Dendrochronological analysis and growth-climate response of Chamaecyparis thyoides and Chamaecyparis thyoides var. henryae in northwest Florida

Dendrochronology methods were used to analyze tree-ring growth response to climate in Atlantic white cedar (Chamaecyparis thyoides) in northwest Florida, near the southern range limit. A species variant ( C. thyoides var. henryae) exists only in the western Florida panhandle and Alabama area. Neither has been previously analyzed in the Gulf Coast using dendrochronology. Precipitation, temperature, drought indices, and cyclic climate indices were correlated with standardized tree-ring widths to determine what climate factors influenced tree growth, and if any differences in growth-response existed between the main species and the variant. Findings indicate that year-round dry conditions in the year prior to growth are favorable for the main species, while dry winter conditions immediately preceding the growing season and in the year prior to growth are significantly correlated to increased tree-ring width in the species variant. It is unclear if the growth-response differences are attributable to genetic differences between the species and variant, or to localized environmental conditions. The findings may help forest managers formulate better management plans for the species and variant, which are often found in association with listed plant species because of the unique wetland habitat conditions where the tree thrives.