Changes in Ammophila cover and plant richness over a 21-year period from 1988 to 2009.

‘Switch’ refers to transects that had substantial A. arenaria in 1988 and were dominated by A. breviligulata in 2009. “Estab.’ refers to transects that were dominated by A. breviligulata in both 1988 and 2009. (A) Mean relative Ammophila cover ± S.E.; (B) Relative Ammophila cover across the dune gradient; (C) Mean plant richness ± S.E.; (D) Plant richness across the dune gradient. Light red denotes switched transects in 1988; light blue denotes established transects in 1988; dark red denotes switched transects in 2009; dark blue denotes established transects in 2009. Three separate linear contrasts shown at different heights in (A) and (C), stars signify significance (p Ammophila cover between switched and established transects in 1988 but not in 2009. For (D), there were no significant differences in richness along the dune gradient within either 1988 or 2009. See Table 1 for full models.