Tree Basal Growth Response to Flooding in a Bottomland Hardwood Forest in Central Ohio

Tree basal growth in response to flooding regime was evaluated at a 5.2-ha bottomland forest along the Olentangy River in central Ohio. Tree-ring analysis was used to develop a 14-year basal area increment (BAI) (cm(2)/year) series for 42 canopy trees (representing 10 species) throughout the bottomland. Mean annual BAI was evaluated relative to the frequency and duration of bankfull (> 70 m(3)/s) and high-flood (> 154 m(3)/s) river discharge for a given water year (October 1-September 30) and growing season (April 1-September 30). A significant polynomial relationship was detected between the number of days of high-flood river discharge over a combined two-year period (Year i + Year i - 1) and mean annual BAI. No significant relationships were detected when only the concurrent-year or previous-year flood regimes were considered or when growing season was considered. A similar relationship was detected when duration of high-flood discharge days and BAI were both evaluated in two-year increments (Year i + Year i - 1). Mean annual BAI was most influenced by boxelder (Acer negundo) which was the dominant species and exhibited strong agreement with the overall BAI series. In each case, the resulting parabolic curve of tree basal growth in response to flooding suggests an optimal number of flooding days, a response to perturbation consistent with the subsidy-stress model. Dendrochronology may be a useful tool for managers looking to restore environmental flows to regulated rivers.