Plant communities converge to resource-dependent transient states during succession on old fields

The community composition of plants during succession may follow trajectories driven by the resource-dependent coexistence of plant species. This predicts the convergence of trajectories to resource-dependent transient or stable states. Here, we report the analyses of yearly vegetation surveys between 1987 and 2022 from two pairs of experimental plots on which agricultural use ceased in 1986. On one plot of each pair, nutrients (N, P, K) were added in an amount similar to the Park Grass Experiment at Rothamsted. We found a decrease in species richness with ongoing secondary succession. After 15 years of succession, species richness levelled off and was ≈ 50% lower for surveys on the fertilised plots. An indicator species analysis found five species characterising the fertilised plots and almost 30 species characterising the non-fertilised plots. As expected, the mean N Ellenberg indicator values of the species typical for fertilised plots were higher (mean 6.3) than for those typical for non-fertilised plots (mean 4.4). Furthermore, the stable state was transient, as indicated by the increase in the distance of plots from their respective medians of the ordination scores after an additional 10-year period.