Influence of Nothofagus pumilio forest management on Hg content and accumulation in organic matter rich soil horizons

GÓMEZ-ARMESTO, A; MÉNDEZ-LÓPEZ, M.; ARIAS-ESTÉVEZ, M.; MORETTO, A.;; MANSILLA, R.; NÓVOA-MUÑOZ, J.C

Congreso; 8th International Symposium on Interactions of Soil Minerals with Organic Components and Microorganisms, International Congress of the Division 2.5 of the International Union of Soil Sciences (IUSS).; 2019

Forest soils play an important role as mercury pool (HgTRes) in its biogeochemical cycle within terrestrial ecosystems. Mercury accumulation occurs primarily in the uppermost soil layers (O and A horizons) which receive the input of atmospheric Hg through wet and dry deposition as well as litterfall. However, forest management could substantially modify soil ability to store Hg.This study assess the effect of elapsed time (1 5 and 50 years) since the management of Nothofagus pumilio forests from Tierra del Fuego (Argentina) in the accumulation of Hg in organic-C rich soil layers (O A). For each time period three representative lenga forest plots were selected in which three composite samples were taken from the 0-10cm soil layer. Soil samples from an unexploited forest plot (control) close to those managed were sampled similarly (three composite samples of the 0-10 cm layer). Thus total Hg (HgT) was determined using a DMA-80 analyzer in a total of 54 soil samples from 9 managed forests and 9 control plots. Average of HgT was 250 ng g-1(range 159-441 ng g-1) being significantly higher (p0.05) in the managed forests considering the time elapsed since exploitation but it is closely correlated to total organic C (r=0.680 p=0.000) and total N (r=0.719 p=0.000).Soil Hg pool (HgTRes) in the 0-10 cm layer was similar in plots managed 1 year ago and their controls (10.2 and 9.9 mg m-2 respectively) but it was somewhat higher than controls in the case of plots managed 5 years ago (9.8 and 9.0 mg m-2 respectively).The opposite occurs in the forests managed 50 years ago where HgTRes is lower in managed than in control forest plots (9.2 and 11.2 mg m-2 respectively). These results suggest that HgTRes in the studied soil layers does not depend too much of the recovery degree of the forest rather than soil organic matter dynamics.