Black spruce trees from uneven-aged, old-growth stands produce more dimensionally stable wood than trees from fire-origin even-aged stands
WOOD SCIENCE AND TECHNOLOGY(2021)
Abstract
In the eastern Canadian boreal forest, long fire return intervals lead to over 60% of stands having an irregular, uneven-aged structure, which is associated with slower growth. The aim of this study was to evaluate the effect of stand structure on the dimensional stability of black spruce wood [ Picea mariana (Mill.) B.S.P.]. Sixty trees were sampled from stands with regular and irregular structures from the North Shore region of Quebec, Canada. Nonlinear mixed-effect models were developed for each stand structure to describe the variation in two indicators of dimensional stability, the differential volumetric shrinkage ratio ( G V ) and the dimensional hygroexpansion coefficient ( R -ratio), in small defect-free wood samples as functions of cambial age and annual ring width. G V and R -ratio were strongly related to cambial age, but there was a limited effect of ring width. After accounting for these variables, samples from stands of irregular structure had greater dimensional stability than those from stands with a regular structure, although G V and R -ratio differences were more pronounced in the upper stem compared with breast height. The fixed effects of the models explained between 44 and 60% of the variation in G V , and between 7 and 44% of the variation in R -ratio. A higher presence of mild reaction wood or lower within-ring variation in wood density in trees of layer origin from irregular stands may explain the observed differences between stand structures.
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Key words
black spruce trees,dimensionally stable wood,uneven-aged,old-growth,fire-origin
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