Het voorkomen van Rhytidiadelphus triquetrus, R. loreus en Thuidium tamariscinum in Nederland

Distribution maps of Rhytidiadelphus triquetrus, R. loreus en Thuidium tamariscinum in The Netherlands are presented. Rhytidiadelphus triquetrus has become a rare species in the pleistocene part of The Netherlands whereas the presence of this species seems to be more or less stable in coastal areas. However, even here the species has become less common although this is not apparent on maps based on a 5x5 km2 grid. Indirect effects of air pollution form a possible explanation for the reduced number of accounts, at least in coastal areas where scrub and tall grasses replaced the low vegetation in which R. triquetrus has its optimum. The occurrence of Rhytidiadelphus loreus and Thuidium tamariscinum did not change very much during the last decennia. However, in the center of The Netherlands recent accounts of both species are rather rare. This might be a result of a lack of bryological excursions to this area.