Since the 1970s, 35% of wetlands have been lost worldwide, causing major ecological impacts and reducing the ecosystem services they provide. Certain forest management practices, such as mechanical soil preparation in forest plantations, can potentially create habitats resembling wetlands. For example, mounding during plantation establishment creates water-filled depressions that share similarities with wetlands. However, the hydrological processes behind the formation of these depressions and their persistence in time remain poorly understood. The goal of this study was to characterize the hydroperiod of these depressions across plantations of various age, identify its drivers and compare their dynamics with those of wetlands in deciduous forests. In the summer of 2024, depressions in 18 plantations of hybrid poplar (Populus x canadensis) of various age (young = < 7 years, intermediate = 8 to 11 years, old = > 11 years) as well as wetlands in 6 deciduous forests were monitored. The hydroperiod was assessed through monthly visits during which the number of water-filled depressions was counted along transects of 100 m. Soil texture and compaction, LiDAR-derived microtopography, and vegetation density were analysed to determine the factors controlling the hydroperiod. Results show that depressions in young plantations have significantly longer hydroperiods than those in older plantations and than wetlands in deciduous forests, primarily due to differences in fine-scale topography. These findings improve our understanding of hydrological processes in plantations created with mounding-mechanical soil preparation and can help guide more sustainable management of forests and wetlands.