The long-term sustainability of the Northern Forest depends on successful tree regeneration, yet increasing evidence suggests that overstory and understory species compositions are becoming decoupled due to climate change, land-use history, invasive species, and anthropogenic disturbances. This project will assess patterns of overstory-understory dissimilarity and identify key environmental and human-driven factors influencing regeneration dynamics. Leveraging landscape-scale Forest Inventory and Analysis (FIA) data, this study will: (1) analyze patterns of similarity of overstory-understory vegetation across the Northern Forest; (2) identify landscape and climatic drivers influencing spatial patterns of decoupling; and (3) explore how different environmental and anthropogenic factors impact forest regeneration dynamics. Overstoryunderstory similarity will be quantified using ecological indices (Jaccard, Sørensen-Dice, Bray- Curtis, Morisita-Horn) and integrated with landscape and climate data through geospatial and statistical modeling to detect regeneration hotspots, calculate inferences, and forecast future forest composition. This research supports NSRC’s “Forest Health and Resilience” and “Decision Support and Management Tools” priorities by delivering actionable insights on climate change impacts for sustainable forest management. Expected outcomes include (1) spatial maps of regeneration patterns, (2) predictive models for strategic reforestation, and (3) targeted outreach to land managers and policymakers. By improving understanding of forest regeneration dynamics, this project will enhance the ability of forest managers and conservationists to maintain biodiversity, promote climate resilience, and develop adaptive management strategies. Additionally, this study will inform overstory-understory biomass dynamics, critical for carbon sequestration modeling. Deliverables include peer-reviewed publications, interactive geospatial datasets, and conference presentations to ensure broad knowledge transfer across the Northern Forest region.