Recovery after fire
Context:Landscape and local factors govern tree regeneration across heterogeneous post-fire forest environments. But their relative influence is unclear—limiting the degree that managers can consider landscape context when delegating resources to help stand-replacing patches restock successfully.
Objectives: We investigated how landscape and local factors shape tree regeneration across heterogeneous post-fire forest environments. Our research questions were: What is the relative influence of landscape and local factors on tree species presence (RQ1) and stocking density (RQ2) at stand-replacing patches? Do thresholds occur when landscape factors are influential (RQ3)?
Methods: We sampled landscape and local variables at 71 plots near Jackson, Wyoming, United States. We used Random Forests to investigate how local and landscape variables affect post-fire tree recovery. Relative influence was determined using mean decrease in accuracy. Partial dependence plots were used to visualize whether thresholds occurred for variables with mean decrease in accuracy > 15%.
Results: Landscape factors like seed source area were associated with subalpine fir presence and stocking density. But different thresholds occurred. Specifically, subalpine fir presence required 10% seed source area, while stocking density required 40%. Northeast aspects surrounded by > 10% seed source area were most likely to support subalpine fir presence. Conversely, local factors like soil nutrients were associated with lodgepole pine presence, highlighting effects of different regeneration strategies.
Conclusions: Landscape factors bolster spatial resilience and help stand-replacing patches restock naturally. But landscape factors do not support tree regeneration equally across heterogeneous post-fire forest environments. Consequently, considering stand-replacing patches in their landscape context will be critical for future spatial action planning.