2 research outputs found
Needle age and precipitation as drivers of Hg accumulation and deposition in coniferous forests from a southwestern European Atlantic region
Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGVegetation and climate are critical in the biogeochemical cycle of Hg in forest ecosystems. The study assesses the
influence of needle age and precipitation on the accumulation of Hg in needle biomass and its deposition by
litterfall in thirty-one pine plantations spread throughout two biogeographical regions in SW Europe. Welldeveloped
branches of Pinus pinaster were sampled and pine needles were classified according to 4 age classes
(y0, y1, y2, y3). The concentration of total Hg (THg) was analyzed in the samples and Hg content in needle
biomass and its deposition by litterfall were estimated. The concentration of total Hg (THg) increased with
needle age ranging from 9.1 to 32.7 μg Hg kg−1 in the youngest and oldest needles, respectively. The rate of Hg
uptake (HgR) three years after needle sprouting was 10.2 ± 2.3 μg Hg kg−1 yr−1, but it decreased with needle age
probably due to a diminution in photosynthetic activity as needles get older. The average total Hg stored in
needle biomass (HgWt) ranged from 5.6 to 87.8 mg Hg ha−1, with intermediate needle age classes (y1 and y2)
accounting for 70% of the total Hg stored in the whole needle biomass. The average deposition flux of Hg
through needle litterfall (HgLt) was 1.5 μg Hg m−2 yr−1, with the y2 and y3 needles contributing most to the total
Hg flux. The spatial variation of THg, HgWt and HgLt decreased from coastal pine stands, characterized by an
oceanic climate, to inland pine stands, a feature closely related to the dominant precipitation regime in the study
area. Climatic conditions and needle age are the main factors affecting Hg accumulation in tree foliage, and
should be considered for an accurate assessment of forest Hg pools at a regional scale and their potential consequences
in the functioning of terrestrial ecosystems.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C 2021/46-GRCXunta de Galicia | Ref. ED431F2018/06-EXCELENCIAXunta de Galicia | Ref. ED431C2018/0
Mercury in a birch forest in SW Europe: Deposition flux by litterfall and pools in aboveground tree biomass and soils
Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAtmospheric mercury (Hg) is largely assimilated by vegetation and subsequently transferred to the soil by litterfall,
which highlights the role of forests as one of the largest global Hg sinks within terrestrial ecosystems. We assessed
the pool of Hg in the aboveground biomass (leaves, wood, bark, branches and twigs), the Hg deposition flux through
litterfall over two years (by sorting fallen biomass in leaves, twigs, reproductive structures and miscellaneous) and its
accumulation in the soil profile in a deciduous forest dominated by Betula alba from SW Europe. The total Hg pool in
the aboveground birch biomass was in the range 532–683 mg ha−1, showing the following distribution by plant tissues:
well-developed leaves (171 mg ha−1) > twigs (160 mg ha−1) > bark (159 mg ha−1) > bole wood (145 mg
ha−1) > fine branches (25 mg ha−1) > thick branches (24 mg ha−1) > newly sprouted leaves (20 mg ha−1). The
total Hg deposition fluxes through litterfall were 15.4 and 11.7 μg m−2 yr−1 for the two years studied, with the
greatest contribution coming from birch leaves (73 %). In the soil profile, the pool of Hg in the mineral soil
(37.0 mg m−2) was an order of magnitude higher than in the organic horizons (1.0 mg m−2), mostly conditioned
by parameters such as soil bulk density and thickness, total C andNcontents and the presence of certain Al compounds.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C2021/46-GRCXunta de Galicia | Ref. ED431F2018/06- EXCELENCI