Permafrost Thawing and Vegetation Change Effects on Cryoturbation Rates and C and CH4 Dynamics. Final Report

• Main Authors: Gonzalez-Meler, Miquel A., Welker, Jeffrey M., Sturchio, Neil C.
• Language: unknown
• Published: 2018
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic; permafrost; Tundra
• Online Access: http://www.osti.gov/servlets/purl/1374443; https://www.osti.gov/biblio/1374443; https://doi.org/10.2172/1374443

Permafrost Thawing and Vegetation Change Effects on Cryoturbation Rates and C and CH4 Dynamics Permafrost soils cover 8.6% of the Earth land area but contain 50% of the global soil organic carbon (SOC) pool, 20-25% of which may be stored in the upper 30 cm, making it highly vulnerable to changes in climate. Predicted warming in northern latitudes may lead to strong forcing feedbacks on the climate system. It has been shown that the C content in the active layer of cryoturbated soils can be roughly 60% higher than in non-cryoturbated ones. However other cryogenic processes can affect the Arctic soil C pool at shorter time scales. For instance, warming may lead to increases winter precipitation resulting in a deeper snow cover with consequent thermal insulation of Arctic soils. Warmer soils may elicit summer and winter decomposition rates decreasing the SOC pool. We developed multi isotope methods to measure the soil carbon effects of snow pack accumulation on Arctic SOC dynamics in a moist acidic tundra by exposing soils to experimental accumulated snow pack (using fence experiments, Toolik Lake) in order to increase soil thermal insulation. We found that carbon dynamics were not linear and transient. At the beginning of the experiment C was lost in great quantities but they were partly recovered after about two decades. Snow cover also slows the C lost from permafrost thaw but increases CH4 emissions and heterotrophic respiration. Carbon was redistributed along the soil profile and moisture rather than temperature appeared to be the factor controlling decomposability.