Constraints to nitrogen acquisition of terrestrial plants under elevated CO2 |
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| Authors: | Zhaozhong Feng Tobias Rütting Håkan Pleijel Göran Wallin Peter B Reich Claudia I Kammann Paul CD Newton Kazuhiko Kobayashi Yunjian Luo Johan Uddling |
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| Affiliation: | 1. Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden;2. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco‐Environmental Sciences, Chinese Academy of Sciences, Beijing, China;3. Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden;4. Department of Forest Resources, University of Minnesota, St. Paul, MN, USA;5. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia;6. Department of Plant Ecology, Justus‐Liebig‐University Giessen, Giessen, Germany;7. AgResearch Grasslands, Palmerston North, New Zealand;8. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo‐ku, Tokyo, Japan;9. Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China |
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| Abstract: | A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO2 (eCO2), and whether or not this constraint will become stronger over time. We explored the ecosystem‐scale relationship between responses of plant productivity and N acquisition to eCO2 in free‐air CO2 enrichment (FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong (r2 = 0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO2 likely acquired less N than ambient CO2‐grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO2, and this decrease was independent of the presence or magnitude of eCO2‐induced productivity enhancement, refuting the long‐held hypothesis that this effect results from growth dilution. (iii) Effects of eCO2 on productivity and N acquisition did not diminish over time, while the typical eCO2‐induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO2‐induced terrestrial productivity enhancement is associated with negative effects of eCO2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation. |
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| Keywords: | carbon dioxide crops diversity
FACE
fertilization forest grassland growth dilution meta‐analysis nitrogen |
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