Can beavers canopy alterations affect managed forests more than natural forests?

Beavers, as ecosystem engineers, significantly affect riparian ecosystems, mostly through foraging and dams construction. This study examines how beaver-related tree cutting altered canopy openness and affected microhabitats and forest floor vegetation in the Northern Poland’s Tuchola Forest. Woody plant characteristics, forest floor vegetation abundance, and canopy openness were assessed at three sites varying in forest naturalness, with canopy openness being measured using hemispherical photography. Results show that selective tree removal by beavers from all diameter classes significantly increased canopy openness. This alteration leads to transformative changes in forest habitat properties, notably increasing light availability, and to nutrient status changes as evidenced by shifts in Ellenberg indicator values. Consequently, these changes result in increased forest floor total vegetation cover, diversity and composition. The cascading effects of beaver tree-cutting on canopy alterations have been comprehensively modelled using structural equation models. The study also reveals distinct spatial patterns in canopy alterations, with the most pronounced effects near riverbanks. The intensified impact of beaver activities, could be linked to the naturalness of the forest, and might be especially pronounced in more altered environments, particularly where pioneer aspen trees dominate the tree stand composition. These findings underscore the role of beavers in shaping forest dynamics, particularly in managed or disturbed forests. By creating canopy gaps, beavers initiate processes that enhance habitat heterogeneity and biodiversity, suggesting that their presence may be crucial for the restoration of natural processes in disturbed ecosystems.