Effects of forestry practices on relict plant species on limestone cliffs in the northern Swiss Jura mountains

Limestone cliffs in the forests of the Swiss Jura mountains harbour a highly diverse plant community including glacial relict species. This unique cliff vegetation is increasingly threatened by overgrowing forest and recreational activities (sport climbing and picnicking). Management objectives of the surrounding forest focus on the conservation of the cliff vegetation. The most suitable forestry practice to achieve this goal is, however, still unknown. We examined the effects of two different forestry practices (clear-cutting and shelter tree cutting) on the species richness and abundance of vascular plants on the face, at the base and on the talus of three cliffs. As controls we considered areas with no management in the past 80 years (forest reserves) at the same cliffs. Plant species density (number of species/m2) and vegetation cover were higher in shelter cut areas than in the forest reserves both on the talus and at the cliff base. Clear-cut areas had a higher vegetation cover than forest reserves on the talus. Shelter cut areas showed a larger proportion of plants with high light demand and a higher mean light score of plants than clear-cut areas and forest reserves. We conclude that selective cutting of trees (shelter tree cutting) is the best forestry practice for the conservation of a high biodiversity and a multitude of relict plant species on limestone cliffs in the Jura mountains. However, this forestry practice is time-consuming and thus expensive. To preserve the specialised cliff flora, sponsorship for this forestry practice is needed from governmental and non-governmental organisations.