Analyse de la structure morphologique des cernes de Croissance et détermination des âges de deux espèces sahéliennes : Acacia Tortilis (Forsk.) Hayne Ssp. Raddiana (Savi) Brenan, Acacia Senegal (L.) Willd

Abstract

Knowledge of the dendrochonology of Sahelian species is very limited. However, dendrochronology may be a way of furthering the knowledge of the growth dynamics the African dry area species. The purpose of the study was to better understand the anatomical structure of the tress rings of the Sahelian species in order to determine the age and estimation of trees and shrubs. It was conducted out in the Ferlo, an area located in the north of Senegal, and focused on 14 and 12 wood slices of Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan and from Acacia senegal (L.) Willd respectively. Identification and dating methods were used to study the morpho-anatomical structure of the ring and determine the age of individuals. The rings were identified and very high-resolution (1200 dpi) pictures taken with a Leica (M80) binocular magnifier equipped with a digital camera. Then the pictures were assembled with the Adobe Photoshop software.The results showed that both species had distinct growth rings with parenchymal cells. Significant correlations between 0.33 and 0.82 was then calculated between the radii of the same individual. Estimated ages of the Acacia raddiana ranged from 10 to 27 years, whereas the Acacia senegal seemed older white 13 to 35 years of age. The difficulty to read the rings of the Acacias is related to the anatomical structure of the wood because boundaries between dark circles are often hidden by parenchyma clusters. The study helps put in place strategies and methods which enable to control the growth dynamics of the species in order to valorize them.