A Dendroecological Approach for Dating Individual Small-Scale Canopy Disturbance Events, Great Smoky Mountains National Park, Tennessee, USA

Cseke, Jacob

ABSTRACT: Canopy disturbance events may be the most influential factor on tree growth in temperate environments where temperature and rainfall are not the limiting growth factors. Trees respond to these disturbances by ring growth releases or, if injury results, by growth suppression. Creation dates of canopy gap events may be obtained by analyzing tree-ring patterns that arise directly from the disturbance event. Creation dates of fourteen individual, small-scale canopy gap events were obtained by the dendroecological methods developed in this study. Trees were cored in and on the perimeter of canopy gaps to determine if they recorded evidence of the gap-making event in their ring patterns. Ring widths were measured and each sample was crossdated using the computer program COFECHA. Graphs were created from the measurements and visually examined for large-magnitude growth releases and suppressions that persisted for a minimum of five years. The computer program JOLTS was also used to detect growth releases. Synchronous release events were detected in several trees at each gap site, which presented the most direct evidence for establishing the date of a disturbance event. Growth suppressions and JOLTS data were used to provide additional evidence for the estimated creation dates. Some gap creation dates could be assigned to a single year, while the majority of gaps were dated to a range of two to four years. Creation dates were identical or overlapped for several sites, forming date clusters, which may have indicated they occurred during the same storm event. The dates of three large storm events coincided with the clustered dates, which provided additional, if circumstantial supporting evidence for the estimated dates. These results suggested that individual gap events could be accurately dated by the techniques developed in this study.