Influence of microhabitat on tree seedling establishment in salvaged and unsalvaged 1938 hurricane blowdown sites

Gardner, Amanda
Tom Wessels, MA
Department of Environmental Studies
1996
This study explored species-specific patterns of tree seedling establishment on hurricane-created microhabitats in salvaged and unsalvaged blowdown sites. Three forest floor microhabitats created by the Hurricane of 1938 were evaluated: pits, mounds and, in the unsalvaged site, decaying boles. A fourth microhabitat, the open forest floor, was also evaluated for comparison. Twenty-five, 1 m² quadrats were surveyed for each microhabitat in both salvaged and unsalvaged sites. All stems of tree species within each quadrat were identified and counted. The height class of each stem was recorded individually. Shrub and herbaceous cover, canopy density and composition, extent of decomposition of the bole, and depth of the litter in each quadrat were also recorded. Based on an analysis of frequency of occurrence, species-specific patterns of establishment were identified in both the salvaged and unsalvaged sites. In addition, differences in the number and distribution of different tree species were found between the two sites. The number of stems recorded in the salvaged site was less than half the number found in the unsalvaged site, despite similar overstory composition. Quercus rubra established preferentially on the pit and forest floor microhabitats in the unsalvaged site. This pattern was not evident in the salvaged site, although this may be due to the lower number of Quercus rubra seedlings. Betula lenta and Betula allegheniensis established almost exclusively on the mound and decomposing bole microhabitats in the unsalvaged site. In the salvaged site, seedlings and saplings of these species occur almost exclusively on mounds. Acer rubrum showed no microhabitat preference in either site but, in the unsalvaged site, occurred more frequently on the pit-facing side of the mound than on the bole-facing side. Ten other tree species were recorded but did not appear frequently enough for statistical analysis. These results provide valuable knowledge about successional patterns that persist for many decades on a hurricane-impacted landscape. In addition, this study indicates that salvaging an area following a hurricane may have an impact on the numbers and distribution of seedlings that emerge in subsequent years. Although most of the seedlings observed will not survive to maturity, their presence as a persistent, regularly replaced understory may help to determine patterns of vegetation development after future disturbances.

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