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Ramirez JA, Craven D, Herrera D, Posada JM, Reu B, Sierra CA, Hoch G, Handa IT, Messier C. Non-structural carbohydrate concentrations in tree organs vary across biomes and leaf habits, but are independent of the fast-slow plant economic spectrum. FRONTIERS IN PLANT SCIENCE 2024; 15:1375958. [PMID: 38766471 PMCID: PMC11099217 DOI: 10.3389/fpls.2024.1375958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 04/19/2024] [Indexed: 05/22/2024]
Abstract
Carbohydrate reserves play a vital role in plant survival during periods of negative carbon balance. Under a carbon-limited scenario, we expect a trade-offs between carbon allocation to growth, reserves, and defense. A resulting hypothesis is that carbon allocation to reserves exhibits a coordinated variation with functional traits associated with the 'fast-slow' plant economics spectrum. We tested the relationship between non-structural carbohydrates (NSC) of tree organs and functional traits using 61 angiosperm tree species from temperate and tropical forests with phylogenetic hierarchical Bayesian models. Our results provide evidence that NSC concentrations in stems and branches are decoupled from plant functional traits. while those in roots are weakly coupled with plant functional traits. In contrast, we found that variation between NSC concentrations in leaves and the fast-slow trait spectrum was coordinated, as species with higher leaf NSC had trait values associated with resource conservative species, such as lower SLA, leaf N, and leaf P. We also detected a small effect of leaf habit on the variation of NSC concentrations in branches and roots. Efforts to predict the response of ecosystems to global change will need to integrate a suite of plant traits, such as NSC concentrations in woody organs, that are independent of the 'fast-slow' plant economics spectrum and that capture how species respond to a broad range of global change drivers.
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Affiliation(s)
- Jorge Andres Ramirez
- Facultad de Ciencias Agrarias, Universidad del Cauca, Popayán, Colombia
- Centre d’Étude de la Forêt (CEF), Université du Québec à Montréal, Montréal, QC, Canada
| | - Dylan Craven
- GEMA Center for Genomics, Ecology and Environment, Universidad Mayor, Huechuraba, Santiago, Chile
- Data Observatory Foundation, and Technology Center, Santiago, Chile
| | - David Herrera
- Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany
| | - Juan Manuel Posada
- Department of Biology, Faculty of Natural Sciences, Universidad del Rosario, Bogotá, Colombia
| | - Bjorn Reu
- School of Biology, Universidad Industrial de Santander, Bucaramanga, Colombia
| | | | - Guenter Hoch
- Department of Environmental Sciences – Botany, University of Basel, Basel, Switzerland
| | - Ira Tanya Handa
- Centre d’Étude de la Forêt (CEF), Université du Québec à Montréal, Montréal, QC, Canada
| | - Christian Messier
- Centre d’Étude de la Forêt (CEF), Université du Québec à Montréal, Montréal, QC, Canada
- Institut des Sciences de la Foret Tempérée, Université du Québec en Outaouais, Ripon, QC, Canada
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Lamour J, Davidson KJ, Ely KS, Le Moguédec G, Anderson JA, Li Q, Calderón O, Koven CD, Wright SJ, Walker AP, Serbin SP, Rogers A. The effect of the vertical gradients of photosynthetic parameters on the CO 2 assimilation and transpiration of a Panamanian tropical forest. THE NEW PHYTOLOGIST 2023; 238:2345-2362. [PMID: 36960539 DOI: 10.1111/nph.18901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 03/14/2023] [Indexed: 05/19/2023]
Abstract
Terrestrial biosphere models (TBMs) include the representation of vertical gradients in leaf traits associated with modeling photosynthesis, respiration, and stomatal conductance. However, model assumptions associated with these gradients have not been tested in complex tropical forest canopies. We compared TBM representation of the vertical gradients of key leaf traits with measurements made in a tropical forest in Panama and then quantified the impact of the observed gradients on simulated canopy-scale CO2 and water fluxes. Comparison between observed and TBM trait gradients showed divergence that impacted canopy-scale simulations of water vapor and CO2 exchange. Notably, the ratio between the dark respiration rate and the maximum carboxylation rate was lower near the ground than at the top-of-canopy, leaf-level water-use efficiency was markedly higher at the top-of-canopy, and the decrease in maximum carboxylation rate from the top-of-canopy to the ground was less than TBM assumptions. The representation of the gradients of leaf traits in TBMs is typically derived from measurements made within-individual plants, or, for some traits, assumed constant due to a lack of experimental data. Our work shows that these assumptions are not representative of the trait gradients observed in species-rich, complex tropical forests.
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Affiliation(s)
- Julien Lamour
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Kenneth J Davidson
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, 11974, USA
| | - Kim S Ely
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Gilles Le Moguédec
- AMAP, Université Montpellier, INRAE, Cirad CNRS, IRD, Montpellier, 34000, France
| | - Jeremiah A Anderson
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Qianyu Li
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Osvaldo Calderón
- Smithsonian Tropical Research Institute, Balboa, 0843-03092, Republic of Panama
| | - Charles D Koven
- Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - S Joseph Wright
- Smithsonian Tropical Research Institute, Balboa, 0843-03092, Republic of Panama
| | - Anthony P Walker
- Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Shawn P Serbin
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Alistair Rogers
- Environmental & Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
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3
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Davidson KJ, Lamour J, Rogers A, Ely KS, Li Q, McDowell NG, Pivovaroff AL, Wolfe BT, Wright SJ, Zambrano A, Serbin SP. Short-term variation in leaf-level water use efficiency in a tropical forest. THE NEW PHYTOLOGIST 2023; 237:2069-2087. [PMID: 36527230 DOI: 10.1111/nph.18684] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
The representation of stomatal regulation of transpiration and CO2 assimilation is key to forecasting terrestrial ecosystem responses to global change. Given its importance in determining the relationship between forest productivity and climate, accurate and mechanistic model representation of the relationship between stomatal conductance (gs ) and assimilation is crucial. We assess possible physiological and mechanistic controls on the estimation of the g1 (stomatal slope, inversely proportional to water use efficiency) and g0 (stomatal intercept) parameters, using diurnal gas exchange surveys and leaf-level response curves of six tropical broadleaf evergreen tree species. g1 estimated from ex situ response curves averaged 50% less than g1 estimated from survey data. While g0 and g1 varied between leaves of different phenological stages, the trend was not consistent among species. We identified a diurnal trend associated with g1 and g0 that significantly improved model projections of diurnal trends in transpiration. The accuracy of modeled gs can be improved by accounting for variation in stomatal behavior across diurnal periods, and between measurement approaches, rather than focusing on phenological variation in stomatal behavior. Additional investigation into the primary mechanisms responsible for diurnal variation in g1 will be required to account for this phenomenon in land-surface models.
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Affiliation(s)
- Kenneth J Davidson
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
- Department of Ecology and Evolution, Stony Brook University, 650 Life Sciences Building, Stony Brook, NY, 11794, USA
| | - Julien Lamour
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
| | - Alistair Rogers
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
| | - Kim S Ely
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
| | - Qianyu Li
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
| | - Nate G McDowell
- Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, PO Box 999, Richland, WA, 99352, USA
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164-4236, USA
| | | | - Brett T Wolfe
- School of Renewable Natural Resources, Louisiana State University, Room 227, Renewable Natural Resources Bldg, Baton Rouge, LA, 70803, USA
- Smithsonian Tropical Research Institute, Apartado, 0843-03092, Balboa, Panama
| | - S Joseph Wright
- Smithsonian Tropical Research Institute, Apartado, 0843-03092, Balboa, Panama
| | - Alfonso Zambrano
- Smithsonian Tropical Research Institute, Apartado, 0843-03092, Balboa, Panama
| | - Shawn P Serbin
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Building 490A, Upton, NY, 11973, USA
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4
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Kullberg AT, Slot M, Feeley KJ. Thermal optimum of photosynthesis is controlled by stomatal conductance and does not acclimate across an urban thermal gradient in six subtropical tree species. PLANT, CELL & ENVIRONMENT 2023; 46:831-849. [PMID: 36597283 DOI: 10.1111/pce.14533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 12/29/2022] [Indexed: 06/17/2023]
Abstract
Modelling the response of plants to climate change is limited by our incomplete understanding of the component processes of photosynthesis and their temperature responses within and among species. For ≥20 individuals, each of six common subtropical tree species occurring across steep urban thermal gradients in Miami, Florida, USA, we determined rates of net photosynthesis (Anet ), maximum RuBP carboxylation, maximum RuBP regeneration and stomatal conductance, and modelled the optimum temperature (Topt ) and process rate of each parameter to address two questions: (1) Do the Topt of Anet (ToptA ) and the maximum Anet (Aopt ) of subtropical trees reflect acclimation to elevated growth temperatures? And (2) What limits Anet in subtropical trees? Against expectations, we did not find significant acclimation of ToptA , Aopt or the Topt of any of the underlying photosynthetic parameters to growth temperature in any of the focal species. Model selection for the single best predictor of Anet both across leaf temperatures and at ToptA revealed that the Anet of most trees was best predicted by stomatal conductance. Our findings are in accord with those of previous studies, especially in the tropics, that have identified stomatal conductance to be the most important factor limiting Anet , rather than biochemical thermal responses.
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Affiliation(s)
- Alyssa T Kullberg
- Department of Biology, University of Miami, Coral Gables, Florida, USA
| | - Martijn Slot
- Smithsonian Tropical Research Institute, Panama, Republic of Panama
| | - Kenneth J Feeley
- Department of Biology, University of Miami, Coral Gables, Florida, USA
- Fairchild Tropical Botanic Garden, Coral Gables, Florida, USA
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5
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Vicente E, Didion-Gency M, Morcillo L, Morin X, Vilagrosa A, Grossiord C. Aridity and cold temperatures drive divergent adjustments of European beech xylem anatomy, hydraulics and leaf physiological traits. TREE PHYSIOLOGY 2022; 42:1720-1735. [PMID: 35285500 DOI: 10.1093/treephys/tpac029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 03/08/2022] [Indexed: 06/14/2023]
Abstract
Understanding plant trait coordination and variance across climatic gradients is critical for assessing forests' adaptive potential to climate change. We measured 11 hydraulic, anatomical and leaf-level physiological traits in European beech (Fagus sylvatica L.) along a moisture and temperature gradient in the French Alps. We assessed how traits covaried, and how their population-level variances shifted along the gradient. The intrapopulation variances of vessel size and xylem-specific conductivity reduced in colder locations as narrow vessels were observed in response to low temperature. This decreased individual-level water transport capacity compared with the warmer and more xeric sites. Conversely, the maximum stomatal conductance and Huber value variances were constrained in the arid and warm locations, where trees showed restricted gas exchange and higher xylem-specific conductivity. The populations growing under drier and warmer conditions presented wide variance for the xylem anatomical and hydraulic traits. Our results suggest that short-term physiological acclimation to raising aridity and heat in southern beech populations may occur mainly at the leaf level. Furthermore, the wide variance of the xylem anatomical and hydraulic traits at these sites may be advantageous since more heterogeneous hydraulic conductivity could imply populations' greater tree-tree complementarity and resilience against climatic variability. Our study highlights that both intrapopulation trait variance and trait network analysis are key approaches for understanding species adaptation and the acclimation potential to a shifting environment.
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Affiliation(s)
- Eduardo Vicente
- Department of Ecology, Faculty of Sciences, IMEM Ramón Margalef, University of Alicante, C. San Vicente del Raspeig, s/n, Alicante 03080, Spain
- CEAM Foundation, Joint Research Unit University of Alicante-CEAM, Department of Ecology, University of Alicante, PO Box 99, C. San Vicente del Raspeig, s/n, Alicante 03080, Spain
| | - Margaux Didion-Gency
- Ecosystem Ecology, Forest Dynamics Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL, Zürcherstrasse 111, Birmensdorf 8903, Switzerland
| | - Luna Morcillo
- CEAM Foundation, Joint Research Unit University of Alicante-CEAM, Department of Ecology, University of Alicante, PO Box 99, C. San Vicente del Raspeig, s/n, Alicante 03080, Spain
| | - Xavier Morin
- CEFE UMR 5175 (CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, IRD), 1919 Route de Mende, Montpellier Cedex 5 F-34293, France
| | - Alberto Vilagrosa
- CEAM Foundation, Joint Research Unit University of Alicante-CEAM, Department of Ecology, University of Alicante, PO Box 99, C. San Vicente del Raspeig, s/n, Alicante 03080, Spain
| | - Charlotte Grossiord
- Plant Ecology Research Laboratory PERL, School of Architecture, Civil and Environmental Engineering, EPFL, PO box 96, Lausanne CH-1015, Switzerland
- Functional Plant Ecology, Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL, PO box 96, Lausanne CH-1015, Switzerland
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6
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Davidson KJ, Lamour J, Rogers A, Serbin SP. Late-day measurement of excised branches results in uncertainty in the estimation of two stomatal parameters derived from response curves in Populus deltoides Bartr. × Populus nigra L. TREE PHYSIOLOGY 2022; 42:1377-1395. [PMID: 35134232 DOI: 10.1093/treephys/tpac006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 01/17/2022] [Indexed: 06/14/2023]
Abstract
Many terrestrial biosphere models depend on an understanding of the relationship between stomatal conductance and photosynthesis. However, unlike the measurement of photosynthetic parameters, such as the maximum carboxylation capacity, where standard methods (e.g., CO2 response or ACi curves) are widely accepted, a consensus method for empirically measuring parameters representing stomatal response has not yet emerged. Most models of stomatal response to environment represent stomatal conductance as being bounded by a lower intercept parameter (g0), and linearly scaled based on a multivariate term described by the stomatal slope parameter (g1). Here we employ the widely used Unified Stomatal Optimization model, to test whether g1 and g0 parameters are impacted by the choice of measurement method, either on an intact branch or a cut branch segment stored in water. We measured paired stomatal response curves on intact and excised branches of a hybrid poplar clone (Populus deltoides Bartr. × Populus nigra L. OP367), measured twice over a diurnal period. We found that predawn branch excision did not significantly affect measured g0 and g1 when measured within 4 h of excision. Measurement in the afternoon resulted in significantly higher values of g1 and lower values of g0, with values changing by 55% and 56%, respectively. Excision combined with afternoon measurement resulted in a marked effect on parameter estimates, with g1 increasing 89% from morning to afternoon and a 25% lower g1 for cut branches than those measured in situ. We also show that in hybrid poplar the differences in parameter estimates obtained from plants measured under different conditions can directly impact models of canopy function, reducing modeled transpiration by 18% over a simulated 12.5-h period. Although these results are only for a single isohydric woody species, our findings suggest that stomatal optimality parameters may not remain constant throughout the day.
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Affiliation(s)
- Kenneth J Davidson
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA
- Department of Ecology and Evolution, Stony Brook University, 650 Life Sciences Building, Stony Brook, NY 11794, USA
| | - Julien Lamour
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Alistair Rogers
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Shawn P Serbin
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA
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7
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Schönbeck L, Grossiord C, Gessler A, Gisler J, Meusburger K, D'Odorico P, Rigling A, Salmon Y, Stocker BD, Zweifel R, Schaub M. Photosynthetic acclimation and sensitivity to short- and long-term environmental changes in a drought-prone forest. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2576-2588. [PMID: 35134157 DOI: 10.1093/jxb/erac033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Future climate will be characterized by an increase in frequency and duration of drought and warming that exacerbates atmospheric evaporative demand. How trees acclimate to long-term soil moisture changes and whether these long-term changes alter trees' sensitivity to short-term (day to months) variations of vapor pressure deficit (VPD) and soil moisture is largely unknown. Leaf gas exchange measurements were performed within a long-term (17 years) irrigation experiment in a drought-prone Scots pine-dominated forest in one of Switzerland's driest areas on trees in naturally dry (control), irrigated, and 'irrigation-stop' (after 11 years of irrigation) conditions. Seventeen years of irrigation increased photosynthesis (A) and stomatal conductance (gs) and reduced gs sensitivity to increasing VPD and soil drying. Following irrigation-stop, gas exchange decreased only after 3 years. After 5 years, maximum carboxylation (Vcmax) and electron transport (Jmax) rates in irrigation-stop recovered to similar levels as to before the irrigation-stop. These results suggest that long-term release from soil drought reduces the sensitivity to VPD and that atmospheric constraints may play an increasingly important role in combination with soil drought. Moreover, our study indicates that structural adjustments lead to an attenuation of initially strong leaf-level acclimation to strong multiple-year drought.
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Affiliation(s)
- Leonie Schönbeck
- Plant Ecology Research Laboratory, School of Architecture, Civil and Environmental Engineering, EPFL, Station 2, 1015 Lausanne, Switzerland
- Functional Plant Ecology, Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Station 2, 1015 Lausanne, Switzerland
| | - Charlotte Grossiord
- Plant Ecology Research Laboratory, School of Architecture, Civil and Environmental Engineering, EPFL, Station 2, 1015 Lausanne, Switzerland
- Functional Plant Ecology, Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Station 2, 1015 Lausanne, Switzerland
| | - Arthur Gessler
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
- Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 2, 8092 Zürich, Switzerland
| | - Jonas Gisler
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Katrin Meusburger
- Biogeochemistry Unit, Swiss Federal Research Institute for Forest, Snow and Landscape research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Petra D'Odorico
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Andreas Rigling
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
- Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 2, 8092 Zürich, Switzerland
| | - Yann Salmon
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, 00014 University of Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, PO Box 68, 00014 University of Helsinki, Finland
| | - Benjamin D Stocker
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
- Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 2, 8092 Zürich, Switzerland
| | - Roman Zweifel
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Marcus Schaub
- Forest Dynamics Research Unit, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
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8
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Gardner A, Ellsworth DS, Crous KY, Pritchard J, MacKenzie AR. Is photosynthetic enhancement sustained through three years of elevated CO2 exposure in 175-year-old Quercus robur? TREE PHYSIOLOGY 2022; 42:130-144. [PMID: 34302175 PMCID: PMC8754963 DOI: 10.1093/treephys/tpab090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/07/2021] [Indexed: 05/15/2023]
Abstract
Current carbon cycle models attribute rising atmospheric CO2 as the major driver of the increased terrestrial carbon sink, but with substantial uncertainties. The photosynthetic response of trees to elevated atmospheric CO2 is a necessary step, but not the only one, for sustaining the terrestrial carbon uptake, but can vary diurnally, seasonally and with duration of CO2 exposure. Hence, we sought to quantify the photosynthetic response of the canopy-dominant species, Quercus robur, in a mature deciduous forest to elevated CO2 (eCO2) (+150 μmol mol-1 CO2) over the first 3 years of a long-term free air CO2 enrichment facility at the Birmingham Institute of Forest Research in central England (BIFoR FACE). Over 3000 measurements of leaf gas exchange and related biochemical parameters were conducted in the upper canopy to assess the diurnal and seasonal responses of photosynthesis during the 2nd and 3rd year of eCO2 exposure. Measurements of photosynthetic capacity via biochemical parameters, derived from CO2 response curves, (Vcmax and Jmax) together with leaf nitrogen concentrations from the pre-treatment year to the 3rd year of eCO2 exposure, were examined. We hypothesized an initial enhancement in light-saturated net photosynthetic rates (Asat) with CO2 enrichment of ≈37% based on theory but also expected photosynthetic capacity would fall over the duration of the study. Over the 3-year period, Asat of upper-canopy leaves was 33 ± 8% higher (mean and standard error) in trees grown in eCO2 compared with ambient CO2 (aCO2), and photosynthetic enhancement decreased with decreasing light. There were no significant effects of CO2 treatment on Vcmax or Jmax, nor leaf nitrogen. Our results suggest that mature Q. robur may exhibit a sustained, positive response to eCO2 without photosynthetic downregulation, suggesting that, with adequate nutrients, there will be sustained enhancement in C assimilated by these mature trees. Further research will be required to understand the location and role of the additionally assimilated carbon.
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Affiliation(s)
- A Gardner
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, B15 2TT, UK
- School of Biological Sciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - D S Ellsworth
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
| | - K Y Crous
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
| | - J Pritchard
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, B15 2TT, UK
- School of Biological Sciences, University of Birmingham, Edgbaston, B15 2TT, UK
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9
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Rapid estimation of photosynthetic leaf traits of tropical plants in diverse environmental conditions using reflectance spectroscopy. PLoS One 2021; 16:e0258791. [PMID: 34665822 PMCID: PMC8525780 DOI: 10.1371/journal.pone.0258791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 10/06/2021] [Indexed: 11/20/2022] Open
Abstract
Tropical forests are one of the main carbon sinks on Earth, but the magnitude of CO2 absorbed by tropical vegetation remains uncertain. Terrestrial biosphere models (TBMs) are commonly used to estimate the CO2 absorbed by forests, but their performance is highly sensitive to the parameterization of processes that control leaf-level CO2 exchange. Direct measurements of leaf respiratory and photosynthetic traits that determine vegetation CO2 fluxes are critical, but traditional approaches are time-consuming. Reflectance spectroscopy can be a viable alternative for the estimation of these traits and, because data collection is markedly quicker than traditional gas exchange, the approach can enable the rapid assembly of large datasets. However, the application of spectroscopy to estimate photosynthetic traits across a wide range of tropical species, leaf ages and light environments has not been extensively studied. Here, we used leaf reflectance spectroscopy together with partial least-squares regression (PLSR) modeling to estimate leaf respiration (Rdark25), the maximum rate of carboxylation by the enzyme Rubisco (Vcmax25), the maximum rate of electron transport (Jmax25), and the triose phosphate utilization rate (Tp25), all normalized to 25°C. We collected data from three tropical forest sites and included leaves from fifty-three species sampled at different leaf phenological stages and different leaf light environments. Our resulting spectra-trait models validated on randomly sampled data showed good predictive performance for Vcmax25, Jmax25, Tp25 and Rdark25 (RMSE of 13, 20, 1.5 and 0.3 μmol m-2 s-1, and R2 of 0.74, 0.73, 0.64 and 0.58, respectively). The models showed similar performance when applied to leaves of species not included in the training dataset, illustrating that the approach is robust for capturing the main axes of trait variation in tropical species. We discuss the utility of the spectra-trait and traditional gas exchange approaches for enhancing tropical plant trait studies and improving the parameterization of TBMs.
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10
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Wang X, Chen G, Du S, Wu H, Fu R, Yu X. Light Intensity Influence on Growth and Photosynthetic Characteristics of Horsfieldia hainanensis. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.636804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Due to both anthropogenic and natural causes, the number of Horsfieldia hainanensis has been decreasing each year in the Tongza Branch nursery (109.534 525°E, 18.763 516°N) of the Hainan Academy of Forestry, China. Consequently, the protection of H. hainanensis is urgent, as is that of most rare tree species. To develop a more comprehensive understanding of the H. hainanensis growth environment, we took 3-year-old H. hainanensis saplings as the research object. We controlled the light intensity by setting different shade amounts to explore the growth and photosynthetic characteristics of H. hainanensis under different light intensities. We found that shade can promote growth and increase the contents of certain substances. Light transmittance of 44.41% can increase plant height (by 29.545%) and biomass (by 66.676%). Light transmittance of 16.19% can increase the pigment content; Chl increased by 40.864%, Chl a increased by 38.031%, and Chl b increased by 48.412%. Light transmittance of 7.30% can increase the soil plant analysis development (SPAD) value of each part of the leaf; the leaf base increased by 41.000%, the leaf margin increased by 32.574%, the blade tip increased by 49.003%, and the leaf average increased by 40.466%. The specific leaf area can reduce the specific leaf weight. We also found that compared to full light, reducing the light transmittance can increase the total chlorophyll (Chl), chlorophyll A (Chl a), and chlorophyll B (Chl b) contents, and the Chl-SPAD-leaf base, leaf edge, leaf tip, average content, and light-saturated net photosynthetic rate. This can in turn reduce the apparent quantum efficiency (AQY), light compensation point (LCP), and dark respiration rate (Rd). In addition, we found a strong correlation between seven of the photosynthetic pigment indicators (Chl, Chla, Chl b, Chl-SPAD-leaf base, leaf margin, leaf tip, and mean) and the three photosynthesis physiological parameters (AQY, LCP, and Rd). The light transmittance of 44.41% (one layer of shading net) treatment group was conducive to the growth of H. hainanensis and photosynthetic characteristic improvement. Therefore, our light transmittance selection of approximately 44.4% is significant for the natural return of H. hainanensis.
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