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Gallup SM, Baker IT, Gallup JL, Restrepo‐Coupe N, Haynes KD, Geyer NM, Denning AS. Accurate Simulation of Both Sensitivity and Variability for Amazonian Photosynthesis: Is It Too Much to Ask? JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS 2021; 13:e2021MS002555. [PMID: 34594478 PMCID: PMC8459247 DOI: 10.1029/2021ms002555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/22/2021] [Accepted: 07/28/2021] [Indexed: 06/13/2023]
Abstract
Estimates of Amazon rainforest gross primary productivity (GPP) differ by a factor of 2 across a suite of three statistical and 18 process models. This wide spread contributes uncertainty to predictions of future climate. We compare the mean and variance of GPP from these models to that of GPP at six eddy covariance (EC) towers. Only one model's mean GPP across all sites falls within a 99% confidence interval for EC GPP, and only one model matches EC variance. The strength of model response to climate drivers is related to model ability to match the seasonal pattern of the EC GPP. Models with stronger seasonal swings in GPP have stronger responses to rain, light, and temperature than does EC GPP. The model to data comparison illustrates a trade-off inherent to deterministic models between accurate simulation of a mean (average) and accurate responsiveness to drivers. The trade-off exists because all deterministic models simplify processes and lack at least some consequential driver or interaction. If a model's sensitivities to included drivers and their interactions are accurate, then deterministically predicted outcomes have less variability than is realistic. If a GPP model has stronger responses to climate drivers than found in data, model predictions may match the observed variance and seasonal pattern but are likely to overpredict GPP response to climate change. High or realistic variability of model estimates relative to reference data indicate that the model is hypersensitive to one or more drivers.
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Affiliation(s)
- Sarah M. Gallup
- Graduate Degree Program in EcologyColorado State UniversityFort CollinsCOUSA
| | - Ian T. Baker
- Department of Atmospheric ScienceColorado State UniversityFort CollinsCOUSA
| | - John L. Gallup
- Department of EconomicsPortland State UniversityPortlandORUSA
| | - Natalia Restrepo‐Coupe
- Department of Ecology and Evolutionary BiologyUniversity of ArizonaTucsonAZUSA
- School of Life SciencesUniversity of Technology SydneyUltimoNSWAustralia
| | | | - Nicholas M. Geyer
- Department of Atmospheric ScienceColorado State UniversityFort CollinsCOUSA
| | - A. Scott Denning
- Graduate Degree Program in EcologyColorado State UniversityFort CollinsCOUSA
- Department of Atmospheric ScienceColorado State UniversityFort CollinsCOUSA
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Powell TL, Wheeler JK, de Oliveira AAR, da Costa ACL, Saleska SR, Meir P, Moorcroft PR. Differences in xylem and leaf hydraulic traits explain differences in drought tolerance among mature Amazon rainforest trees. GLOBAL CHANGE BIOLOGY 2017; 23:4280-4293. [PMID: 28426175 DOI: 10.1111/gcb.13731] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 02/23/2017] [Indexed: 05/24/2023]
Abstract
Considerable uncertainty surrounds the impacts of anthropogenic climate change on the composition and structure of Amazon forests. Building upon results from two large-scale ecosystem drought experiments in the eastern Brazilian Amazon that observed increases in mortality rates among some tree species but not others, in this study we investigate the physiological traits underpinning these differential demographic responses. Xylem pressure at 50% conductivity (xylem-P50 ), leaf turgor loss point (TLP), cellular osmotic potential (πo ), and cellular bulk modulus of elasticity (ε), all traits mechanistically linked to drought tolerance, were measured on upper canopy branches and leaves of mature trees from selected species growing at the two drought experiment sites. Each species was placed a priori into one of four plant functional type (PFT) categories: drought-tolerant versus drought-intolerant based on observed mortality rates, and subdivided into early- versus late-successional based on wood density. We tested the hypotheses that the measured traits would be significantly different between the four PFTs and that they would be spatially conserved across the two experimental sites. Xylem-P50 , TLP, and πo , but not ε, occurred at significantly higher water potentials for the drought-intolerant PFT compared to the drought-tolerant PFT; however, there were no significant differences between the early- and late-successional PFTs. These results suggest that these three traits are important for determining drought tolerance, and are largely independent of wood density-a trait commonly associated with successional status. Differences in these physiological traits that occurred between the drought-tolerant and drought-intolerant PFTs were conserved between the two research sites, even though they had different soil types and dry-season lengths. This more detailed understanding of how xylem and leaf hydraulic traits vary between co-occuring drought-tolerant and drought-intolerant tropical tree species promises to facilitate a much-needed improvement in the representation of plant hydraulics within terrestrial ecosystem and biosphere models, which will enhance our ability to make robust predictions of how future changes in climate will affect tropical forests.
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Affiliation(s)
- Thomas L Powell
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Earth and Environmental Sciences Area, Lawrence Berkeley National Lab, Berkeley, CA, USA
| | - James K Wheeler
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Alex A R de Oliveira
- Museu Paraense Emílio Goeldi, Programa de Pós-Graduação em Biodiversidade e Evolução, Belém, Pará, Brazil
| | | | - Scott R Saleska
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
| | - Patrick Meir
- Research School of Biology, Australian National University, Canberra, ACT, Australia
- School of GeoSciences, University of Edinburgh, Edinburgh, UK
| | - Paul R Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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Restrepo-Coupe N, Levine NM, Christoffersen BO, Albert LP, Wu J, Costa MH, Galbraith D, Imbuzeiro H, Martins G, da Araujo AC, Malhi YS, Zeng X, Moorcroft P, Saleska SR. Do dynamic global vegetation models capture the seasonality of carbon fluxes in the Amazon basin? A data-model intercomparison. GLOBAL CHANGE BIOLOGY 2017; 23:191-208. [PMID: 27436068 DOI: 10.1111/gcb.13442] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 04/18/2016] [Indexed: 06/06/2023]
Abstract
To predict forest response to long-term climate change with high confidence requires that dynamic global vegetation models (DGVMs) be successfully tested against ecosystem response to short-term variations in environmental drivers, including regular seasonal patterns. Here, we used an integrated dataset from four forests in the Brasil flux network, spanning a range of dry-season intensities and lengths, to determine how well four state-of-the-art models (IBIS, ED2, JULES, and CLM3.5) simulated the seasonality of carbon exchanges in Amazonian tropical forests. We found that most DGVMs poorly represented the annual cycle of gross primary productivity (GPP), of photosynthetic capacity (Pc), and of other fluxes and pools. Models simulated consistent dry-season declines in GPP in the equatorial Amazon (Manaus K34, Santarem K67, and Caxiuanã CAX); a contrast to observed GPP increases. Model simulated dry-season GPP reductions were driven by an external environmental factor, 'soil water stress' and consequently by a constant or decreasing photosynthetic infrastructure (Pc), while observed dry-season GPP resulted from a combination of internal biological (leaf-flush and abscission and increased Pc) and environmental (incoming radiation) causes. Moreover, we found models generally overestimated observed seasonal net ecosystem exchange (NEE) and respiration (Re ) at equatorial locations. In contrast, a southern Amazon forest (Jarú RJA) exhibited dry-season declines in GPP and Re consistent with most DGVMs simulations. While water limitation was represented in models and the primary driver of seasonal photosynthesis in southern Amazonia, changes in internal biophysical processes, light-harvesting adaptations (e.g., variations in leaf area index (LAI) and increasing leaf-level assimilation rate related to leaf demography), and allocation lags between leaf and wood, dominated equatorial Amazon carbon flux dynamics and were deficient or absent from current model formulations. Correctly simulating flux seasonality at tropical forests requires a greater understanding and the incorporation of internal biophysical mechanisms in future model developments.
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Affiliation(s)
- Natalia Restrepo-Coupe
- Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
| | - Naomi M Levine
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Bradley O Christoffersen
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
- Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - Loren P Albert
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
| | - Jin Wu
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
- Biological, Environmental & Climate Sciences Department, Brookhaven National Lab, Upton, NY, USA
| | - Marcos H Costa
- Department of Agricultural Engineering, Federal University of Vicosa, Vicosa, Brazil
| | | | - Hewlley Imbuzeiro
- Department of Agricultural Engineering, Federal University of Vicosa, Vicosa, Brazil
| | - Giordane Martins
- Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil
| | - Alessandro C da Araujo
- Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil
- Embrapa Amazônia Oriental, Belem, Brazil
| | - Yadvinder S Malhi
- Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, UK
| | - Xubin Zeng
- Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - Paul Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Scott R Saleska
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
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Powell TL, Galbraith DR, Christoffersen BO, Harper A, Imbuzeiro HMA, Rowland L, Almeida S, Brando PM, da Costa ACL, Costa MH, Levine NM, Malhi Y, Saleska SR, Sotta E, Williams M, Meir P, Moorcroft PR. Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental drought. THE NEW PHYTOLOGIST 2013; 200:350-365. [PMID: 23844931 DOI: 10.1111/nph.12390] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 05/20/2013] [Indexed: 05/08/2023]
Abstract
Considerable uncertainty surrounds the fate of Amazon rainforests in response to climate change. Here, carbon (C) flux predictions of five terrestrial biosphere models (Community Land Model version 3.5 (CLM3.5), Ecosystem Demography model version 2.1 (ED2), Integrated BIosphere Simulator version 2.6.4 (IBIS), Joint UK Land Environment Simulator version 2.1 (JULES) and Simple Biosphere model version 3 (SiB3)) and a hydrodynamic terrestrial ecosystem model (the Soil-Plant-Atmosphere (SPA) model) were evaluated against measurements from two large-scale Amazon drought experiments. Model predictions agreed with the observed C fluxes in the control plots of both experiments, but poorly replicated the responses to the drought treatments. Most notably, with the exception of ED2, the models predicted negligible reductions in aboveground biomass in response to the drought treatments, which was in contrast to an observed c. 20% reduction at both sites. For ED2, the timing of the decline in aboveground biomass was accurate, but the magnitude was too high for one site and too low for the other. Three key findings indicate critical areas for future research and model development. First, the models predicted declines in autotrophic respiration under prolonged drought in contrast to measured increases at one of the sites. Secondly, models lacking a phenological response to drought introduced bias in the sensitivity of canopy productivity and respiration to drought. Thirdly, the phenomenological water-stress functions used by the terrestrial biosphere models to represent the effects of soil moisture on stomatal conductance yielded unrealistic diurnal and seasonal responses to drought.
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Affiliation(s)
- Thomas L Powell
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - David R Galbraith
- School of Geography, University of Leeds, Leeds, LS2 9JT, UK
- Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK
| | | | - Anna Harper
- College of Engineering, Mathematics, and Physical Science, University of Exeter, Exeter, EX4 4QF, UK
- Department of Atmospheric Science, Colorado State University, Fort Collins, CO, 80523, USA
| | - Hewlley M A Imbuzeiro
- Grupo de Pesquisas em Interação Atmosfera-Biosfera, Universidade Federal de Viçosa, Viçosa, CEP 36570-000, Minas Gerias, Brazil
| | - Lucy Rowland
- School of GeoSciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
| | - Samuel Almeida
- Museu Paraense Emilio Goeldi, Belém, CEP 66077-530, Pará, Brazil
| | - Paulo M Brando
- Instituto de Pesquisa Ambiental da Amazônia, CEP 71503-505, Brasília, Distrito Federal, Brazil
| | | | - Marcos Heil Costa
- Grupo de Pesquisas em Interação Atmosfera-Biosfera, Universidade Federal de Viçosa, Viçosa, CEP 36570-000, Minas Gerias, Brazil
| | - Naomi M Levine
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Yadvinder Malhi
- Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK
| | - Scott R Saleska
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
| | | | - Mathew Williams
- School of GeoSciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
| | - Patrick Meir
- School of GeoSciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
| | - Paul R Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
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Sun Y, Gu L, Dickinson RE. A numerical issue in calculating the coupled carbon and water fluxes in a climate model. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012jd018059] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Miguez-Macho G, Fan Y. The role of groundwater in the Amazon water cycle: 2. Influence on seasonal soil moisture and evapotranspiration. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012jd017540] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Rosolem R, Gupta HV, Shuttleworth WJ, Zeng X, de Gonçalves LGG. A fully multiple-criteria implementation of the Sobol′ method for parameter sensitivity analysis. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011jd016355] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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