An article “Nitrate is an important nitrogen source for Arctic tundra plants” is published in PNAS.

Xue-Yan Liu, Keisuke Koba, Lina A. Koyama, Sarah E. Hobbie, Marissa S.Weiss, Yoshiyuki Inagaki, Gaius R. Shaver, Anne E. Giblin, Satoru Hobara, Knute J. Nadelhoffer, Martin Sommerkorn, Edward B. Rastetter, George W.Kling, James A. Laundre, Yuriko Yano, Akiko Makabe, Midori Yano, Cong-Qiang Liu (2018) Proceedings of the National Academy of Sciences Mar 2018, 115 (13) 3398-3403; DOI:10.1073/pnas.1715382115

Thanks to Liu-san!