Management alters interspecific leaf trait relationships and trait-based species rankings in permanent meadows

Question Plant functional traits have the potential to characterize species ecological strategies and predict ecosystem responses to environmental changes. (1) Do trait responses to land-use intensification alter trait-based species rankings, and (2) does land-use intensification alter relationships among interrelated leaf traits? Location Solling Mountains, Central Germany (Grassland management experiment, GrassMan). Methods Over the course of 2 yr with differing weather conditions, we analysed the specific leaf area (SLA) of eight grassland species and related it to leaf nitrogen per mass (Nmass) or area (Narea) in an old-growth grassland with two fertilization levels (none vs NPK fertilization, 180-30-100 kg center dot ha-1 center dot yr-1) and two cutting frequencies (one vs three cuts per season). Results NPK fertilization led to an expected increase in SLA, Nmass and Narea, while the effect of altered cutting frequency on leaf traits was more species-specific. Species-specific responses to management significantly altered trait-based species rankings. A significant SLANmass relationship occurred in unfertilized plots, whereas the SLANarea relationship was stronger in fertilized plots. This was mostly caused by a decrease in the among-species variation in Nmass upon fertilization. Conclusions Although our results reflect only short-term community responses, they indicate that trait-based species ranking and the relationships between plant functional traits are not always consistent across different management regimes. Hence, trait values used to characterize species and communities should never be discussed without consideration of the set of environmental conditions under which they were measured.