Native and non-native monumental trees in cultural landscapes: a spatially heterogeneous source of biodiversity

Monumental trees hold considerable ecological, cultural, and socio-economic values, providing crucial ecosystem services. Updated catalogues of monumental trees represent an essential starting point for the study and appropriate management of these entities. This study offers comprehensive insights into the composition, distribution, and ecological significance of the Italian monumental tree community. We used the Italian monumental trees inventory (4657 spatially explicit records) provided by the Ministry of Agriculture, Food Sovereignty, and Forestry. While native species dominate the monumental trees community, the noteworthy presence of non-native trees highlights ecological and historical dynamics at the national scale. Non-native species dominate the urban monumental trees community. Spatial analysis reveals clustering of monumental trees at provincial and local levels, suggesting the existence of biodiversity and cultural hotspots (e.g., parks, churches, historic villas, and royal palaces). We showed discrepancies concerning the application of monumentality criteria between native and non-native species, which also depend on their surrounding environment (e.g., urban settings favoring historical and architectural significance criteria). Native species are positively associated with criteria used to identify monumental trees such as age, circumference, crown size, shape, and ecological value, while non-native species are linked with historical, landscape, architectural, and botanical rarity values. Our findings highlight the multifaceted nature of the monumental tree community.