Forest fire occurrence increases the distribution of a scarce forest type in the Mediterranean Basin

Arnan X., Quevedo L., Rodrigo A. (2013) Forest fire occurrence increases the distribution of a scarce forest type in the Mediterranean Basin. Acta Oecologica. 46: 39-47.
Enllaç
Doi: 10.1016/j.actao.2012.10.005

Resum:

Here we report how fire recurrence increases the distribution of a scarce forest type in NE Spain that is dominated by the resprouter tree species Arbutus unedo. We used a combination of GIS and field surveys to determine the effect of fire and pre-fire vegetation on the appearance of A. unedo forests. In the field, we also analyzed the factors that promote fire and lead to the appearance of A. unedo forests. Our results reveal an increased occurrence of A. unedo forests in NE Spain in recent years; this phenomenon was strongly related to fire recurrence and the vegetation type present prior to fire. Most Pinus halepensis forests that burned more than once gave rise to A. unedo forests. Our results indicate that these conversions were related to a reduction in pine density coupled with increases in the density and size of A. unedo trees due to recurrent fires. Given that fires are increasing in number and magnitude in the Mediterranean, we predict a major change in landscape structure and composition at the regional scale. © 2012 Elsevier Masson SAS.

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

Quevedo L., Arnan X., Rodrigo A. (2013) Selective thinning of Arbutus unedo coppices following fire: Effects on growth at the individual and plot level. Forest Ecology and Management. 292: 56-63.
Enllaç
Doi: 10.1016/j.foreco.2012.12.007

Resum:

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. © 2012 Elsevier B.V.

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