Urban flora varies between urban habitats within a city and between cities. We used a particular urban habitat - tree-circles to compare floristic differences between urban agglomerations along a long climatic gradient on a continental scale. We recorded flora of this unique habitat in seven West Balkan cities and compared it to seven cities from Western and Central Europe. On average, 91 species were found on tree-circles in every city in the Balkans (compared to 81 in continental Europe). Climate was the most important factor influencing species composition. Western and Central European tree-circles floras are much more uniform and homogeneous than Balkan ones, which have richer species pools.

中文翻译：

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长期气候梯度下的树圈自发植被

城市植物区系在城市内部以及城市之间的城市栖息地之间有所不同。我们使用了特定的城市栖息地-树形圆圈来比较大陆集上沿长气候梯度的城市群之间的植物区系差异。我们记录了西巴尔干七个城市这种独特栖息地的动植物，并将其与西欧和中欧的七个城市进行了比较。在巴尔干半岛的每个城市，平均每个树木的圆环中发现了91种（欧洲大陆为81种）。气候是影响物种组成的最重要因素。与拥有丰富物种库的巴尔干地区相比，西欧和中欧的树圈植物群更加统一和均匀。