Chlorophyll fluorescence–based assessment of carbon sink–source shifts in Arctic tundra during the growing season

The Arctic is warming approximately four times faster than the global average, driving rapid transformations across Arctic and Boreal ecosystems. Among these, modifications in vegetation structure, shrubbification, and changes in photosynthetic activity are particularly relevant, as vegetation strongly influences ecosystem–atmosphere carbon exchange. A warmer and increasingly CO₂-rich environment has stimulated photosynthetic activity and widespread greening; however, the persistence of these responses under continued climate warming remains uncertain.

In the ArcticSIF project, we investigate how tundra vegetation landscapes have evolved over the past two decades by examining multiple datasets of solar-induced chlorophyll fluorescence (SIF), gross primary productivity (GPP), ecosystem respiration (ER), and net CO₂ ecosystem exchange (NEE). Assessing the dynamics of these complementary records with meteorological datasets, we evaluate how carbon uptake and emission have shifted across different Arctic tundra regions during the growing season and to what extent SIF records support such an observation.

Our results show that in the circumpolar region, tundra landscapes exhibit a higher sensitivity to variations in air temperature compared to boreal ecosystems, with pronounced NEE shifts in graminoid and prostrate-shrub tundra environments modulated by growing season length. This study contributes to determining the speed at which some Arctic tundra ecosystems may shift from carbon sinks to carbon sources during the growing season in the context of Arctic warming and its influence on high-latitude carbon dynamics.