Abstract (from ScienceDirect): Climate change poses threats to forests, creating a need for adaptation to novel and changing conditions. This need has led to the creation of adaptation frameworks including the resistance, resilience, transition (RRT) framework, which proposes management strategies along a gradient of change and adaptation. Although management within this framework is grounded in theory and past management experience, little is known about how these approaches may influence regeneration, a critical phase in forest development. To address this gap, we examined five-year outcomes of treatments implemented using the RRT framework as part of the Adaptive Silviculture for Climate Change network in northern hardwood forests. The resistance approach employed traditional single-tree selection, resilience single-tree and group selection, and the transition variable density thinning and irregular shelterwood. All treatments reflected multi-aged regeneration methods with varying levels of canopy gap formation and retention with our study goal to determine how treatments influenced natural and planted regeneration composition, abundance, and functional identity, as well as projected compatibility with future climate conditions. We found that the seedling size class reflected recent adaptive silviculture treatments while sapling composition was associated with longer-term historic management in all treatments. Treatments shifted regeneration composition toward desired future conditions, with resistance resulting in a regeneration profile similar to the canopy, while transition regeneration composition diverged from the overstory with the highest proportion of shade-intolerant species. Resilience included regeneration conditions found in both resistance and transition offering the potential to absorb a broad range of climate change and disturbance impacts. Functional trait profiles of regeneration in each treatment showed slight differences, with assisted migration plantings in transition contributing to its divergence from the other treatments, highlighting the value of including planted species in adaptation treatments. As a whole, the adaptive treatments resulted in regeneration profiles that aligned well with objectives related to the RRT framework, although changes were small in some cases and it may require second, or even third, entries for stands to continue on adaptation-oriented trajectories.
