THE ECOLOGY OF THE STRANDLINE ANNUALS CAKILE-MARITIMA AND SALSOLA-KALI .1. ENVIRONMENTAL-FACTORS AFFECTING PLANT PERFORMANCE

(1) Cakile maritima and Salsola kali, two annual strandline species, show marked differences in growth dependent on their position of establishment on sandy shores. Large, rapidly growing plants are associated with sand containing macroalgal litter, whereas small stunted plants are found on foredunes above the limit of tidal inundation. (2) Edaphic variables and plant nutrient concentrations were monitored throughout the growing season of 1988 at Harlech, Wales to establish potential causes of this difference in performance. (3) Differences in performance of plants on the foredune and strandline were not the result of any difference in the availability of water or potassium. (4) Nitrogen was more concentrated in strandline sand and was at much higher concentrations in the leaves of C. maritima and S. kali growing on this sand, compared with foredune sand, especially at the end of the growing season. (5) This difference in growth was probably caused by higher nitrogen availability on the strandline, and might have been exacerbated by a nitrogen-dependent salt stimulation of growth of strandline established plants and the greater demand on leaf nitrogen for the accumulation of nitrogenous solutes in the nitrogen-deficient plants on the foredune. (6) A difference in the availability of phosphorus between foredune and strandline sand may also have contributed to this difference in growth.