Sammy King, School of Renewable Natural Resources, LSU, sking16@lsu.edu
Sanjeev Joshi, School of Renewable Natural Resources, LSU, joshi.sanjeev@ymail.com (Presenter)
Richard F. Keim, School of Renewable Natural Resources, LSU, rkeim@lsu.edu
Karen S. Doerr, , kdoerr1@tigers.lsu.edu


Hydrologic alterations of forested wetlands frequently lead to vegetation changes. In central Louisiana, hydrologic alterations have apparently led to an expansion of water elm (Planera aquatica) into Catahoula Lake, a Ramsar Wetland of International Importance. Water elm is a flood tolerant species; so as baldcypress we also expect it to respond more with hydrology. The expansion of water elm has reduced herbaceous vegetation valuable for waterfowl and shorebirds. In this study, we used dendrochronological techniques and aerial photography to test hypotheses that growth rates of water elm are correlated more with hydrologic regime than climate and that expansion of water elm in the lake is a consequence of construction of a diversion canal built on the lake in 1971 that resulted in reduced hydrologic variability. In contrast to our hypothesis, tree radial growth was correlated more with climatic variables than water levels in the lake. We also found that younger trees did not regenerate under older stands, but were a result of new colonization of former non-forested habitats. Hence, our results indicate that hydrologic conditions following the construction of diversion structure are responsible for establishment of numerous water elm trees in the lake. Their growth, however, is dependent on a combination of early spring to summer temperature, precipitation and available soil moisture content.