Disturbance history and canopy structure drive growing season albedo dynamics in boreal forests

Surface albedo plays a key role in forest–climate interactions by controlling the amount of solar radiation reflected back to the atmosphere. However, the effects of forest management practices, including total and partial disturbances, on these processes remain poorly understood, despite their importance for climate change mitigationThis study analyses how forest characteristics and disturbances influence the spatial and temporal dynamics of albedo during the growing season, through their effect on forest structure and cover. It also aims to highlight the importance of accounting for the influence of forest-related variables when predicting surface albedo. To achieve this objective, the apparent surface albedo was estimated over a 400 km2 humid boreal forest in eastern Canada using 22 snow-free Landsat 8 images from 2015 to 2021. Validation against observations from two flux towers yielded satisfactory results, with root mean square errors (RMSE) (0.013 ± 0.003 and 0.017 ± 0.004), and low biases (0.002 ± 0.005 and 0.004 ± 0.005) where the uncertainties correspond to 95% confidence intervals estimated by bootstrap resampling. Albedo estimates were then integrated into a random forest regression model along with predictors derived from Airborne Laser Scanning (ALS) and ecoforestry maps, including canopy metrics, forest disturbances, vegetation type and topographic derivatives. The model showed strong performance, with Kling-Gupta efficiencies (KGE) ranging from 0.85 (±0.0015) to 0.95 (±0.0006), RMSE from 0.005 to 0.013 (±0.00015) and mean absolute errors (MAE) ranging from 0.003 to 0.008 (±0.0001), demonstrating its robustness throughout the growing season. The average height of forest cover and the number of years since disturbances occurred were identified as key factors influencing albedo, demonstrating the importance of considering canopy structure and forest disturbance history when predicting surface albedo. This study underscores the critical importance of incorporating surface albedo considerations into forest management strategies aimed at optimizing climate regulation.