The carbon balance of a managed boreal landscape measured from a tall tower in northern Sweden.

• A managed boreal landscape in northern Sweden was a net sink for atmospheric CO 2. • A managed boreal landscape was a weaker CO 2 sink compared to a mature forest stand. • Earlier spring and sunnier autumn enhanced net CO 2 uptake in the boreal landscape. • Tall tower EC together with footprint model provide accurate landscape CO 2 estimates. Boreal forests exchange large amounts of carbon dioxide (CO 2) with the atmosphere. A managed boreal landscape usually comprises various potential CO 2 sinks and sources across forest stands of varying age classes, clear-cut areas, mires, and lakes. Due to this heterogeneity and complexity, large uncertainties exist regarding the net CO 2 balance at the landscape scale. In this study, we present the first estimate of the net CO 2 exchange over a managed boreal landscape (∼68 km2) in northern Sweden, based on tall tower eddy covariance measurements. Our results suggest that from March 1, 2016 to February 28, 2018, the heterogeneous landscape was a net CO 2 sink with a 2-year mean uptake of −87 ± 6 g C m−2 yr−1. Due to an earlier and warmer spring and sunnier autumn, the landscape was a stronger CO 2 sink during the first year (−122 ± 8 g C m−2) compared to the second year (−52 ± 9 g C m−2). Footprint analysis shows that 87% of the CO 2 flux measurements originated from forests, whereas mires, clear-cuts, lakes, and grassland contributed 11%, 1%, 0.7%, and 0.2%, respectively. Altogether, the CO 2 sink strength of the heterogeneous landscape was up to 38% lower compared to the sink strength of a mature stand surrounding the tower. Overall, this study suggests that the managed boreal landscape acted as a CO 2 sink and advocates tall tower eddy covariance measurements to improve regional carbon budget estimates. [ABSTRACT FROM AUTHOR]