Abstract
During the life cycle of Scirpus maritimus, ramets produce photosynthetic shoots that are active for a single growing season and only the belowground parts persist into the next year. Several authors have described that the growing season of S. maritimus in Europe and North America occurs between April and September of each year. In the Mondego estuary (western coast of Portugal) the life cycle of S. maritimus showed an opposite seasonal pattern, with a growing season from January to April/May. It was hypothesised that seasonal fluctuations in salinity, connected to salinity tolerance, could explain this contrasting annual cycle. This hypothesis was tested using a greenhouse experiment. Exposure to different salinities significantly affected plant survival. During the first 10 days, the survival curves were very similar, which suggested that the plants were able to tolerate high salinity for short periods. After 2 weeks of exposure, the plants started to show differences, with increased mortality following the increase in salinity. Results show that a peculiar seasonal variation of salinity in the Mondego estuary affected the S. maritimus life cycle in this ecosystem and may explain the differences between these western Portugese populations and other European and North American populations.
Published Version
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