Long-term effects of prescribed burning for oak woodland restoration in Missouri, USA: A case study of sassafras (Sassafras albidum) and white oak (Quercus alba) competitive dynamics

Abstracts: Oak (Quercus spp.) woodlands are vital ecosystems, heavily dependent on prescribed fire to support the regeneration and dominance of oak species. Despite this, the varied responses of non-oak species to fire and their potential ecological feedback remain underrepresented in current literature. One such example involves the emergence of sassafras (Sassafras albidum) saplings in an oak woodland subjected to regular prescribed burns since 1999 that had not been burned in over 80 years. These saplings began appearing in sample plots 14 years after the transition from biennial to triennial fire treatments (2015) but started to become dominant by 2020. This study took place within the 1200-hectare Drury-Mincy Conservation Area (DMCA), associated with the Bull Shoals Field Station in Taney County, Missouri (MO). Following a spring burn in March 2021, we monitored community- and ecosystem-scale responses by measuring sapling density, height, and specific leaf weight (SLW) for white oak (Quercus alba) and sassafras (saplings <1.0 m tall) from Fall 2021 to Fall 2022. In Fall 2021, sassafras saplings reached a density of 560 per 0.1 ha, with an average height of 25.42 cm and a SLW of 4.36 mg/cm². In comparison, white oak saplings had a density of 171 per 0.1 ha, an average height of 10.2 cm, and a SLW of 6.8 mg/cm². By Fall 2022, sassafras density slightly increased to 582 per 0.1 ha, with a notable rise in average height to 71.69 cm and a decline in SLW to 3.6 mg/cm². White oak density rose to 213 per 0.1 ha, with an average height of 50.54 cm and an SLW of 4.3 mg/cm². To evaluate decomposition, we analyzed the mass loss of both species over a 198-day period. Sassafras exhibited a mass loss of 0.86 ± 0.13 g after 61 days, compared to 0.79 ± 0.11 g for white oak. Over longer durations, sassafras mass loss increased to 1.94 ± 0.12 g (day 105), 3.34 ± 0.13 g (day 153), 4.22 ± 0.18 g (day 198), and 4.82 ± 0.12 g (day 244). White oak followed a similar trend, with mass loss values of 1.87 ± 0.14 g, 2.86 ± 0.16 g, 3.34 ± 0.23 g, and 4.28 ± 0.19 g at the respective time intervals. Further investigation into the nutrient profiles and carbon storage potential of sassafras and white oak is essential to fully understand their roles within fire-adapted management strategies in degraded oak woodlands of the southwest MO Ozarks.