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.