Oak and red maple seedling survival and growth following periodic prescribed fire on xeric ridgetops on the Cumberland Plateau

Abstract

To test the hypothesis that repeated prescribed fires alone can improve the status of oak regeneration, a long-term seedling population study was established to follow permanently tagged chestnut oak ( Q. prinus L.) , scarlet oak ( Q. coccinea Muenchh.), and red maple ( Acer rubrum L.) seedlings over 8 years in sites where fire was excluded, and where fire was applied either three (3×) or four (4×) times. After 8 years, seedling survival was higher on fire-excluded sites (78.2%) compared to burned sites (3×: 66.4%; 4×: 67.1%). Scarlet oak seedlings had significantly higher survival than red maple seedlings in both burn treatments (3×: 85.7% vs. 62.3%; 4×: 75.5% vs. 61.9%). In contrast, chestnut oak survival was not significantly greater than red maple in either burn treatment. Multiple fires resulted in taller seedlings, with red maple seedlings taller than the oak seedlings, and red maples burned 4× the tallest (RM: 39.3 cm; CO: 21.2 cm; SO: 25.3 cm). In year 8, all species had greater annual height growth on the burned sites than on the fire-excluded sites. Scarlet oak seedlings had significantly greater annual height growth in year 8 on the 4×-burned (6.8 cm) compared to 3×-burned (4.0 cm), while annual height growth of red maple (9.1 cm) and chestnut oak (6.0 cm) on the 4×-burned was not different from the 3×-burned (RM: 6.8 cm; CO: 5.0 cm). When analyzed based on the number of growing seasons since burning, the greatest height growth occurred the first year after burning for all species. On all treatments, red maple seedlings had greater basal diameter than oak seedlings in year 8, and basal diameter of scarlet oak seedlings was greater than that of chestnut oak. For all species, basal diameter of seedlings burned 4× was significantly greater than those burned 3×, and basal diameter of those burned 3× was significantly greater than the fire-excluded. While multiple prescribed fires reduced the number of red maple seedlings and improved growth of oak seedlings, surviving red maples remained competitive. Our results support the need for further experimentation with seasonality and intensity of prescribed burning, and increased use of silvicultural treatments in conjunction with fire to reduce midstory competition.