Arctic tundra active-layer soils are at risk of soil organic carbon (SOC) depletion and degradation upon global climate warming because they are in a stage of relatively early decomposition. Non-growing season (NGS) warming is particularly pronounced, and observed increases of CO2 emissions during experimentally warmed NGSs give concern for great SOC losses to the atmosphere. Here, we used snow fences in Arctic Spitsbergen dwarf shrub tundra to simulate 1.86 degrees C NGS warming for 9 consecutive years, while growing season temperatures remained unchanged. In the snow fence treatment, the 4-11 cm thick A-horizon had a 2% lower SOC concentration and a 0.48 kg Cm-2 smaller pool size than the controls, indicating SOC pool depletion. The snow fence treatment's A-horizon's alkyl/O-alkyl ratio was also significantly increased, indicating an advance of SOC degradation. The underlying 5 cm of B/C-horizon did not show these effects. Our results support the hypothesis that SOC depletion and degradation are connected to the long-term transience of observed ecosystem respiration (ER) increases upon soil warming. We suggest that the bulk of warming induced ER increases may originate from surface and not deep active layer or permafrost horizons. The observed losses of SOC might be significant for the ecosystem in question, but are in magnitude comparatively small relative to anthropogenic greenhouse gas enrichment of the atmosphere. We conclude that a positive feedback of carbon losses from surface soils of Arctic dwarf shrub tundra to anthropogenic forcing will be minor, but not negligible. (C) 2018 Elsevier B.V. All rights reserved.
1.UiT Arctic Univ Norway, Fac Biosci Fisheries & Econ, Dept Arctic & Marine Biol, N-9037 Tromso, Norway 2.Umea Univ, Dept Ecol & Environm Sci, Climate Impacts Res Ctr, SE-98107 Abisko, Sweden 3.Univ Vienna, Div Conservat Biol Vegetat Ecol & Landscape Ecol, Dept Bot & Biodivers Res, Rennweg 14, A-1030 Vienna, Austria 4.Swedish Univ Agr Sci, Dept Soil & Environm, SE-75007 Uppsala, Sweden 5.Umea Univ, Dept Chem, SE-90187 Umea, Sweden 6.Univ Georgia, Odum Sch Ecol, Athens, GA 30606 USA
Recommended Citation:
Semenchuk, Philipp R.,Krab, Eveline J.,Hedenstrom, Mattias,et al. Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard[J]. SCIENCE OF THE TOTAL ENVIRONMENT,2019-01-01,646:158-167