Abstract
We studied the effects of logging history, topography, and potential insolation on the lower-elevation limit of existing spruce-fir forest in Great Smoky Mountains National Park (GRSM). Dummy-variable regression, analysis of variance, and classification trees were applied to environmental data within a geographic information system framework. The effect of logging history on the lower limit of spruce-fir depended on aspect. On north-facing slopes (270°– 90°), the presence of spruce-fir was independent of both logging history and potential insolation. On south-facing sites (90°–270°), the elevation of spruce-fir was significantly higher (by 122 m) in areas that had been logged historically. Classification-tree models suggested an even greater logging effect, indicating that both the lower limit and the upper dominance zone of spruce-fir forest are, on average, nearly 200 m higher in historically logged landscapes. Presence of spruce-fir on south aspects was also significantly related to potential insolation, but the strength of this effect was not dependent on logging history. Classification-tree models, developed separately using data from logged sites versus unlogged sites, were used to estimate the current area of spruce-fir forest in the park expected under the hypothetical scenario that no spruce-fir had been logged (38,675 ha) versus the alternate scenario that it had hall been logged (11,727 ha). At present the area of spruce-fir forest in the park is 21,242 ha. We found greater prevalence of spruce-fir on the Tennessee side of the divide on south aspects and historically logged sites, possibly due to greater occurrence of westerly winds and associated cloud cover.
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