In the context of forest dieback on acid soils, low chemical soil fertility is thought to be a major predisposing factor, whereas water stress is classified as a factor triggering large scale forest decline. The objective of this research is to test whether tree reactivity to water stress depends on chemical soil fertility. Dendrochronological series from amended and non treated stands (Picea abies (L.) Karst.; Fagus sylvatica L.) will be compared to analyse (i) the impacts of fertilizer application and climatic parameters on radial increment, (ii) as well as the interactions between climatic events and mineral amendments applications.