The prediction of the flexural lumber properties from standing South African-grown Pinus patula trees

Abstract

Pinus patula is the most intensively planted conifer in the tropics and sub-tropics. The increased proportion of corewood that results when rotation ages of pine plantations are shortened has become a wood quality factor of growing concern worldwide. The purpose of this study was to develop empirically based models for predicting the flexural properties of the wood produced from relatively young Pinus patula trees. Models were based on the properties of standing trees and their effectiveness was evaluated at board, tree and compartment levels. Sample material was obtained 1 from 170 Pinus patula trees, 16-20 years old, established in 17 compartments on the Mpumalanga escarpment of South Africa. Multiple regression models were developed which managed to explain 68%, 60% and 95% of the variation in the dynamic modulus of elasticity (MOE) on individual boards, trees and compartments levels respectively. At compartment level, 80% of the variation in the 5 th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time-of-flight, wood density and ring width were influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler's buckling theory and the bending stress theory. The results from this study indicated that the MOE dyn and MOR of lumber can be accurately predicted on especially a compartment level. The predictive models developed can be used as management tools to improve operational decisions around tree breeding, silvicultural practices and rotation ages.

The flexural lumber properties of Pinus patula Schiede ex Schltdl. & Cham. improve with decreasing initial tree spacing

“…There is consensus between many authors that the rapid initial decline in MFA is associated with mechanical constraints related to tree slenderness (Spatz and Bruechert 2000;Watt et al 2006;Lachenbruch et al 2011;Waghorn and Watt 2013;Wessels et al 2015b). Saplings with small diameters produce higher MFA, which endows trees with considerable flexibility of the stem, acting as a safeguard against external forces.…”

“…In response to wood quality concerns, initial research in South Africa focussed on establishing the current resource characteristics and variation of mechanical and physical properties of wood, as well as the non-destructive prediction thereof (Wessels et al 2011(Wessels et al , 2014(Wessels et al , 2015bDowse and Wessels 2013;Muller et al 2017). Much like international research (Moore and Cown 2017;Schimleck et al 2018), these studies clearly indicate that the nature of wood material from modern plantations has changed and that certain forest management interventions should be considered in order to improve wood quality-particularly stiffness properties.…”

The effect of surface fire on tree ring growth of Pinus radiata trees

“…The burnt trees further showed lower latewood/earlywood ratios as an effect of fire, leading to the rejection of hypothesis 2. This is particularly relevant to practical forestry since the latewood percentage contributes positively to wood density and thus mechanical strength in pines (Wessels et al 2015). In conifers, earlywood is composed of cells with larger lumen and thin walls.…”

Kızılağaç (Alnus glutinosa subsp. barbata (C.A. Mey.) Yalt.) Kontrplaklarının Bazı Teknolojik Özellikleri Üzerine Dikim Aralığının Etkisi

“…Türkiye'de geniş alanlara yayılmış, suyun ve nemin bulunduğu yerlerde, saf meşçereler oluşturmuş, yerine göre son derece hızlı büyüyen ve iyi gövde yapısıyla, ekonomiye katkısı olabilecek ağaçlardandır [4]. [14][15][16]. Dikim aralığı ayrıca, kereste işletmeleri için ekonomik değeri olan ağaçların düzgünlüğünü de etkileyebilir.…”

“…Dikim aralığı ayrıca, kereste işletmeleri için ekonomik değeri olan ağaçların düzgünlüğünü de etkileyebilir. Hem kereste veriminin hem de kalitesinin, çarpık gövdelerden büyük ölçüde etkilendiği [13][14][15][16][17], düzgün olmayan gövdeler nedeniyle kereste biçme işleminde kabaca yüzde 10'luk değer kayıplarının olduğu belirtilmektedir [18]. Bununla birlikte, dikim aralığının gövde düzgünlüğü üzerindeki etkisi her zaman belirgin olmamasına rağmen, dar aralıklarla dikilen plantasyonlardaki ağaçların daha iyi gövde düzgünlüğü gösterdiği ve hacim iyileşmesini sağladığı literatürde belirtilmiştir [19][20][21][22][23].…”