Climate-tree-growth relationships of European beech (Fagus sylvatica L.) in the French Permanent Plot Network (RENECOFOR)

The influence of climate on the radial growth of Fagus sylvatica was investigated using 15 chronologies developed from mature stands of the French Permanent Plot Network (RENECOFOR) growing under different climatic and soil conditions. The relationships between climate and ring widths were analyzed using extreme growth years, simple correlations and response functions analysis. Monthly climatic regressors were derived by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. The three most frequent negative pointer years (1959, 1989, 1976) result from a particularly intense and durable drought, whereas positive years (1977, 1958) coincide with wet conditions. The total ring chronology variance attributable to climate averages 34.1% (15.8% –57%). Current early-summer soil water deficit enters in 10 models and the deficit in June explains alone a large part of the radial growth variability (mean value: 26.6%). Temperature or soil water deficit for the other months and weather conditions during the previous season were of little consistency across stands. The response pattern of earlywood is very similar and the percentage of variance explained is higher (16.2% –57.8%). Latewood widths present a different response pattern. High minimum temperature in August and/or September often favour wide latewood widths and monthly water deficits play a secondary role. The percentage of variance explained ranges from 8.8% to 67.4%. Soil water capacity strongly modulates ring characteristics and climate-growth relationships. Mean sensitivity, expressed population signal, signal-to-noise ratio and the strength of growth-climate correlations increase with decreasing soil water capacity.