Supplementary material to "Physiological and climate controls on foliar mercury uptake by European tree species"

Abstract. The exchange of gaseous elemental mercury, Hg(0), between the atmosphere and terrestrial surfaces remains poorly understood mainly due to difficulties in measuring net Hg(0) fluxes on the ecosystem scale. Emerging evidence suggests foliar uptake of atmospheric Hg(0) to be a major deposition pathway to terrestrial surfaces. Here, we present a bottom-up approach to calculate Hg(0) uptake fluxes to aboveground foliage by combining foliar Hg uptake rates normalized to leaf area with species-specific leaf area indices. This bottom-up approach incorporates systematic variations in crown height and needle age. We analyzed Hg content in 583 foliage samples from six tree species at 10 European forested research sites along a latitudinal gradient from Switzerland to northern Finland over the course of the 2018 growing season. Foliar Hg concentrations increased over time in all six tree species at all sites. We found that foliar Hg uptake rates normalized to leaf area were highest at the top of the tree crown. Foliar Hg uptake rates decreased with needle age of multiyear-old conifers (spruce and pine). Average species-specific foliar Hg uptake fluxes during the 2018 growing season were 18 ± 3 µg Hg m−2 for beech, 26 ± 5 µg Hg m−2 for oak, 4 ± 1 µg Hg m−2 for pine and 11 ± 1 µg Hg m−2 for spruce. For comparison, the average Hg(II) wet deposition flux measured at 5 of the 10 research sites during the same period was 2.3 ± 0.3 µg Hg m−2, which was 4 times lower than the site-averaged foliar uptake flux of 10 ± 3 µg Hg m−2. Scaling up site-specific foliar uptake rates to the forested area of Europe resulted in a total foliar Hg uptake flux of approximately 20 ± 3 Mg during the 2018 growing season. Considering that the same flux applies to the global land area of temperate forests, we estimate a foliar Hg uptake flux of 108 ± 18 Mg. Our data indicate that foliar Hg uptake is a major deposition pathway to terrestrial surfaces in Europe. The bottom-up approach provides a promising method to quantify foliar Hg uptake fluxes on an ecosystem scale.

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Physiological and climate controls on foliar mercury uptake by European tree species

10.5194/bg-2021-239 ◽

2021 ◽

Author(s):

Lena Wohlgemuth ◽

Pasi Rautio ◽

Bernd Ahrends ◽

Alexander Russ ◽

Lars Vesterdal ◽

...

Keyword(s):

Stomatal Conductance ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Tree Species ◽

Physiological Activity ◽

Growing Season ◽

Relevant Parameter ◽

Uptake Rates ◽

Mercury Uptake

Abstract. Despite the importance of vegetation uptake of atmospheric gaseous elemental mercury (Hg(0)) within the global Hg cycle, little knowledge exists on the physiological, climatic and geographic factors controlling stomatal uptake of atmospheric Hg(0) by tree foliage. We investigate controls on foliar stomatal Hg(0) uptake by combining Hg measurements of 3,569 foliage samples across Europe with data on tree species traits and environmental conditions. To account for foliar Hg accumulation over time, we normalized foliar Hg concentration over the foliar life period from the simulated start of the growing season to sample harvest. The most relevant parameter impacting daily foliar stomatal Hg uptake was tree functional group (deciduous versus coniferous trees). On average, we measured 3.2 times higher daily foliar stomatal Hg uptake rates in deciduous leaves than in coniferous needles of the same age. Across tree species, for foliage of beech and fir, and at two out of three forest plots with more than 20 samples, we found a significant (p < 0.001) increase in foliar Hg values with respective leaf nitrogen concentrations. We therefore suggest, that foliar stomatal Hg uptake is controlled by tree functional traits with uptake rates increasing from low to high nutrient content representing low to high physiological activity. For pine and spruce needles, we detected a significant linear decrease of daily foliar stomatal Hg uptake with the proportion of time, during which vapor pressure deficit (VPD) exceeded the species-specific threshold values of 1.2 kPa and 3 kPa, respectively. The proportion of time within the growing season, during which surface soil water content (ERA5-Land) in the region of forest plots was low correlated negatively with corresponding foliar Hg uptake rates of beech and pine. These findings suggest that stomatal uptake of atmospheric Hg(0) is inhibited under high VPD conditions and/or low soil water content due the regulation of stomatal conductance to reduce water loss under dry conditions. We therefore propose, that foliar Hg measurements bear the potential to serve as proxy for stomatal conductance. Other parameters associated with forest sampling sites (latitude and altitude), sampled trees (average age and diameter at breast height) or regional satellite observation-based transpiration product (GLEAM) did not significantly correlate with daily foliar Hg uptake rates. We conclude that tree physiological activity and stomatal response to VPD and soil water content should be implemented in a stomatal Hg model, to assess future Hg cycling under different anthropogenic emission scenarios and global warming.

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Supplementary material to "Modelling tree-ring cellulose δ18O variations of two temperature-sensitive tree species from North and South America"

10.5194/cp-2017-93-supplement ◽

2017 ◽

Author(s):

Aliénor Lavergne ◽

Fabio Gennaretti ◽

Camille Risi ◽

Valérie Daux ◽

Etienne Boucher ◽

...

Keyword(s):

South America ◽

Tree Ring ◽

Tree Species ◽

Temperature Sensitive ◽

Supplementary Material ◽

North And South America ◽

North And South ◽

Two Temperature ◽

Tree Ring Cellulose

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Supplementary material to "Carbon, nitrogen, and phosphorus stoichiometry of organic matter in Swedish forest soils and its relationship with climate, tree species, and soil texture"

10.5194/bg-2021-346-supplement ◽

2021 ◽

Author(s):

Marie Spohn ◽

Johan Stendahl

Keyword(s):

Organic Matter ◽

Forest Soils ◽

Soil Texture ◽

Tree Species ◽

Nitrogen And Phosphorus ◽

Supplementary Material

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Supplementary material to "Differential response of plant water consumption to rainwater uptake for dominant tree species in the semiarid Loess Plateau"

10.5194/hess-2021-351-supplement ◽

2021 ◽

Author(s):

Yakun Tang ◽

Lina Wang ◽

Yongqiang Yu ◽

Dongxu Lu

Keyword(s):

Loess Plateau ◽

Water Consumption ◽

Tree Species ◽

Differential Response ◽

Plant Water ◽

Supplementary Material

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Supplementary material to "Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species"

10.5194/bg-2018-256-supplement ◽

2018 ◽

Author(s):

Boaz Hilman ◽

Jan Muhr ◽

Susan E. Trumbore ◽

Mariah S. Carbone ◽

Päivi Yuval ◽

...

Keyword(s):

Tree Species ◽

Supplementary Material

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A bottom-up quantification of foliar mercury uptake fluxes across Europe

10.5194/bg-2020-289 ◽

2020 ◽

Author(s):

Lena Wohlgemuth ◽

Stefan Osterwalder ◽

Carl Joseph ◽

Ansgar Kahmen ◽

Günter Hoch ◽

...

Keyword(s):

Leaf Area ◽

Tree Species ◽

Growing Season ◽

Deposition Flux ◽

Foliar Uptake ◽

Bottom Up ◽

Needle Age ◽

Uptake Rates ◽

Mercury Uptake ◽

Species Specific

Abstract. The exchange of gaseous elemental mercury, Hg(0), between the atmosphere and terrestrial surfaces remains poorly understood mainly due to difficulties in measuring net Hg(0) fluxes on the ecosystem scale. Emerging evidence suggests foliar uptake of atmospheric Hg(0) to be a major deposition pathway to terrestrial surfaces. Here, we present a bottom-up approach to calculate Hg(0) uptake fluxes to aboveground foliage by combining foliar Hg uptake rates normalized to leaf area with species-specific leaf area indices. This bottom-up approach incorporates systematic variations in crown height and needle age. We analyzed Hg content in 583 foliage samples from six tree species at 10 European forested research sites along a latitudinal gradient from Switzerland to Northern Finland over the course of the 2018 growing season. Foliar Hg concentrations increased over time in all six tree species at all sites. We found that foliar Hg uptake rates normalized to leaf area were highest at the top of the tree crown. Foliar Hg uptake rates decreased with needle age of multi-year old conifers (spruce and pine). Average species-specific foliar Hg uptake fluxes during the 2018 growing season were 18 ± 3 µg Hg m−2 for beech, 26 ± 5 µg Hg m−2 for oak, 4 ± 1 µg Hg m−2 for pine and 11 ± 1 µg Hg m−2 for spruce. For comparison, the average Hg(II) wet deposition flux measured at 5 of the 10 research sites during the same period was 2.3 ± 0.3 µg Hg m−2, which was four times lower than the site-averaged foliar uptake flux of 10 ± 3 µg Hg m−2. Scaling up site-specific foliar uptake rates to the forested area of Europe resulted in a total foliar Hg uptake flux of approximately 20 ± 3 Mg during the 2018 growing season. Considering that the same flux applies to the global land area of temperate forests, we estimate a foliar Hg uptake flux of 108 ± 18 Mg. Our data indicate that foliar Hg uptake is a major deposition pathway to terrestrial surfaces in Europe. The bottom up approach provides a promising method to quantify foliar Hg uptake fluxes on an ecosystem scale.

Download Full-text