Short-term variations and long-term changes in oak productivity in northeastern France. The role of climate and atmospheric CO2

International audienc

Le rôle clé des déficits hydriques dans le dépérissement de chênaies en Forêt de la Harth (Alsace du Sud) établi par une analyse dendroécologique et écophysiologique

National audienceThe 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

Confirmation du rôle important des facteurs prédisposants lors du dépérissement des chênes en forêt de Haguenau par une étude dendrochronologique

National audienceThe quantification of radial growth losses and an analysis of the causes and mechanisms of oak decline in the Haguenau forest (Alsace, northeastern France) were made based on a dendroecological analysis of 450 trees. Comparison between defoliated and non-defoliated trees proved the substantial negative impact of defoliation by Lymantria dispar L. on radial growth (39 % loss on average). These losses were entirely due to a decrease in latewood width while earlywood remained constant, suggesting the triggering role of winter carbon storage in tree mortality. The trees which died during this decline showed significantly lower levels of growth since the beginning of the XXth century than survivors. Among the factors explaining these susceptibility differences, soil variation appeared to play an important role in Quercus robur decline