Plant type mediates rhizospheric microbial activities and soil aggregation in a semiarid Mediterranean salt marsh

This study was carried out in a Mediterranean salt marsh from semiarid Southeastern Spain, to determine the influence of eight halophytes (Asteriscus maritimus (L.) Less., Arthrocnemum macrostachyum (Moric.) Moris, Frankenia corymbosa Desf., Halimione portulacoides (L.) Aellen, Limonium cossonianum O. Kuntze, Limonium caesium (Girard) O. Kuntze, Lygeum spartum L., and Suaeda vera Forsskål ex J.F. Gmelin growing in a homogeneous area with regard to salt content, on the rhizosphere soil microbiological and biochemical properties (labile C fractions, biomass C, oxidoreductases and hydrolases) and aggregate stabilisation. Rhizosphere soil of H. portulacoides showed the highest values of water-soluble C, water-soluble carbohydrates, microbial biomass C and dehydrogenase, urease, protease-BAA and acid phosphatase activities. S. vera had the lowest microbial activity. The soil under A. maritimus, L. cossonianum, L. spartum and H. portulacoides had the highest percentages of stable aggregates (on average, about 52%) and the soil under S. vera the lowest (about 27% of stable aggregates). There was a good correlation between enzyme activities, the C-biomass, root colonisation of the eight halophytes and the levels of stable aggregates. Our results suggest that soil microbial activity and soil properties related to microbial activity, such as aggregate stability, are determined by the type of the halophytic species.