Bark composition changes along the trunk of three softwood species: Picea abies, Abies alba Mill. and Pseudotsuga menziesii

Abstract

ABSTRACT In the context of global warning, sustainable development, bioeconomy and circular economy, it is of great interest to find better valorizations of by-products of the wood processing industry. The aims of this study were to investigate the effects of the longitudinal position on the stem and of the silviculture on bark chemical composition of three softwood species used in wood industry. Bark was sampled at three different heights (top, middle and bottom) on the trunk of four trees of Picea abies, Abies alba and Pseudotsuga menziesii grown under different silvicultural treatments and subjected to analytical procedures to determine holocellulose, lignin, suberin, hemicelluloses, α-cellulose, ash and extractives contents. Contents of the different polymers tend in general to decrease slightly with tree height, while extractives content increased with height. These results were explained by higher amount of outer bark at the bottom of the trunk containing more polymerized materials and more unpolymerized free sugars in the young tissues at the top of trunk. The effect of the silvicultural treatment has been more difficult to characterize. Chemical composition of the bark differs slightly according to the position of sampling along the trunk. Suberin content is particularly important at the bottom of P. menziesii trees.