Alter forest structure or composition to reduce the risk or severity of wildfire

Forest structure and composition may increase the risk of wildfire, particularly with changing patterns of precipitation, increased temperatures, and longer growing seasons. Management actions that decrease risk of wildfire by altering forest structure or species composition can reduce risk of wildfire or fire severity. Reducing the severity of fires from fuel reduction treatments can have benefits from lowered carbon emissions from fires when they do occur due to reduced fuel consumption (Mitchell et al. 2009). Additionally, decreased fire severity may lower the negative impacts on tree mortality, regeneration, or creation of hydrophobic soil conditions that can have long-lasting effects on forest productivity and forest carbon recovery (Carlson et al. 2012).

Natural disturbance events—including insect pests and diseases, damage from wind and ice, drought, and wildfire—typically reduce near-term forest carbon stocks while initiating long-term and gradual recovery. These disturbances are both a major causes of carbon loss in forests (Williams et al. 2016) and influence future sequestration rates through impacts on species composition, ecosystem structure, rates of photosynthesis and respiration, and flows through various carbon pools (Noormets et al. 2015). While forest regrowth offsets carbon losses following human and natural disturbances over time allowing U.S. forests to remain a net carbon sink (Pan et al. 2011), enhanced disturbance frequency, severity, or extent from climate change may enhance large-scale forest carbon release (Peterson et al. 2014). Shifting climatic conditions, including earlier snowmelt, low precipitation, and warmer temperatures contribute to increases in fire size, frequency, and the area burned annually in the U.S. (Littell et al. 2009; Westerling et al. 2006). Impacts of wildfire on forest carbon sequestration can be long lasting and profound, particularly when they occur outside of the historical fire regime. Not only do wildland fires emit carbon stored in trees that have been burned, but mineral soils and forest floor carbon stocks can also be reduced significantly (Nave et al. 2011; Pellegrini et al. 2018). Additionally, carbon sequestration rates can be lowered in burned areas because of negative impacts on vegetation productivity following severe fire (Hicke et al. 2013). While many actions associated with this strategy can result in a short-term, low magnitude, or fine-scale forest carbon loss, this strategy aims to avoid or reduce long-term, large magnitude, or broad-scale carbon losses through management actions intended to decrease natural disturbance frequency, extent, intensity, or severity.