Floodplains are liable to rapid changes in land uses. Within the Champagne-Ardenne region in France, the surface area covered by forests in the Seine, Aube and Marne valleys has decreased by 27% between 1970 and 1990, in favour of other land uses, such as agriculture, urbanisation, gravel mining, or hybrid poplar plantation. As a consequence, land-use change probably impacts biodiversity both on a local and landscape scale. To assess the role of landscape composition in land-use types on local assemblages, we compared carabid communities between contrasted landscapes in the valleys along the Seine, Aube and Marne rivers. We tested the two following hypotheses: 'Ha - the possibility for poplar plantations to host open-habitat species increases with the proportion of surface area covered by agricultural fields in the surrounding landscape' "Hb - the possibility for poplar plantations to host forest species increases with the proportion of surface area covered by forests or poplar plantations in the surrounding landscape'. Ground beetles were sampled with pitfall traps in 20 young and 20 adult poplar plantations, surrounded by varying proportions of poplar plantations and agricultural fields. Relying on aerial photographs and ArcGIS 9.2, we digitised every patch of habitat detected within a 500-m radius around each sampling plot and characterised its land-use type, surface area and perimeter. In our 40-plot sampling scheme, farmland cover (0-62%) was inversely correlated to poplar plantation cover (6-95%) on a 500-m radius scale. Contrary to our hypothesis, the proportions of surface area covered by agricultural land and, inversely, by poplar plantations, played a rather limited role: only open-habitat eurytopic species showed a higher species richness when farmland cover increased in the surrounding landscape. Conversely, forest cover, although varying on a shorter range (0-41%), had more influence: (1) a positive effect on the richness of forest stenotopic species, and (2) a negative effect on the richness of open-habitat species, especially on eurytopic open-habitat species. Except for the forest stenotopic species, these landscape effects were generally stronger in young poplar plantations than in adult poplar plantations. To conclude, it seemed that carabid community assembly rules in poplar plantations were affected by land-use composition of the floodplain landscape.