Nieuwe vondsten in Nederland van de witkring, Sporodophoron (voorheen Schismatomma) cretaceum, in de Biesbosch (N-Br.) en op Havezate Mensinge (Dr.)
Buxbaumiella , Volume 106 p. 15- 24
Two recent finds of Sporodophoron cretaceum in The Netherlands, in the Biesbosch (prov. N-Br.) and at Havezate Mensinge (prov. Dr.). In April 2016 the very rare Sporodophoron (previous name: Schismatomma) cretaceum was discovered in The Netherlands at two new stations. Until recently only six records were known from The Netherlands, four of them from the nineteenth and one from the twentieth century. In the Biesbosch, a National Park in the freshwater tidal environment near the city of Dordrecht, Sporodophoron cretaceum was found in two willow forests called ‘Benedenste Jannezand’ and ‘St.-Jansplaat’. Both are former willow coppices, abandoned respectively 45 and 60 years ago. Developments are now taking place towards more natural, structurally rich Salicion albae vegetations. Sporodophoron cretaceum was found 0.5 to 3 m high on the dry, east facing bark of old vertical or slanting willow stems with a diameter ranging from 25 to 60 cm. In the Benedenste Jannezand a fairly large and apparently expanding population was discovered. One stem base was nearly completely covered with the lichen and on six stems in the near vicinity a total of about 35 small colonies could be traced. In the woods of the Biesbosch fallen willow trees rejuvenate on a large scale by forming vertical branches. On such young branches, not far from the Sporodophoron cretaceum locality, several other interesting epiphytes were discovered that are very rare in The Netherlands, e.g. Habrodon perpusillus, Phaeographis smithii, Arthonia cinnabaria and Bacidia laurocerasi. From a floristic point of view the recent influx of epiphytic forest lichens shows that the unmanaged willow stands in the Biesbosch are rapidly developing into a more mature forest ecosystem. In the same period two smaller populations of Sporodophoron cretaceum were found at Havezate Mensinge, a historical estate in the province of Drenthe in the northern part of the country. At Mensinge S. cretaceum covers the dry sheltered part of an old Quercus on the edge of a canal. It is accompanied by Dendrographa decolorans (previous name: Schismatomma decolorans), Diploicia canescens and Haematomma ochroleucum, a set of species diagnostic of the Ramalinetum duriaei. This community is usually associated with ancient woodland. In The Netherlands it is rare and restricted to old, slow growing roadside trees. A provisional distribution map of S. cretaceum in Europe is presented based on literature. From this map the species shows a rather distinct Atlantic distribution.
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A. van der Pluijm, & K.W. van Dort. (2016). Nieuwe vondsten in Nederland van de witkring, Sporodophoron (voorheen Schismatomma) cretaceum, in de Biesbosch (N-Br.) en op Havezate Mensinge (Dr.). Buxbaumiella, 106, 15–24.
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