Potential of dendrochronology to assess annual rates of biomass productivity in savanna trees of West Africa.

摘要

We examined the potential of dendrochronology to assess biomass productivity of individual savanna species from a semi-arid ecosystem in southern Senegal. The 9 tree species examined in this dendrochronologial study included: Acacia macrostachya, Acacia seyal, Balanites aegyptiaca, Combretum glutinosum, Cordyla pinnata, Pterocarpus erinaceus, Terminalia macroptera, Daniellia oliveri, and Combretum nigricans. Dendrochronologial analyses were applied on cross-sectional disks obtained from the tree stem to reconstruct past tree growth (diameter and biomass) histories. Despite challenges with discerning annual tree rings in these savanna species (associated with ring suppression, wedging, indistinct ring boundaries, and fires), tree species (A. macrostachya, A. seyal, and T. macroptera) with the highest dendrochronology potential produced a clear thin band of marginal parenchyma. A. macrostachya had rapid annual diameter and biomass growth increments in the juvenile years (ages 1-10), compared to T. macroptera which showed greater growth past this early juvenile period. Given the same species, generally wetter forests had lower annual and cumulative growth rates that were likely due to increased inter-tree and tree-grass competition for soil moisture in the wetter forests. We concluded that dendrochronology is well suited for retrospective annual biomass assessment in savanna trees of Senegal, West Africa.