Effect of Urban Environmental Stress on Mycorrhization and Root Morphology of Roadside Acer and Tilia Trees

People in cities rely on roadside trees to provide a number of valuable services, such as shading, filtration of pollutants, and the cooling of air via evapotranspiration. In providing these services, roadside trees are exposed to numerous stress factors such as traffic pollution, drought, and contamination with de-icing salts. Urban trees therefore have a shorter lifespan than their forest counterparts, which results in city administrations incurring costs for replacing dying or dead individuals and in the loss of ecosystem services until replacement trees reach maturity. Mycorrhiza can help to mitigate stress in trees by increasing access to water and nutrients, by reducing vulnerability to attack by root pathogens, and by mitigating (salinity) stress. However, mycorrhization in roadside trees may also be negatively affected by urban stress factors, and isolated planting pits may hamper colonization. Despite the relevance for tree performance, the effect of traffic and de-icing salts on mycorrhization and root morphology of roadside trees in European cities has been largely neglected. This study examines ectomycorrhizal colonization rates and morphotype diversity in roadside Tilia trees, as well as root morphology, microbial activity, and soil chemistry in both Tilia and Acer roadside trees in Vienna, Austria. Differences in mycorrhizal or root morphological traits at different stress intensities within the urban environment will be presented.