Search

Wetlands are highly effective systems mitigating the negative effects of N excess, but at the same time they contribute to global warming through greenhouse gas emissions. The present study aimed to ascertain the role of Phragmites australis in N transformations in eutrophic semiarid salt marshes, under low (NO 3 − = 20 mg L − 1 ) and high (NO 3 − = 200 mg L − 1 ) nutrient level and alternating flooding-drying phases. Methacrylate mesocosms were filled with a saline soil, with and without the presence of Phragmites stands, and subjected to alternating flooding-drying conditions. For 44 weeks the soil Eh was regularly monitored at two depths and the N-NO 3 − and N-NH 4 + concentration in pore water and drainage and the potential soil N-N 2 O emissions to the atmosphere measured. In the surface soil layers, more than the 80% of N-NO 3 − was removed regardless of the presence of plants, the nutrient level and the season of the year. Denitrification seemed to be the main responsible of this. In the subsurface soil layers N-NO 3 − decreased an average of ~ 83% in presence of Phragmites and ~ 32% without plants during the warmer period (soil temp. ~ 15 to ~ 30 °C), but the effectiveness was reduced to < 10% during the colder period (soil temp. ~ 10 to ~ 15 °C). The N-NH 4 + increased during the flooding phases (reaching 2–6 mg L − 1 ), and the results indicated that it was nitrified during the following drying phases. A tendency to lower potential soil N-N 2 O emissions was observed in treatments with Phragmites during drying phases, pointing that the plants absorbed this newly formed N-NO 3 − . Hence, we propose harvesting Phragmites stands at the beginning of the summer, but after a lag time to permit N-NO 3 − absorption by plants before the complete drying of the watercourses. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to evaluate the combined effects of liming and behaviour of Sarcocornia fruticosa as a strategy of phytomanagement of metal polluted salt marsh soils. Soils were taken from two polluted salt marshes (one with fine texture and pH∼6.4 and the other one with sandy texture and pH∼3.1). A lime amendment derived from the marble industry was added to each soil at a rate of 20gkg−1, giving four treatments: neutral soil with/without liming and acidic soil with/without liming. Cuttings of S. fruticosa were planted in pots filled with these substrates and grown for 10 months. The pots were irrigated with eutrophicated water. As expected, lime amendment decreased the soluble metal concentrations. In both soils, liming favoured the growth of S. fruticosa and enhanced the capacity of the plants to phytostabilise metals in roots. [Copyright &y& Elsevier]