Rhinanthus: A tool for restoring diverse grassland?

The restoration of species-rich grasslands is often hindered by high residual soil fertility as a result of, e.g., intensive farming. The establishment of a diverse range of target species on such sites requires the reduction of soil fertility or of the vigour of competitive plants. Current methods to achieve these aims are often unsuccessful or complicated and expensive. It has been suggested that Rhinanthus species could be used to decrease the growth of competitive plants and enhance species diversity. We review evidence for this potential and suggest five key attributes that make Rhinanthus species a practical restoration tool. Rhinanthus species are natural components of species-rich grasslands (attribute 1), and seed of some species is relatively low cost and easily obtainable (2). Recent work has shown that certain Rhinanthus species reduce the vigour of competitive species, especially agricultural grasses, and allow establishment and persistence of target species (3). We analyze demographic data and show that certain Rhinanthus species have the ability for rapid population growth and spread, even in fertile grasslands (4). We also show that it is relatively easy for land managers to limit the population size of Rhinanthus species and prevent damage (e.g. excessive loss in production or invasion by weeds) to grasslands by excessive densities (5). We give suggestions for further research, including: the range of species-poor grasslands into which Rhinanthus can be introduced successfully and which Rhinanthus species should be used; the mechanisms by which Rhinanthus enhances diversity in restored grasslands; whether the ecotype or subspecies of Rhinauthus used affects restoration success; how management methods affect population growth and spread of Rhinanthus; and whether other parasitic plants could be used in habitat restoration.