Long-term shifts in the functional diversity of abandoned wet meadows: Impacts of historical disturbance and successional pathways.

Investigating the direction of changes in functional diversity involving successional pathways and historical disturbances may be a promising tool for predictions of the effectiveness of the seminatural meadows conservation, with great emphasis on formulation of more cost-effective restoration strategies. The goal of this research was to assess the differences in long-term shifts in the functional diversity of plant species in seminatural wet meadows unmanaged for the last 40 years, under the influence of different successional pathways and historical disturbances. Using ordination techniques, linear mixed-effect models, a set of plant functional traits and parameters of functional diversity, we assessed the importance of habitat filtering, competition, and niche partitioning in shaping community assembly changes over time. The most dramatic shifts in functional diversity were found in the Carex acutiformis successional pathway after topsoil removal, where colonization by successional inhibitors was the main driver causing decreases in functional dispersion and divergence. This was expressed as a decrease in the importance of habitat filtering and replacement of specialized species by competitors with heavier seeds and higher specific leaf area. Regarding the C. cespitosa and Salix cinerea pathways, the magnitudes of shifts in functional diversity were milder and differed less between the historical topsoil removal and mowing treatments, thereby maintaining a large role for niche partitioning in shaping the vegetation structure. The results of our study highlight the importance of tussock sedges and shrubs as effective buffers against the functional homogenization of meadows driven by the decreases in functional diversity of plant species, even from a long-term perspective.