Recent developments in bryophyte population ecology

Bryophytes abound in a wide variety of habitats, and despite their low stature play a significant role in many ecosystems. Earlier views of bryophytes as being ‘evolutionary failures’ are being questioned since the discovery of high genetic variability in those species and populations which have been studied. At the same time, there is growing evidence that in many taxa the maintenance of populations is almost completely dependent on asexual propagation; sexual reproduction may result in an enormous spore output, but establishment from spores in the field seems to be very difficult. The remarkably rapid fine-scale dynamics found in many bryophyte populations may play a role in the maintenance of genetical variability; it may also partly determine community diversity

Ecological notes on Carex aquatilis communities

Carex aquatilis spp. aquatilis grows in mesotrophic fens and has a boreal circumpolar distribution. The species is most frequent in areas north of the 66° N line. In Europe the southern limits of its distribution is ca 53°N. Here Carex aquatilis is found in eutrophic flood plains. However, mesotrophic communities of C. aquatilis have been reported from these areas as well. Nowadays the peripheral populations in NW Europe appear to be relics of former mesotrophic communities which at present are under heavy pressure from human activities such as drainage and fertilizing. In the northern part of the Netherlands C. aquatilis stands are restricted to areas with a steady supply of cool groundwater. A decreased groundwater discharge has a negative influence on the development of inflorescences. It is expected that further interference with the hydrology will promote a further decline of the peripheral populations. The species will not be able to survive in drained, eutrophic, warmed up habitats.