Abstract Environmental change as result of urbanisation can influence soil microbial communities in green areas. In cities, forests are among the most frequent types of green areas and provide a wide variety of ecosystem services for the residents, such as air cleaning, nutrient cycling and area for recreational activities. Mycorrhizal fungi play an important role for the establishment of trees and therefore for the natural regeneration of forests. We examined the effect of urbanisation on the arbuscular mycorrhizal (AM) fungal symbiosis and performance of Acer pseudoplatanus saplings in a controlled field experiment in forests situated in the city of Basel and its suburbs in Switzerland. A total of 660 one-year-old A. pseudoplatanus saplings were planted in plots in 11 forests, which differed in degree of urbanisation in the surroundings and size. Saplings including their full root systems were harvested after 4, 6 and 13 months. AM fungal colonisation was 15–45 % lower on roots of saplings growing in forests located in areas with a high degree of urbanisation than that on sapling roots in forests in less urbanised areas. Furthermore, AM fungal colonisation of saplings decreased with decreasing forest size. Sapling survival was not influenced by urbanisation, but by forest size. In particular, sapling survival was reduced in small and medium-sized forests. Sapling survival also increased with increasing percentage of AM fungal colonisation after 13 months. These urbanisation- and forest-size induced changes became more pronounced with the time elapsed since the saplings were planted. Our findings demonstrate the negative impact of urbanisation on AM fungal symbiosis and the performance of A. pseudoplatanus saplings and indicate that urbanisation is a threat for the long-term maintenance of intact small urban forests.

中文翻译：

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城市森林中的植物菌根关联：城市化程度和森林面积对梧桐树（Acer pseudoplatanus）树苗性能的影响

摘要 城市化导致的环境变化会影响绿地土壤微生物群落。在城市中，森林是最常见的绿地类型之一，为居民提供多种生态系统服务，例如空气净化、养分循环和休闲活动区。菌根真菌对树木的形成以及森林的自然更新起着重要作用。我们在位于瑞士巴塞尔市及其郊区的森林中进行的受控田间试验中，研究了城市化对丛枝菌根 (AM) 真菌共生和 Acer pseudoplatanus 树苗性能的影响。在11个森林中，根据周边城市化程度和规模大小，共种植了660棵1年生A.pseudoplatanus树苗。在 4、6 和 13 个月后收获包括完整根系在内的树苗。与城市化程度较低地区森林中的树苗根部相比，位于城市化程度较高的地区的森林中生长的树苗根部的 AM 真菌定植率低 15-45%。此外，随着森林面积的减少，树苗的 AM 真菌定植减少。树苗存活不受城市化的影响，而是受森林大小的影响。特别是中小型森林中的树苗存活率降低。13 个月后，幼苗存活率也随着 AM 真菌定植百分比的增加而增加。这些城市化和森林规模引起的变化随着树苗种植后的时间推移变得更加明显。