Sensitivity of ephemeral wetland swards with Isoetes histrix Bory to environmental variables: Implications for the conservation of Mediterranean temporary ponds

Small-scale landscape elements such as freshwater ponds and pools remain poorly characterized and vulnerable to destruction, despite their significant contribution to regional aquatic biodiversity. Ephemeral wetland swards supporting Isoetes histrix, which are considered priority interest habitats by the European Habitats Directive on the conservation of wild fauna and flora (codex 3170* - Mediterranean temporary ponds), typify concave pond shorelines (Habitat A) and very shallow flat temporary ponds (Habitat B). It is hypothesized that although this sward type is highly specialized for growth in waterlogged soils, it is highly sensitive to changes in composition and seasonal dynamics related to varied environmental conditions. The present study was aimed at comparing plant assemblages, and successional processes and dynamics during the growing season between different habitat types; and identifying the key factors influencing spatial variability. Vegetation was sampled three times during the growing season in the two habitat types (i.e A and B). At each site a range of environmental variables was also recorded. PERMANOVA analysis indicated that plant assemblages differed between the two habitat types throughout the growing season. The different hydroperiod length was the main factor responsible for the specificity of the two habitats, revealed by CCA. However, the pattern of successional processes and seasonal dynamics was similar between the two habitats. The results confirmed the hypothesis, and strengthened the understanding of the relevance of hydroperiod length to plant assemblages in ephemeral ponds. The two habitats exhibit unique characteristics, and represent different aspects of priority habitat 3170*; therefore, to ensure that the highest level of biodiversity is maintained, measures must be taken to protect both sward habitats. © 2012 John Wiley & Sons, Ltd.