Dating branch growth units in a tropical tree using morphological and anatomical markers: the case of Parkia velutina Benoist (Mimosoïdeae)

Abstract

In tropical areas, studies based on the retrospective analysis of tree development have focused principally on growth ring research. The interpretation of primary growth markers is overlooked although it opens perspectives to provide long time-series on tree-crown development. This study focused on Parkia velutina, an emergent tree of neotropical rain forests. Our objectives were (1) to characterize the phenological cycle of this species, and (2) to identify temporally interpretable morphological and anatomical markers. We collected dominant branches in 14 adult trees and identified growth markers that limit longitudinal and radial increments. We coupled this approach with a 2-year phenological survey of 20 trees. Leaf shedding, growth unit elongation and growth ring formation define the phenological cycle. At tree scale, this cycle is synchronous and affects all axes. At population scale, trees can be desynchronized. This cycle is annual despite some slight variability. Successive growth units and growth rings are easily identifiable. Dating a branch by counting the number of growth units or growth rings is possible in many years with a reasonable error. Nevertheless, estimating their precise month of formation in order to study climatic influences remains difficult.