Prescribed Fires Pave the Way for Improved Oak Regeneration in Canopy Gaps

Oak dominance is declining in the central hardwoods region, as canopy oaks are being replaced by shade-tolerant trees that are abundant in the understory of mature stands.  Although prescribed fire can reduce understory density, oak seedlings often fail to show increased vigor after fire, as the canopy remains intact.  In this study, we examine the response of tree regeneration to a sequence of repeated prescribed fires followed by canopy gap formation.  We sampled advance regeneration (stems >30 cm tall) in 52 gaps formed by synchronous mortality of white oak (Quercus alba L.); 28 gaps were in three burned stands and 24 gaps were in three unburned stands.  Five years after gap formation, unburned gaps were being filled by shade-tolerant saplings and poles and were heavily shaded (7% of full sun).  By contrast, tolerant saplings had been virtually eliminated in the burned gaps, which averaged 19% of full sun.  Larger oak and hickory regeneration was much more abundant in burned gaps, as was sassafras, while shade-tolerant stems were equally abundant in burned and unburned gaps.  Our results suggest that the regeneration of oak, particularly that of white oak, may be improved with multiple prescribed fires followed by the creation of moderate-sized canopy gaps (200-400m²). 

by Todd Hutchinson, USFS Northern Research Station

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