Abstract
Improved predictions of tree species mortality and growth metrics following fires are important to assess fire impacts on forest succession, and ultimately forest growth and yield. Recent studies have shown that North American conifers exhibit a ‘toxicological dose-response’ relationship between fire behavior and the resultant mortality or recovery of the trees. Prior studies have not been conclusive due to potential pseudo-replication in the experimental design and time-limited observations. We explored whether dose-response relationships are observed in ponderosa pine (Pinus ponderosa) saplings exposed to surface fires of increasing fire behavior (as quantified by Fire Radiative Energy—FRE). We confirmed equivalent dose-response relationships to the prior studies that were focused on other conifer species. The post-fire growth in the saplings that survived the fires decreased with increasing FRE dosages, while the percentage mortality in the sapling dosage groups increased with the amount of FRE applied. Furthermore, as with lodgepole pine (Pinus contorta), a low FRE dosage could be applied that did not yield mortality in any of the replicates (r = 10). These results suggest that land management agencies could use planned burns to reduce fire hazard while still maintaining a crop of young saplings. Incorporation of these results into earth-system models and growth and yield models could help reduce uncertainties associated with the impacts of fire on timber growth, forest resilience, carbon dynamics, and ecosystem economics.
Highlights
Land management professionals are faced with increasing challenges of how to manage woodlands and forests in the face of larger and more destructive wildfires, while increasing the use of planned fires as a pre-emptive mitigation approach [1,2]
H4: As hypothesized by [4], the dose-response relationships observed for Pinus ponderosa saplings during laboratory fires will exhibit a higher probability of mortality at lower dose levels as compared to similar age/size saplings burned during field experiments
The hypotheses we sought to test in the current study were: (1)
Summary
Land management professionals are faced with increasing challenges of how to manage woodlands and forests in the face of larger and more destructive wildfires, while increasing the use of planned fires as a pre-emptive mitigation approach [1,2]. A challenge in using planned fires is determining what thresholds of different fire behavior characteristics (intensity, heat release, residence time, etc.) will yield the desired levels of mortality for various species/size classes [4,5]. If desirable trees die from planned fires or wildfires, land managers must either allocate and invest more time, money, and resources to replanting and replacing them, or forgo having those species in that location for the rotation of that stand. If the desirable trees survive but are damaged, any reductions in vigor or growth could impact carbon stocks and timber yield for that area [6]. This could delay harvests or reduce the volume expected, resulting in a potentially lower profit margin
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