The vegetation of Is-Simar : a wetland reserve in the making

Abstract

Is-Simar in St Paul's Bay, has recently been declared as a Nature Reserve, and it is one of the few saline marshlands still extant in the Maltese Islands. The saltmarsh consists of a central pool of brackish water, with ten small islets and two larger islands populated by a dense plantation of Tamarix africana, thus constituting a Tamarisk grove. An embankment, composed of a clay substrate surrounds the entire reserve. It is about 3m high and almost 1 km in length . Planted trees are found throughout its entire length. An olive grove is found on the South-Eastern side of the reserve. The vegetation communities of the ditch banks and the embankment were studied by means of line-transects. That of the islands was studied by observation from strategic points along the reserve and by means of photographs. The vegetation forming the undergrowth of the Olive grove and that of an open area found behind the embankment was studied by means of random quadrat sampling. Frequency and coverage data were calculated and the vegetation communities of the different habitats studied were compared. Water and soil analysis were conducted in order to assess their affect on the presence and distribution of plant species. The distribution of the vegetation of the saltmarsh is determined by the hydrology of the saltmarsh, the substrate and the elevation of the marsh. Phragmites australis and Afelilotus messanensis are the most dominant species along the ditch banks and on the islets. T. africana is also very common and also growing very rapidly along the ditch banks and the islets. Juncus acutus and Typha domingensis, which have been introduced in the area, are also growing but at a much slower rate. The distribution and the growth patterns of the annual Salsola soda depend on the hydrological dynamics of the water in the marsh. The embankment is characterised by a vegetation typical of a disturbed habitat with species like Sonchus oleraceus, Avena sterilis, Oxalis pes-caprae and Beta maritima being the most dominant. The same can be said for the species sampled from the area behind the embankment. A salinity gradient is found along the reserve with the substrate and the water being more saline towards the Western side. This in turn affects the abundance of the halophytic vegetation present in the marshland. Moreover the salinity of the water is highly correlated to the amount of rainfall, hence the reserve is maintained by direct precipitation during the wet season.