Seed source pattern and terrain have scale-dependent effects on post-fire tree recovery

Context: Distance to seed source is often used to estimate seed dispersal—a process needed for post-fire tree recovery. However, distance, especially in mountainous terrain, does not capture pattern or scale-dependent effects controlling seed supply and delivery. Measuring seed source pattern (area and arrangement) could provide insights on how these spatial dynamics shape recovery. Objectives: We tested metrics and investigated how seed source pattern, tree regeneration traits, scale, and terrain interact to shape post-fire tree recovery. Our research questions were: Does seed source pattern outperform distance when modeling tree species presence and regeneration density? If yes, does seed source pattern have scale-dependent or terrain-dependent effects on regeneration density? Methods: We measured seed source pattern at nested spatial extents around 71 plots and related measurements to local post-fire tree recovery. We used generalized linear models to test metrics and visualize scale-dependent and terrain-dependent effects on regeneration density. Results: Distance sufficiently modeled presence, but seed source pattern outperformed distance when modeling regeneration density. Relevant spatial extents and relationships were species-dependent. For wind-dispersed species, regeneration was associated with more seed source area and more complex arrangements, but terrain mediated these relationships. For serotinous and resprouting species, regeneration was associated with less seed source area and less complex arrangements, which are consistent with high-severity burn sites that promote recovery. Conclusions: Seed source pattern supports spatial resilience and interacts with scale and terrain to shape regeneration density. Accounting for these spatial dynamics could help steward forests facing changing fire regimes.