Abstract
AbstractIn the eastern United States, American chestnut (Castanea dentata) was historically a major component of forest communities, but was functionally extirpated in the early 20th century by an introduced pathogen, chestnut blight (Cryphonectria parasitica). Because chestnut is fast‐growing, long‐lived, and resistant to decay, restoration of American chestnut using blight‐resistant stock could have the potential to increase carbon sequestration or storage in forested landscapes. However, carbon dynamics are also affected by interspecific competition, succession, natural disturbance, and forest management activities, and it is unknown how chestnut restoration might interact with these other processes. We used the PnET‐Succession extension of the LANDIS‐II forest landscape model to study the implications of chestnut restoration on forest composition and carbon storage in the context of other disturbances, including timber harvest and insect pest outbreaks. Our results imply that it could take a millennium or more for chestnut to fully occupy landscapes without aggressive restoration efforts. When successful, chestnut restoration activities displaced other species approximately in proportion to their abundance on the landscape, rather than replacing a single species or genus (e.g., Quercus). Insect pests increased the rate of chestnut colonization by reducing the abundance of competitors, and also had a dominant effect on carbon dynamics. Although chestnut is fast‐growing, moderately shade‐tolerant, and decomposes very slowly, our results suggest that it can only modestly increase the carbon storage potential of eastern forests. However, our results also demonstrate that compositional changes in forest communities can have noticeable effects on biomass accumulation, even with the large uncertainties introduced by invasive pests.
Highlights
Carbon sequestration is an important ecosystem service provided by forests globally and represents a driving motivation for reforestation and conservation efforts worldwide
Caterpillar (FTC; Malacosoma disstria), gypsy moth (GM; Lymantria dispar), and hemlock wooly adelgid (HWA; Adelges tsugae), as well as imminent potential invasions by the emerald ash borer (EAB; Agrilus planipennis) and Asian long-horned beetle (ALB; Anoplophora glabripennis), may fundamentally change the ability of these forests to continue serving as a regional carbon sink (Flower and Gonzalez-Meler 2015)
Description of study site We conducted our study in the Ridge and Valley physiographic province of western Maryland (USA) because it is in the approximate center of the former American chestnut range (Little 1977; Fig. 1) and allowed us to capitalize on previous studies for initial conditions and disturbance parameters (Sturtevant and Seagle 2004, Foster 2011)
Summary
Carbon sequestration is an important ecosystem service provided by forests globally and represents a driving motivation for reforestation and conservation efforts worldwide. The potential for carbon sequestration in many forested regions may be limited by competing land uses (Drummond and Loveland 2010), transitions in forest age structure (Xu et al 2016), and disturbance processes that in many cases are accelerated by human activities (e.g., Lovett et al 2016). Assuming that the amount of forested land will remain relatively stable, it is reasonable to hypothesize that future carbon dynamics will depend, at least in part, on the mix of tree species that occupy those forests. Predicting the consequences of compositional change is not a trivial task because in addition to species’ establishment and growth rates, potential size, spacing, and life span, carbon dynamics depend on disturbance rates and intensities
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