Silvicultural intensification increases forest floor disturbance and surface disturbance diversity in boreal and temperate forests

Forest floor disturbance influences seedbed availability, microsite diversity, and early regeneration dynamics, yet the effects of increasing silvicultural intensity on forest floor structure remain poorly quantified across operational forest management systems. Using the long-term NEBIE (Natural disturbance and Extensive, Basic, Intensive, and Elite silvicultural intensities) experimental network across six boreal and northern temperate forest sites in Ontario, Canada, we evaluated how increasing silvicultural intensity affects forest floor disturbance, cover type composition, and cover type diversity. Treatments ranged from unharvested natural forest to harvesting followed by combinations of mechanical site preparation, planting, vegetation control, and intensive tending. Forest floor cover was quantified using line-intercept sampling along 449 transects (∼45 km). Disturbance increased significantly along the silvicultural intensification gradient, rising from an average of 11% in Natural stands to 45% in Elite treatments. Mechanical site preparation methods, including drag scarification, disc trenching, and bulldozing/blading, produced the greatest increases in berm formation, mineral soil exposure, and overall disturbance, whereas chemical vegetation management caused comparatively little direct physical alteration of the forest floor. Forest floor cover type diversity increased significantly with disturbance and was strongly related to the proportion of disturbed forest floor. Multivariate analyses revealed significant compositional differences among silvicultural intensity classes, with mechanically prepared sites characterized by greater proportions of exposed mineral soil and reduced coverage of disturbed forest floor. Forest floor composition was also influenced by climate, fire regime, vegetation management, and stand composition. Contrary to expectations that intensification homogenizes forest conditions, silvicultural intensification increased short-term forest floor heterogeneity, particularly where mechanical site preparation was applied. Our results demonstrate that operational practices, particularly mechanical site preparation, are more important determinants of forest floor disturbance than silvicultural intensity class alone. Because forest floor structure influences regeneration, biodiversity, and ecosystem resilience, these findings highlight the importance of considering both management practices and environmental context when designing silvicultural systems that balance productivity and ecological function.