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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 9
Biogeosciences, 13, 2689–2699, 2016
https://doi.org/10.5194/bg-13-2689-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 2689–2699, 2016
https://doi.org/10.5194/bg-13-2689-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 10 May 2016

Research article | 10 May 2016

Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis

Junyi Liang1, Xuan Qi1, Lara Souza1,2, and Yiqi Luo1,3 Junyi Liang et al.
  • 1Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma 73019, USA
  • 2Oklahoma Biological Survey, University of Oklahoma, Norman, Oklahoma 73019, USA
  • 3Center for Earth System Science, Tsinghua University, Beijing 100084, China

Abstract. The nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive research has explored whether or not progressive N limitation (PNL) occurs under CO2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in the terrestrial N cycle with meta-analysis of CO2 experimental data available in the literature. The results showed that CO2 enrichment significantly increased N sequestration in the plant and litter pools but not in the soil pool, partially supporting one of the basic assumptions in the PNL hypothesis that elevated CO2 results in more N sequestered in organic pools. However, CO2 enrichment significantly increased the N influx via biological N fixation and the loss via N2O emission, but decreased the N efflux via leaching. In addition, no general diminished CO2 fertilization effect on plant growth was observed over time up to the longest experiment of 13 years. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO2 conditions in spite of the increases in plant N sequestration and N2O emission. Moreover, our syntheses indicate that CO2 enrichment increases soil ammonium (NH4+) to nitrate (NO3) ratio. The changed NH4+/NO3 ratio and subsequent biological processes may result in changes in soil microenvironments, above-belowground community structures and associated interactions, which could potentially affect the terrestrial biogeochemical cycles. In addition, our data synthesis suggests that more long-term studies, especially in regions other than temperate ones, are needed for comprehensive assessments of the PNL hypothesis.

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It is unclear how the nitrogen (N) cycle regulates climate change through influencing carbon sequestration. By using meta-analysis, we tested a popular hypothesis, progressive N limitation (PNL), which postulates that greater N sequestration in organisms leads to declining N availability for further plant growth under elevated CO2. Our analyses suggest that extra nitrogen supply by increased biological N fixation and decreased leaching may potentially alleviate PNL.
It is unclear how the nitrogen (N) cycle regulates climate change through influencing carbon...
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