Nitrogen dynamics after two years of elevated CO 2 in phosphorus limited Eucalyptus woodland
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Nitrogen dynamics after two years of elevated CO2 in phosphorus limited Eucalyptus woodland Louise C. Andresen . Yolima Carrillo . Catriona A. Macdonald Laura Castan˜eda-Go´mez . Samuel Bode´ . Tobias Ru¨tting
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Received: 20 December 2019 / Accepted: 28 August 2020 The Author(s) 2020
Abstract It is uncertain how the predicted further rise of atmospheric carbon dioxide (CO2) concentration will affect plant nutrient availability in the future through indirect effects on the gross rates of nitrogen (N) mineralization (production of ammonium) and depolymerization (production of free amino acids) in soil. The response of soil nutrient availability to increasing atmospheric CO2 is particularly important for nutrient poor ecosystems. Within a FACE (FreeAir Carbon dioxide Enrichment) experiment in a native, nutrient poor Eucalyptus woodland (EucFACE) with low soil organic matter (B 3%), our results suggested there was no shortage of N. Despite this, microbial N use efficiency was high (c. 90%). The Responsible Editor: Stephen D. Sebestyen.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10533-020-00699-y) contains supplementary material, which is available to authorized users. L. C. Andresen (&) T. Ru¨tting Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden e-mail: [email protected] Y. Carrillo C. A. Macdonald L. Castan˜eda-Go´mez Hawkesbury Institute for the Environment (HIE), Western Sydney University, Richmond, Australia S. Bode´ Department of Green Chemistry and Technology, Ghent University, Gent, Belgium
free amino acid (FAA) pool had a fast turnover time (4 h) compared to that of ammonium (NH4?) which was 11 h. Both NH4-N and FAA-N were important N pools; however, protein depolymerization rate was three times faster than gross N mineralization rates, indicating that organic N is directly important in the internal ecosystem N cycle. Hence, the depolymerization was the major provider of plant available N, while the gross N mineralization rate was the constraining factor for inorganic N. After two years of elevated CO2, no major effects on the pools and rates of the soil N cycle were found in spring (November) or at the end of summer (March). The limited response of N pools or N transformation rates to elevated CO2 suggest that N availability was not the limiting factor behind the lack of plant growth response to elevated CO2, previously observed at the site. Keywords Gross N mineralization rate Depolymerization Free amino acids Phosphorus limitation
Introduction Ecosystem effects of elevated atmospheric carbon dioxide (CO2) concentration are a global concern, with the atmospheric CO2 concentrations recently having
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Biogeochemistry
surpassed 415 ppm (McGee 2019). Worldwide, several experiments manipulate atmospheric CO2 concentration at the field scale in open air by the FACE (Free Air Carbon dioxide Enrichment) technique (Miglietta 2001; Ellsworth et al. 2017) to investiga
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