Ailanthus altissima is a widespread invasive species in Europe and poses significant challenges for ecosystem management and conservation. However, its patterns of spread and ecological impacts are still not fully understood. The objective of this study was to elucidate the ecological patterns and processes associated with Ailanthus altissima invasion in a riparian landscape and to provide a basis for evidence-based management strategies. To address this objective, we analysed invasion foci within the Brenta riverscape (northeastern Italy). We identified invasion foci within a Natura 2000 site located along the middle course of the river. For each stem (>4000) within 18 invaded sites, we recorded its location and size (i.e., height and diameter). We then examined the spatial arrangement of A. altissima individuals and their relationship with landscape factors (i.e., distance from the main channel of the Brenta River and main land cover). Clustered spatial distribution was observed within invasion foci. Furthermore, invasion dynamics appear to be associated with localised management activities (e.g., paths, mowing). Our results provide ecological insights that may support more effective prevention and control strategies. Furthermore, analysing these dynamics improves our understanding of the structural development of Ailanthus stands and helps predict the evolution of invasion foci in riparian landscapes.

Urban trees and green spaces provide a wide range of ecosystem services. Among urban green infrastructures, monumental trees represent key elements in these environments. Despite the growing recognition of their value, monumental trees in urban areas face multiple challenges, underscoring the need for targeted research to inform conservation and management strategies. This study investigates the ecological role of 124 urban monumental trees in the Veneto region (Italy) using tree-related microhabitats (TreMs) as a proxy for potential biodiversity support. Our analysis demonstrated that dendrometric characteristics (namely, diameter at breast height) and monumental tree configuration (namely, individual trees vs. those in groups) strongly affect the richness, abundance and composition of TreMs, highlighting that both native and non-native species contribute substantially to urban ecosystem functioning. Furthermore, complex relationships between monumentality criteria and TreMs were observed. These results are intended to support the management of urban green spaces, helping to enhance the biodiversity potential of monumental trees while preserving their multifaceted values.

Urban biodiversity is increasingly threatened by land-use change, habitat fragmentation, and intensive management practices. Within this context, urban trees represent a key nature-based solution (NbS) that simultaneously supports biodiversity, improves ecosystem functioning, and contributes to human well-being. Among the structural features provided by trees, tree-related microhabitats (e.g., cavities, deadwood, bark features, and epiphytic substrates), also called TreMs, are crucial for hosting a wide range of organisms, yet they remain underinvestigated in urban environments. This study examines the distribution and drivers of TreMs in an urban park ecosystem, focusing on Parco Colletta in Turin (NW Italy). A total of 423 trees were surveyed from a population of approximately 1,700 individuals. For each tree, we collected information on species identity, functional group (conifer versus broadleaf), origin (native versus non-native), diameter, height, planting configuration (groups, rows, or isolated trees), management intensity, and presence and type of TreMs. Overall, 97% of the surveyed trees hosted at least one TreM, with a total of 1,194 structures identified and an average of three TreM types per tree (range: 0–9). The most common types were dead branches, bark microsoil, and fork split at the intersection. Broadleaf species, particularly Fagus sylvatica L., Acer saccharinum L., and Quercus rubra L., exhibited the highest abundance of TreMs. Trees with low management intensity and standing dead individuals showed substantially higher TreM richness, highlighting the influence of management practices on habitat availability in urban environments. While several variables impacted TreM presence in univariate analyses, diameter and management intensity stood out as the primary explanatory factors. These findings highlight the value of TreMs as effective structural indicators of urban biodiversity and NbS performance. Incorporating biodiversity-focused management into urban green infrastructure planning can enhance the ecological value and resilience of urban ecosystems under ongoing environmental change.