ALBERT

Description: Permafrost soils contain a large quantity of soil organic carbon (SOC) potentially available for decomposition, and its permanence depends on the net ecosystem carbon balance (NECB), including both vertical and lateral fluxes. In most polygonal tundra landscapes, the CO2 flux is known to be a sink on the annual scale, but less is known about the role of lateral carbon flows. To fill this gap, we present and contextualize lateral export rates from a polygonal tundra site in northern Siberia, Russia. Furthermore, we present the vertical carbon (C) fluxes of CO2 and CH4 from this study site. Thus, we derive the NECB in one growing season. The results show cumulative lateral DIC and DOC fluxes of 0.25 – 0.28 and 0.05 – 0.06 g C m-2, respectively, during the observation period (8 June – 8 September). The vertical fluxes of CO2 and CH4 accumulate to -19.0 ± 1.2 and 1.1 ± 0.02 g C m-2, respectively. The lateral carbon export thus represents 1.6 – 1.8% of the net ecosystem exchange (NEE). However, the relationship between lateral and vertical fluxes changed over the observation period. At the beginning of the growing season (early June), the lateral carbon flux outpaces the vertical CO2 flux, causing the polygonal tundra landscape to be a carbon source at this time of the year. With ongoing growing season, the vertical CO2 flux dominates the NECB. We conclude that lateral carbon fluxes can have a considerable influence on the NECB on short time scales (days), especially during the early growing season. However, their impact decreases on seasonal time scales. Therefore, the vertical carbon flux can be seen as a good approximation for the NECB of this study site on the time scale of months.