Impact of Tree Age and Size on Selected Properties of Black Locust (Robinia pseudoacacia L.) Wood

Szymon Bijak,Hubert Lachowicz

doi:10.3390/f12050634

Abstract

Black locust (Robinia pseudoacacia L.) is a non-native tree species that occupies a remarkable area in the forests of western Poland. It is mainly cultivated for the bee-keeping purposes as well as for its high quality wood. We investigated the impact of tree age and diameter on the selected structural, physical and mechanical attributes of wood of black locust that grows in conditions of mesic oligotrophic site. We analysed 200 samples originating from 18 trees that varied with age (38, 60 and 71 years old) and diameter (thin, medium and thick specimen selected according to Hartig’s method). Individual wood properties were determined along with corresponding European or Polish standards. Structural and mechanical attributes were determined for moisture of 12%. We found significant impact of tree age on tree-ring width, latewood proportion, density, oven-dry density, basic density, share of woody substance, porosity, as well as radial, tangential, longitudinal and volumetric shrinkage, compression strength parallel to grain, static bending, coefficient of compression strength parallel to grain and coefficient of static bending. The older the trees, the higher values of individual attributes were observed. In turn, the effect of tree diameter was less profound and no significant impact of that feature was found for latewood proportion, anisotropy and almost all of the shrinkage parameters. Thin trees exhibited the lowest values of the analysed parameters, while medium ones—the highest. In general, the highest technical quality of the investigated wood can be found in the youngest trees, whose wood characterises with the properties significantly exceeding native Polish tree species such as oak or beech.

Highlights

European forests have been influenced by the human activity for a long time experiencing various forms of utilisation as well as alteration of their shape, organisation and structure [1]
We found in general significant effect of age on investigated structural, physical and mechanical properties of black locust wood, while tree size was of lesser importance
This study analysed the impact of tree age or size on the selected structural, physical and mechanical properties of wood of black locust growing in greater abundance in western Poland

Summary

Introduction

European forests have been influenced by the human activity for a long time experiencing various forms of utilisation as well as alteration of their shape, organisation and structure [1]. 145 non-native tree species introduced to the forests of Europe and almost half of them originate from North America [3]. (Fabaceae)), that originates from the eastern part of North America, namely the Appalachian Mountains and the Ozark Plateau, was introduced to Europe by Jean Robin as early as 1601, as one of the first over-seas tree species [4,5,6]. Used as a park or garden tree, the species was extensively brought into the cultivation in European forests in mid-1700s and 1800s. Further on, it was widely applied in windbreaks and shelterbelts or as a nitrogen-fixing species for land reclamation

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