Soil organic matter characteristics in surficial permafrost sediments on Herschel Island, Yukon Territory, Canada

• Main Authors: Baltruschat, Stefan, Fritz, Michael, Obu, Jaroslav, Lantuit, Hugues, Hinderer, Matthias
• Format: Conference Object
• Language: unknown
• Published: GFZ German Research Centre for Geosciences 2015
• Subjects: Arctic; Canada; Herschel Island; Yukon; Herschel; Ice; permafrost; Tundra
• Online Access: https://epic.awi.de/id/eprint/38826/; https://epic.awi.de/id/eprint/38826/1/book_of_abstracts_geoberlin_2015.pdf; http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:1314059/component/escidoc:1314718/Geoberlin_2015.pdf; https://hdl.handle.net/10013/epic.46093; https://hdl.handle.net/10013/epic.46093.d001

Recent mobilisation of soil organic matter (SOM) in permafrost of the northern high latitudes is thought to have a significant impact on the carbon balance in the atmosphere. However, the environmental processes which influence SOM accumulation and remobilisation still need to be investigated more accurately. This study investigates the quantity and quality of SOM on Herschel Island in the western Canadian Arctic in relation to various landscape characteristics. To reach this goal, soil moisture, total organic carbon (TOC) and total nitrogen (TN) contents, stable carbon isotopes (∂¹³C) and TOC/TN ratios (C/N) were determined on 128 samples from twelve sediment cores reaching up to 250 cm depth. Drilling locations were chosen based on morphology, vegetation and soil properties and supported by satellite imagery and air photos. Seasonal thaw depths (active layer depths) correlate with ground disturbance and vegetation cover and lie between 20 and 100 cm. Well-preserved SOM is accumulated in the active layer and subjacent ice-rich permafrost of wet polygonal tundra. Uplands, hummocky tussock tundra and alluvial fans cover more than 50 % of the island and show heterogeneous SOM storage characteristics with considerable TOC contents being limited to the active layer. Disturbed areas with slope gradients greater than 6° show strong SOM degradation with low TOC contents throughout the active layer and permafrost strata. Linear regression and principal component analysis (PCA) shows that a decreasing SOM content is driven by increasing ground disturbance and reduced vegetation cover. Improved drainage decreases the preservation of SOM in the active layer. Future deepening of the active layer because of increasing temperatures and ground disturbance will remobilise SOM stored in ice-rich permafrost. This might increase carbon dioxide and methane emissions from permafrost landscapes.