5th Symposium on Fire and Forest Meteorology and the 2nd International Wildland Fire Ecology and Fire Management Congress

Monday, 17 November 2003
Stand structure after six years: effects of fire exclusion and prescribed fire on ridgetop forest composition and structure
Beth A. Blankenship, University of Kentucky, Lexington, KY; and M. A. Arthur
Decades of fire suppression, in addition to other influences such as loss of Castanea dentata and cessation of logging, have resulted in changing ridgetop forest composition of the Daniel Boone National Forest in eastern Kentucky's Red River Gorge. USDA Forest Service personnel began reintroducing fire as late winter, low intensity prescribed burns in the 1980s in oak-dominated stands. We began documenting the effects of these burns on stand structure in 1995. Here we present results from over 6 years examining areas with a single prescribed fire, multiple prescribed fires, and continued fire exclusion. While a single prescribed burn killed shade-tolerant, fire-sensitive midstory trees such as Pinus strobus and Acer rubrum, mortality was variable from site to site. Multiple burns resulted in higher mortality rates over the 6 years compared to single burn. Midstory P. strobus stems were reduced by 14-60% after 6 years and one fire. After 2 to 3 fires, midstory P. strobus stems declined 66-100%. Midstory A. rubrum stems decreased 56-76% on single burn sites and 92-99% on multiple burn sites. Midstory densities of Oxydendrum arboreum, Nyssa sylvatica, and Quercus spp. also decreased on multiple burn sites. Average midstory density decreased on multiple burn sites from 1530 stems/ha pre-burn to 122 stems/ha in 2001 (p=0.0014). Multiple fires decreased mean overstory density from 626 stems/ha pre-burn to 449 stems/ha in 2001 (p=.0035). Quercus spp. were the only overstory species with a significant decrease in density (from 364 to 283 stems/ha, p=0.0014).

Stand structure of fire-excluded sites changed significantly as well. Average midstory density decreased from 1646 stems/ha in 1995 to 1126 stems/ha in 2001 (p=0.0369). A. rubrum midstory density decreased from 704 to 427 stems/ha (p=0.0092), but overstory A. rubrum density increased from 114 to 194 stems/ha (p=0.0117). O. arboreum was the only overstory species to decrease in density.

Cornus florida declined on all sites over the 6 year period regardless of treatment. With average density of 137 stems/ha in 1995, Cornus florida had an average density of only 3 stems/ha in 2001, a decline of 98%, most likely due to the effects of dogwood anthracnose.

Fire resulted in basal sprouting on all sites. While the fires may reduce canopy densities, increasing light availability to the forest floor, intense basal sprouting may negate any light increases. Fire has been suggested as a tool in promoting oak regeneration, but the complexity of the influences on stand structure make the use of fire an imprecise tool. Long term results of prescribed burning may or may not support the goals of many managers in promoting oak regeneration through the use of prescribed fire.

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