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Nitrate is an important nitrogen source for Arctic tundra plants TEXT SIZE: A A A
Plant nitrogen (N) use is a key component of the N cycle in terrestrial ecosystems. The supply of N to plants affects community species composition and ecosystem processes such as photo-synthesis and carbon (C) accumulation. However, the availabilities and relative importance of different N forms to plants are not well understood. While nitrate (NO3-) is a major N form used by plants worldwide, it is discounted as a N source for Arctic tundra plants because of extremely low NO3- concentrations in Arctic tundra soils, undetectable soil nitrification, and plant-tissue NO3- that is typically below detection limits. Here we reexamine NO3- use by tundra plants using a sensitive denitrifier method to analyze plant-tissue NO3-. Soil-derived NO3- was detected in tundra plant tissues, and tundra plants took up soil NO3- at comparable rates to plants from relatively NO3--rich ecosystems in other biomes. Nitrate assimilation determined by N-15 enrichments of leaf NO3- relative to soil NO3- accounted for 4 to 52% (as estimated by a Bayesian isotope-mixing model) of species-specific total leaf N of Alaskan tundra plants. Our finding that in situ soil NO3- availability for tundra plants is high has important implications for Arctic ecosystems, not only in determining species compositions, but also in determining the loss of N from soils via leaching and denitrification. Plant N uptake and soil N losses can strongly influence C uptake and accumulation in tundra soils. Accordingly, this evidence of NO3- availability in tundra soils is crucial for predicting C storage in tundra.
 

Publication name

 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 115 (13):3398-3403; 10.1073/pnas.1715382115 MAR 27 2018

Author(s)

 Liu, Xue-Yan; Koba, Keisuke; Koyama, Lina A.; Hobbie, Sarah E.; Weiss, Marissa S.; Inagaki, Yoshiyuki; Shaver, Gaius R.; Giblin, Anne E.; Hobara, Satoru; Nadelhoffer, Knute J.; Sommerkorn, Martin; Rastetter, Edward B.; Kling, George W.; Laundre, James A.; Yano, Yuriko; Makabe, Akiko; Yano, Midori; Liu, Cong-Qiang

Corresponding author(s) 

 LIU Xueyan 
 liuxueyan@tju.edu.cn  
 Tianjin Univ, Inst Surface Earth Syst Sci, Tianjin 300072, Peoples R China 
 Tokyo Univ Agr & Technol, Inst Agr, Tokyo 1838509, Japan 
 Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550002, Guizhou, Peoples R China 

 Koba, Keisuke
 keikoba@ecology.kyoto-u.ac.jp
 Tokyo Univ Agr & Technol, Inst Agr, Tokyo 1838509, Japan
 Kyoto Univ, Ctr Ecol Res, Shiga 5202113, Japan

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