Identification of Source‐Water Oxygen Isotopes in Trees Toolkit (ISO‐Tool) for Deciphering Historical Water Use by Forest Trees

Sargeant, Christopher; Singer, Michael Bliss; Vallet‐Coulomb, Christine

doi:10.1029/2018wr024519

Cited by 11 publications

(11 citation statements)

References 169 publications

(269 reference statements)

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“…One of the main purposes of developing semi‐mechanistic models of cellulose isotopic variation, is to be able to invert the model to estimate parameters of interest, which are retrospectively difficult to assess. For example, the cellulose isotope models have been used to infer leaf temperature (Helliker & Richter, 2008); deuterium deviations (as a proxy for relative humidity) (Voelker et al, 2014); stomatal conductance induced changes in water‐use efficiency (Guerrieri et al, 2019); origin of plant material (Cueni et al, 2021); and, source of water for trees (Sargeant et al, 2019); as well as estimate the fraction of isotopic exchange in sink cell water (e.g., Cheesman & Cernusak, 2016; Song et al, 2014). However, to perform these calculations, the values of isotopic exchange and/or biosynthetic isotope fractionation are generally assumed constant across species and environmental conditions.…”

Section: Discussionmentioning

confidence: 99%

Species variation in the hydrogen isotope composition of leaf cellulose is mostly driven by isotopic variation in leaf sucrose

Holloway‐Phillips

Baan

Nelson

et al. 2022

Plant Cell & Environment

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Experimental approaches to isolate drivers of variation in the carbon‐bound hydrogen isotope composition (δ2H) of plant cellulose are rare and current models are limited in their application. This is in part due to a lack in understanding of how 2H‐fractionations in carbohydrates differ between species. We analysed, for the first time, the δ2H of leaf sucrose along with the δ2H and δ18O of leaf cellulose and leaf and xylem water across seven herbaceous species and a starchless mutant of tobacco. The δ2H of sucrose explained 66% of the δ2H variation in cellulose (R2 = 0.66), which was associated with species differences in the 2H enrichment of sucrose above leaf water ( ε sucrose ${\unicode{x003B5}}_{sucrose}$ : −126% to −192‰) rather than by variation in leaf water δ2H itself. ε sucrose ${\unicode{x003B5}}_{sucrose}$ was positively related to dark respiration (R2 = 0.27), and isotopic exchange of hydrogen in sugars was positively related to the turnover time of carbohydrates (R2 = 0.38), but only when normalε sucrose ${\unicode{x003B5}}_{sucrose}$ was fixed to the literature accepted value of − 171 $\unicode{x02212} 171$ ‰. No relation was found between isotopic exchange of hydrogen and oxygen, suggesting large differences in the processes shaping post‐photosynthetic fractionation between elements. Our results strongly advocate that for robust applications of the leaf cellulose hydrogen isotope model, parameterization utilizing δ2H of sugars is needed.

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Section: Discussionmentioning

confidence: 99%

Species variation in the hydrogen isotope composition of leaf cellulose is mostly driven by isotopic variation in leaf sucrose

Holloway‐Phillips

Baan

Nelson

et al. 2022

Plant Cell & Environment

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“…1d) can capture the seasonally integrated response of trees to air temperature and environmental moisture (Rebetez et al, 2003;Liu et al, 2017). However, the shape and nature of the relationship alone might be difficult to interpret without separating the effects of oxygen isotopic fractionation in leaves and source water variability on δ 18 O R (Barnard et al, 2012;Roden and Siegwolf, 2012;Sargeant et al, 2019). But when ring width variations are simultaneously negatively related to δ 18 O R and positively to 13 C R variations, as observed in Fontainebleau (Fig.…”

Section: Constraining Model Processes With the Growth-isotope Tree-ring Tripletmentioning

confidence: 96%

A triple tree-ring constraint for tree growth and physiology in a global land surface model

et al. 2021

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Abstract. Annually resolved tree-ring records extending back to pre-industrial conditions have the potential to constrain the responses of global land surface models at interannual to centennial timescales. Here, we demonstrate a framework to simultaneously constrain the representation of tree growth and physiology in the ORCHIDEE global land surface model using the simulated variability of tree-ring width and carbon (Δ13C) and oxygen (δ18O) stable isotopes in six sites in boreal and temperate Europe. We exploit the resulting tree-ring triplet to derive integrative constraints for leaf physiology and growth from well-known mechanistic relationships among the variables. ORCHIDEE simulates Δ13C (r=0.31–0.80) and δ18O (r=0.36–0.74) better than tree-ring width (r<0.55), with an overall skill similar to that of a tree-ring model (MAIDENiso) and another isotope-enabled global vegetation model (LPX-Bern). The comparison with tree-ring data showed that growth variability is not well represented in ORCHIDEE and that the parameterization of leaf-level physiological responses (stomatal control) to drought stress in the temperate region can be constrained using the interannual variability of tree-ring stable isotopes. The representation of carbon storage and remobilization dynamics emerged as a critical process to improve the realism of simulated growth variability, temporal carryover, and recovery of forest ecosystems after climate extremes. Simulated forest gross primary productivity (GPP) correlates with simulated tree-ring Δ13C and δ18O variability, but the origin of the correlations with tree-ring δ18O is not entirely physiological. The integration of tree-ring data and land surface models as demonstrated here should guide model improvements and contribute towards reducing current uncertainties in forest carbon and water cycling.

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“…Tree ring oxygen isotope ratios (δ 18 O) can be used to infer water sources accessed by the tress over the years through retrospective analyses stemming from inverse-modelling (Sargeant et al 2019). This is another promising approach because it could allow reconstructing the multi-year changes in the water source trees have used, including groundwater uptake, and improving our predictive capacity of which trees, stands, species or forests will experience dieback due to drought.…”

Section: Reconciling Process-based and Empirical Approachesmentioning

confidence: 99%

The drought‒dieback‒death conundrum in trees and forests

Camarero

2021

Plant Ecology & Diversity

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Background: Climate warming is amplifying and exacerbating drought stress worldwide. Long-term trends of increasing evaporative demand and decreasing soil moisture availability occur superimposed on severe spells of drought. These rare, extreme droughts have triggered episodes of forest dieback that have led to reduced productivity and rising mortality rates, usually at small scales (dieback hotspots), but affecting biomes worldwide. Aims: This review summarizes and discusses the drivers, patterns and mechanisms of forest dieback caused by drought. Methods: I review studies on forest dieback and tree death linked to dry spells with a focus on tools to forecast dieback. Results: Several mechanisms have been described as physiological drivers of dieback, including hydraulic failure and carbon starvation, however hydraulics-based models have shown little predictive power of dieback and mortality. Field proxies of tree vigour, including changes in canopy defoliation and water content, combined with surrogates of tree functioning (tree-ring growth, wood anatomy, tree-ring δ 13 C or δ 18 O composition) may improve predictions of forest dieback or at least render early-warning signals of impending tree death. Conclusions: Drought-induced dieback and mortality are concerning phenomena which lack forecasting tools with sufficient predictive power. Surrogates of tree vigour, growth and functioning should be used to build more accurate models of tree death in response to extreme climate events linked to drought. Here, I argue for combining and comparing those surrogates to better forecast forest dieback.

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Identification of Source‐Water Oxygen Isotopes in Trees Toolkit (ISO‐Tool) for Deciphering Historical Water Use by Forest Trees

Cited by 11 publications

References 169 publications

Species variation in the hydrogen isotope composition of leaf cellulose is mostly driven by isotopic variation in leaf sucrose

Species variation in the hydrogen isotope composition of leaf cellulose is mostly driven by isotopic variation in leaf sucrose

A triple tree-ring constraint for tree growth and physiology in a global land surface model

The drought‒dieback‒death conundrum in trees and forests

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