Inter-tree competition analysis in undebarked cork oak plantations as a support tool for management in Portugal

Abstract

Scheduling the first thinning in young cork oak stands is an important decision in management that is usually subjectively defined by each manager. An analysis of competition in cork oak plantations is extremely relevant as a support for this important decision. This study aimed to understand the relationship between stand characteristics and tree growth efficiency, and subsequently help identify the presence or absence of an inter-tree competition pattern in cork oak stands that were never debarked. The inter-tree competition was assessed by looking to several stand characteristics: (1) comparison with the self-thinning line; (2) stand density measures, such as stand spacing coefficient and relative spacing; (3) stand structure measures evaluated through the skewness and variability; and (4) tree relative growth rate pattern over tree size. Data used for this analysis were gathered from permanent plots that were established in even-aged stands located across the cork oak distribution area in Portugal. The study shows that the most common stand densities on young cork oak plantations might not lead to serious inter-tree competition before the first cork extraction. This information is relevant to support the potential timing and severity of the first thinning in order to retain more trees until the second cork extraction when cork quality can be taken into account in the selection of the trees to be removed.