Enkele notities over de mosvegetatie van een oude Kleigroeve te Venlo

Some details are given on the bryophyte vegetation in an old clay pit near Venlo. Due to burrowing activities, the bottom of the pit has a very broken surface, and in the upper soil layer sand, sandy clay and pure clay (from the Tiglien formation) replace each other. On some places water comes out of the soil. Some locally important bryophyte unions (in the sense of Barkman 1973) are described. An impoverished form of the Haplomitrium- Fossombronia incurva union occurs on moist sandy ground. On a steep, south-exposed, dry clay edge a fragment of the Aloinetum rigidae was found. The wet clayey parts are occupied by a vegetation mainly consisting of Leiocolea badensis and Anisothecium varium, for which a new union is proposed, the Leiocolea badensis- Anisothecium varium union. On a steep sandy side the rare species Anisothecium rufescens, Mniobryum lutescens and Trichodon cylindricus were found; the last two species have not been reported from the Netherlands before. In conclusion, the importance of such clay pits in general and this one in particular as refugia for bryophyte flora and vegation is stressed.