How ecosystems change following invasion by Robinia pseudoacacia: Insights from soil chemical properties and soil microbial, nematode, microarthropod and plant communities

1. Biological invasions represent a global threat to biodiversity conservation. The spread of invasive alien plants may lead to a plethora of impacts. Thus, an integrate approach, assessing the effects of invasive plants across several ecosystem components, is needed for a correct understanding of the invasion process and its consequences. Among invasive plants, the nitrogen-fixing tree Robinia pseudoacacia (Black Locust: BL) is one of the most widespread species worldwide. However, while its effects on plant communities and soils are well known, studies on the soil fauna and microbes are scant and urgently demanded. 2. In Europe BL invades managed forests, replacing the dominant native species. We investigated the impacts of BL on several ecosystem components throughout a multidisciplinary approach aiming to join evidences from soil chemical properties and soil microbial, nematodes, microarthropods and plant communities. We sampled soil and vegetation in managed forests, comparing those dominated by BL with native deciduous oak stands. 3. We found qualitative and quantitative changes in all the components we analysed, such as the well-known soil nitrification and acidification in stands invaded by BL. Bacterial richness was the only component favoured by the invasion. On the contrary, abundance and richness of microarthropods as well as richness of nematodes and richness and diversity of plant communities decreased significantly in invaded stands. Moreover, the invasion process caused a compositional shift in all the biotic communities and in the relationships among the different ecosystem components. 4. Synthesis. We provide clear insights concerning the effects of BL replacement of native managed forests. Our data confirm that BL transforms several components of the invaded ecosystems, modifying the plant-soil community and affecting biodiversity at different levels. A correct management of this aggressive invader across forests of temperate climate is urgently required, also considering its use in forestry production.