Is photosynthetic enhancement sustained through three years of elevated CO2 exposure in 175-year-old <i>Quercus robur</i>?

Gardner, A; Ellsworth, David S.; Crous, K.Y.; Pritchard, Jeremy; Ar, MacKenzie

doi:10.1093/treephys/tpab090

Cited by 25 publications

(18 citation statements)

References 72 publications

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“…There were, however, significant increases in herbivory noted in our study for hazel and sycamore in 2019, suggesting a potential rise in herbivory for certain tree species under eCO 2 . The overall weak herbivory response to eCO 2 at the BIFoR may be due to the limited biochemical response of dominant and more mature oak trees, with no significant change in the foliar N of oak from 2015-2019 [43].…”

Section: Leaf-level Insect Herbivorymentioning

confidence: 97%

“…Oak leaves were collected from the top of the canopy in each month from 2017-2019 and stored immediately at −25 • C. Two upper canopy leaves from one tree per plot were selected for elemental analyses. Dried leaves were ground and analyzed for total C and N using an elemental analyzer interfaced with an isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK; [43]).…”

Section: Leaf Nutrients and Productionmentioning

confidence: 99%

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Effects of Elevated Atmospheric CO2 Concentration on Insect Herbivory and Nutrient Fluxes in a Mature Temperate Forest

Roberts

Crowley²,

Sadler³

et al. 2022

Forests

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Insect herbivory is one of the most important ecological processes affecting plant–soil feedbacks and overall forest ecosystem health. In this study, we assess how elevated carbon dioxide (eCO2) impacts (i) leaf level insect herbivory and (ii) the stand-level herbivore-mediated transfer of carbon (C) and nitrogen (N) from the canopy to the ground in a natural mature oak temperate forest community in central England at the Birmingham Institute of Forest Research Free Air CO2 Enrichment (BIFoR FACE) site. Recently abscised leaves were collected every two weeks through the growing season in August to December from 2017–2019, with the identification of four dominant species: Quercus robur (pedunculate oak), Acer pseudoplatanus (sycamore), Crataegus monogyna (common hawthorn) and Corylus avellana (hazel). The selected leaves were scanned and visually analyzed to quantify the leaf area loss from folivory monthly. Additionally, the herbivore-mediated transfer of C and N fluxes from the dominant tree species Q. robur was calculated from these leaf-level folivory estimates, the total foliar production and the foliar C and N contents. This study finds that the leaf-level herbivory at the BIFoR FACE has not changed significantly across the first 3 years of eCO2 treatment when assessed across all dominant tree species, although we detected significant changes under the eCO2 treatment for individual tree species and years. Despite the lack of any strong leaf-level herbivory response, the estimated stand-level foliar C and N transferred to the ground via herbivory was substantially higher under eCO2, mainly because there was a ~50% increase in the foliar production of Q. robur under eCO2. This result cautions against concluding much from either the presence or absence of leaf-level herbivory responses to any environmental effect, because their actual ecosystem effects are filtered through so many (usually unmeasured) factors.

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Section: Leaf-level Insect Herbivorymentioning

confidence: 97%

Section: Leaf Nutrients and Productionmentioning

confidence: 99%

Effects of Elevated Atmospheric CO2 Concentration on Insect Herbivory and Nutrient Fluxes in a Mature Temperate Forest

Roberts

Crowley²,

Sadler³

et al. 2022

Forests

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“…A potentially fruitful area of research would be to modify these schemes to reflect observations at individual sites, for example, by adjusting the underlying parametrizations, or through some combination of Bayesian data assimilation and machine learning. A point of caution is that observations in forests tend to be sparse in space (e.g., wind measurements) and sometimes time (e.g., spore releases), and are often measured using proxies or with indirect techniques (e.g., photosynthetic capacity; Gardner et al, 2021). Machine learning techniques should therefore be carefully adapted to account for uncertainty in our knowledge of the underlying physical processes (Geer, 2021).…”

Section: Customized Numerical Models Of Real Sitesmentioning

confidence: 99%

Realistic Forests and the Modeling of Forest‐Atmosphere Exchange

Bannister

MacKenzie

Cai

2022

Reviews of Geophysics

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Forests cover nearly a third of the Earth's land area and exchange mass, momentum, and energy with the atmosphere. Most studies of these exchanges, particularly using numerical models, consider forests whose structure has been heavily simplified. In many landscapes, these simplifications are unrealistic. Inhomogeneous landscapes and unsteady weather conditions generate fluid dynamical features that cause observations to be inaccurately interpreted, biased, or over‐generalized. In Part I, we discuss experimental, theoretical, and numerical progress in the understanding of turbulent exchange over realistic forests. Scalar transport does not necessarily follow the flow in realistic settings, meaning scalar quantities are rarely at equilibrium around patchy forests, and significant scalar fluxes may form in the lee of forested hills. Gaps and patchiness generate significant spatial fluxes that current models and observations neglect. Atmospheric instability increases the distance over which fluxes adjust at forest edges. In deciduous forests, the effects of patchiness differ between seasons; counter intuitively, eddies reach further into leafy canopies (because they are rougher aerodynamically). Air parcel residence times are likely much lower in patchy forests than homogeneous ones, especially around edges. In Part II, we set out practical ways to make numerical models of forest‐atmosphere more realistic, including by accounting for reconfiguration and realistic canopy structure and beginning to include more chemical and physical processes in turbulence resolving models. Future challenges include: (a) customizing numerical models to real study sites, (b) connecting space and time scales, and (c) incorporating a greater range of weather conditions in numerical models.

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“…1.). In each plot, canopy access to Q. robur trees was gained through a rope canopy access system (CAS) (Total Access Ltd., UK) (Gardner et al 2021). One oak tree per plot (n = 3) was accessible using the CAS system as set up during this study.…”

Section: Site Descriptionmentioning

confidence: 99%

“…Increasing atmospheric carbon dioxide (CO 2 ) is expected to affect processes within terrestrial ecosystems, such as in forests, by increasing photosynthesis (Bader et al 2010;Ellsworth et al 2017;Gardner et al 2021). However, trees grown in elevated CO 2 (eCO 2 ) have also been hypothesised to reallocate nitrogen (N) as a critical growth resource to maximise productivity with limited resource availability (Drake et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Are chlorophyll concentrations and nitrogen across the vertical canopy profile affected by elevated CO2 in mature Quercus trees?

Gardner

Ellsworth²,

Pritchard³

et al. 2022

Trees

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Key message In mature Q. robur, chlorophyll varied with season and canopy height, whilst eCO2-driven changes were consistent with Marea, highlighting key factors for consideration when scaling photosynthetic processes and canopy N-use. Nitrogen-rich chlorophyll and carotenoid pigments are important in photosynthetic functioning. Photosynthetic pigments have been found to decrease with elevated CO2 (eCO2), but few such studies have been done in aged forest trees. This study aimed to assess the effects of eCO2 (150 μmol mol−1 above ambient) and canopy position on chlorophyll content in mature Quercus robur (Q. robur). Over 5000 in situ chlorophyll absorbance measurements, alongside laboratory chlorophyll extractions, were collected on canopy-dominant Q. robur in the 3rd and 4th season of CO2 fumigation of a free-air CO2 enrichment (FACE) study in central England. Mass-based chlorophyll concentration (Chlmass, mg g−1) was significantly higher in the lower canopy compared to upper canopy foliage (P < 0.05). In contrast, significantly higher chlorophyll content (Chlarea, mg m−2) was observed in the upper canopy. ECO2 did not affect Chlmass but Chlarea significantly increased, attributable to increased leaf mass per unit area (Marea, g m−2). We found no effect of eCO2 on mass-based or area-based nitrogen (Nmass, mg g−1 or Narea g m−2); however, Narea significantly increased with canopy height, again attributable to Marea. The parallel relationships between Marea, Narea and Chlarea suggest the allocation of N to light harvesting is maintained with eCO2 exposure as well as in the upper canopy, and that increased photosynthetic mass may help regulate the eCO2 variation. An understanding of changes in the light-harvesting machinery with eCO2 will be useful to assess canopy processes and, at larger scales, changes in biogeochemical cycles in future climate scenarios.

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Is photosynthetic enhancement sustained through three years of elevated CO2 exposure in 175-year-old Quercus robur?

Cited by 25 publications

References 72 publications

Effects of Elevated Atmospheric CO2 Concentration on Insect Herbivory and Nutrient Fluxes in a Mature Temperate Forest

Effects of Elevated Atmospheric CO2 Concentration on Insect Herbivory and Nutrient Fluxes in a Mature Temperate Forest

Realistic Forests and the Modeling of Forest‐Atmosphere Exchange

Are chlorophyll concentrations and nitrogen across the vertical canopy profile affected by elevated CO2 in mature Quercus trees?

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