Fine root parameters and mycorrhizal colonization of horse chestnut trees (Aesculus hippocastanum L.) in urban and rural environments

Horse chestnut trees (Aesculus hippocastanum L.) are stable and important elements of urban and rural landscapes. So far most studies that have investigated horse chestnut trees have observed their above ground characteristics, whereas the roots structure and symbiotic associations with mycorrhizal arbuscular fungi have been poorly recognized. Therefore, our objective was to perform a detailed study of horse chestnut fine roots and the extent of their colonization by mycorrhizal fungi in urban and rural environments. In the urban area two different study sites were selected: one in the street and the second in city parks. Two rural sites comprised the roadside verges planted with horse chestnut trees in open countryside. The chemical composition of soils revealed significant differences between study sites. The biometric parameters of fine roots are only partly related to soil characteristics. The results revealed a lack of a clear negative effect of the urban environment on fine root parameters, which may suggest a high degree of plasticity in this species in response to heterogeneity of the soil. At all study sites the fine roots of horse chestnut were colonized by arbuscular fungi (AM) and fungal endophytes. Trees from all study sites revealed a similar range of AM colonization. Significant differences were found only between one rural and one urban park site. The results from urban and rural sites revealed horse chestnut as a tree species well adapted to both rural and urban conditions and presented well-established mycorrhizal symbiosis with arbuscular fungi.