Greater Increase in Surface Albedo Following Clear-Cutting Than Wildfire in Pine Dominated Northern Swedish Boreal Forests

There is a public debate on how boreal forests can deliver climate change mitigation benefits. While most debates regarding Fennoscandian forests have centered on the contrasting effects of actively managed and old-growth unmanaged forests on carbon uptake and storage, the impact of surface albedo has often been overlooked. According to the new EU forest strategy for 2030, with aim of improving quantity and quality of forests by promoting primary old-growth forests and avoiding clear-cutting, among others, we examined how albedo across a wide age range of boreal Pinus-dominated forests develops over time after wildfire (defined as unmanaged) and clear-cutting (defined as managed). We find that albedo decreases over time after disturbance, but mainly in managed forests. Annual mean albedo in young (<30 years) managed forests (0.36 +/- 0.04) is markedly larger than in young unmanaged forests (0.18 +/- 0.04). This difference is particularly prominent during winter, when snow-covered ground is present. The mean albedo over the entire unmanaged forest-age gradient (0.17 +/- 0.05) is significantly lower (p < 0.05) than that of the managed forest-age gradient (0.23 +/- 0.10). Considering the typically higher frequency of clear-cuts compared to wildfires in Fennoscandian forests, these albedo differences would be even larger over long time scales. Our findings reveal the importance of considering the climatic cooling potential of albedo when making decisions on how to optimize future forest management in northern boreal forests to mitigate climate change.