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

[摘要] Climatic changes in the northeastern US are expected to cause coniferousstands to transition to deciduous stands over the next hundred years.Mercury (Hg) sequestration in forest soils may change as a result. In orderto understand potential effects of such a transition, we studied abovegroundvegetation and soils at paired coniferous and deciduous stands on eightmountains in Vermont and New Hampshire, USA. Organic horizons at coniferousstands accumulated more total Hg (THg; 42 ± 6 g ha⁻¹) thandeciduous stands (30 ± 4 g ha⁻¹). Total Hg pools in the mineralhorizons were similar for coniferous (46 ± 8 g ha⁻¹) anddeciduous stands (45 ± 7 g ha⁻¹). Soil properties (C, % clay,and pH) explained 56 % of the variation in mineral soil Hg concentrationwhen multiply regressed. Foliar and bole wood Hg concentrations weregenerally greater for coniferous species than deciduous species. Usingallometric equations, we estimated that aboveground accumulation of Hg infoliage and woody biomass was similar between vegetation types but thatconiferous 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 vegetationtype but mineral horizon Hg accumulation is primarily controlled by soilproperties. Further investigations into the effect of vegetation type onvolatilization, atmospheric deposition, and leaching rates are needed toconstrain regional Hg cycling rates.

[学科分类] 地球化学与岩石