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COORDINATION: Francisco Moreira (CEABN InBIO).

CEABN TEAM: Ana Águas, António Ferreira, Filipe Xavier Catry, Francisco Moreira, Francisco Castro Rego, Joaquim Sande Silva, Miguel Bugalho.

OTHER INSTITUTIONS: Centro de Estudos do Ambiente e do Mar (CESAM/UA), Centro de Investigação e Tecnologias Agro-Ambientais e Biológicas (CITAB/UTAD).

The post-fire management of Mediterranean burned forests has been given much less attention than fire prevention or suppression. The usual procedure for post-fire management of many burned forests in the Mediterranean region is to fell the burned trees (salvage logging). After clear felling, there is a strong political pressure to actively reforesting burned areas (the simplistic approach of comparing areas burned and actively reforested) and this has been a common practice since mainly in conifer forests. These reforestation efforts are usually carried out by means of active restoration techniques such as plantation or direct seeding.

Taking advantage of passive restoration, by allowing natural re-growth (either from seeds or resprouts) to occur has not been frequently used as a restoration technique in a Mediterranean context, even if it usually has a lower financial cost. Conflicts between these two approaches (active or passive) for restoration are even possible if governments subsidise active restoration in areas where natural regeneration is occurring. However, one disadvantage of using passive (or assisted restoration) is when the vegetation type that is regrowing does not suit the management objectives for the area. This may happen, for example, if there is excessive regeneration or if exotic invasive species are being promoted by fire disturbance, which may cause a threat to native plant diversity and increase the risk of future wildfires.

In the last decade, wildfires in Portugal have burned in average ca. 160,000 ha every year. Maritime pine (Pinus pinaster), a native species, and eucalyptus (Eucalyptus globulus), an exotic species, are the two major timber and pulp species in the country, respectively. They occur in the same ecological regions, mainly in Northern and Central Portugal, and occupy a similar surface area (ca. 700,000 ha) totalling around one half of the whole Portuguese forests. Their stands (both pure and mixed) are highly fire-prone. The responses of both maritime pine and eucalyptus to fire are different, limiting the post-fire management options for both species and posing different research questions with management relevance.

The pine is partly serotinous and seeds stored in the canopy are the major source for the post-fire regeneration, as the seed bank in the soil is scarce and transient. Frequently there is abundant post-fire regeneration from seed in burned adult stands. Adult trees are often killed by fire, depending on the degree of crown and cambium damage, and there is no resprouting in the species. So, the typical postfire management is salvage logging of burned trees and either active (plantation or seeding) or passive (natural regeneration from seeds) restoration. Evaluating in which conditions natural regeneration occurs has management implications, as it would allow the identification, after fires, of areas where poor regeneration can be expected, and thus where active restoration may be needed. On the other hand it can also provide indication of sites where active restoration is not needed, and where the predominant approach should consist of managing natural regeneration.

The eucalyptus resprout readily after fire. Thus, the typical post-fire management is cutting of burned trees and either taking advantage of resprouts or carry out new plantations. Additionally, in its region of origin, eucalyptus may also regenerate from seeds, either stored in the seed bank or in the crown. In Portugal this feature is not used in post-fire management, as natural regeneration from seeds is supposedly not common and has no economic interest when compared to the coppice system. Thus, the main concern with post-fire regeneration in eucalyptus is in a biodiversity perspective: the species has not been considered invasive so far, although there is increasing scattered information on the occurrence of large densities of eucalyptus seedlings in some burned areas. Evaluating in which conditions natural regeneration occurs, and assessing its potential invasive behaviour and impacts on the occurrence of other plant species, would provide relevant information for forest managers.

In summary, for the purposes of both post-fire management and biodiversity conservation it is important to increase our knowledge on the factors determining the amount of natural regeneration in both maritime pine and eucalyptus in Portugal, so that predictive models can be built and used by forest managers as guidance for post-fire management practices. This was the global aim of this project, and it was accomplished by assessing the amount of regeneration in areas burned 4 to 5 years ago, and exploring the factors, related to pre-fire vegetation structure, fire severity and environmental conditions, that explain the observed variability.