| Popis: |
A survey of historical records revealed that the disappearance of characteristic rich-fen bryophytes such as Scorpidium scorpioides, S. revolvens and Campylium stellatum from the springs of De Mosbeek, the Netherlands, has taken place between 1951 and 1956. A study of the present ecohydrological situation suggests that the present water chemistry (pH, EC and Ionic Ratio) and trophic status (P concentrations) fall within the range suitable for S. scorpioides and that the water is well-buffered. To test the hypothesis that the present absence of rich-fen bryophytes is due to past habitat change rather than ecohydrological conditions, a transplantation experiment with S. scorpioides was carried out. Reintroduction of the species resulted in establishment of new shoots throughout the spring channel up to a distance of 2 m from the initial transplants within three years, which confirmed that the water composition is not detrimental to the species. It is unknown what caused the disappearance of the species in the 1951–1956 period. An unusual rainfall pattern, increased atmospheric deposition and changes in management all could have played a role. Historical data suggest a strong expansion of Sphagnum spp. and, via this, the disappearance of S. scorpioides and associated species. The present absence of S. scorpioides seems to be due to poor dispersal and establishment rather than habitat conditions. |
