The relationship between chemical composition and mechanical strength in the wood of English ash (Fraxinus excelsior Linn.)

Abstract

IN the great majority of woods which have been investigated there is a strong correlation between specific gravity and certain mechanical characteristics. As a rule the higher the specific gravity the stronger the wood, although it is known that, in any single species, wide variations in strength may occur throughout a range of matched specimens ofequal specific gravity. These latter variations have been ascribed [Clarke, 1935;1936] to concomitant variations in the chemical composition of the wood cell walls which at the present time are not fully understood. Despite its obvious importance the relationship between chemical composition and strength in woody plants has hitherto received comparatively little attention. Dadswell & Hawley [1929] observed a higher cellulose content in tough white oak than in a single brash specimen of the same species, and Uno [1932] concluded that the strength of various species of bamboo increases with increasing cellulose content. The investigation by Luxford [1931] of the influence of minor components or extractives on the strength of wood will be referred to later.The object of the present study was in the first instance to determine whether the chemical composition of ash wood varies within a single tree as well as from tree to tree in a single locality, and in the second instance to attempt to correlate chemical composition with strength figures already obtained for the same material [Armstrong, 1936].EXPERIMENTAL. A 2-ft. bolt was cut at the same height from the ground from each of six representative English ash trees (Fraxinus excelsior) obtained from Holkham, Norfolk. Each bolt was sawn into two discs measuring 15 and 9 in. in diameter respectively and the pairs of discs were marked out on the transverse surfaces exposed by the common cross-cuts into the following concentric zones.A. Sapwood containing starch. B, C. Intermediate zones containing small amounts of starch decreasing from B to C. D. Heartwood containing no starch. The 15-in. discs being reserved for mechanical tests [Armstrong, 1936] each 9-in. disc was sawn into the respective zones which, after air-drying, were separately converted into sawdust. The 80-100 mesh material was analysed according to the method of Schorger [1926] except that the digestion with 72 % sulphuric acid in the lignin determinations was carried out at 10 + 0.50 using 12-5 ml. of acid per 2 g. sample of air-dry wood flour (Table I).

Biological Flora of the British Isles: Fraxinus excelsior

“…Ash wood, in common with other ring‐porous trees, contains tyloses to seal off embolized vessels (Schmitt, Richter & Muche ). Detailed descriptions of wood composition and timber properties of ash are given by Bamford & Van Rest () and Crivellaro et al . (), and hydraulic architecture by Burggraaf (), Cochard et al .…”

“…Ash wood, in common with other ring-porous trees, contains tyloses to seal off embolized vessels (Schmitt, Richter & Muche 1997). Detailed descriptions of wood composition and timber properties of ash are given by Bamford & Van Rest (1936) and Crivellaro et al (2013), and hydraulic architecture by Burggraaf (1972), Cochard et al (1997) and Bettiati, Petit & Anfodillo (2012). Height growth and form are under high genetic control (Savill et al 1999); the additive genetic coefficient of variation ranged between 10.2 and 12.7% for height and 1.5 and 2.1% for dbh (Mwase, Savill & Hemery 2008).…”