Linking Structural Forest Heterogeneity and Ecological Processes Using Sentinel-2 and FAD-Based Zoning

Structural heterogeneity within forests strongly influences ecological function, yet zone-specific diagnostics remain limited. This study presents a reproducible, zone-aware framework that links forest configuration to ecological processes using open remote-sensing and inventory data. In the Tuchola Forest Biosphere Reserve (Poland), we assessed degradation, moisture stress, habitat quality, and structural maturity across Foreground Area Density (FAD)–based zones—Core (≥ 90%), Transitional (40–60%), and Rare (≤ 10%)—by integrating multi-temporal Sentinel-2 imagery (2016, 2020, 2024) with field-observed ecological attributes. Interpretable ensemble models (Extra Trees, LightGBM) and partial-dependence analyses revealed consistent contrasts: Rare zones exhibited early-stage canopy stress linked to structural openness and edge exposure, while Core interiors maintained stable moisture regimes and mature canopy structure. Site-type and stand-age patterns showed that spectral similarity at open edges can mimic maturity, underscoring the importance of combining spectral and structural information in future monitoring. Validated against field observations, the workflow offers a spatially explicit, transferable benchmark for diagnosing ecological variability from open data. The results support zone-specific management strategies—preserving Core interiors, stabilizing Transitional areas through adaptive corridors, and restoring connectivity in Rare zones.