Geographic Variation in Survival and Growth of Atlantic White-Cedar (Chamaecyparis Thyoides [L.] B.S.P.): Implications for Artificial Regeneration of a Declining Species

Atlantic white-cedar (Chamaecyparis thyoides [L.] B.S.P.; AWC), a wetland tree species native to the eastern United States, is declining rangewide. This decline has stimulated interest in restoring AWC in parts of its range. However, restoration could benefit from more research on this species, especially that focus on where to source seedlings for artificial reforestation. This study presents results out to years 18–20 from a southern New Jersey common garden established in the early 2000s as part of the first rangewide provenance planting of AWC. The goal of this research was to expand our understanding of intraspecific variation in AWC linked to the geographic origin of genetic sources. Results indicated that genotype performance was linked to their geographic origin and that local sources were among the top performers when taking all metrics into consideration (e.g., survival, height, basal area). Top-performing provenances were sourced within plus or minus two decimal degrees latitude of the planting site. Although local sources remain suitable for artificial regeneration of this species in southern New Jersey, nearby southern sources could be deployed to achieve out-planting success and conservation of this imperiled species in a warming climate. We hope this work will inform AWC restoration efforts and bring visibility to this declining wetland species. Study Implications: Common garden studies can help inform management decisions regarding tree species or genotypes to deploy for reforestation under current and future climate. Local sources of plant material remain a viable option for artificial regeneration of Atlantic white-cedar (Chamaecyparis thyoides [L.] B.S.P.) in southern New Jersey. However, Mid-Atlantic sources to the south of New Jersey, especially those within two decimal degrees latitude south of the planting site, could be deployed for restoration planting. Not only could planting seedlings sourced from south of a planting site achieve reforestation objectives, but the deliberate northward movement of southern genotypes within the species’ range, that is, assisted migration, could enhance climate resilience of this declining wetland species.