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Description

Canopy gaps, openings created by tree mortality, are fundamental drivers of forest regeneration, structural diversity, and long-term resilience. Despite their ecological importance, landscape-scale characterizations of gap dynamics over decadal timescales remain limited, particularly in temperate mixedwood forests. This study used three airborne laser scanning datasets acquired in 2012, 2018, and 2022 to map and quantify canopy gap dynamics across the 10,000-hectare Petawawa Research Forest in Ontario, Canada. A fixed 3-metre height threshold was applied to normalized 1-metre canopy height models to delineate gaps, filtered to 5–20,000 m² and classified into four dynamics categories - formation, expansion, persistence, and closure - across three intervals. Gap counts declined from 139,488 in 2012 to 121,986 in 2022, while total gap area increased from 604 to 652 hectares, reflecting a shift toward fewer but larger openings. Although small gaps (5–50 m²) numerically dominated across all years, large gaps (>200 m²) accounted for over 56% of total gap area, highlighting the disproportionate structural influence of infrequent large openings. Over the full decade, formation and closure were nearly equal at 396.1 and 409.2 hectares respectively, indicating dynamic equilibrium consistent with mature mixedwood systems dominated by fine-scale disturbance. Gap-size distributions followed a power-law scaling relationship across all years, with lambda values near 2.0, consistent with a disturbance regime driven predominantly by individual-tree mortality. These findings provide a decade-long baseline of canopy gap dynamics at PRF and demonstrate that repeat airborne laser scanning surveys can reliably detect fine-scale structural change at landscape scale, supporting long-term forest monitoring and resilience assessment.