Effects of the Invasive Tree Species Ailanthus altissima on the Floral Diversity and Soil Properties in the Pannonian Region

Tree-of-heaven (Ailanthus altissima) is one of the most dangerous and widespread invasive woody plant species in Europe. Despite the fact that A. altissima is in the focus of an increasing number of research projects, the impact of its mass spread on native vegetation, its diversity, and changes in soil quality are still incomplete. The current study addresses the effects of this invasive species on plant diversity and soil parameters simultaneously. The main objective of our research is to determine the impact of cover and mass of A. altissima on the diversity of each forest layer; the examined soil parameters and on other selected environmental variables. For botanical and pedological investigations we selected nine A. altissima-dominated sites in Central Europe, in the Pannonian Biogeographical Region. Based on our results, it can be stated that fully grown A. altissima-dominated stands can displace other taxa by their shading and allelopathy, thereby reducing canopy layer diversity. The increase in the species richness of the shrub layer had a positive correlation with the diversity of the floor layer and also with the humus and ammonia content of the soil. As the diversity of shrub layer and floor layer positively correlated with many soil parameters, the diverse vegetation of these layers can represent a potential opportunity for the regeneration of areas infected with A. altissima.