Seasonality of Biennial Burning Has No Adverse Effects on Mature Longleaf Pine Survival or Productivity

Abstract

Emulating natural disturbance has become an increasingly important restoration strategy. In the fire-maintained woodlands of the southeastern United States, contemporary restoration efforts have focused on approximating the historical fire regime by burning at short intervals. Due to concerns over escape and damage to mature trees, most prescribed burning has occurred in the dormant season, which is inconsistent with the historical prevalence of lightning-initiated fire in the region. This discordance between contemporary prescribed burning and what is thought to be the historical fire regime has led some to question whether dormant season burning should remain the most common management practice; however, little is known about the long-term effects of repeated growing season burning on the health and productivity of desirable tree species. To address this question, we report on a long-term experiment comparing the effects of seasonal biennial burning (winter, spring, and summer) and no burning on the final survival status, height, diameter, and volume growth of 892 mature longleaf pine (Pinus palustris) over 23 years in three mature even-aged stands in southern Alabama, United States. Overall, longleaf pine survival across all treatments averaged 81 ± 2% [s.e]. Among seasonal burn treatments, survival was highest in the spring burns (82 ± 4%) but did not vary significantly from any other treatment (summer – 79 ± 4%, winter – 81 ± 4%, unburned – 84 ± 4%). However, survival was statistically influenced by initial diameter at breast height, as survival of trees in the largest size class (30 cm) was 40% higher than trees in the smallest size class (5 cm). Productivity of longleaf pine was not significantly different among treatment averages in terms of volume (38.9–44.1 ± 6.0 m3 ha–1), diameter (6.0–6.7 ± 0.3 cm), and height (2.5–3.4 ± 0.4 m) growth. Collectively, our results demonstrate that burning outside the dormant season will have little impact on mature longleaf pine survival and growth. This finding has important implications for the maintenance of restored southeastern woodlands, as interest in burning outside the dormant season continues to grow.

Hardwoods influence effect of climate and intraspecific competition on growth of woodland longleaf pine trees

“…Because of this limitation, we only asked whether prescribed fire resulted in altered growth in the year of burning and refrained from addressing interactions such as those investigated by Ames et al (2015), who found that longleaf pine growth diminished when prescribed fire was applied except during warmer years when growth increased. Typically, juvenile longleaf pines exhibit decreased growth in the year of burning up to 25 years of age (Boyer, 1987; Ford et al, 2010; Haywood & Grelen, 2000) but long‐term studies on mature trees rarely show growth depression in frequently burned stands (e.g., Willis et al, 2021). Our finding of no effect of fire on growth of mature longleaf pines was consistent with these other studies.…”

Effects of Prescribed Burning on Surface Dead Fuel and Potential Fire Behavior in Pinus yunnanensis in Central Yunnan Province, China

“…The mortality rate of P. yunnanensis under natural conditions was approximately 0.93% to 1.27%, while under prescribed burns, it was 1.33%, indicating that P. yunnanensis has some fire resistance and that prescribed burns on it are safe. Furthermore, regular programmed burning was shown to not affect the survival and productivity of mature coniferous forests [48][49][50]. Even after repeated burning over 60 years, there was minimal impact on the structure, composition, or growth of overstory trees [51].…”