In the past decades, the tall native invasive grass, Elytrigia atherica, has been increasing in frequency and dominance on salt marshes along the Wadden Sea coast. Is this rapid expansion an outcome of natural succession or is it driven by anthropogenic eutrophication resulting from atmospheric deposition?Location
Salt marshes on four back-barrier islands, Wadden Sea on the coast of the Netherlands and Germany.Methods
We used a combination of time series of vegetation maps and chronosequence data of four naturally developed salt marshes to address our questions. These salt marshes have not been grazed by livestock or subject to other management regimes. By comparing development within and between four different salt marshes, we were able to study the spatial and temporal dynamics of the community dominated by E. atherica on natural salt marshes.Results
The expansion rate of the E. atherica community was highest on young salt marshes (up to 30 yr old) with vertical accretion rates of 0.35 cm·yr−1. The rate of expansion decreased on older marshes and the direction reversed, becoming negative, on the oldest marshes (around 90 yr old), which have no vertical accretion and are under waterlogged conditions.Conclusions
The expansion of E. atherica on natural, back-barrier islands along the Wadden Sea coast is more influenced by the age of the salt marsh and patterns in vertical accretion of soil than by uniformly spread atmospheric deposition.
In the past decades an increase of monotonous stands of E. atherica is observed on salt marshes along the Wadden Sea coast. In this study we address the question whether this rapid expansion is driven by anthropogenic eutrophication or is it an outcome of natural succession. Secondly we reveal that there is a world beyond E. atherica.