Above Ground biomass stocks, pool ages and fluxes in the largest arctic delta, the Lena Delta in Siberia

• Main Authors: Heim, Birgit, Shevtsova, Iuliia, Buchwal, Agata, Rachlewicz, Grzegorz, Lisovski, Simeon, Runge, Alexandra, Fuchs, Matthias, Grosse, Guido, Kruse, Stefan, Herzschuh, Ulrike, Bartsch, Annett
• Format: Conference Object
• Language: unknown
• Published: American Geophysical Union 2021
• Subjects: Arctic; Laptev Sea; laptev; lena delta; Subarctic; Tundra; Yakutia; Siberia
• Online Access: https://epic.awi.de/id/eprint/55336/; https://hdl.handle.net/10013/epic.a5194378-5385-472a-938e-f2ece3393d7e

Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments. We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10 °C July isotherm at 72° Northern Latitude in the Laptev Sea region. During the LENA2018 expedition, we set up plots for plant projective cover and Above Ground Biomass (AGB) and sampled shrubs for shrub-ring analyses. AGB is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. AGB data and shrub age data clearly show a separation between i) low disturbance landscape types with dominant AGB moss contribution, but always low vascular plant AGB (<0.5 kg m-2) characterised by old shrubs of several decades of stand age versus ii) a much higher vascular plant AGB contribution (> 0.5 kg m-2) with only young shrubs in high disturbance regimes. The low disturbance regimes are represented on the Holocene and Pleistocene delta terraces in form of azonal polygonal tundra complexes and softly dissected valleys with zonal tussock tundra. In contrast, the high disturbance regimes are sites of thermo-erosion such as along thermo-erosional valleys and on floodplains. We upscaled AGB and above ground carbon pool ages using a Sentinel-2 satellite acquisition from early August 2018. We classified via classification training using Elementary Sampling Units that are the 30 m x 30 m vegetation field plots. We then used the land cover classes and grouped them according to their settings either in high disturbance or low disturbance regimes with each associated AGB value ranges and shrub age regimes. We also evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under https://doi.org/10.1594/PANGAEA.897916 and https://doi.org/10.1594/PANGAEA.897045. ESA GlobPermafrost land cover and vegetation height remote sensing products and our Sentinel-2 derived AGB product for the central Lena Delta shows realistic spatial patterns of landcover classes and biomass distribution at landscape level. However, in all products, the high biomass patches of high shrubs in the tundra landscape could not spatially be resolved as they are confined to patchy and linear distribution, not representing large enough areas suitable for upscaling. We found that high disturbance regimes with linked high and rapid AGB fluxes are distributed mainly on the floodplains and as patches along thermoerosioal features, e.g. valleys. Whereas the low disturbance landscapes on Yedoma upland tundra and Holocene terraces occur with larger area coverage representing decades slower and in magnitude smaller AGB fluxes.