Original article

Decreasing trend and fluctuations in the mean ring density of Norway spruce through the twentieth century

¹ AgroParisTech, ENGREF, UMR 1092 Laboratoire d’Étude des Ressources Forêt Bois (LERFoB), 14 rue Girardet, 54000 Nancy, France
² INRA, Centre de Nancy, UMR 1092 Laboratoire d’Étude des Ressources Foret Bois (LERFoB), 54280 Champenoux, France
³ Inventaire Forestier National, Direction Technique, Château des Barres, 45290 Nogent-sur-Vernisson, France

^* Corresponding author: leban@nancy.inra.fr

Received: 13 July 2010
Accepted: 22 July 2010

Abstract

• Studies on wood density variations are necessary for estimating the forest carbon pool. Further, they can help predict the technological properties of wooden end-products. While there have been frequent reports on the relationships between wood density, cambial age, and ring width, there is little information about the historical trend in wood density for the last century, particularly in the context of global climate change.

• In this study, different sources of variations in mean ring density (site, tree, ring age, ring width, and calendar date) were studied using an original sampling design. A total of 105 Norway spruce (Picea abies Karst.) trees were sampled in north-eastern France, from thirteen sites with trees of different ages growing at the same site and in similar conditions. X-ray densitometry measurements were performed on samples taken at breast height. The chronology of the mean ring density over the 20th century was estimated by using a statistical modelling approach based on linear mixed-effects models after accounting for the effect on the mean ring density introduced by different ring widths, cambial ages, sites, and trees.

• The mean ring density of Norway spruce was seen to decrease by about 18 kg m^-3 relative to the year 1900. The chronology showed no evolution between 1900 and 1950, a steep decline from 1950 to 1980 (reaching a maximum decrease of 30 kg m^-3), followed by an increase from 1980 to 2000.

• The observed decrease was consistent with the results of previous works and supports the hypothesis that this could indicate a global trend and that this trend is independent of the wood structure. Moreover, high inter-annual density variations were found. In future studies, the influence of climate on the wood density and within-ring properties must be clarified to identify the anatomic causes for wood density variations.