Establishment of hemiparasitic Rhinanthus spp. in grassland restoration: lessons learned from sowing experiments

Questions What are the factors limiting the establishment of hemiparasitic R hinanthus spp., ecosystem engineers promoting diversity and stability of communities, in restoration of species‐rich meadows? How can these constraints be overcome? Location C zech R epublic, C entral E urope. Methods Sowing of R hinanthus seeds in grasslands of different history, biotic and abiotic properties accompanied by a variety of management practices. Followed by consequent monitoring of establishment and population dynamics and synthesis of relevant literature resources. Results Appropriate timing of seed sowing is needed for successful R hinanthus introduction. R hinanthus seeds must be sown at latest in November to break their dormancy (valid for Central European populations; might be different e.g. in oceanic regions). R hinanthus is able to establish a viable population mainly in low‐ to moderately‐productive grasslands with biomass production below 500 g·DW·m −2 . Its establishment is difficult in grasslands of higher productivity due to the effect of competition for light on the seedlings. R hinanthus requires grasslands with appropriate management including mowing and removal of litter, if it accumulates. Otherwise, the litter layer strongly suppresses seedling establishment. Litter removal can allow establishment even in some productive communities such as stands of C alamagrostis epigejos . However, early mowing (i.e. mowing conducted before ripening of seeds) can lead to a strong decline or even local eradication of the hemiparasitic annuals. Soil conditions on the site of seed origin and the target site can play an important role, as indicated by failures of establishment of R hinanthus originating from slightly acidic soils on sites with soil pH values around 8. Suitability of a given site for R hinanthus introduction can be estimated on the basis of its species composition using the Beals index or less formal expert knowledge of local floristic associations of R hinanthus spp. In the case of suitable conditions, sowing density of 200–500 seeds·m −2 should be sufficient for R hinanthus establishment. Conclusion Mowing or grazing, litter removal, proper timing of sowing, and use of the seeds from local seed sources should considerably increase probability of R hinanthus successful introduction. However, stochastic events like adverse weather conditions or damage through herbivory make the prediction of introduction success difficult.