Manage for species and genotypes with wide moisture and temperature tolerances

Inherent scientific uncertainty surrounds climate projections at finer spatial scales, making it necessary to base decisions upon a wide range of predictions of future climate (Brandt et al. 2017). Although projections of future climate differ across regions, models generally highlight increasing average annual temperatures, along with varying impacts on precipitation (USGCRP 2017). Rising temperatures along with greater variation in precipitation patterns has increased the year-to-year variability in growing season soil moisture conditions for some regions in the US (Hubbart et al. 2016; Easterling et al. 2017). This increased climate variance, which can result in conditions of both drought and excessive wetness across short time periods, has important consequences for potential declines in forest health that negatively impact productivity and carbon sequestration (Hubbart et al. 2016; Kutta and Hubbart 2018). Forest management actions that favor a variety of species and genotypes with a wide range of moisture and temperature tolerances may better distribute risk than attempting to select species with a narrow range of tolerances that are best adapted to a specific set of future climate conditions (The Nature Conservancy 2009). Diversifying forest composition to include species with wider climatic tolerances can increase the capacity of forest stands to sequester carbon in the future as conditions change (Duveneck and Scheller 2015; Hof et al. 2017). Likewise, even-aged forest stands that reach the economic optimum of the rotation age that transition to alternative species with wider environmental tolerances can maintain or increase profitability and carbon sequestration rates (Susaeta et al. 2014).

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.