Impacts of the alien trees Ailanthus altissima and Robinia pseudoacacia on soil nutrients and microbial communities
Ailanthus altissima (Simaroubaceae: EPPO List of Invasive Alien Plants) and Robinia pseudoacacia (Fabaceae) are two invasive alien tree species which have invaded riparian systems in Central Spain. Both species have been recorded to have negative impacts on native biodiversity by competing with native plant species for resources and, where they form dense monocultures, both species can reduce the abundance and diversity of native species. The impact of A. altissima and R. pseudoacacia on soil properties (soil organic matter, nitrogen, phosphorus, nitrate, ammonium and pH) and the structure and activity of soil bacterial communities was evaluated in riparian plant communities dominated by the native tree Populus alba (Salicaeaceae). A field study, comparing soil properties between established invaded and uninvaded sites, coupled with a greenhouse experiment where A. altissima, R. pseudoacacia and P. alba were grown in separate pots for six months containing soil collected from beneath stands of P. alba, was used to evaluate potential impacts. Both the field study and the greenhouse experiment showed A. altissima to decrease soil total nitrogen whereas R. pseudoacacia increased soil mineral nitrogen. Differences in the soil bacterial communities were only observed in the field study and were more pronounced between A. altissima and P. alba compared with R. pseudoacacia and P. alba. Although the greenhouse experiment indicated some differences in soil properties over the short experimental period, an accumulation of soil changes over time may be needed to have an impact on soil bacterial communities.
Sources
Medina-Villar S, Rodríguez-Echeverría S, Lorenzo P, Alonso A, Pérez-Corona E (2016) Impacts of the alien trees Ailanthus altissima (Mill.) Swingle and Robinia pseudoacacia L. on soil nutrients and microbial communities. Soil Biology and Biochemistry 96, 65-73.