Methods and implications of canopy base height characterization for modeling crown fire potential

Canopy base height (CaBH; distinct from tree-level crown base height, CrBH) represents the lowest height at which canopy fuel, aggregated across multiple tree crowns, can propagate fire vertically and serves as an essential variable for modeling crown fire transition and hazard to inform fuel reduction treatment planning. However, as fire models have been applied to increasingly diverse forest structures and remote sensing technologies have advanced, a variety of methods for characterizing CaBH have emerged. Here, we review the primary approaches for CaBH characterization using field observation, airborne Lidar, and satellite-based mapping. We then apply these methods across four conifer forest types in northern New Mexico (USA) to evaluate how method choice and forest structure influence CaBH characterization and predicted fire behavior using a Rothermel-Van Wagner crown fire modeling framework. Our results show that CaBH characterizations vary widely among measurement methods (mean within-plot range = 6 m), and that these differences lead to substantial variation in predicted torching index (mean within-plot range = 14 km h −1 ), demonstrating that method choice strongly shapes modeled crown fire hazard. Further, we found that divergence among methods increases with tree height variability. These results highlight the need for forest managers and fire behavior modelers to be deliberate in selecting and justifying their choice of CaBH characterization, particularly in structurally complex forests.