Ponderosa Pine Forest Restoration Treatment Longevity: Implications of Regeneration on Fire Hazard

Abstract

Abstract:Restoration of pine forests has become a priority for managers who are beginning to embrace ideas of highly heterogeneous forest structures that potentially encourages high levels of regeneration. This study utilizes stem-mapped stands to assess how simulated regeneration timing and magnitude influence longevity of reduced fire behavior by linking growth and yield model outputs to a crown fire prediction model. Treatment longevity was assessed as return time to within 10% of pre-treatment predicted wind speeds for the onset of passive (Torching) and active (Crowning) crown fire behavior. Treatment longevity in terms of Torching and Crowning was reduced 5 years for every 550 and 150 seedlings ha´1, respectively. Introducing regeneration as a single pulse further reduced Torching treatment longevity 10 years compared to other regeneration distributions. Crowning treatment longevity increased at higher site indices, where a 6 m increase in site index increased longevity 4.5 year. This result was contrary to expectations that canopy openings after treatments would close faster on higher productivity sites. Additionally, Torching longevity was influenced by the rate of crown recession, were reducing the recession rate decreased longevity in areas with higher site indices. These dependencies highlight a need for research exploring stand development in heterogeneous sites.

Long-Term Impacts of Fuel Treatment Placement with Respect to Forest Cover Type on Potential Fire Behavior across a Mountainous Landscape

“…Even after 50 years, however, mean CBD was far less than pretreatment levels, indicating long-lived resistance to active crown fire (Figure 3). These findings are consistent with recent work that also showed long-lived reduction in CBD following treatments such as those simulated here, translating to prolonged reductions in the potential for active crown fire [20]. Treated stands in the Douglas-fir cover type did experience an~10% increase in CBD per decade compared to only a slight increase over the simulation period for ponderosa pine-dominated stands, which we attribute to the systematic differences in composition, productivity and tree regeneration rates between cover types in this study.…”

“…Because most of the simulated landscape was untreated, this ultimately resulted in all simulations showing a decrease in fire size, mean rate of spread, and active and passive crown fire proportions through time (Figure 5a,b and Figure 6). These findings are consistent with the outcomes of similar studies conducted in dry forest types in California and contribute to a growing body of literature that suggests a better understanding of crown recession is critical for improving our ability to predict the longevity of fuel treatment effects [20,60,61]. These studies also highlight the importance of accounting for stand dynamics in untreated areas when assessing the longevity of treatment effects for project areas that include many stands.…”

“…Rates of fuel hazard development are potentially distinguished between cover types in this region by systematic differences in tree regeneration rates, species composition, and productivity. The influence of tree regeneration rates may be particularly strong [20]. In the Colorado Front Range, regeneration rates have been shown to be 200%-400% greater for Douglas-fir (Pseudotsuga menziesii var.…”

Evidence of fuels management and fire weather influencing fire severity in an extreme fire event

“…, Tinkham et al. ), or (4) local feedbacks between fire weather, topography, and fuels. A previous study found that both an extended time since previous fire and the occurrence of extreme fire behavior were associated with moderate to high‐severity fire in the Rim Fire (Lydersen et al.…”

New Research and BMPs in Natural Areas: A Synthesis of the Pollinator Management Symposium from the 44th Natural Areas Conference, October 2017

“…Various natural disturbance processes of forest ecosystems have dramatic impacts on the structure of western coniferous forests, particularly fire and bark beetles (Tinkham et al 2016). These disturbances can significantly alter floral resource availability, which has a corresponding impact on bee pollinators.…”