Managed and unmanaged silver fir-beech forests show similar structural features in the western Pyrenees

Abstract

Abstract: Forest structure is considered one of the basic features of the forest ecosystem and it is widely studied with the aim of developing sustainable management strategies. The usual approach is to compare structural features of stands in managed and unmanaged forests. Managed stands are those disturbed in some way by silvicultural practices, whereas unmanaged stands are subject to natural disturbance dynamics and may serve as a reference. Up to now, there has been insufficient research into sustainable management strategies for Pyrenean silver fir-beech forests and the structure of managed and unmanaged stands has not yet been evaluated. The aim of this study is to provide a detailed characterisation of the structural attributes of these mixed mountain forests in the western Pyrenees and compare managed and unmanaged stands regarding selected stand parameters. Potential differences between managed and unmanaged stands were assessed with Mann-Whitney U-tests. Diameter distribution was modelled using third-order polynomials and non-linear regression was performed to compare the tree heights in managed and unmanaged stands. Stand structure was similar in both management categories. The diameter distribution of Pyrenean unmanaged silver fir-beech stands showed a tendency towards a rotated sigmoid distribution. Our results indicate that the recommended diameter distribution has been preserved in managed stands despite they were intensively managed in the past, whilst the unmanaged stands are still in the process of developing old-growth attributes because management was abandoned too recently for significant changes in forest structure to have occurred.