Stand spatial structure outcomes of forest adaptation treatments in northern hardwood forests in North America

Spatial arrangement of trees is determined by a complex suite of factors, including disturbance history, competition, and resource availability. These spatial patterns drive adaptive capacity by influencing arrangement of growing space, neighborhood competitive relationships, and disturbance response, with irregular patterns supporting higher adaptive capacity. While spatial structure in relation to disturbance and climate change resilience has been studied in dry conifer forests and old-growth temperate forests, it has never been explored in the context of climate adaptive management in mesic, second-growth forests. To address this gap, we analyzed tree spatial patterns in second-growth northern hardwood forests under four different climate adaptation management approaches: no action; resistance or resilience to impacts of climate change; and transition to future-adapted forest types. We used spatial point statistics approaches to describe how patterns differed among the four treatments. We found that the treatments focused on future adaptation led to patterns with variable tree spacing and clumping, while those focused on perpetuating current conditions resulted in less pattern variation. This indicates that adaptation strategies that include uneven-aged regeneration methods that restore and maintain tree spatial patterns historically generated by gap dynamics can be successful in altering resource availability patterns and adaptation space in forest stands.