Grassland restoration on former arable land: Fine‐scale grass accumulation and damaged soil conditions limit species establishment

Abstract Question Which vegetation and soil parameters limit species establishment in restored grasslands? Do these parameters operate predominantly on a fine or a community scale? Location White Carpathian Mountains, SE Czech Republic. Methods We compared 16 grasslands restored on former arable land with 9 well‐preserved reference grasslands. We sampled cover of plant species in plots of 2 m × 2 m (community scale) in which four 20 cm × 20 cm subplots (fine scale) were nested. We quantified fine‐scale heterogeneity as the mean Sørensen dissimilarity index among the species composition of the subplots. To characterize site conditions, we analyzed soil properties, above‐ground plant biomass and its nutrient content. Results Restored grasslands had a lower number of plant species at both the community and fine scales. Species number at the community scale was positively associated with the species number at the fine scale (irrespective of grassland type), but was not associated with fine‐scale heterogeneity. This indicates the importance of fine‐scale biotic interactions for overall species diversity. In support of this, in both grassland types, the species number was negatively associated with the cover of grasses, but only at the fine scale. Total cover (but not the biomass) was lower in restored grasslands, and was positively related with species number, particularly in restored grasslands. This indicates that the lower species number in the restored grasslands mainly resulted from deteriorated abiotic conditions. Such deterioration of the plant environment can be attributed particularly to the soil of the restored, formerly plowed grasslands. They had a lower soil organic matter content and a higher proportion of fine soil particles (silt and clay), indicating reduced soil water availability. The lower soil N content of restored grasslands was also reflected in the nutrient content of plant biomass, where lower N:P and N:K ratios indicated a limitation of plant growth by N‐supply. Conclusion The species number was generally driven by fine‐scale biotic interactions, which operated similarly in both grassland types. The reduced number of plant species in restored grasslands is the result of several factors among which altered soil conditions in the former arable land appears to be highly important.