Tree growth in three South Carolina (USA) swamps after Hurricane Hugo: 1991–2001

Abstract

While coastal forested wetlands of the southern United States have developed with hurricanes as normal aperiodic events and suffer little damage or mortality due to wind, they can be heavily impacted by saltwater storm surges. Three wetland stands (Boardwalk, Crabhaul, and Marsh Road) were studied on Hobcaw Barony, SC, USA, from 1991 to 2001 to determine the recovery of trees following Hurricane Hugo. Five 0.05 ha plots were established during the spring and summer of 1990 in each stand, and diameter measurements were made annually. In terms of the number of trees, basal area, and importance value, baldcypress ( Taxodium distichum) and swamp blackgum ( Nyssa sylvatica var. biflora) were the most important tree species in the Boardwalk and Marsh Road sites, while baldcypress, water tupelo ( Nyssa aquatica), and swamp blackgum were most important in the Crabhaul site. The influx of saltwater from the storm surge killed all individuals of five species (sweetgum ( Liquidambar styraciflua), red maple ( Acer rubrum), sugarberry ( Celtis laevigata), redbay ( Persea borbonia), and waxmyrtle ( Myrica cerifera)) in the Boardwalk site, as well as three species (sweetgum, red maple, and laurel oak ( Quercus lauriflolia)) in the Marsh Road site. Of the remaining trees in both of these sites, baldcypress was the most impacted by saltwater, and mortality continued for several years after the hurricane. No saltwater damage occurred in the Crabhaul site. Mean annual growth rate of baldcypress was greater than other species in all three sites. Diameter change of baldcypress in the Boardwalk site averaged 1.80±0.77 mm per year (±1S.D.), followed by swamp blackgum at 0.85±0.39 mm per year and water tupelo at 0.46±0.84 mm per year. In the Crabhaul site, average growth of baldcypress was 2.00±0.52 mm per year, followed by water tupelo at 1.35±0.62 mm per year and swamp blackgum at 0.51±0.59 mm per year. Baldcypress growth was 2.12±1.2 mm per year in the Marsh Road site, while only 0.60±0.84 mm per year and 0.55±0.45 mm per year growth occurred for water tupelo and swamp blackgum, respectively. The loss of a majority of the mature trees in the Boardwalk and Marsh Road sites, combined with the lack of a viable seed bank and the loss of most of the shrub layer, means that it will take years before these stands fully recover. The Crabhaul site, on the other hand, had less than 3% mortality from the hurricane, and canopy recovery was complete after only one growing season.