The taxonomic status of oak species on 70 plots selected from the 134 plots of the Harth Forest Ecological Observation Areawas identified using leaf morphological analysis. About 40 % of teh studied trees were pedunculate oaks (Quercus Robur), the other trees being mainly sessile oaks (Quercus petraea). A strong reduction of radial growth has been pointed out in recent years throught a dendroecological study, this decline being stronger for pedunculate oaks. Both a restricting pedoclimat(shallow and stony soils) and a hight leaf area index (old coppice with standards) are responsible dor severe and frequent droughts. Reduction of radial growth has been clearly related to water shortage as computed from a daily soil water balance model.