Lack of fire in eastern forests has caused shifts from early-succession forests, often dominated by oaks, to forests dominated by later succession species such as maple. Chestnut oak, a rare forest community type restricted to areas with shallow, well-drained soils, is thought to depend on fire for regeneration and survival. Lack of fire in these forests may favor late-succession, more shade-tolerant species such as red maple. Mohonk Preserve, located within the Shawanagunk geologic formation in NY, has implemented a prescribed fire program to restore chestnut oak forests by increasing chestnut oak seedling recruitment and survival. We used paired burned and unburned sites to determine whether a 2014 prescribed fire increased seedling abundance of chestnut oak vs. red maple, and whether chestnut oak seedlings have a greater capacity to physiologically acclimate to high-light, post-burn environments. We used transects to estimate seedling abundance relative to stand-level basal area, and estimated crown mortality and basal sprouting for each species. We also measured seedling photosynthetic light responses (maximum net photosynthesis, light compensation point) as well as leaf thickness, stomatal density, and specific leaf area.
Results/Conclusions
After accounting for differences in stand-level basal area between sites, prescribed fire increased seedling density for chestnut oak and decreased it for red maple. However, overall seedling density was higher for red maple than chestnut oak at both sites. Red maple, which dominated smaller, mid-story size-classes at both sites, experienced much higher crown mortality from the burn than chestnut oak, and basal sprouting on stems with dead crowns was substantially higher for red maple. Seedlings of both species showed evidence of physiological acclimation to higher light in the burn area. However, chestnut oak had higher overall photosynthetic rates than red maple at both sites, and light compensation points were significantly higher in the burn site for chestnut oak but not for red maple. We conclude that prescribed fire is providing a net benefit for chestnut oak due to crown mortality of mid-story red maple, and potentially greater capacity for physiological acclimation to high light conditions in chestnut oak. Follow-up studies are needed to determine long-term effects of fire, especially the fate of prolific basal sprouting in red maple. Our study suggests that prescribed fire is a useful management tool for restoration of fire-dependent forests in the eastern US.