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Woodland fragments, in small historical cities, are commonly regarded as temporary voids in an urban matrix, yet to be allocated a land-use, under city planning regulations. However, they could display relevant plant diversity, and contribute to urban ecosystem services. This study combined surveys at 100 m², and at patch level, with the aim to investigate how patch size, stand and urbanization, affected the structure of plant communities in thirty woodland fragments (0.1–2 ha), spontaneously developing in the small, historical city of Padova (Northern Italy). Trees, shrubs and other perennial species dominated the plant communities in these patches. Alien species were common, in both the understory (freq. = 97 %, mean richness = 4.33) and tree layer (freq. = 90 %, mean richness = 1.50). Species typical of native communities also occurred. Understory communities were associated with ancient forest, nitrophilous, and ruderal species; highlighting an overall heterogeneity. Road and railway density was moderately correlated with total species richness in the understory, whereas, urbanity (i.e. the concentration of built environment excluding road and railway density), and tree density were not. Furthermore, alien tree dominance negatively influenced total and native tree layer species richness and, moderately positively, native understory species richness. These results highlight that spontaneous novel woodland patches, even if they are minor fragments in small historical cities, maintain diverse green infrastructures that may supply an array of urban ecosystem services, when adequately recognised by city plans.
