Victims of agricultural intensification: Mowing date affects Rhinanthus spp. regeneration and fruit ripening

The recent population declines of annual hemiparasitic Rhinanthus species may be a result of changes in mowing dates associated with the intensification of grassland management, but the causal mechanisms are not well understood. We aimed to determine the dynamics of Rhinanthus regeneration after cutting and of fruit ripening under silage or hay making. Mowing was simulated on several dates from mid-May to mid-July in populations of a vernal ecotype of Rhinanthus minor and an aestival ecotype of Rh. alectorolophus. Survival and regeneration of clipped plants, as well as fruit ripening were monitored in the experiments. We showed that Rhinanthus species were capable of resprouting, albeit with high mortality, but only in early spring before the lower leaves were shed. The time of fruit ripening differed among phenological types by over a month and a considerable number of fruits ripened during hay making. If meadows are mown in the period when plants are not able to regenerate and not enough fruits have ripened, Rhinanthus populations could undergo a massive decline. Postponing the first cut until fruits start to ripen is necessary for the protection of these species. Current Czech agri-environmental measures (AEMs) subsidize postponing the first cut only in protected areas, which limits the distribution of Rhinanthus. Moreover, the earliest date for a postponed cut is mid-July, which is too late considering forage quality. We suggest implementing a late-June mowing, which would diversify the mosaic of various mowing dates within protected areas, and could be widely acceptable for farmers in non-protected landscapes.