Old landfills as emergent vulnerable ecosystems to salinization: soil characteristics and response of the plant species to increasing Na and anion contents

Abstract

The anion contents of soil samples taken from the discharge and slope areas of landfills are considerably elevated with respect to soils collected from ecosystems surrounding these landfills. In this study, greatest concentrations were observed for the more soluble ions Cl- , NO3- and SO4-2- and lowest concentrations for F- and PO4-3 . Species such as Bromus tectorum, Desmazeria rigida, Trifolium tomentosum, Anacyclus clavatus, Carduus tenuiflorus, and Diplotaxis virgata showed a preference for soils containing appreciable amounts of chlorides, sulfates, and sodium, and high electrical conductivities (EC). Of the species listed in the four ecological profile tables provided, Hordeum murinum, Bromus rubens, B. tectorum, Hirschfeldia incana and Polygonum aviculare, also showed a preference for soils with high values of these four factors and were followed by B. hordeaceus, Juncus bufonius, Spergularia rubra, Trifolium cernuum, Medicago polymorpha, Crepis vesicaria, Plantago coronopus and Reseda lutea. Trifolium tomentosum and Crepis capillaris predominantly grew in soils with “certain levels” of chlorides and sodium. Carduus tenuiflorus was most often found in high sodium soils with high conductivity. Diplotaxis virgata preferred soils with high contents of sulfates and sodium. Finally, Desmazeria rigida only grew in soils with a high EC. The species listed comprise the plants that are currently revegetating the steep slopes, “saline” soils and discharge zones of many landfills. These species are helping to reduce the pollutant leachates that eventually reach nearby streams, marshes and pastures.