Selective thinning of Arbutus unedo coppices following fire: Effects on growth at the individual and plot level

Abstract

In recent years, several Mediterranean forests subject to fire are becoming increasingly dominated by the resprouter species Arbutus unedo L. (strawberry tree). However, there is little information available about the management of these areas, and it is not clear if the approaches utilized for other, more abundant Mediterranean resprouter species such as Quercus ilex and Quercus cerrioides would produce similar results for A. unedo. In this study, performed in the NE Iberian Peninsula, we analyzed the effect of two post-fire treatment types, selective thinning and selective thinning plus understory clearing, on the growth of retained A. unedo resprouts and the new resprouting induced by the treatment itself. Treatment effects were analyzed at both the individual and plot level. Our results showed that, in the short term, retained resprouts on treated trees grew more in height and diameter (absolute and relative) than those on control trees, with no differences seen between treatment types. In the intermediate term, all the strawberry trees occurring on treated plots grew longer, and this growth was greater in plots that had been both thinned and cleared. New, induced resprouts were unaffected by the type of treatment applied. In contrast to other studies, we failed to find a negative relationship between the degree of induced resprouting and retained resprout growth We therefore conclude that, irrespective of understory clearing, the selective thinning of A. unedo improves coppice vertical structure. Retained resprouts grow more in diameter and will thus more rapidly become exploitable as firewood and timber. Also, the tree is kept free of dead fuel, reducing the risk of spreading fire.