Drought avoidance strategy drives the assembly of plant communities in grasslands restored on former arable land

Restoring species-rich grasslands on former arable land is challenging due to persistent tillage effects. Comparing community- and individual-level traits between restored and ancient grasslands may identify environmental limitations. In 10 restored and 9 ancient reference grasslands (White Carpathian region, Czechia), we measured five functional traits for 110 grassland species, representing a nutrient acquisitive-conservative spectrum - specific leaf area (SLA), leaf area, leaf dry matter content (LDMC), and plant height, plus water potential at turgor loss point to assess drought-resistance strategy (avoidance or tolerance). We sampled species composition on the community scale (2 m × 2 m) and the fine scale of plant-to-plant interactions (20 cm × 20 cm). We then quantified for each trait the community-weighted means (CWM) and patterns of functional diversity (trait convergence - environmental filtering for a specific trait; or trait divergence - selection for differences between species). For six species, we also measured intraspecific trait variability, assessing the individual species responses to restored and ancient grasslands. Lower CWM_SLA and CWM_{leaf area}, and their convergence on fine scale indicates higher dominance of a nutrient-conservative strategy in restored grasslands. Intraspecific trait variability for these traits showed opposite values, suggesting that the environment affects seed germination or plant seedling establishment differently from the performance of adult plants. Both scales (community and fine) showed difference in drought-stress resistance mechanisms between grasslands. Higher values of CWM for turgor loss point and its convergence indicate strong environmental filtering of species with an avoidant drought-resistance strategy, suggesting strong limitation by disrupted water regime in restored grasslands.