Long-term responses of Mediterranean birds to forest fuel management.
Abstract
Mechanical management of forest fuels is increasingly used in the Euro-Mediterranean region in response to the abandonment of traditional agroforestry and the concurrent increase in fire hazard. Although fuel management may have positive side effects for biodiversity, its long-term impacts remain largely unknown. We used a 70-year post-management chronosequence to investigate the influence of time since fuel management and management frequency on bird assemblages in cork oak Quercus suber forests. Fuel management strongly affected bird species richness, abundances and assemblage composition, with rapid changes often occurring during the first 10-20 years, followed in the next decades by a slow convergence to pre-management levels. In winter, overall species richness and abundance, and that of frugivores and shrub foragers, were negatively affected by recent and recurrent management, only recovering in stands unmanaged for >50 years. In spring, insectivore abundance and the richness and abundance of shrub foragers declined immediately following management, increased to a maximum about 20 years later, and declined thereafter. Breeding granivores and ground foragers were the only groups that benefitted from fuel management. There were no overall effects on species of conservation concern, although a few species with unfavourable status benefitted from fuel management. Synthesis and applications. Our study confirmed that mechanical fuel management has positive effects on some early-successional bird species of conservation concern, although its effects were limited. These benefits should be compared with the strong negative impacts on key bird species such as wintering frugivores, which play a pivotal role in ecosystems by promoting seed dispersal. To reconcile the positive and negative aspects, fuel management should be used to create heterogeneous mosaics of forest patches encompassing a range of sizes (10-100 ha) and successional stages of understorey vegetation, including stands undisturbed for >50 years. This management strategy will likely maintain conditions for a wide range of species with contrasting ecological requirements while also reducing fire hazard.