Soil Requirements of Three Salt Tolerant, Endemic Species from South-East Spain

The edaphic requirements of three endemic species from SE Spain have been investigated. Limonium, dufourii is a narrow endemic, critically endangered; Thalictrum maritimum and Centaurea dracunculifolia are SE Iberian endemics, considered vulnerable and near threatened, respectively. The three taxa inhabit the same type of saline habitats, salt marshes called "malladas". Several soil parameters (pH, electrical conductivity, soil chloride and sodium contents) were determined in sampling sites where plants of the selected taxa were present. In all the studied zones, soils are basic, with small differences in their pH. The presence of high amounts of chloride and sodium ions indicates sodic-alkaline soils, with NaCl of marine origin as the major salt. There are, however, dear differences in soil salinity, as revealed by electric conductivity (EC) measurements. The extension and size of the populations of the three taxa, as well as their degree of threat, correlate with the edaphic characteristics of their habitats. Limonium, dufourii, by Far the scarcest and most endangered species, was found only in the zones with the highest soil EC, where neither of the other two taxa were present. On the other hand, C. dracunculifolia, relatively frequent and with minimal risk of extinction, tolerates a wide range of variation of electric conductivity in the soil. Thalictrum maritimum shares some of the C. dracunculifolia habitats, those with relatively higher soil salinity, and shows higher salt tolerance tinder controlled greenhouse conditions.