Mossfloran vid vattenkvarnar i sydöstra Sverige

Sammanfattning: Bryophytes play an important role in ecosystems in running waters and are common growing on structures in and around watermills. These watermill habitats differ from other parts of the watercourse in terms of microclimate and disturbance regime, and in providing more suitable and variable substrates. Bryophytes were sampled in and around five watermills and five reference sites 300 meters up or downstream from the watermill in the province Småland, in south-eastern Sweden. Species richness was compared between the sites and differences in community structure were analysed by a Discriminant Analysis. In 90% of the cases, the species composition was found to be specific for watermills and reference sites, and the mean species number was 57% higher at watermills than at the reference sites. Rocks and boulders in a wide range of sizes, concrete and mortar structures with pH-levels higher than that of the underlying bedrock, and stronger currents were identified as some of the causes of the higher diversity at the watermills. Restauration projects in rivers, including dam removal, constitute a potential threat to the bryophyte flora of watermills since the structures they grow on may either be removed or destroyed. Changes in microclimate and disturbance regime are other potential threats to species in these habitats.