From leaf to landscape: multi-scale measurements of solar-induced chlorophyll fluorescence in a tundra ecosystem

Rapid climate warming in the Arctic tundra has driven fast and diverse land surface change in recent decades, including shrub cover expansion, enhanced vegetation productivity, extended growing season, and permafrost thaw. The impact of these changes in the contemporary Arctic carbon balance is highly uncertain, and there is a growing body of evidence indicating a shift toward net source activity linked to increases in cold season labile carbon release in Arctic tundra. Ultimately, these changes are fueled by accelerating vegetation carbon uptake by gross primary production (GPP). Both the spatial and temporal variations of GPP are poorly captured and modeled, and the measurements of solar-induced chlorophyll fluorescence (SIF) may provide an additional constraint on GPP estimation in the Arctic Tundra. Here, we present an analysis of the multi-scale measurements of SIF at the leaf, canopy, to regional scales from 2017 to 2019. We show that leaf-level SIF tracks the diel pattern of net photosynthesis. Tower-based SIF observations agree well with satellite observations from TROPOMI in terms of both seasonal pattern and magnitude. Tower-based SIF measurements are also in good agreement with eddy covariance measurements at the tower. Finally, we used TROPOMI and the tower-based SIF-GPP relationship to estimate the landscape-level carbon uptake by the Arctic tundra ecosystems.