Determinants of floristic diversity and vegetation composition on the islands of Lake Burollos, Egypt

Abstract

Abstract. A floristic and environmental survey was carried out on 22 uninhabited islands (0.1‐8.4 ha) in Lake Burollos, Egypt. A total of 58 vascular plant species was recorded. The number of habitats on each island was counted. There was a positive correlation between island area and number of habitat types. Island area was significantly positively correlated with various measures of floristic diversity, including the total number of species present, and the numbers of annual, herbaceous, and shrublet species. Perennial and shrub species numbers did not differ significantly with island area. In addition to island area, elevation and soil salinity, as well as distance to the Mediterranean Sea, all contributed significantly to variation in species composition in the terrestrial habitats. Water salinity and transparency accounted for 69% of the variation in aquatic species numbers. There was a weak effect of isolation on similarity of species composition on islands.Eight vegetation types, represented by 13 indicator species identified after TWINSPAN analysis, were distinguished by soil characteristics. Species richness was inversely correlated with clay, organic carbon and total nitrogen in the soil, but positively correlated with calcium carbonate content.From a management perspective, long‐term monitoring of threatened habitats in the lake is urgently required as a starting point to preserve biodiversity. Finally, we conclude that the present study supports the hypothesis indicating that larger areas feature higher species richness due to increased numbers of habitats.