Abstract
Ancient trees present structural and functional characteristics fundamental for sustaining complex and unique assemblages of species. They are a resource globally threatened by both intensive land uses and lack of recruitment. Their disappearance would involve not only the loss of majestic organisms with high intrinsic value, but may also result in the disappearance of rare and endangered species. Italy is currently implementing a new list of noteworthy ancient trees (i.e. monumental trees) and the preliminary results of this new inventory have been analysed as a case study of a national initiative. The provisional list included 950 complete records, corresponding to 65 genera and 118 species. The most abundant species was Quercus pubescens Willd while the most common genera were Quercus, Larix, Cedrus, Fagus and Platanus. Age and size were the most used criteria for inclusion of trees in the census. The fundamental novelty of the new inventory is that it is based on a set of well-defined criteria of monumentality and that it clearly recognised the ecological value of ancient trees. Preserving a tree for its ecological role requires a profound cultural shift. The value of microhabitats, structures that have historically been considered defects, should be recognised and managed accordingly. Ancient trees are often part of disappearing cultural landscapes: to preserve the richness and diversity of these habitats, new policies and regulations are needed. The preservation of landscapes, where there is still a high density of ancient trees, should be a priority for all European countries in order to conserve their unique associated fauna and for their irreplaceable functional value for biodiversity conservation.
Highlights
Ancient trees, historically preserved for their aesthetic value, are nowadays recognised as key resources that sustain broad and unique assemblages of species
These trees may reach a biomass and complexity not achieved by any other living organism (Blicharska and Mikusiński 2014). Having long passed their silvicultural maturity, they tend to present special features that contribute to increasing their ecological value, such as cavities, decaying wood and bark losses (Siitonen and Ranius 2015). It is their age and size, together with the environmental conditions that occur where they live, which determine the occurrence of complex decay processes (Lindenmayer et al 2014) and which lead to the development of a diversified array of microhabitats
Tree microhabitats are small distinctive substrates, used by several species for forage and shelter (Vuidot et al 2011) and they are gaining increasing attention as indicators of sustainable forest management (e.g. FOREST EUROPE 2015).The contribution of ancient trees for the conservation of saproxylic species is unmatched since they present an exceptional diversity of microhabitats, some of which may last for centuries (Siitonen and Ranius 2015)
Summary
Historically preserved for their aesthetic value, are nowadays recognised as key resources that sustain broad and unique assemblages of species. Several names have been used to identify them, such as champion or heritage trees (Orłowski and Nowak 2007), large old trees (Lindenmayer et al 2012), ancient trees (Hall and Bunce 2011) and veteran trees (Read 2000) With time, these trees may reach a biomass and complexity not achieved by any other living organism (Blicharska and Mikusiński 2014). These trees may reach a biomass and complexity not achieved by any other living organism (Blicharska and Mikusiński 2014) Having long passed their silvicultural maturity, they tend to present special features that contribute to increasing their ecological value, such as cavities, decaying wood and bark losses (Siitonen and Ranius 2015). The decline of old and hollow trees threatens the conservation of numerous endangered species (Sebek et al 2013)
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