Edaphic factors controlling the distribution of inland halophytes in an ephemeral salt lake "Sabkha ecosystem" at North African semi-arid lands.

ABSTRACT

This study aims to characterize soil properties and to investigate how these parameters, including soil salinity, are related to zonation and distributional patterns of halophytic plants occurring at edges of the Djendli Sabkha (northeastern Algeria). Soil samples were collected from four stations at Sabkha edges with seven samples for each station. Physicochemical soil parameters were analysed in each vegetation belt of halophytes. Relationships between soil traits were tested to determine spatial variation and their effects on vegetation cover of the principal halophyte species. The influence of pedological factors on the distribution and establishment of halophytes was considered using a redundancy analysis (RDA) and generalized linear models. Positive correlations were found between organic matter, carbon and nitrogen which were negatively correlated with electrical conductivity (EC), pH, gypsum, Na+ and Cl- concentrations. Sharp limits were found between halophyte communities even though there is a gradual change in the physicochemical environment along the gradient centre-to-edge of the Sabkha. RDA showed that edaphic variables that best explained the data were EC, pH, organic matter (OM), carbon and nitrogen contents, Na+ and Cl- concentrations. Sarcocornia fruticosa grew under higher soil salinity (EC=7.2-13.8dS/m) compared to Suaeda fruticosa and Suaeda vermiculata that afford moderate soil salinity, than Atriplex halimus established in soils with low EC values (5.5-7.3dS/m) but with high values of OM, carbon and nitrogen contents and low values of Na+, Cl- and pH. Sarcocornia fruticosa grew in soils characterized with high pH, Na+, Cl- values but relatively low in OM, carbon and nitrogen contents.