New Approaches to Understand Mercury in Trees: Radial and Longitudinal Patterns of Mercury in Tree Rings and Genetic Control of Mercury in Maple Sap

Yanai, Ruth D.; Yang, Yang; Wild, Adam D.; Smith, Kevin T.; Driscoll, Charles T.

doi:10.1007/s11270-020-04601-2

Cited by 15 publications

(8 citation statements)

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“…The third scenario relates to tree physiology. Hg is transported downwards in trees via the phloem and has been reported to translocate from phloem to xylem (sapwood) throughout this process (Arnold et al, 2018;Yanai et al, 2020;Nováková et al, 2021). As sapwood ages it undergoes a physiological transition to heartwood, which is drier, contains predominantly dead cells, and is used for structure rather than transport (Bertaud and Holmbom, 2004;Metsä-Kortelainen et al, 2006).…”

Section: Sapwood (Hydroactive Xylem) Rings Enriched In Hgmentioning

confidence: 99%

“…As sapwood ages it undergoes a physiological transition to heartwood, which is drier, contains predominantly dead cells, and is used for structure rather than transport (Bertaud and Holmbom, 2004;Metsä-Kortelainen et al, 2006). Hg that remains in the tree rings after the transition to heartwood likely binds to components that endure this change, but there are caveats in our knowledge of this process (Yanai et al, 2020;Nováková et al, 2021). Since we use dry-weight THg concentrations, if all the Hg translocated from phloem to xylem was conserved in the wood during the transition from sapwood to heartwood, then we would not expect to see any sapwood enrichment.…”

Section: Sapwood (Hydroactive Xylem) Rings Enriched In Hgmentioning

confidence: 99%

“…Once oxidised to Hg(II) species in the leaves/needles, it likely associates with phytochelatin, cysteine compounds for phloem transport (O'Connor et al, 2019;Dennis et al, 2019). Phloem-to-xylem translocation (new xylem makes up sapwood and forms tree rings) is expected to occur throughout this downward transport (Arnold et al, 2018;Yanai et al, 2020;Nováková et al, 2021Nováková et al, , 2022. This translocation likely proceeds via rays, parenchyma cells that radially connect xylem and phloem conductive tissues and mediate water and nutrient transport, tree growth, and biotic and abiotic stressors (Nagy et al, 2014;Pfautsch et al, 2015;Gustin et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

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Internal tree cycling and atmospheric archiving of mercury: examination with concentration and stable isotope analyses

et al. 2022

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Abstract. Trees predominantly take up mercury (Hg) from the atmosphere via stomatal assimilation of gaseous elemental Hg (GEM). Hg is oxidised in leaves/needles and transported to other tree anatomy including bole wood, where it can be stored long-term. Using Hg associated with growth rings facilitates archiving of historical GEM concentrations. Nonetheless, there are significant knowledge gaps on the cycling of Hg within trees. We investigate Hg archived in tree rings, internal tree Hg cycling, and differences in Hg uptake mechanisms in Norway spruce and European larch sampled within 1 km of a HgCl2-contaminated site using total Hg (THg) and Hg stable isotope analyses. Tree ring samples are indicative of significant increases in THg concentrations (up to 521 µg kg−1) from the background period (BGP; facility closed; 1992–present) to secondary industrial period (2ndIP; no HgCl2 wood treatment; 1962–1992) to primary industrial period (1stIP; active HgCl2 wood treatment; ≈ 1900–1962). Mass-dependent fractionation (MDF) Hg stable isotope data are shifted negative during industrial periods (δ202Hg of 1stIP: −4.32 ± 0.15 ‰, 2ndIP: −4.04 ± 0.32 ‰, BGP: −2.83 ± 0.74 ‰; 1 SD). Even accounting for a ≈ −2.6 ‰ MDF shift associated with stomatal uptake, these data are indicative of emissions derived from industrial activity being enriched in lighter isotopes associated with HgCl2 reduction and Hg0 volatilisation. Similar MDF (δ202Hg: −3.90 ± 0.30 ‰; 1 SD) in bark Hg (137 ± 105 µg kg−1) suggests that stomatal assimilation and downward transport is also the dominant uptake mechanism for bark Hg (reflective of negative stomatal-uptake MDF shift) rather than deposition to bark. THg was enriched in sapwood of all sampled trees across both tree species. This may indicate long-term storage of a fraction of Hg in sapwood or xylem solution. We also observed a small range of odd-isotope mass-independent fractionation (MIF). Differences in Δ199Hg between periods of different industrial activities were significant (Δ199Hg of 1stIP: 0.00 ± 0.03 ‰, 2ndIP: −0.06 ± 0.04 ‰, BGP: −0.13 ± 0.03 ‰; 1 SD), and we suggest MIF signatures are conserved during stomatal assimilation (reflect source MIF signatures). These data advance our understanding of the physiological processing of Hg within trees and provide critical direction to future research into the use of trees as archives for historical atmospheric Hg.

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Section: Sapwood (Hydroactive Xylem) Rings Enriched In Hgmentioning

confidence: 99%

Section: Sapwood (Hydroactive Xylem) Rings Enriched In Hgmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Internal tree cycling and atmospheric archiving of mercury: examination with concentration and stable isotope analyses

et al. 2022

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“…Plant foliage take up Hg deposited on leaf surfaces through the stomata (ie. Photosynthesis) and leaf cuticles (Hanson et al 1995;Jiskra et al 2018;Li et al 2017;Lodenius et al 2003;Maillard et al 2016;Rea et al 2002;Yanai et al 2020) where it accumulates with minimal mobility and small portions released back into the atmosphere or transfers the Hg through the other plant organs (Cavallini et al 1999;Hanson et al 1995;Li et al 2017;Lodenius et al 2003;Schwesig and Krebs 2003). Water and soil are another uptake Hg source through roots (Bishop et al 1998;Li et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…This atmospheric deposition that has declined in recent decades can be shown in the declining concentration from the older to newer tree rings suggesting a more important uptake through the foliage than the roots. Hg dendrochemistry can help investigate Hg past impacts on terrestrial ecosystems and also help predict future changes in the cycle of Hg in forests (Yanai et al, 2020). The recent studies on Hg uptake by vegetation have highlighted the importance of the role of different parameters as vapor pressure deficit, soil water content, climatic conditions, date of sampling, leaf mass area, tree functional groups, stomatal conductance affecting potentially the root uptake of Hg dissolved in soil water and the absorption rate via stomata and eventually the Hg leaf content (Blackwell & Driscoll, 2015;Rea et al, 2002;Wohlgemuth et al, 2021;Yang et al, 2018b).…”

Section: Introductionmentioning

confidence: 99%

Seasonal variation of mercury concentration of ancient olive groves of Lebanon

Tabaja

Amouroux

Chalak

et al. 2022

Preprint

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Abstract. This study aimed to investigate the olive, iconic tree of the Mediterranean basin, seasonality of (Hg) mercury pollution. Hg concentrations of foliage, stems, soil surface, and litter were analyzed on monthly basis in ancient olive trees growing in two groves in Lebanon, Bchaaleh and Kawkaba (1300 and 672 m.a.s.l respectively). A significantly lower concentration was registered in stems (~7–9 ng/g) with respect to foliage (~35–48 ng/g) in both sites with the highest foliage Hg concentration in late winter-early spring and the lowest in summer. It is noteworthy that olive fruits also have the lowest Hg concentration (~7–11 ng/g). The soil has the highest Hg content (~62–129 ng/g) likely inherited through the cumulated litter biomass (~ 63–76 ng/g). good covariation observed between our foliage Hg time-series analysis and those of pCO2 and Hg concentrations of the atmospheric Northern hemisphere confirms that mercury pollution can be studied through olive trees. More precisely, spring sampling is recommended if the objective is to assess the tree's susceptibility to Hg uptake. This may draw an adequate baseline for global inventories on Hg vegetation uptake and for new studies on olive trees in the Mediterranean for reconstructing regional Hg pollution concentrations in the past and present.

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The Roles of the Moss Layer in Mediating Tree Seedling Environmental Stress, Mercury Exposure, and Regeneration in High-Elevation Conifer Forests

et al. 2022

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The persistence of future forests depends on the success of tree seedlings which are experiencing increasing physiological stress from changing climate and air pollution. Although the moss layer can serve as an important substrate for tree seedlings, its potential for reducing environmental stress and enhancing the establishment of seedlings remains poorly understood. We tested if the moss layer decreased environmental stress and increased the abundance of balsam fir seedlings dominant in high-elevation forests of northeastern United States that are sensitive to changing climate and mercury deposition. We surveyed balsam fir seedling density by substrate (moss, litter, other) on 120 quadrats (1 × 1 m) in two contrasting canopy environments (in gaps and under canopies), measured seedling stress, and quantified mercury content in seedlings and substrates. We observed that, in both canopy environments, tree seedlings established on moss exhibited (i) increased density, (ii) decreased physiological stress, and (iii) higher potential to recruit into larger size classes, compared to seedlings established in litter. Regardless of canopy environment, seedling foliar mercury levels did not correspond to substrate mercury despite large differences in substrate mercury concentrations (relative to moss, litter concentrations were ~ 4-times greater and soil concentrations were ~ 6-times greater), likely reflecting the dominance of foliar over root uptake of mercury. Because the moss layer appeared to mitigate seedling drought stress, and to increase seedling establishment and recruitment compared to other substrates, these microsite effects should be considered in models predicting forest regeneration and dynamics under increased drought stress associated with the ongoing climate warming.

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New Approaches to Understand Mercury in Trees: Radial and Longitudinal Patterns of Mercury in Tree Rings and Genetic Control of Mercury in Maple Sap

Cited by 15 publications

References 59 publications

Internal tree cycling and atmospheric archiving of mercury: examination with concentration and stable isotope analyses

Internal tree cycling and atmospheric archiving of mercury: examination with concentration and stable isotope analyses

Seasonal variation of mercury concentration of ancient olive groves of Lebanon

The Roles of the Moss Layer in Mediating Tree Seedling Environmental Stress, Mercury Exposure, and Regeneration in High-Elevation Conifer Forests

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