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Conserving the flora on erratic boulders


Erratic boulders harbour special rock-dwelling bryophytes and ferns and thus contribute to the regional biodiversity. This is especially the case in areas where erratic boulders constitute the only natural rock habitats or where their chemical composition contrasts with bedrock composition. In the calcareous Swiss Plateau and Jura Mountains, many bryophyte and one fern species exclusively occur on siliceous erratic boulders. These spatially isolated plant communities are threatened by land use change and bouldering. The project aims at establishing the scientific basis for the conservation of the flora on siliceous erratic boulders.


First, bryophyte and vascular plant diversity and their ecological determinants are analysed on siliceous erratic boulders in eight study regions in Switzerland. Second, the effect of chalk, as used in rock climbing, on rock-dwelling bryophytes and ferns is assessed in climate chamber experiments. Third, the population history and connectivity of the fern Asplenium septentrionale and the moss Hedwigia ciliata are studied with genetic methods (SNPs from ddRAD). Fourth, practical conservation measures (e.g. decreased shading of surrounding forests) are evaluated.

Flora of erratic boulders webpage