Strandline colonization by Elymus farctus in relation to sand mobility and rabbit grazing

(1) The strandline of a sandy coast is a highly disturbed habitat compared with the adjacent foredunes. The catastrophic storm surge of January 1978 entirely removed the strandline communities at Holkham National Nature Reserve, Norfolk. (2) Recolonization by Elymus farctus was rapid. Seeds (caryopses) and rhizome fragments were of very similar importance as propagules in founding new clumps; seeds and rhizome fragments also contributed similarly to the overall tiller densities found in a colonizing population. (3) Subsequently E. farctus maintained a significant but tenuous presence in the strandline. Tillers were frequently killed by deep burial in sand, or swept away after erosion by wind or waves. Foredune populations were much more secure and reached higher (× 10) tiller densities, but were subject to intense rabbit grazing for much of the year. (4) Sand accretion and erosion were greatest between February and May when winds fast enough to move sand (> 4.5 ms-1) were predominantly onshore or along-shore. (5) Inflorescence and seed production were poor: in the foredunes this was because of the grazing pressure; but in the strandline flowering was even worse, because tillers rarely survived for more than one season to become vernalized. (6) Populations of E. farctus in the strandline appear to be dependent on repeated colonization by seed and rhizome fragments from the foredunes. Only rarely do conditions suitable for the initiation of a new dune ridge from the strandline population occur