A comparison of wetland tree growth response to hydrologic regime in Louisiana and South Carolina

Numerous investigations have examined the growth of wetland tree species under a variety of hydrologic conditions. Most studies have compared flooded versus non-flooded conditions in greenhouses or in one to a few field sites near each other or within the same region. Comparisons of wetland tree growth among widely separated areas of the country are rare. This study compared the diametet; growth of Nyssa sylva/ica var. biflora, Nyssa aqua/ica, and Taxodium dis/ichum trees from Louisiana (Gulf Coastal Plain) and South Carolina (Atlantic Coastal Plain), In both regions. individual trees were distributed along a gradient of hydrologic regimes from infrequent to permanent flooding. Nyssa sylva/ica var. biflora was restricted to periodic.ally flooded sites in both regions. Within these sites. this species showed little response to differences in mean water depth. In contrast, significant differences among hydrologic regimes were detected for N. aqua/ica in both regions. In Louisiana. patterns of growth response did not correlate with the gradient of hydrologic regimes. but in South Carolina maximum growth was inversely related to mean water levels during the growing season. Maximum growth of T. dis/ichum trees was observed at sites with shallow, permanent flooding in both regions. K~ywords: Flooding; Hydrologic regime; Louisiana: Soulh Carolina; Tree growlh; USA 1