Response of woody and herbaceous fuel to repeated fires in Mediterranean gorse shrublands

Abstract

Differences in both species flammability and post-fire regenerative abilities can be the key to understanding fire regimes and vegetation dynamics. We hypothesised that woody species that accumulate the greatest amount of dead fuel and also have fire-stimulated recruitment would benefit when fire occurrence is increased, thus establishing a positive fire–vegetation flammability feedback. To test this hypothesis, we compared successional change over a 25-year period in gorse shrublands that were burnt once and twice. We assessed change in life forms, species traits with respect to the kind of fuel (i.e. woody and herbaceous) and the abundance of standing dead fuel. We found that, at the community level, accumulation of dead fuel was unrelated to recurrent fires because a second fire in the period of maximum fire risk created a community with less dead fuel. This result implies a lack of positive fire–dead fuel accumulation feedback. In contrast, herbaceous species may establish a positive feedback with fire as they were increased by a second fire.