Allocation of Wood Density in European Oak (Quercus robur L.) Trees Grown under a Canopy of Scots Pine

Marcin Jakubowski,Marek Dobroczyński

doi:10.3390/f12060712

Abstract

The allocation of wood density in trees depends on many factors, but mainly on the tree species. A great number of studies have analysed wood density in dominant or codominant trees, but only a few have focused on trees grown under canopy. We examined the basic wood density and fresh wood density of natural origin oaks growing under canopy of artificially planted Scots pine. The major purpose of the work was to study the wood density allocation in different parts of the trees such as the trunk and branches. From a total of 80 oaks we selected eight model trees and measured biometric features of their trunks and crowns. Wood samples from different parts of the trunk and crown were collected after the trees were felled. We observed significant differences between the average basic wood density (595 kg·m−3) and the average fresh wood density (1031 kg·m−3). The central part of the trunk and heartwood shows much higher density than the outer part of the trunk and sapwood, which corresponds to the model of ring-porous trees. Both types of wood density (basic and fresh) were also higher in the trunk than in the branches. The wood density of the branches differed between two zones: A1, which was closer to the trunk and had higher density; and A2, which was farther away from the trunk with lower density. Wood density shows positive correlation with crown length but not with crown width, which was more connected with diameter at breast height. We found lower value of slenderness than the value reported by other authors in oaks planted without canopy. The allocation of wood density in trees is associated with the potential mechanical load.

Highlights

IntroductionThere are several types of wood density, which are defined differently in different scientific works
Wood density is one of the most important quality predictors that is often used in various fields of research, such as biology, ecology [1,2,3], species population studies [4,5,6,7], forest biomass estimation [8,9,10] and even as predictor of tree mortality under drought [11]
Wood density is defined as density of oven-dry wood density [6,12,13,14], basic density or relative density [6,10], green density or fresh density (FD) [15], the density at 12% moisture content, according to various technical standards [16,17], or density calculated for unconventional levels of moisture content [18]

Summary

Introduction

There are several types of wood density, which are defined differently in different scientific works. Some researchers have used relative density based on various types of interpolation [19,20,21,22,23,24,25]. Each type of wood density shows results on different scales, so comparing the results of various works is difficult and sometimes impossible. Predicting other wood properties based on various types of wood density is complicated [29]. Many researchers have used another type of densityspecific gravity, which is used as an equivalent to wood density. The work of Gao [24,25] is helpful for understanding types of wood density. We used two types of wood density as described below

Objectives

Methods

Results