Régions humides oligotrophes dans notre paysage eutrophe. Augmentation de l'expulsion anthropogène de matières nutritives (N, P)

Abstract

Oligotrophic wetlands in eutrophicated landscape. Augmentation of the antropogenic output of nutrients (N, P). - Our industrial and agricultural activities provoke a general eutrophication of our wetlands, lakes and swamps, not only due to the changing chemistry of our precipitations but also by seepage from cultivated areas and by inundations with nutrient-rich water from lakes, ditches and other waterbodies. This new state of the environment initiates a series of changes in most wet sites, e.g. reed-death, pseudoreedbelts on fens, «macrophorbisation» of oligotrophic straw meadows (Molinion, Eriophorion latifolii, etc.). Also protected areas undergo such changes. Nutrient gradients are assessed along transects from eutrophic to oligotrophic sites to be alble to detect nutrient fluxes and consequently buffer endangered sites (e.g. quaking mats).

Key Words:

• eutrophication
• macrophorbisation
• nutrient gradients
• eutrophic and oligotrophic sites