in the regression models. Precipitation seasonality and soil moisture gradients were the most important gradients affecting vegetation features. This finding suggests that water availability is an important determinant of vegetation features in these vegetation transitions.