Tree growth performance and xylem functional arrangements of Macrolobium Schreb. (Fabaceae) in different wetland forests in the Central Amazon basin

Tree growth is influenced by a combination of genetic, ontogenetic, physiological and morphological responses to environmental factors. However, the challenge still is to identify the trigger of tree growth and different combinations of functional traits that make the same genus develop to adapt or survive in different environments. To fill this gap, functional characteristics related to anatomy, structure and growth of wood were selected, and the diameter increment rate and monthly phenology were monitored to discover the rhythm and period of growth of a congeneric pair of Macrolobium Schreb. (M. duckeanum and M. bifolium) in different wetland ecosystems (white-sand ecosystem and black-water floodplain forest) of the Central Amazon. Hydrological, climatic and edaphic data were used to characterize the wetland habitats. The results indicate that the growth period and rhythm of congeneric Macrolobium species differ in response to limiting environmental conditions. The rhythm was influenced by the water deficit in the white-sand ecosystem, while it was controlled by anoxic conditions (flooding) in the black-water floodplain forest. The trees developed different functional strategies to deal with the specific environmental conditions of each wetland, indicating an enormous functional diversity of this genus to adjust to environmental variations and changes.