Are similar landscapes the result of similar histories?

This landscape study was based on the sampling of 20 replicated landscape sites (1 km(2) each) that were located within the floodplain of the river Seine. For each site, 13 landscape variables were measured at three dates (1963-1985-2000). The aim of this study was to investigate the overall landscape variability through its different dimensions (space vs. time) and to assess the relative importance of each dimension. We used a new statistical method, i.e., partial triadic analysis (PTA), which allowed us to assess both (1) the spatial variability of the floodplain landscape and its dynamics in time and (2) the dynamic trajectories of the landscape variables for each site. The results showed, at the floodplain scale, the same landscape pattern has emerged since 1963, although a major trend was observed which consisted in a decrease in meadows resulting from an increase in arable crops. At the site scale, landscape sites, even if they were all influenced by this general trend during the 40-year period, showed contrasting trajectories. These results suggest that similar sites in 2000 do not necessarily share common histories and that contrasting sites in 2000 may have originated from similar patterns in 1963. The issue of biodiversity surrogates is then discussed, suggesting that new landscape metrics should be developed, emphasising spatial variability and (or) temporal dynamics.