Yellow pines (Pinus rigida, P. virginiana, P. echinata, and P. pungens) and oaks (Quercus spp.) dominate xeric slopes and ridges in western Great Smoky Mountains National Park (GSMNP). In the late nineteenth and early twentieth centuries, these sites burned frequently. Since about 1940, the Park Service has suppressed fire, prompting concerns over possible changes in forest composition and structure. This study documents changes in xeric forests using non-permanent plots sampled in 1936-37, permanent plots established in 1977-79, and a subset of those permanent plots resampled in 1995. Some permanent plots burned just prior to sampling in the 1970s, while others have not burned since before 1940.
Between the 1930s and 1970s, canopy density, basal area, and canopy richness increased dramatically on fire-suppressed sites. While high-intensity fires reduced canopy density and basal area to low levels, low-intensity fires did not significantly reduce canopy density or basal area relative to fire-suppressed sites. Between the 1970s and 1995, canopy density on fire-suppressed and low-intensity fire sites remained relatively stable, while that on sites of high-intensity fires increased rapidly. During this period, abundant regeneration of yellow pines occurred on some burned sites. On fire-suppressed sites, densities of Acer rubrum, Nyssa sylvatica, Pinus strobus and Tsuga canadensis have increased. Changes in the canopies of xeric forests since the onset of fire suppression may alter response to future fire events and complicate the restoration of historical composition and structure in these communities.