Controls of albedo in two common plantation systems in southern Quebec, Canada: effects of development stage, tree species, fertilization, and seasonality

Forestry practices such as forest conservation, improved management, and afforestation offer important pathways for climate change mitigation through carbon sequestration. However, forests also influence the surface energy balance via changes in albedo, which can offset or enhance climate benefits depending on stand characteristics. Despite its importance, empirical data on albedo dynamics in plantation systems remain limited. This study evaluated surface albedo in hybrid poplar and white spruce plantations of varying ages and fertilization treatments in southern Quebec using drone-mounted pyranometers. Measurements were conducted during the growing season and under leaf-off and snow-covered conditions to capture structural and seasonal variability. Albedo remained below 0.3 during the growing season and was primarily controlled by stand development, with higher values in younger plantations and lower, more stable values in mature plantations. Species effects emerged with canopy closure, as hybrid poplar exhibited higher albedo than white spruce at intermediate to late stages. Fertilization had no consistent effect and was mainly associated with early stages of plantation development. Leaf senescence did not lead to systematic increases in albedo, whereas snow cover substantially increased surface reflectance. These results highlight the central role of canopy structure and surface conditions in controlling albedo dynamics in plantation systems. Higher albedo in young plantations and under snow-covered conditions may contribute to radiative cooling, particularly in short-rotation systems such as hybrid poplar.