Abstract

PIAZZA, M. Victoria; KITZBERGER, Thomas  and  CHANETON, Enrique J. Volcanic ash deposition modulates leaf-litter decomposition in Nothofagus dombeyi forests of NW Patagonia. Ecol. austral [online]. 2018, vol.28, n.1, pp.28-39. ISSN 1667-782X.

Disturbances produced by volcanic eruptions are part of natural ecosystem dynamics. Soil formation and nutrient cycling depend on the decomposition both of organic matter buried under the ashes and on the litter produced after the disturbance. Here we evaluated leaf litter decomposition in Nothofagus dombeyi (coihue) forests affected by massive ash deposition from the 2011 eruption of the Volcán Puyehue-Cordón Caulle complex in NW Patagonia, Argentina. The study comprised two sites at different distances from the volcano, with different amounts of ash and annual precipitation (1600-1900 mm/year). In each site, two plots were delimited, with and without long-term livestock grazing (>50 years). N. dombeyi litter mass loss after one year was estimated in three positions (n=8 blocks/plot): on organic soil and under the ash layer, on organic soil after removal of ashes, and on top of the ash layer. Leaf litter beneath the ash layer was decomposed 74% faster in the wetter site than in the drier site. Decomposition was generally slower onto the ash layer surface than on the organic soil, and this effect was stronger in the wetter site near the volcano than in the driest and farthest site (19% vs. 9%). Litter decomposition on the soil layer was equivalent to treatments with or without the ash surface. Decomposition was slower in livestock-occupied plots than in livestock-free plots, but livestock history did not affect litter decomposition of ash topped soil vs. lower soil organic layers. Our results show that decomposer communities remain active in forest soils under ash-fall layers, thus maintaining nutrient supply to vegetation after volcanic eruptions.

Keywords : Natural disturbances; Volcanic eruptions; Ecosystem functioning; Environmental gradient; Historical grazing.

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