Salinity rather than nutrients reduces alien plant abundance and sustain native diversity in coastal dunes
Description
Biological invasion is recognized as one of the major threats to biodiversity, particularly in coastal dune ecosystems. Many studies have associated alien plant invasion of dune ecosystem to human disturbances, but less is known about the role of soil properties in invasion after disturbance. Soil properties exert a particular role at early stages of succession, where changes in the initial species composition might shape the final success of the invaders. The aim of this study is to understand if it is possible to curb alien species success on highly invaded dunes by manipulating soil properties. In a barrier island of the Marano and Grado’s lagoon, Northern Adriatic Sea, we mechanically removed all the vegetation present in the back dune, triggering a new ecological succession and further altered soil properties by salt, nitrogen, and organic matter addition in a full factorial design with randomized blocks. Soil disturbance reduced the overall diversity and abundance of alien plants. Soil treatment interactions strongly shaped total plant species abundance, diversity and composition. Soil salinity had a positive effect on native species abundance while decreasing the overall number of alien species, especially in soil with added organic matter. Our findings suggest that soil salinity, and its interplay with other soil properties, might reduce the initial alien species propagule pressure linked to soil seed bank and, hence, shape plant community trajectories. This study highlights that alien plant containment should be focused on early stages of succession.