Impacts of Thermo-erosion on Organic Matter Stocks - Analysis of Total Organic Carbon and Total Nitrogen Distribution in three Thermo-erosional Valleys in the Lena River Delta

• Main Author: Kuhl, Nadja
• Format: Thesis
• Language: unknown
• Published: 2018
• Subjects: Arctic; Climate change; lena river; permafrost
• Online Access: https://epic.awi.de/id/eprint/49112/; https://epic.awi.de/id/eprint/49112/1/Kuhl_2018_MA.pdf; https://hdl.handle.net/10013/epic.8af1c579-239b-4c9a-92b7-230319d5d5ae; https://hdl.handle.net/

The ongoing climate change has a huge impact on the Arctic, including its underlaying permafrost soils. Due to increased warming the permafrost thaws and gets degraded, for example by thermo-erosional processes. As a result, the biogeochemical cycling increases because of the redistribution of organic carbon (OC) and nitrogen. This study examines the spatial distribution of OC and its availability within three thermo-erosional valleys in the Yedoma-underlain Lena River Delta that were formed by thermo-erosional processes. Therefore, permafrost soil samples were investigated on their total organic carbon (TOC) content, total nitrogen (TN) content and soil organic carbon (SOC) storage as well as the total organic carbon to total nitrogen (C/N) ratio. The resulting datasets were divided into different categories (transects, geomorphological unit and depth) and tested on their statistical difference to estimate the impact of thermo-erosional processes on the spatial distribution of the investigated geochemical parameters. The mean SOC storages of the three thermo-erosional valleys for 0-100 cm ranged between 19.7 ± 13.9 kg ∙ m-2 and 27.0 ± 15.3 kg ∙ m-2, the average TN content between 0.3 ± 0.1 wt% and 0.4 ± 0.2 wt%. The average C/N-ratio was ranging between 15.3 ± 3.4 and 17.2 ± 2.6. All parameters showed great differences in spatial distribution within the valleys. In most cases, the highest values of the parameters occurred in areas of the valleys with lower erosion rates (in the upstream transect and on the upland), whereas the lowest values were found in areas of higher erosion rates (in the midstream and downstream transect and on the slopes). This variability within the valleys was traced back to the geomorphology and thermo-erosional processes. The results of this study showed that those thermo-erosional processes have an impact on the SOC storage within thermo-erosional valleys as well as on the degradation and availability of this stored OC.