Abstract
High-Arctic ecosystems are strongly affected by climate change, and it is still unclear whether they will become a carbon source or sink in the next few decades. In turn, such knowledge gaps on the drivers and the processes controlling CO2 fluxes and storage make future projections of the Arctic carbon budget a challenging goal. During summer 2019, we extensively measured CO2 fluxes at the soil–vegetation–atmosphere interface, together with basic meteoclimatic variables and ecological characteristics in the Bayelva river basin near Ny Ålesund, Spitzbergen, Svalbard (NO). By means of multi-regression models, we identified the main small-scale drivers of CO2 emission (Ecosystem Respiration, ER), and uptake (Gross Primary Production, GPP) in this tundra biome, showing that (i) at point scale, the temporal variability of fluxes is controlled by the classical drivers, i.e. air temperature and solar irradiance respectively for ER and GPP, (ii) at site scale, the heterogeneity of fractional vegetation cover, soil moisture and vegetation type acted as additional source of variability for both CO2 emissions and uptake. The assessment of the relative importance of such drivers in the multi-regression model contributes to a better understanding of the terrestrial carbon dioxide exchanges and of Critical Zone processes in the Arctic tundra.
Highlights
High-Arctic ecosystems are strongly affected by climate change, and it is still unclear whether they will become a carbon source or sink in the few decades
Point-scale samplings were performed for 24 h across 2 days of clear sky and stable meteorological conditions at a fixed point, mostly covered with Carex spp
Given the relevant role played by vascular vegetation in the carbon flux budget, we explored whether different vascular species were associated with a different behavior of the carbon fluxes through species-specific samplings focused on the local vascular species pool: Carex spp. (CX), Dryas octopetala (DR), Salix polaris (SL), Saxifraga oppositifolia (SX) and Silene acaulis (SI)
Summary
High-Arctic ecosystems are strongly affected by climate change, and it is still unclear whether they will become a carbon source or sink in the few decades. Current field data do not solve the issue: annual measurements around the Arctic suggest that the tundra behaves either as a weak carbon s ink[21,22], as a s ource[23], that the annual balance is close to z ero[24], or that high interannual variability masks the true long-term behavior[25] Such large uncertainties on the estimate of carbon fluxes hamper a reliable prediction of the expected effects of climate change[26], and a better understanding of the Arctic carbon drivers is urgently needed. In such a patchy ecosystem, landscape-scale (or finer-scale) studies allow to identify the relevant carbon flux drivers, isolating individual ecosystem components and assessing their interactions
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