A Quantitative Study of the Influence of Tide Upon Populations of Salicornia Europea

1. An investigation was carried out at the Ynyslas end of the Dovey salt marshes in order to examine the relation between the density and vigour of populations of Salicornia europea and frequency of submergence by tides. 2. Data for density of individuals and wet weight were collected from five transects, 1000 ft. in length; four lying across the spring- and neap-tide zones, and one lying entirely within the neap-tide zone. The densities along one transect were taken in April 1934, and again in July, from which information the percentage mortality of seedlings along this transect was calculated. 3. Within the neap-tide zone, where populations are submerged every 12 hours, only 25 per cent. of the seedlings survive. In the spring-tide zone, across which the periods between successive tides vary from 1 to 15 days, about 65 per cent. of the seedlings survive. 4. From these data it is concluded that a "threshold" time of about 2 or 3 days undisturbed by tides, is necessary for the establishment of a dense population of Salicornia. Longer periods between successive tides do not reduce the mortality of the seedlings. 5. From a comparison of chart-quadrats taken in April and July, and from an inspection of the morphology of the surviving plants, it is seen that the daily tides act deleteriously by dragging the seedlings from their anchorage in the mud. 6. The number of germinating seeds of Salicornia is greater in the spring-tide zone than in the neap-tide zone. 7. From the data for wet weights it is concluded that once a plant has become established, daily submergence by the tide does not inhibit its growth.