Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 22
Biogeosciences, 12, 6737–6749, 2015
https://doi.org/10.5194/bg-12-6737-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 6737–6749, 2015
https://doi.org/10.5194/bg-12-6737-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 26 Nov 2015

Research article | 26 Nov 2015

Mercury in coniferous and deciduous upland forests in northern New England, USA: implications of climate change

J. B. Richardson1,2 and A. J. Friedland2 J. B. Richardson and A. J. Friedland
  • 1Department of Earth Science, Dartmouth College, Hanover, NH 03755, USA
  • 2Environmental Studies Program, Dartmouth College, Hanover, NH 03755, USA

Abstract. Climatic changes in the northeastern US are expected to cause coniferous stands to transition to deciduous stands over the next hundred years. Mercury (Hg) sequestration in forest soils may change as a result. In order to understand potential effects of such a transition, we studied aboveground vegetation and soils at paired coniferous and deciduous stands on eight mountains in Vermont and New Hampshire, USA. Organic horizons at coniferous stands accumulated more total Hg (THg; 42 ± 6 g ha−1) than deciduous stands (30 ± 4 g ha−1). Total Hg pools in the mineral horizons were similar for coniferous (46 ± 8 g ha−1) and deciduous stands (45 ± 7 g ha−1). Soil properties (C, % clay, and pH) explained 56 % of the variation in mineral soil Hg concentration when multiply regressed. Foliar and bole wood Hg concentrations were generally greater for coniferous species than deciduous species. Using allometric equations, we estimated that aboveground accumulation of Hg in foliage and woody biomass was similar between vegetation types but that coniferous stands have significantly smaller annual litterfall fluxes (0.03 g ha−1 yr−1) than deciduous stands (0.24 g ha−1 yr−1). We conclude that organic horizon Hg accumulation is influenced by vegetation type but mineral horizon Hg accumulation is primarily controlled by soil properties. Further investigations into the effect of vegetation type on volatilization, atmospheric deposition, and leaching rates are needed to constrain regional Hg cycling rates.

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Our study investigated the effect of coniferous and deciduous vegetation on Hg cycling. We quantified Hg in aboveground vegetation and soil horizons at eight paired forest sites. Organic horizons at coniferous stands had greater Hg concentrations and pools than deciduous stands. Mineral soil Hg pools did not vary with vegetation type but varied with soil chemical properties. Estimated Hg litterfall flux was greater at deciduous stands. A shift in vegetation type may impact Hg accumulation.
Our study investigated the effect of coniferous and deciduous vegetation on Hg cycling. We...
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