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Many wet closed depressions are located in low attitude “ancient” forests of the Lorrain plateau on the Keuper marl substratum. The origin ofthese depressions remains hypothetical. Some of these depressions are filled with peat and colonized by acid peat bog vegetation. A 440 cm deep peat core from the Römersberg forest was analysed for pollen and radiocarbon dated. Sediment and palynological records begin during the 8th century in forested context marked by a direct anthropogenic impact corresponding to Carolingian clearance. Aquatic taxa (Potamogeton, Nymphaea) colonized the structure which can be compared to a small pond bordered by Alnus and Salix. The main period of anthropogenic impact occurs during the 12th century linked with salt factory establishment in Dieuze town which used a part of the Römersberg forest for wood supply. Anthropogenic impact increases during the 14th century with salt industry development. Peat formation begins during this period along with acid vegetation development. In the 15th century, Römersberg forest becomes an exclusive forestry supply area for rock salt industry with short tree exploitation cycle. During the industrial revolution, salt industry substitute wood by coal as fuel and Römersberg forest exploitation switch from short exploitation cycle to actual forestry exploitation system.