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Caldararu S, Thum T, Yu L, Zaehle S. Whole-plant optimality predicts changes in leaf nitrogen under variable CO 2 and nutrient availability. New Phytol 2020; 225:2331-2346. [PMID: 31737904 DOI: 10.1111/nph.16327] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
Vegetation nutrient limitation is essential for understanding ecosystem responses to global change. In particular, leaf nitrogen (N) is known to be plastic under changed nutrient limitation. However, models can often not capture these observed changes, leading to erroneous predictions of whole-ecosystem stocks and fluxes. We hypothesise that an optimality approach can improve representation of leaf N content compared to existing empirical approaches. Unlike previous optimality-based approaches, which adjust foliar N concentrations based on canopy carbon export, we use a maximisation criterion based on whole-plant growth, and allow for a lagged response of foliar N to this maximisation criterion to account for the limited plasticity of this plant trait. We test these model variants at a range of Free-Air CO2 Enrichment and N fertilisation experimental sites. We show that a model based solely on canopy carbon export fails to reproduce observed patterns and predicts decreasing leaf N content with increased N availability. However, an optimal model which maximises total plant growth can correctly reproduce the observed patterns. The optimality model we present here is a whole-plant approach which reproduces biologically realistic changes in leaf N and can thereby improve ecosystem-level predictions under transient conditions.
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Affiliation(s)
- Silvia Caldararu
- Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, Jena, 07745, Germany
| | - Tea Thum
- Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, Jena, 07745, Germany
| | - Lin Yu
- Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, Jena, 07745, Germany
| | - Sönke Zaehle
- Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, Jena, 07745, Germany
- Michael Stifel Center Jena for Data-Driven and Simulation Science, Jena, 07745, Germany
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Zaehle S, Medlyn BE, De Kauwe MG, Walker AP, Dietze MC, Hickler T, Luo Y, Wang YP, El-Masri B, Thornton P, Jain A, Wang S, Warlind D, Weng E, Parton W, Iversen CM, Gallet-Budynek A, McCarthy H, Finzi A, Hanson PJ, Prentice IC, Oren R, Norby RJ. Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies. New Phytol 2014; 202:803-822. [PMID: 24467623 PMCID: PMC4288990 DOI: 10.1111/nph.12697] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 12/19/2013] [Indexed: 05/22/2023]
Abstract
We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2 ] (eCO2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections.
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Affiliation(s)
- Sönke Zaehle
- Biogeochemical Integration Department, Max Planck Institute for BiogeochemistryHans-Knöll-Str. 10, D-07745, Jena, Germany
| | - Belinda E Medlyn
- Department of Biological Science, Macquarie UniversitySydney, NSW, 2109, Australia
| | - Martin G De Kauwe
- Department of Biological Science, Macquarie UniversitySydney, NSW, 2109, Australia
| | - Anthony P Walker
- Oak Ridge National Laboratory, Environmental Sciences Division, Climate Change Science InstituteOak Ridge, TN, 37831, USA
| | - Michael C Dietze
- Department of Earth and Environment, Boston UniversityBoston, MA, 02215, USA
| | - Thomas Hickler
- Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für NaturforschungD-60325, Frankfurt am Main, Germany
- Department of Physical Geography, Goethe UniversityD-60438, Frankfurt am Main, Germany
| | - Yiqi Luo
- Department of Microbiology & Plant Biology, University of OklahomaNorman, OK, 73019, USA
| | - Ying-Ping Wang
- CSIRO Marine and Atmospheric ResearchPMB 1, Aspendale, Vic., 3195, Australia
| | - Bassil El-Masri
- Department of Atmospheric Sciences, University of IllinoisUrbana, IL, 61801, USA
| | - Peter Thornton
- Oak Ridge National Laboratory, Environmental Sciences Division, Climate Change Science InstituteOak Ridge, TN, 37831, USA
| | - Atul Jain
- Department of Atmospheric Sciences, University of IllinoisUrbana, IL, 61801, USA
| | - Shusen Wang
- Canada Centre for Mapping and Earth Observation, Natural Resources CanadaOttawa, ON, K1A 0Y7, Canada
| | - David Warlind
- Department of Physical Geography and Ecosystem Science, Lund UniversitySE-22362, Lund, Sweden
| | - Ensheng Weng
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrinceton, NJ, 08544, USA
| | - William Parton
- Natural Resource Ecology Laboratory, Colorado State UniversityFort Collins, CO, 80523, USA
| | - Colleen M Iversen
- Oak Ridge National Laboratory, Environmental Sciences Division, Climate Change Science InstituteOak Ridge, TN, 37831, USA
| | - Anne Gallet-Budynek
- INRA, UMR1220 TCEMF-33882, Villenave d'Ornon, France
- Université de Bordeaux, UMR1220 TCEMF-33175, Gradignan, France
| | - Heather McCarthy
- Department of Microbiology & Plant Biology, University of OklahomaNorman, OK, 73019, USA
| | - Adrien Finzi
- Department of Biology, Boston UniversityBoston, MA, 02215, USA
| | - Paul J Hanson
- Oak Ridge National Laboratory, Environmental Sciences Division, Climate Change Science InstituteOak Ridge, TN, 37831, USA
| | - I Colin Prentice
- Department of Biological Science, Macquarie UniversitySydney, NSW, 2109, Australia
- AXA Chair of Biosphere and Climate Impacts, Department of Life Sciences and Grantham Institute for Climate Change, Imperial College LondonSilwood Park, Ascot, SL5 7PY, UK
| | - Ram Oren
- Division of Environmental Science & Policy, Nicholas School of the Environment, Duke UniversityDurham, NC, 27708, USA
- Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU)SE-901 83, Umeå, Sweden
| | - Richard J Norby
- Oak Ridge National Laboratory, Environmental Sciences Division, Climate Change Science InstituteOak Ridge, TN, 37831, USA
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