Hurricane impacts on coastal forests in Louisiana.
Faulkner, Stephen*,1, Whitbeck, Julie 2, Barrow, Wylie 1, Conner, William 3, Couvillion, Brady1, 1 USGS National Wetlands Research Center, Lafayette, LA2 University of New Orleans, New Orleans, LA3 Clemson University, Clemson, SC
ABSTRACT- Hurricanes have short- and long-term effects on coastal forest structure, ecosystem processes, and services. Hurricanes Katrina and Rita were particularly destructive in the northern Gulf Coast, damaging or destroying an estimated 13.6 million m3 of timber on nearly 450,000 ha in Louisiana. Pearl River floodplain forests suffered 50% mortality in plots not dominated by baldcypress-tupelo gum, while mortality was only 12% in baldcypress-tupelo gum plots. These results are similar to those measured in Lake Verret forests following Hurricane Andrew in 1992. Advanced Very High Resolution Radiometer (AVHRR) weekly composites were used to calculate a Normalized Difference Vegetation Index (NDVI) to characterize vegetative density, health, and vigor for the Pearl River floodplain. These composites were compared to "average" NDVI values calculated from weekly composites from 1989-2003 to create a "departure from average" statistic. Below-average NDVI values were observed throughout the study area following Hurricane Katrina with particularly low NDVI values concentrated in the bottomland hardwood forests. Katrina caused a large litterfall pulse followed by the flushing of new leaves late in the growing season. We assess hurricane impacts on annual litterfall productivity, the temporal distribution of litterfall, and litter quality for a Barataria Basin bottomland forest. These impacts correspond with a shift in migratory bird use from Pearl River bottomlands to adjacent upland forests. Similarly, changes to forest structure can eliminate key foraging substrates used by migratory birds such as vines, epiphytes, live foliage, fruits, and shift regeneration patterns including expansion of opportunistic exotic species (e.g., Chinese tallow tree). The long-term impacts of these changes on avian habitat, food resources, species composition, and ecosystem processes will also be discussed.
Key words: coastal forest, disturbance, hurricane
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