Guidance: Pre-treatment has a significant effect in the early years of saltmarsh establishment but soon diminishes. Salicornia colonisation is higher in the areas of grass and stubble, probably because the dead vegetation prevented seeds being removed by tidal currents or invertebrates. These effects disappear in later years. Topographical 'roughness' (of the former ploughed sites) remains visible and provides surfaces in some lower zones, which are differentially colonised by algae.