Biologie

Micropatterns induced by sheep grazing, were studied in three consecutive years in a Festuca rubra-dominated salt marsh in a grazing trial with five different stocking rates (0, 1.5, 3, 4.5 and 10 sheep ha-1). The micropatterns were formed by a mosaic of short and tall F. rubra stands on a scale of square decimeters. Permanent transects of 2 m ×

In January 2015 Lejeunea lamacerina was found for the first time in the Netherlands, near Hoogezand, in the province of Groningen in the north of the country.
Plants were growing 1,5 m high on an oak stem in a 25-year old, mixed plantation of Corsican Pine (Pinus nigra) and Common Oak (Quercus robur) called ‘Drevenbos’. Accompanying species were Kindbergia praelonga, Rhynchostegium confertum, Hypnum cupressiforme, Brachythecium salebrosum, Orthotrichum affine, O. stramineum, Metzgeria furcata, Frullania dilatata, Lophocolea heterophylla and the lichens Anisomeridium polypori and Dimerella pineti. In the vicinity, regionally rare epiphytes such as Homalia trichomanoides (sometimes up to 1,5 m high on a tree), Thamnobryum alopecurum and Cololejeunea minutissima occur in some quantity, others like Neckera crispa, N. complanata, N. pumila, Metzgeria fruticulosa and Orthotrichum pallens are found on a single tree. The young wood is very dense and probably has a damp and shaded microclimate.
The new locality is at the northernmost border of its range on the European continent. Further north, only one other observation (from 2004) is known from SW-Norway. Diaspores of L. lamacerina may have travelled 300 to 400 kilometres from the nearest populations in Belgium or England. In surrounding countries L. lamacerina is usually found on rocks and boulders in or near streams in sheltered, humid wooded valleys in lowland areas. This habitat probably provides protection against frost and drought for this southern, oceanic species. Remarkably however, the new Dutch find is an epiphytic one and is situated in a rather open landscape. The dense, protective structure of the plantation and very mild winter temperatures in recent years may have favoured this new establishment so far to the north.
No perianths with sporophytes were found in the Dutch patch of Lejeunea lamacerina. Nevertheless lower on the same tree some young, separate colonies were observed. On the margin or in the lamina of old, weathered leaves of L. lamacerina sometimes buds of young plants are formed. These regenerants probably can act as a means of vegetative propagation.
On fresh plants a mucilage papilla can be found not only on the apical tooth of the postical lobe, but often also on the distal basic cell of the postical and the antical lobe of the leaves (Figure1). We have not found earlier reports of these papillae in literature for this species of Lejeunea.