Reversing expansion of <italic>Calamagrostis epigejos</italic> in a grassland biodiversity hotspot: Hemiparasitic <italic>Rhinanthus major</italic> does a better job than increased mowing intensity.

Abstract: Questions: Can hemiparasitic <italic>Rhinanthus major</italic> originating from a local population suppress the competitive clonal grass <italic>Calamagrostis epigejos</italic> and reverse its expansion in species‐rich semi‐natural grasslands? Does sowing seeds of <italic>R. major</italic> facilitate restoration of target meadow vegetation? Is <italic>R. major</italic> more beneficial for biodiversity restoration/conservation than increased mowing intensity, a conventional measure to suppress <italic>C. epigejos</italic>? Location: Čertoryje National Nature Reserve, Bílé Karpaty (White Carpathians) Protected Landscape Area, Czech Republic. Methods: We conducted a before‐after‐control‐impact experiment in meadow patches heavily infested by <italic>C. epigejos</italic>: eight blocks, each containing four plots with four treatment combinations: (1) traditional management, i.e. mowing once in summer, (2) mowing in summer and autumn (3) mowing in summer and seed sowing of <italic>R. major</italic>, (4) mowing in summer and autumn and seed sowing of <italic>R. major</italic>. Above‐ground biomass of <italic>C. epigejos</italic> and vegetation composition of each of the plots were monitored every year from 2013 to 2016. To assess the effects of treatments, we analysed biomass production of <italic>C. epigejos</italic>, herb layer cover and vegetation composition. Results: Both sowing <italic>R. major</italic> and an additional autumn meadow cut significantly suppressed <italic>C. epigejos</italic>. Their effects were additive and of comparable size. Both treatments also had significant but markedly different effects on community composition. <italic>Rhinanthus major</italic> facilitated directional community composition change towards the regional <italic>Brachypodio‐Molinetum</italic> meadows. In contrast, increased mowing intensity significantly decreased frequency of threatened species, which however may have also been influenced by <italic>R. major</italic>. Conclusions: Sowing of autochthonous <italic>R. major</italic> seeds was demonstrated as an efficient tool to suppress <italic>C. epigejos</italic> and facilitate community restoration. It can be combined with an additional meadow cut to further accelerate decline of the grass. The additional cut should however be used as a short‐term practice (1–2 years) only to minimize potential negative effects of its long‐term application on some threatened plant species. The effects of <italic>R. major</italic> are comparable to those of <italic>Rhinanthus alectorolophus</italic> reported previously. As a species occurring naturally in species‐rich dry grasslands, <italic>R. major</italic> has a broader and longer‐term application potential than <italic>R. alectorolophus</italic> in ecological restoration and conservation of these communities. [ABSTRACT FROM AUTHOR]