Increase stocking on well-stocked or understocked forest lands

When risk of carbon loss from natural disturbance is low, maintaining greater carbon stocks in live tree biomass can provide significant carbon benefits over long periods of time (Galik and Jackson 2009). In uneven-aged systems, greater carbon stocks can be achieved through increased duration of time between harvest entry (D’Amato et al. 2011) greater rates of retention when harvest does occur (Duveneck et al. 2014; Hoover and Stout 2007; Nunery and Keeton 2010; Puhlick et al. 2016; Russell-Roy et al. 2014). In a modeling study conducted in the Upper Midwest region, increasing retention of live tree biomass during harvest increased total forest carbon stocks in hardwood and conifer stands by 25% and 37%, respectively (Peckham et al. 2013). Additionally, greater carbon stocks can be maintained in even-aged systems from increasing rotation lengths (Duveneck and Scheller 2016; Mika and Keeton 2015; Law et al. 2018). For example, increasing rotation ages 15 years in softwood stands in New England could sequester an additional 0.82 MgC ha-1 yr-1 (Perschel et al. 2007), while extending rotations on private lands in Oregon from 45 to 80 years would increase state-level carbon stocks by 17% (Law et al. 2018).

Increasing stand stocking levels on understocked forestlands (land with >10% cover of live trees) that are considered understocked (<60% of fully stocked) has the potential to increase carbon density in live biomass carbon pools. For example, Hoover and Heath (2011) estimate ~49% of timberland in the Northeast is understocked, with the potential to store an additional 454 TgC over 40 years if fully stocked. Land managers can improve forest productivity and the amount of carbon stored within forests by managing the stand density (e.g., basal area, or trees per hectare) and species composition, often in comparison to a reference stand of similar age and productivity potential that is considered fully stocked. The benefits of increasing stand stocking levels, however, may need to be compared to the increased risk of carbon loss from disturbance (e.g., from wildfire or drought-induced tree mortality) resulting from increased tree densities. Stands where vulnerability to carbon losses is determined to be low may provide additional carbon benefits from increasing stocking rates.

Climate change is projected to increase the potential for severe disturbance events that reduce forest ecosystems carbon stocks (Williams et al. 2016), while additionally affecting the growth and regeneration of extant species. Many forest management decisions aim to limit the negative impacts of disturbances while enhancing the growth of residual trees and the regeneration of desired species that represent the current and future capacity of the ecosystem to sequester carbon (McKinley et al. 2011). Often these management actions aim to enhance existing forest conditions, such as species composition and stand structural diversity that are key to the desired services provided by the forest. Slight adjustments in forest conditions can improve the retention of carbon within various forest carbon pools or enhance the rate of recovery following a disturbance event without dramatically altering the character of forest ecosystems.