Restoring a Keystone Tree Species for the Future: American Chestnut Assisted Migration Plantings
Species ranges are forecast to change in response to warming temperatures and altered precipitation patterns, yet tree migration rates fail to track the pace of climate change. In anticipation of these changes, various forest adaptation management strategies have been broadly proposed, including intentionally modifying species composition via assisted migration of future climate adapted species. Despite the potential utility of these adaptation measures, practical evaluations are limited, particularly those applied to meet other ecological objectives such as supporting the restoration of vulnerable, underrepresented, or degraded populations of cultural and ecological keystone species.
In a recent study published in Forest Ecology and Management, a team of NE CASC researchers, including Peter Clark, Anthony D’Amato and Al Freeman, test the seedling growth and survival response of American chestnut, a functionally extirpated species, to assess the restoration and northerly migration potential of the species. The article, "Restoring a Keystone Tree Species for the Future: American Chestnut Assisted Migration Plantings in an Adaptive Silviculture Experiment," is based on a co-developed (manager-scientist designed), operational-scale silvicultural trial located in a northern-hardwood forest in northern New Hampshire.
Outcomes from this work highlight many of the biophysical factors that control chestnut reintroductions, principally from naturally occurring vegetative competition. Nevertheless, chestnut exhibited rapid growth rates and flexible photosynthetic capacity which allowed it to perform as well under the pressures from northern hardwood regeneration. Despite these promising results, extreme cold temperatures strongly limited growth, resulting in repeated winter injury to sensitive plant parts and poor (shrub-like) growth forms. Still, the combined survival-growth response for American chestnuts ranked among the highest relative to the other species tested and even outperformed other assisted migration species introduced from outside of their parental range.
The implications of these findings highlight the potential for American chestnut plantings to be incorporated within both restoration and broader climate adaptation frameworks. Given the paucity of reproductively viable American chestnuts or disease resistant breeding programs along northern range limits, this may generate a reliance on plant material obtained from outside of historically recognized safe transfer distances. Nevertheless, the broader applicability of this work illustrates the potential for cultural and ecological keystone species restoration efforts to be incorporated within climate adaptation frameworks to assist in the establishment of compositionally diverse and future climate-adapted forests.
