Alter forest structure to reduce severity or extent of wind and ice damage

Wind disturbance from microbursts, tornadoes, hurricanes, or other high wind events is a fundamental natural disturbance process that contributes to tree mortality in many forest ecosystems (Dale et al. 2001). Damage from wind events is estimated to be one of the most prominent disturbances in the Midwest and Northeast (Boose et al. 2001; Frehlich 2002; Seymour et al. 2002). A warming atmosphere is driving more frequent and intense storms, including hurricanes and thunderstorms with high winds (USGCRP 2017) that may be contributing to greater transfers of carbon from live to dead forest carbon pools (Williams et al. 2016). Interactions between severe wind events and altered temperature and precipitation patterns may further increase windthrow occurrence in some forests due to impacts on tree anchorage and wind exposure (Seidl et al. 2017). Similarly, ice storms have important consequences for carbon dynamics in forests systems from loss of productivity from leaf area losses, crown loss from stem breakage, or damage to stems that increases susceptibility to insects and disease (Dale et al. 2001). Management actions that alter the structure or species composition may reduce the vulnerability of forest stands to carbon losses from these agents.

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.