RESTORATION ECOLOGY OF RIVERINE WETLANDS .3. VEGETATION SURVEY AND MONITORING OPTIMIZATION

A restoration experiment was carried out in a former channel of the Rh one River, France. To evaluate restoration success or failure, aquatic vegetation was surveyed monthly from March to October, one year prior to and 2 years following restoration. This was done in both the chann el restored by the dredging of fine organic nutrient-rich sediments an d in a similar reference channel. Whereas both species richness and to tal vegetational cover per transect of aquatic vegetation showed the s ame temporal pattern each year in each zone, these two variables exhib ited a different pattern in the restored channel after restoration. Sp ecies richness generally increased continuously during the first year following restoration, then followed a seasonal pattern during the sec ond year. Total vegetational cover was very low the first year followi ng restoration and remained low afterwards, except in the upstream zon e of the restored channel, which was fully colonized by aquatic vegeta tion the second year. Post-restoration changes were thus very clear in the upstream zone of the restored channel. A multivariate analysis de picted changes in the floristic composition: whereas vegetation compos ition was quite stable in the reference channel, eutrophic species wer e replaced by mesotrophic species in the restored channel.