GROWTH-RATE EFFECTS ON CORRELATIONS AMONG RING WIDTH, WOOD DENSITY, AND MEAN TRACHEID LENGTH IN NORWAY SPRUCE (PICEA-ABIES)

The main hypothesis tested in this paper is whether heavy thinnings af fect the correlations among ring width, wood density, and mean trachei d length. Within-tree correlations were calculated between time series of yearly measurements. Among-tree correlations were computed (1) bet ween averages over a growing period and (2) year by year. Correlations were analyzed on 20 fast-grown and 20 slow-grown Norway spruces (Pice a abies (L.) Karst.) from an even-aged, plantation-grown stand near Re ndeux, Belgian Ardennes. In the within-tree approach, fast-grown spruc es showed a stronger negative correlation between ring width and fiber length. In among-tree approach 1, the widely held negative correlatio n between ring width and wood density vanished when the spruce growth rate was above 2.2 cm/year in circumference. Among-tree approach 2 dem onstrated that the magnitude and sign of the correlations also depende d on the year; a few years showed a significant correlation between ri ng width and wood density for the fast-grown Norway spruces, whereas t he correlation was systematically negative and significant on many yea rs for the slow-grown spruces. This study may explain part of the cont radictory results reported in the literature concerning hypotheses sim ilar to ours.