Since the nineteenth century, street trees have become a significant component of urban landscapes, with multiple ecological roles and social-economic functions. However, data about their abundance and diversity, and information about the criteria used for the species selection, are still limited. Besides providing a historical overview, we analyze and compare data on abundance, diversity and criteria of species selection of street trees in 15 Italian cities chosen considering their representativeness along a bioclimatic transect across Italy. The biodiversity of urban street trees resulted quite rich with 277 species (about 60% are exotic); among these, Platanus × hispanica Mill. ex Münchh., Celtis australis L. and Quercus ilex L. resulted as the most common species. Besides the general suitability for the local climatic conditions, several factors seem to concur in the species selection, such as their aesthetic appeal and dimension. Other selection criteria based on the species’ ecology or functionality were not evident.

中文翻译：

---

意大利城市的街头树木：城市环境中的故事，生物多样性和融合

自19世纪以来，街头树木已成为城市景观的重要组成部分，具有多种生态作用和社会经济功能。但是，有关其丰富性和多样性的数据以及有关用于物种选择的标准的信息仍然有限。除了提供历史概述之外，我们还分析和比较了在15个意大利城市中考虑到沿整个生物气候样带的代表性的情况下所选择的意大利城市街道树木的丰度，多样性和物种选择标准的数据。城市街道树木的生物多样性非常丰富，有277种（约60％为外来树种）；其中，Platanus  ×  hispanica Mill。exMünchh。，Celtis australis L.和Quercus ilexL.是最常见的物种。除了对当地气候条件的总体适应性之外，物种选择似乎还需要考虑几个因素，例如它们的美学吸引力和尺寸。基于物种生态或功能的其他选择标准也不明显。