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

Jin Qian; Wen Jin; Jing Hu; Peifang Wang; Chao Wang; Bianhe Lu; Kun Li; Xixian He; Sijing Tang

doi:10.1016/j.scitotenv.2020.143029

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

Sci Total Environ. 2021 Apr 1:763:143029. doi: 10.1016/j.scitotenv.2020.143029. Epub 2020 Oct 21.

Authors

Jin Qian¹, Wen Jin², Jing Hu³, Peifang Wang², Chao Wang², Bianhe Lu², Kun Li², Xixian He², Sijing Tang²

Affiliations

¹ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: hhuqj@hhu.edu.cn.
² Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
³ Wetland Biogeochemistry Laboratory, Soil and Water Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Gainesville, FL, USA.

PMID: 33129526
DOI: 10.1016/j.scitotenv.2020.143029

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 < 0.05) contributions from soil observed among plant species (80.5 ± 4.1, 73.9 ± 2.8 and 58.7 ± 6.1% for A. calamus, C. indica, and P. australis, respectively). Meanwhile, complex water networks, shallow water tables, and high DIN content in rainwater lead to nonignorable N contributions from river water, groundwater and rainwater to plants. Groundwater contributed more percentage of N to P. australis (12.8 ± 3.2%) than A. calamus (6.1 ± 1.9%) and C. indica (8.0 ± 1.5%), which is likely attributed to the deeper roots of P. australis. All plants showed similar N preference for NO₃^- during the growing season. External environmental conditions and plant characteristics and adaption to more abundant soil NO₃^- content are possible explanations. Our research could provide important information for vegetation selections during the process of riparian ecological restoration. Reasonable choice of vegetation is essential to plant growth and water quality management, especially in agricultural watersheds where N concentrations are relatively high in agricultural runoff due to the wide uses of N fertilizers.

Keywords: Acorus calamus; Canna indica; Isosource model; N acquisition; Phragmites australis.

MeSH terms

Ammonium Compounds*
China
Ecosystem
Environmental Monitoring
Isotopes
Lakes
Nitrates / analysis
Nitrogen
Seasons
Water Pollutants, Chemical* / analysis

Substances

Ammonium Compounds
Isotopes
Nitrates
Water Pollutants, Chemical
Nitrogen