SREL Reprint #2141

The effects of water level fluctuations on weekly tree growth in a southeastern USA swamp

Bobby D. Keeland and Rebecca R. Sharitz

Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802

Abstract: Annual growth of wetland trees has been shown to be related to variations in hydrologic regimes, however the relationship between water level fluctuations and tree growth throughout the growing season has not been documented. In a study of weekly growth patterns of three wetland tree species in a southeastern forested wetlands transfer function modeling was used to examine relationships between tree growth and the weekly changes in water levels and weekly changes in the atmospheric water balance (precipitation minus potential evapotranspiration). An autoregressive-moving average model was fit to each time series of water-level changes (input series), and the selected model was then used to filter the tree-growth (output) time series. Cross-correlations between each input and output time series were examined and significant relationships between weekly changes in water levels and tree diameter were found for Nyssa sylvatica and Taxodium distichum trees growing at sites with periodic shallow flooding. There were no significant relationships between changing water levels and tree growth in areas with permanent flooding or soil saturation. Further, changes in growth of N. sylvatica, N. aquatica, and T. distichum were significantly cross-correlated with weekly changes in the atmospheric water balance at sites with either periodic or permanent flooding.

Keywords: flooding; growth response; Nyssa aquatica; Nyssa sylvatica var. biflora; swamp; Taxodium distichum; time series analysis

SREL Reprint #2141

Keeland, B.D. and R.R. Sharitz. 1997. The effects of water level fluctuations on weekly tree growth in a southeastern USA swamp. American Journal of Botany 84:131-139.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).