Timing is everything: Prescribed burn season and the optimization of multiple management objectives

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Agency Name
Cal Department of Forestry
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Area/s of Research
Climate Change Science
Ecology and Evolution

Current rates of fuel reduction in California, particularly the use of prescribed fire, pale in comparison to the effort needed to restore forest health, prevent stand-replacing wildfires, and meet CA’s long-term climate goals. For example, at 2018 treatment rates it would take 40 years to apply health and resiliency treatments to the 10 million acres of federal lands currently considered ‘high priority’ for reducing wildfire threats and maintaining ecological health (Forest Climate Action Team 2018). However, conflicting management priorities such as the need to protect vulnerable species like black oak trees, can limit managers’ logistical ability to apply prescribed fire by restricting the available ‘burn window’. Thus, even while the need to maximize the available burn window mounts by the year (Forest Climate Action Team 2018), managers on the ground can be limited in their ability to utilize prescribe fire as a tool. Understanding how burn season influences the health of forest trees will help managers balance the need to reintroduce fire to the landscape to ensure the resilience of canopy trees with the regeneration needs of target species post-fire. The proposed project investigates how to optimize multiple management goals through prescribed burning: (i) maximizing treated area by maximizing burn window (ii) preserving health of overstory hardwood trees, and (iii) stimulating healthy regeneration dynamics in fire-adapted resprouters. In many parts of the state, fire-adapted resprouters like black oak (Quercus kelloggii) are a major component of forested ecosystems. Black oaks have high ecological and cultural value (e.g. for tribal ecocultural restoration, Long et al. 2017) that make them important management targets to retain in extent stands. There is also an expectation that oaks will increase in dominance with climate warming and stand-replacing wildfire (William K Cornwell 2012, Dolanc et al. 2014, McIntyre et al. 2015). However, oak recruitment limitation (Tyler et al. 2006, Davis et al. 2016, López-Sánchez et al. 2019, Cushman et al. 2020) and recent droughtinduced oak mortality (Brown et al. 2018, Das et al. 2019) highlight the critical need for proactive management of oaks to protect future forest carbon storage, wildlife habitat, and persistence of forested ecosystems. Unfortunately, our understanding of prescribed fire effects on oaks lags considerably behind our understanding of prescribed fire on conifers. The timing of prescribed burns likely influences the physiology of deciduous hardwoods, like black oak, that are often a desired component of forest ecosystems but these effects may depend on tree size and postburn climate.