Tropical cyclone signals within tree-ring chronologies from Weeks Bay National Estuary and Research Reserve, Alabama

This study investigates the relationship between tropical cyclones and tree-ring chronologies within a bottomland forest in coastal Alabama. Tree cores were collected from 36 slash pines in the Swift Track area of the Weeks Bay National Estuary and Research Reserve, Fairhope, Alabama. Tree cores were processed, measured to the nearest 0.01 mm, and cross-dated using standard procedures. A standardized ring index series was computed from the tree-ring measurement for each year from 1890 to 2000. The index series represents a single chronology of the entire forest stand, which we refer to as the stand-scale. An initial comparison of index series values to years of known tropical storm and hurricane strikes within the Weeks Bay area reveals no clear tropical cyclone signal. Statistical tests of the index values for 2-7 y periods before and after tropical storms and hurricanes indicate no statistically significant difference in tree-rings before and after the storms. In contrast, standardized index values computed for each individual tree-ring series (individual tree-scale) display more rapid growth (release) in years following direct hits by tropical cyclones. Individual tree-ring data also indicate slowed growth (suppression) during years when tropical cyclones are infrequent. These results indicate that researchers must be aware of scale of analysis when researching tree-ring chronologies in Gulf Coast forests. For this study, a combination of the two scales of analysis results in a recognizable tree-ring record of suppression and then release generated by tropical cyclones.