Long-term changes in wood density and radial growth of Quercus petraea Liebl. in northern France since the middle of the nineteenth century |
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Authors: | Laurent Bergès Jean-Luc Dupouey Alain Franc |
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Institution: | Unité de Recherches et d'Expertises Ecosystèmes Forestiers et Paysages, Cemagref, Domaine des Barres, 45290 Nogent-sur-Vernisson, France, Unité d'Ecophysiologie Forestière, Equipe Phytoécologie, INRA, 54280 Champenoux, France, Département Mathématiques Appliquées et Informatique, ENGREF, 19 Avenue du Maine, 75732 Paris Cedex 15, France,
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Abstract: | Long-term changes in sessile oak (Quercus petraea Liebl.) growth and wood density were studied using cores collected from 99 even-aged high forest stands between 56 and 187 years old, located in northeastern and north-central France. Growth and density trends were tested by analysis of variance and covariance. Two models were applied to two samples, sample A and sample B (sample B being a sub-sample with limited cambial age and calendar date ranges). Model 1 showed a significant increase in radial growth: +35%, +87% and +66% in earlywood width, latewood width and ring width, respectively, from 1811 to 1993 for sample A. Consequently, there was a positive trend in latewood ratio (+14%). A slight decrease in wood density was found: -3.3% and -5.4% for earlywood and latewood density, respectively. Despite an increase in latewood percentage, mean ring density showed a -2.0% decrease. Model 1 applied to a biomass indicator (density2ring width) showed a 62% increase from 10.4 to 16.8 kg m-3 between 1811 and 1993 for sample A. Results for sample B were slightly different: the increase in latewood ratio was not detected. Model 2 showed a change with time in the positive hyperbolic relationship between mean density and ring width. The results are discussed. The decrease in wood density cannot be explained by N atmospheric deposition or by long-term changes in average temperature. Increasing atmospheric CO2 levels cannot be invoked owing to the present lack of studies. Finally, hypotheses concerning long-term changes in wood anatomical characteristics are proposed. |
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