Mechanical fuel treatment effects on fuel loads and indices of crown fire potential in a south central New Mexico dry mixed conifer forest

The ability of mechanical fuel reduction treatments to mitigate severe fire behavior in dry mixed conifer forests is of interest to land managers as well as the public. We compared fuel loads and indices of crown fire potential to test treatment effectiveness following commercial and non-commercial treatments with differing slash prescriptions in mixed conifer stands at three sites on the Lincoln National Forest in south central New Mexico. Surface and canopy fuels were measured and used to develop custom fuel models in NEXUS 2.0 to estimate torching and crowning indices. Results indicated herbaceous fuel loads were unchanged compared to controls 2 years post-non-commercial and 1 year post-commercial harvest treatment. Sound 1000-h fuels were greater in the scatter and commercial treatments compared to control treatments. The commercial treatment resulted in stand structure closer to historical conditions. Canopy base height increased in all treatments except in stands previously treated 20–30 years ago. Commercial harvest was the only treatment to reduce canopy bulk density and the potential for active crown fire, with the exception of one pile treatment. Non-commercial pile treatments increased the TI. However, due to the danger of crown fire initiation from adjacent stands, further overstory removal is needed in non-commercial treatments to lower crowning potential. Prescribed fire may be used to increase treatment effectiveness in all overstory removal treatments by decreasing surface fuels.