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Towards better representations of carbon allocation in vegetation: a conceptual framework and mathematical tool. THEOR ECOL-NETH 2020. [DOI: 10.1007/s12080-020-00455-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AbstractThe representation of carbon allocation (CA) in ecosystem differs tremendously among models, resulting in diverse responses of carbon cycling and storage to global change. Several studies have highlighted discrepancies between empirical observations and model predictions, attributing these differences to problems of model structure. We analyzed the mathematical representation of CA in models using concepts from dynamical systems theory; we reviewed a representative sample of models of CA in vegetation and developed a model database within the Python package bgc-md. We asked whether these representations can be generalized as a linear system, or whether a more general framework is needed to accommodate nonlinearities. Some of the vegetation systems simulated with the reviewed models have a fixed partitioning of photosynthetic products, independent of environmental forcing. Vegetation is often represented as a linear system without storage compartments. Yet, other structures with nonlinearities have also been proposed, with important consequences on the temporal trajectories of ecosystem carbon compartments. The proposed mathematical framework unifies the representation of alternative CA schemes, facilitating their classification according to mathematical properties as well as their potential temporal behaviour. It can represent complex processes in a compact form, which can potentially facilitate dialog among empiricists, theoreticians, and modellers.
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De Kauwe MG, Lin YS, Wright IJ, Medlyn BE, Crous KY, Ellsworth DS, Maire V, Prentice IC, Atkin OK, Rogers A, Niinemets Ü, Serbin SP, Meir P, Uddling J, Togashi HF, Tarvainen L, Weerasinghe LK, Evans BJ, Ishida FY, Domingues TF. A test of the 'one-point method' for estimating maximum carboxylation capacity from field-measured, light-saturated photosynthesis. THE NEW PHYTOLOGIST 2016; 210:1130-44. [PMID: 26719951 DOI: 10.1111/nph.13815] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/19/2015] [Indexed: 05/24/2023]
Abstract
Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (Vcmax ). Estimating this parameter using A-Ci curves (net photosynthesis, A, vs intercellular CO2 concentration, Ci ) is laborious, which limits availability of Vcmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO2 concentration (Asat ) measurements, from which Vcmax can be extracted using a 'one-point method'. We used a global dataset of A-Ci curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate Vcmax from Asat via this 'one-point method'. If leaf respiration during the day (Rday ) is known exactly, Vcmax can be estimated with an r(2) value of 0.98 and a root-mean-squared error (RMSE) of 8.19 μmol m(-2) s(-1) . However, Rday typically must be estimated. Estimating Rday as 1.5% of Vcmax, we found that Vcmax could be estimated with an r(2) of 0.95 and an RMSE of 17.1 μmol m(-2) s(-1) . The one-point method provides a robust means to expand current databases of field-measured Vcmax , giving new potential to improve vegetation models and quantify the environmental drivers of Vcmax variation.
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Affiliation(s)
- Martin G De Kauwe
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Yan-Shih Lin
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Ian J Wright
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Kristine Y Crous
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, B15 2TT, UK
| | - David S Ellsworth
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Vincent Maire
- Université du Québec à Trois-Rivières, Trois-Rivières, QC, G9A 5H7, Canada
| | - I Colin Prentice
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
- AXA Chair of Biosphere and Climate Impacts, Grand Challenges in Ecosystems and the Environment and Grantham Institute - Climate Change and the Environment, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, SL5 7PY, UK
| | - Owen K Atkin
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, The Australian National University, Building 134, Canberra, ACT, 2601, Australia
| | - Alistair Rogers
- Biological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Ülo Niinemets
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, Tartu, 51014, Estonia
- Estonian Academy of Sciences, Kohtu 6, 10130, Tallinn, Estonia
| | - Shawn P Serbin
- Biological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Patrick Meir
- Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
- School of Geosciences, University of Edinburgh, Edinburgh, EH9 3JN, UK
| | - Johan Uddling
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 461, SE-40530, Gothenburg, Sweden
| | - Henrique F Togashi
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
- Terrestrial Ecosystem Research Network, Ecosystem Modelling and Scaling Infrastructure, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Lasse Tarvainen
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83, Umeå, Sweden
| | - Lasantha K Weerasinghe
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, The Australian National University, Building 134, Canberra, ACT, 2601, Australia
- Faculty of Agriculture, University of Peradeniya, Peradeniya, 20400, Sri Lanka
| | - Bradley J Evans
- Terrestrial Ecosystem Research Network, Ecosystem Modelling and Scaling Infrastructure, The University of Sydney, Sydney, NSW, 2006, Australia
- Department of Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - F Yoko Ishida
- College of Marine and Environmental Sciences, Centre for Tropical Environmental and Sustainability Science, James Cook University, Cairns, Qld, 4870, Australia
| | - Tomas F Domingues
- Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av Bandeirantes, 3900, CEP 14040-901, Bairro Monte Alegre, Ribeirão Preto, São Paulo, Brazil
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Krause K, Cherubini P, Bugmann H, Schleppi P. Growth enhancement of Picea abies trees under long-term, low-dose N addition is due to morphological more than to physiological changes. TREE PHYSIOLOGY 2012; 32:1471-1481. [PMID: 23135740 DOI: 10.1093/treephys/tps109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Human activities have drastically increased nitrogen (N) inputs into natural and near-natural terrestrial ecosystems such that critical loads are now being exceeded in many regions of the world. This implies that these ecosystems are shifting from natural N limitation to eutrophication or even N saturation. This process is expected to modify the growth of forests and thus, along with management, to affect their carbon (C) sequestration. However, knowledge of the physiological mechanisms underlying tree response to N inputs, especially in the long term, is still lacking. In this study, we used tree-ring patterns and a dual stable isotope approach (δ(13)C and δ(18)O) to investigate tree growth responses and the underlying physiological reactions in a long-term, low-dose N addition experiment (+23 kg N ha(-1) a(-1)). This experiment has been conducted for 14 years in a mountain Picea abies (L.) Karst. forest in Alptal, Switzerland, using a paired-catchment design. Tree stem C sequestration increased by ∼22%, with an N use efficiency (NUE) of ca. 8 kg additional C in tree stems per kg of N added. Neither earlywood nor latewood δ(13)C values changed significantly compared with the control, indicating that the intrinsic water use efficiency (WUE(i)) (A/g(s)) did not change due to N addition. Further, the isotopic signal of δ(18)O in early- and latewood showed no significant response to the treatment, indicating that neither stomatal conductance nor leaf-level photosynthesis changed significantly. Foliar analyses showed that needle N concentration significantly increased in the fourth to seventh treatment year, accompanied by increased dry mass and area per needle, and by increased tree height growth. Later, N concentration and height growth returned to nearly background values, while dry mass and area per needle remained high. Our results support the hypothesis that enhanced stem growth caused by N addition is mainly due to an increased leaf area index (LAI). Higher LAI implies that more photosynthetically active radiation is absorbed and therefore canopy-level photosynthesis is increased. We conclude that models assuming that N deposition increases tree growth through higher leaf-level photosynthesis may be mechanistically inaccurate, at least in forest canopies that are not (yet) completely closed.
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Affiliation(s)
- Kim Krause
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland
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