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

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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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.

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A bottom up approach to quantify foliar uptake of gaseous elemental mercury by European forests during the 2018 growing season

10.5194/egusphere-egu2020-9626 ◽

2020 ◽

Author(s):

Lena Wohlgemuth ◽

Stefan Osterwalder ◽

Günter Hoch ◽

Christine Alewell ◽

Martin Jiskra

Keyword(s):

Leaf Area ◽

Tree Species ◽

Elemental Mercury ◽

Growing Season ◽

Accumulation Rates ◽

Bottom Up ◽

Deposition Fluxes ◽

Gaseous Elemental Mercury ◽

Species Specific ◽

Hg Accumulation

The deposition of gaseous elemental mercury, Hg(0), from the atmosphere to terrestrial surfaces remains poorly understood mainly due to difficulties in measuring net Hg(0) fluxes on the ecosystem scale. However, there is emerging evidence that vegetation uptake of atmospheric Hg(0) represents a major deposition pathway to terrestrial surfaces. We will present a novel bottom up approach to calculate Hg(0) deposition fluxes to aboveground foliage by combining foliar Hg accumulation rates on the basis of leaf area with species-specific leaf area indices. We analyzed Hg content in 583 foliage samples from major 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 tree species at all sites. We found that foliar Hg accumulation rates normalized to leaf area increased with crown height and decreased with the age of multi-year old needles. We did not detect a clear latitudinal gradient in foliar Hg accumulation rates.On an ecosystem scale we developed a simple bottom up approach for foliar Hg(0) uptake considering the systematic variations in crown height, needle age and tree species. We calculated species-specific average foliar Hg(0) dry deposition rates for the 2018 growing season of 22 &#177; 4 &#181;g Hg m-2 for beech, 16 &#177; 8 &#181;g Hg m-2 for oak, 3 &#177; 0.4 &#181;g Hg m-2 for birch, 18 &#177; 10 &#181;g Hg m-2 for spruce and 8 &#177; 4 &#181;g Hg m-2 for pine. For comparison, the average Hg wet deposition flux measured at 4 of our 10 research sites during the same time period was 2.5 &#177; 0.2 &#181;g Hg m-2.Scaling up site-specific deposition rates to the forested area of Europe (EU28) resulted in a total aboveground Hg(0) deposition to foliage of approximately 20 Mg during the 2018 growing season. Our results confirm that vegetation uptake of atmospheric Hg(0) represents a major deposition pathway to terrestrial surfaces. The bottom up approach we used is a promising method to quantify Hg(0) deposition fluxes based on easy-to-do Hg concentration measurements in foliage.

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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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Evaluation of O3 Effects on Cumulative Photosynthetic CO2 Uptake in Seedlings of Four Japanese Deciduous Broad-Leaved Forest Tree Species Based on Stomatal O3 Uptake

Forests ◽

10.3390/f10070556 ◽

2019 ◽

Vol 10 (7) ◽

pp. 556 ◽

Cited By ~ 2

Author(s):

Masahiro Yamaguchi ◽

Yoshiyuki Kinose ◽

Hideyuki Matsumura ◽

Takeshi Izuta

Keyword(s):

Leaf Area ◽

Tree Species ◽

Net Primary Production ◽

Forest Tree ◽

Co2 Uptake ◽

Growing Seasons ◽

Whole Plant ◽

Broad Leaved Forest ◽

Leaf Level ◽

Species Specific

The current level of tropospheric ozone (O3) is expected to reduce the net primary production of forest trees. Here, we evaluated the negative effects of O3 on the photosynthetic CO2 uptake of Japanese forest trees species based on their cumulative stomatal O3 uptake, defined as the phytotoxic O3 dose (POD). Seedlings of four representative Japanese deciduous broad-leaved forest tree species (Fagus crenata, Quercus serrata, Quercus mongolica var. crispula and Betula platyphylla var. japonica) were exposed to different O3 concentrations in open-top chambers for two growing seasons. The photosynthesis–light response curves (A-light curves) and stomatal conductance were measured to estimate the leaf-level cumulative photosynthetic CO2 uptake (ΣPn_est) and POD, respectively. The whole-plant-level ΣPn_est were highly correlated with the whole-plant dry mass increments over the two growing seasons. Because whole-plant growth is largely determined by the amount of leaf area per plant and net photosynthetic rate per leaf area, this result suggests that leaf-level ΣPn_est, which was estimated from the monthly A-light curves and hourly PPFD, could reflect the cumulative photosynthetic CO2 uptake of the seedlings per unit leaf area. Although the O3-induced reductions in the leaf-level ΣPn_est were well explained by POD in all four tree species, species-specific responses of leaf-level ΣPn_est to POD were observed. In addition, the flux threshold appropriate for the linear regression of the responses of relative leaf-level ΣPn_est to POD was also species-specific. Therefore, species-specific responses of cumulative photosynthetic CO2 uptake to POD could be used to accurately evaluate O3 impact on the net primary production of deciduous broad-leaved trees.

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Species-specific temporal variation in photosynthesis as a moderator of peatland carbon sequestration

Biogeosciences ◽

10.5194/bg-14-257-2017 ◽

2017 ◽

Vol 14 (2) ◽

pp. 257-269 ◽

Cited By ~ 11

Author(s):

Aino Korrensalo ◽

Pavel Alekseychik ◽

Tomáš Hájek ◽

Janne Rinne ◽

Timo Vesala ◽

...

Keyword(s):

Leaf Area ◽

Vascular Plants ◽

Gross Primary Production ◽

Light Response ◽

Growing Season ◽

Photosynthetic Parameters ◽

Gross Photosynthesis ◽

Ecosystem Level ◽

Species Specific ◽

Photosynthetic Properties

Abstract. In boreal bogs plant species are low in number, but they differ greatly in their growth forms and photosynthetic properties. We assessed how ecosystem carbon (C) sink dynamics were affected by seasonal variations in the photosynthetic rate and leaf area of different species. Photosynthetic properties (light response parameters), leaf area development and areal cover (abundance) of the species were used to quantify species-specific net and gross photosynthesis rates (PN and PG, respectively), which were summed to express ecosystem-level PN and PG. The ecosystem-level PG was compared with a gross primary production (GPP) estimate derived from eddy covariance (EC) measurements.Species areal cover, rather than differences in photosynthetic properties, determined the species with the highest PG of both vascular plants and Sphagna. Species-specific contributions to the ecosystem PG varied over the growing season, which, in turn, determined the seasonal variation in ecosystem PG. The upscaled growing season PG estimate, 230 g C m−2, agreed well with the GPP estimated by the EC (243 g C m−2).Sphagna were superior to vascular plants in ecosystem-level PG throughout the growing season but had a lower PN. PN results indicated that areal cover of the species, together with their differences in photosynthetic parameters, shape the ecosystem-level C balance. Species with low areal cover but high photosynthetic efficiency appear to be potentially important for the ecosystem C sink. Results imply that functional diversity, i.e., the presence of plant groups with different seasonal timing and efficiency of photosynthesis, may increase the stability of C sinks of boreal bogs.

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Species-specific temporal variation in photosynthesis as a moderator of peatland carbon sequestration

10.5194/bg-2016-265 ◽

2016 ◽

Author(s):

Aino Korrensalo ◽

Tomáš Hájek ◽

Pavel Alekseychik ◽

Janne Rinne ◽

Timo Vesala ◽

...

Keyword(s):

Leaf Area ◽

Vascular Plants ◽

Gross Primary Production ◽

Light Response ◽

Growing Season ◽

Photosynthetic Parameters ◽

Gross Photosynthesis ◽

Ecosystem Level ◽

Species Specific ◽

Photosynthetic Properties

Abstract. In boreal bogs plant species are low in number, but they differ greatly in their growth forms and photosynthetic properties. We assessed how ecosystem carbon (C) sink dynamics were affected by seasonal variations in photosynthetic rate and leaf area of different species. Photosynthetic properties (light-response parameters), leaf area development and areal cover (abundance) of the species were used to quantify species-specific net and gross photosynthesis rates (PN and PG, respectively), which were summed to express ecosystem-level PN and PG. The ecosystem-level PG was compared with a gross primary production (GPP) estimate derived from eddy covariance measurements (EC). Species areal cover rather than differences in photosynthetic properties determined the species with the highest PG of both vascular plants and Sphagna. Species-specific contributions to the ecosystem PG varied over the growing season, which in turn determined the seasonal variation in ecosystem PG. The upscaled growing-season PG estimate, 230 g C m−2, agreed well with the GPP estimated by the EC, 243 g C m−2. Sphagna were superior to vascular plants in ecosystem-level PG throughout the growing season but had a lower PN. PN results indicated that areal cover of the species together with their differences in photosynthetic parameters shape the ecosystem-level C balance. Species with low areal cover but high photosynthetic efficiency appear to be potentially important for the ecosystem C sink. Results imply that functional diversity may increase the stability of C sink of boreal bogs.

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Analogy-Based Crop Yield Forecasts Based on Temporal Similarity of Leaf Area Index

Remote Sensing ◽

10.3390/rs13163069 ◽

2021 ◽

Vol 13 (16) ◽

pp. 3069

Author(s):

Yadong Liu ◽

Junhwan Kim ◽

David H. Fleisher ◽

Kwang Soo Kim

Keyword(s):

Time Series ◽

Leaf Area Index ◽

Leaf Area ◽

Crop Yield ◽

Satellite Data ◽

Growing Season ◽

Environmental Data ◽

Area Index ◽

Current Season ◽

Wide Range

Seasonal forecasts of crop yield are important components for agricultural policy decisions and farmer planning. A wide range of input data are often needed to forecast crop yield in a region where sophisticated approaches such as machine learning and process-based models are used. This requires considerable effort for data preparation in addition to identifying data sources. Here, we propose a simpler approach called the Analogy Based Crop-yield (ABC) forecast scheme to make timely and accurate prediction of regional crop yield using a minimum set of inputs. In the ABC method, a growing season from a prior long-term period, e.g., 10 years, is first identified as analogous to the current season by the use of a similarity index based on the time series leaf area index (LAI) patterns. Crop yield in the given growing season is then forecasted using the weighted yield average reported in the analogous seasons for the area of interest. The ABC approach was used to predict corn and soybean yields in the Midwestern U.S. at the county level for the period of 2017–2019. The MOD15A2H, which is a satellite data product for LAI, was used to compile inputs. The mean absolute percentage error (MAPE) of crop yield forecasts was <10% for corn and soybean in each growing season when the time series of LAI from the day of year 89 to 209 was used as inputs to the ABC approach. The prediction error for the ABC approach was comparable to results from a deep neural network model that relied on soil and weather data as well as satellite data in a previous study. These results indicate that the ABC approach allowed for crop yield forecast with a lead-time of at least two months before harvest. In particular, the ABC scheme would be useful for regions where crop yield forecasts are limited by availability of reliable environmental data.

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Species-specific isotope tracking of mercury uptake and transformations by pico-nanoplankton in an eutrophic lake

Environmental Pollution ◽

10.1016/j.envpol.2021.117771 ◽

2021 ◽

pp. 117771

Author(s):

Thibaut Cossart ◽

Javier Garcia-Calleja ◽

Isabelle A.M. Worms ◽

Emmanuel Tessier ◽

Killian Kavanagh ◽

...

Keyword(s):

Eutrophic Lake ◽

Mercury Uptake ◽

Species Specific

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El Niño-Southern Oscillation affects the water relations of tree species in the Yucatan Peninsula, Mexico

Scientific Reports ◽

10.1038/s41598-021-89835-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jorge Palomo-Kumul ◽

Mirna Valdez-Hernández ◽

Gerald A. Islebe ◽

Manuel J. Cach-Pérez ◽

José Luis Andrade

Keyword(s):

Water Potential ◽

Leaf Area ◽

Tropical Forests ◽

Specific Leaf Area ◽

Tree Species ◽

Deciduous Species ◽

Mature Trees ◽

Seasonally Dry ◽

Seasonally Dry Tropical Forests ◽

Dry Tropical Forests

AbstractWe evaluated the effect of ENSO 2015/16 on the water relations of eight tree species in seasonally dry tropical forests of the Yucatan Peninsula, Mexico. The functional traits: wood density, relative water content in wood, xylem water potential and specific leaf area were recorded during the rainy season and compared in three consecutive years: 2015 (pre-ENSO conditions), 2016 (ENSO conditions) and 2017 (post-ENSO conditions). We analyzed tree size on the capacity to respond to water deficit, considering young and mature trees, and if this response is distinctive in species with different leaf patterns in seasonally dry tropical forests distributed along a precipitation gradient (700–1200 mm year−1). These traits showed a strong decrease in all species in response to water stress in 2016, mainly in the driest site. Deciduous species had lower wood density, higher predawn water potential and higher specific leaf area than evergreen species. In all cases, mature trees were more tolerant to drought. In the driest site, there was a significant reduction in water status, regardless of their leaf phenology, indicating that seasonally dry tropical forests are highly vulnerable to ENSO. Vulnerability of deciduous species is intensified in the driest areas and in the youngest trees.

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Impact of Deer Browsing on Regeneration in Mixed Stands in Southern New England

Northern Journal of Applied Forestry ◽

10.1093/njaf/12.3.115 ◽

1995 ◽

Vol 12 (3) ◽

pp. 115-120 ◽

Cited By ~ 41

Author(s):

David B. Kittredge ◽

P. Mark S. Ashton

Keyword(s):

New England ◽

Tree Species ◽

Sugar Maple ◽

Red Maple ◽

White Pine ◽

Mixed Stands ◽

Tree Species Composition ◽

Southern New England ◽

Pine Seedlings ◽

Species Specific

Abstract Browsing preferences by white-tailed deer were evaluated for 6 tree species in northeastern Connecticut. Deer density averaged 23/mile². Deer exhibited no species-specific preferences for seedlings greater than 19 in. For seedlings less than 19 in., hemlock and black birch were preferred. Red maple, sugar maple, and white pine seedlings were avoided. Red oak seedlings were neither preferred nor avoided. A much higher proportion of seedlings greater than 19.7 in. in height was browsed, regardless of species. Browsing preferences for species in the smaller seedling class, combined with a lack of preference for species in the larger class may result in future stands with less diverse tree species composition. Deer densities in excess of 23/mile² may be incompatible with regeneration of diverse forests in southern New England. North. J. Appl. For. 12(3):115-120.

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