Tree rings chemical content fluctuations between acids and calcareous soils of Fagus sylvatica L. stands measured by X-ray microanalysis
Résumé
Differences in mineral nutrients content in beech (Fagus sylvatica L.) tree rings in the HNE network (Beech stands of north-eastern France) have been evaluated on two soils types. Six stands are located on acids soils and six others are located on calcareous soils. Three dominant trees have been cored in each stand. The chemical measurements have been made in the earlywood (12 stands, 3 trees by stand, one core per tree and two periods by core corresponding to ten rings in heartwood and ten rings in sapwood). The microanalysis of mineral nutrients concentration in tree rings have been measured with an energy dispersive spectrometer (EDS) coupled with a low vacuum scanning electron microscope. We found differences between calcareous and acid stands in tree rings element concentration. Calcareous stands have typically high calcium and low manganese concentration in tree rings in comparison to acid stands. These differences are mostly representative of the nutrient richness of the soil and especially saturation rate and soil upper horizon pH. We also undertook to measure element concentration in the bark. It appears that differences in elements concentrations are greater when considering the bark compared to the wood. These results point out the ability of SEM/EDS method to measure differences in two soils type differing in acidity status. We showed that tree nutrient status is reflected in wood and to a better extend when considering the bark only. Bark seems to have a high potential to be used as a tree nutritional status diagnostic