Assessment of effects of the rising atmospheric nitrogen deposition on nitrogen uptake and long‐term water‐use efficiency of plants using nitrogen and carbon stable isotopes

This study assesses the effects of the atmospheric nitrogen (N) deposition on the N uptake and the long‐term water‐use efficiency of two C 3 plants ( Agropyron cristatum and Leymus chinensis ) and two C 4 plants ( Amaranthus retroflexus and Setaria viridis ) using N and C stable isotopes. In addition, this study explores the potential correlation between leaf N isotope (δ 15 N) values and leaf C isotope (δ 13 C) values. This experiment shows that the atmospheric N deposition has significant effects on the N uptake, δ 15 N and leaf N content (N m ) of C 3 plants. As the atmospheric N deposition rises, the proportion and the amount of N absorbed from the simulated atmospheric deposition become higher, and the δ 15 N and N m of the two C 3 plants both also increase, suggesting that the rising atmospheric N deposition is beneficial for C 3 plants. However, C 4 plants display different patterns in their N uptake and in their variations of δ 15 N and N m from those of C 3 plants. C 4 plants absorb less N from the atmospheric deposition, and the leaf N m does not change with the elevated atmospheric N deposition. Photosynthetic pathways may account for the differences between C 3 and C 4 plants. This study also shows that atmospheric N deposition does not play a role in determining the δ 13 C and in the long‐term water‐use efficiency of C 3 and C 4 plants, suggesting that the long‐term water‐use pattern of the plants does not change with the atmospheric N input. In addition, this study does not observe any relationship between leaf δ 15 N and leaf δ 13 C in both C 3 and C 4 plants. Copyright © 2011 John Wiley & Sons, Ltd.