Wood-growth zones in Acacia seyal Delile in the Keita Valley, Niger: Is there any climatic signal?

Acacia trees are a key element in Sahelian semiarid ecosystems, being some of the few tree species surviving in such extreme environments. Understanding their growth dynamics represents a fundamental step to improve forest sustainable management. Dendroclimatology, the study of tree rings and their relationships with climate, could help in understanding how changing climatic conditions may impact these ecosystems. We studied Acacia seyal Delile trees growth in Keita Valley, in the Sahelian zone of Niger. Wood from 8 trees of known age was sampled to study the relationships between growth zones, i.e. ring patterns, and climatic conditions. We present herein, a study based on cross sections instead of cores. Wood-anatomical and dendrochronological analyses enabled us to evaluate the relationships between age and ring formation, and to confirm that one tree ring for rainy season is formed. Moreover, surprisingly for a species growing at such latitudes, acacia tree rings have a climatic signal, mainly due to the precipitation falling during the rainy season but also influenced by the average seasonal temperature.