|Abstract Title:||Quarter of century litterfall record in Norway spruce stands highly impacted by acid rain (Ore Mountains, Czech Republic).|
|Presenter Name:||Tomas Navratil|
|Company/Institution:||Institute of Geology of the Czech Academy of Sciences|
|Session:||Mercury in the Terrestrial Ecosystems|
Abstract Information :
Recent works have provided evidence that litterfall is the dominant way for Hg deposition from atmosphere to the forest ecosystems. We evaluated 25-years long trend (1994?2019) in mercury (Hg) concentrations and fluxes in five litterfall components needles, bark, twigs, cones, and a mixture of unidentified fragments at a research plots situated in mountain forest Norway spruce stand. The study site Na?et¡n is in the Ore Mountains (Erzgebirge) near the Czech-German border in an area known as the Black Triangle due to extensive damage by acid precipitation in the second half of the 20th century. The litterfall Hg deposition averaged 50 ñ 17 æg.m-2.yr-1, while the bulk precipitation and throughfall Hg deposition determined in 2019 were an order of magnitude lower (2.2 and 7.0 æg.m-2.yr-1). Hg concentrations in the individual litter components averaged 256, 234, 119, 95 and 44 æg/kg in bark, unidentified fragments, twigs, needles and cones, respectively. Due to decreasing Czech, German and overall European Hg emissions, Hg concentrations in litter decreased from 1994?2019. Despite that, the litter-associated Hg flux to forest floor increased from 44 to 71 æg.m-2.yr-1 during 1994?2019 due to increase of the litterfall mass fluxes from 407 to 678 g.m-2.yr-1. Using the three soil sampling campaigns in years 1994, 2004 and 2018 we evaluated the effect of the changes in litterfall composition and deposition onto the O horizon soil layers. Mercury concentrations in the Oi horizons decreased significantly from 354, through 295 to 202 æg.kg-1 in years 1994, 2004 and 2018. In contrast, Hg concentrations in more decomposed Oa horizons increased from 453, across 489 to 593 æg.kg-1. Lumped O horizon Hg pool decreased from 7.6 to 5.5 mg.m-2.yr-1 but without statistical significance. We further investigate on the interplay between litterfall chemical composition e.g. Hg/C, Hg/N and Hg/S ratios and its reprint into the soil.