Abstract
Quercus rotundifolia Lam., known as holm oak or evergreen oak, occurs naturally in the western Mediterranean region, mainly as part of the agroforestry or agrosilvopastoral systems in Portugal (“montado”) and Spain (“dehesa”), and is economically important for acorn production. Less attention has been given to Q. rotundifolia wood, and its density variability is not known, namely related to tree growth. The wood density of 20 Q. rotundifolia trees was measured along the radial direction by X-ray densitometry and the factors responsible for ring width and wood density variation within and between trees were investigated at two sites located within the main species region in southern Portugal. Ring width was significantly different between sites, with an average of 1.81 mm and 1.55 mm. Wood density was very high and averaged between 888 kg/m3 and 914 kg/m3 but not significantly different between sites. Ring width and wood density showed a positive and significant correlation at both sites. Cambial age was the main source of variation for ring width and wood density, while between-tree effects accounted for a considerable proportion of wood density variation. The results are an important contribution for the species valorisation aiming at high-value wood products, also adding knowledge on the species growth of interest for tree selection and sustainable management.
Highlights
Quercus rotundifolia Lam., known as holm oak but mostly referred to as a subspecies of Quercus ilex L. (Quercus ilex subsp. rotundifolia; Q. ilex subsp. ballota), is a Mediterranean evergreen oak mainly and naturally distributed in the western Mediterranean region: Portugal, south Spain and Morocco [1,2,3]
The aim of this paper is to study the wood density and ring width variation of
Quercus rotundifolia is characterised as a diffuse or semi-ring porous species [14,17] while
Summary
Quercus rotundifolia Lam., known as holm oak but mostly referred to as a subspecies of Quercus ilex L. (Quercus ilex subsp. rotundifolia; Q. ilex subsp. ballota), is a Mediterranean evergreen oak mainly and naturally distributed in the western Mediterranean region: Portugal (ca. 349,400 ha), south Spain (ca. 2,794,450 ha) and Morocco (ca. 1,415,201 ha) [1,2,3]. Some tree decline or dieback in montado is being reported due to climate change, land desertification, and biotic pathogens threats, with concerns related to their different impacts on this management system and species’ future distribution [9,10]. In this context, physiological and growth traits have been studied aiming at species regeneration mainly for Q. ilex (or Q. ilex subsp ilex if mentioned as subspecies) (e.g., [4,11,12,13]). It is reported that Q. rotundifolia is adapted to more xeric conditions when compared to Q. ilex [14], showing similar or better adaptation than deciduous oak species such as Quercus faginea Lam. [13] and Quercus douglasii (Fagaceae) [15]
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