Talk Greening highway corridors to support butterfly metapopulations in protected areas: new technology for restoration of seminatural vegetation using root hemiparasites

Highway corridors are usually fringed with wide safety verges that are often maintained as grasslands by mulching several times a year. Improperly grassed verges represent a significant threat to native flora and fauna, but verges hosting semi-natural vegetation might serve as new habitats for many endangered butterflies and connect their last isolated metapopulations in neighbouring protected areas. Semi-natural vegetation can be established either by seeding regional grass-forbs mixtures, which is quite expansive and feasible only on new road constructions, or by ecological restoration of contemporary vegetation. In the past, commercial seed mixtures for highway verges in the Czech Republic consisted mainly of the cheapest forage varieties of cultivated grasses (Festuca rubra, F. arundinacea, Lolium perenne, Poa pratensis) which are typical by high biomass production. Thus, current vegetation is usually dominated by these competitive species or by quickly expanding grass Arrhenatherum elatius. Here, new technology using native root hemiparasitic plants is described. This should support butterfly food plants (mostly competitively weak dicotyledonous forbs) without complicated technical reclamation.

Hemiparasites from genus Rhinanthus are green plants sucking water and nutrients from host roots. In last two decades Rhinanthus was locally used in Western Europe to increase diversity of meadows as well as road verges. However, technology has not spread up possibly due to high cost of seeds and poor establishment of selected Rhinanthus species. Five years ago our research team discovered that Rhinanthus alectorolophus, species native to Central Europe and formerly common weed of cereals, is able to establish viable population almost at all grassland habitats and eradicate most grasses in 1–2 vegetation seasons. Dicotyledonous forbs are usually well protected against Rhinanthus parasitism and quickly spread on site at the expense of grasses. As an annual species Rhinanthus is completely dependent on its host plants (i.e. grasses) and after their suppression also Rhinanthus disappears from vegetation opening space in canopy and releasing nutrients for other species. Moreover, R. alectorolophus is a vigorous plant and its seeds are easily multiplied, thus species has the potential for commercial production.

Four-year project connecting biological and agricultural universities with the Czech project office planning construction of highways and supra-national seed-producing company was started in spring 2015. In close interdisciplinary collaboration 10 model sites were selected, highway verges having 1000 m2 in size, which are situated nearby protected areas and their vegetation is dominated by grasses. At first, botanists recorded initial plant species composition and species dominance while entomologists monitored seasonal occurrence of butterflies. After collection of this baseline data Rhinanthus was sown in a density 500 seeds per 1 m2 on one randomly selected half of each site, in order to verify the effect of hemiparasites on vegetation and butterflies in situ experimentally. At IENE conference 2016 results from the first year will be presented and road maintenance specialists will have the chance to assess whether this technology suppressing productive grasses is also able to decrease the necessity of frequent mulching.

protected areas, migration corridors, butterflies, food plants, endangered species, nature conservation, root hemiparasites, reducing productivity, technical conditions for road construction, grass-forb mixtures