Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada

Abstract

Fire suppression and past selective logging of large trees have fundamentally changed frequent‐fire adapted forests in California. The culmination of these changes produced forests that are vulnerable to catastrophic change by wildfire, drought, and bark beetles, with climate change exacerbating this vulnerability. Management options available to address this problem include mechanical treatments (Mech), prescribed fire (Fire), or combinations of these treatments (Mech + Fire). We quantify changes in forest structure and composition, fuel accumulation, modeled fire behavior, inter‐tree competition, and economics from a 20‐year forest restoration study in the northern Sierra Nevada. All three active treatments (Fire, Mech, Mech + Fire) produced forest conditions that were much more resistant to wildfire than the untreated control. The treatments that included prescribed fire (Fire, Mech + Fire) produced the lowest surface and duff fuel loads and the lowest modeled wildfire hazards. Mech produced low fire hazards beginning 7‐years after the initial treatment and Mech + Fire had lower tree growth than controls. The only treatment that produced inter‐tree competition somewhat similar to historical California mixed‐conifer forests was Mech + Fire, indicating that stands under this treatment would likely be more resilient to enhanced forest stressors. While Fire reduced modeled wildfire hazard and reintroduced a fundamental ecosystem process, it was done at a net cost to the landowner. Using Mech that included mastication and commercial restoration thinning resulted in positive revenues and was also relatively strong as an investment in reducing modeled wildfire hazard. The Mech + Fire treatment represents a compromise between the desire to sustain financial feasibility and the desire to reintroduce fire. One key component to long‐term forest conservation will be continued treatments to maintain or improve the conditions from forest restoration. Many Indigenous people speak of ‘active stewardship’ as one of the key principles in land management and this aligns well with the need for increased restoration in western US forests. If we do not use the knowledge from 20+ years of forest research and the much longer tradition of Indigenous cultural practices and knowledge, frequent‐fire forests will continue to be degraded and lost.

Sustaining eastern oak forests: Synergistic effects of fire and topography on vegetation and fuels

“…We also found that topographic-moisture conditions mediated the effects of fire as dry and intermediate sites exhibited larger shifts away from mesophication and toward sustaining future oak dominance. While mechanical treatments alone can be effective in limiting the primary management objective of reduced fire risk in dry western forests (see Hood et al, 2024;Stephens et al, 2023), we found that thinning without fire served to reinforce rather than limit the process of mesophication in eastern oak forests, shifting stands further away from the primary objective of sustaining oak dominance.…”

Prescribed fires effects on actual and modeled fuel loads and forest structure in southern coast redwood (Sequoia sempervirens) forests

“…We used a custom decision matrix based on understory species cover, dominant tree species, fine fuel loads, and coarse woody fuel loads (Appendix 3). Similar to Stephens et al (2024), model selection breaks were determined based on each plot's Litter + FWD and CWD fuel loads relative to the median value (50% percentile) for the group. Plots with loads below the median value were assigned the fuel model with lower fuel loads, and those greater than the median were assigned the model with the greater fuel load.…”