Stable isotope analyses of nitrogen source and preference for ammonium versus nitrate of riparian plants during the plant growing season in Taihu Lake Basin

ABSTRACT Plants are vital components of the nitrogen (N) cycling in the riparian zones. Understanding of N uptake strategies of riparian plants, including N sources and preference in N forms (ammonium (NH4+) vs. nitrate (NO3-)), is essential to advance our knowledge on the role that plants play in regulating nutrient biogeochemical cyclings in the riparian areas. In this study, stable N isotopes (δ15N) of three riparian plants, including Acorus calamus, Canna indica and Phragmites australis, and the δ15N of NH4+ and NO3- in different sources were measured during the plant growing season (June-September) in the Taihu Lake Basin. The dissolved inorganic N (DIN) from river water, groundwater, rainwater and soil were considered as the major N sources for plants in the riparian ecosystem. Our results indicated that soil was the largest source for plant N nutrition, with significantly different (P