Climate-tree-growth relationships of Quercus petraea Mill. stand in the Forest of Bercé ("Futaie des Clos", Sarthe, France)

Abstract

The past history of a 300-year-old Quercus petraea stand (the "Futaie des Clos", 8 ha) located 20 km from the town of Le Mans in the Forest of Bercé in the western part of France (Sarthe) was analysed by a dendroecological approach. According to the number of healthy trees alive (> 400), the stand age (> 300 years), and the dimensions of the trees (dia: 92 cm; height: 45.2 m), this plot constitutes one of the most remarkable oak grove in France. High competition pressure between trees appeared to be the most important factor to explain the high-quality timber (high straight stems without wood defaults, narrow regular rings). After an initial 90-year period of decrease, this stand shows a 1 mm·year-1 growth increment from the 1810s to the present. The growth increase of 40-50% occurring for over than 20 years can be interpreted as a response to the increase of harvesting intensity. The influence of climate was evaluated by comparing earlywood, latewood and total ring indices with monthly climatic data collected at Le Mans over the period 1921-2001. Extreme growth years coincided with wet or dry springs (May-June) (± 40% of rainfall in relation to normal conditions) often associated with warm or fresh July. The climatic models accounted for between 18 and 26% of the variability of ring widths, and suggested that earlywood formation depended mainly on previous autumn hydric balance and winter temperature whereas the growth of the latewood band was maximum in early spring (positive effect of May hydric balance). The ecophysiological interpretations of the climatic correlations are discussed.