Monitoring of CO2 fluxes on Svalbard: land use alters the gas exchange in the arctic tundra

The article summarized the results of long-term observations (2014–2018) of soil emissions and net CO2 fluxes (2017–2018) in natural and anthropogenically modified (AI) ecosystems of Arctic tundra on the territory of the archipelago of Svalbard (Barentsburg, 78°04′N, 14°13′E). Anthropogenic controls associated with local land use, during the period of their active impact may redouble the emissions of carbon dioxide from soil (0.111 ± 0.021 > 0.064 ± 0.011 gС m–2h–1). During the same period, the net C-balance at the sites with active land use is estimated as a source to the atmosphere. Self-recovering after human influence plots (II) demonstrate intermediate values of soil emissions of СО2 between unaffected tundra (I) and plots with active land use (III). With that they demonstrate the greatest net C-sink within the observed range of Photosynthetically Active Radiation as compared to (I) and (III). At the height of the vegetation period unaffected tundra ecosystems demonstrate a neutral net C-balance. The greatest contribution to soil emissions variance make spatial controls (they explain 56–66% of variance), whereas temporal factors are responsible for 3.8–5.5% only. Amongst spatial controls, the thickness of organogenic layer makes the greatest contribution. Inter-annual fluctuations of key factors, among which the most important are the soil moisture and temperature of the upper soil layer, both affect AI and natural ecosystems hence the spatial differences between them remain constant from year to year. According to preliminary estimates, unlike the carbon dioxide, the contribution of methane and nitrous oxide net fluxes in local ecosystems is insignificant and does not depend on human land use.