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Strong Legacy Effects of Prior Burn Severity on Forest Resilience to a High-Severity Fire

Author(s): Lucas B. Harris, Stacy Drury, Alan H. Taylor
Year Published: 2020
Description:

Legacy effects from one disturbance may influence successional pathways by amplifying or buffering forest regeneration after the next disturbance. We assessed vegetation and tree regeneration in non-serotinous Sierra lodgepole pine (Pinus contorta var. murrayana) stands after a 1984 wildfire which burned with variable severity and again after a high-severity subsequent fire in 2012. The legacy effects of the 1984 fire were amplified; seedlings and saplings were abundant in areas initially burned at low severity (1267 stems ha−1) despite high reburn severity, but regeneration was low in areas twice burned at high severity (31 stems ha−1). Our results suggest that the severity of the 1984 fire may have influenced post-2012 tree regeneration by creating variable fuel loading, which may have affected soils, litter cover and shade after the 2012 fire and therefore affected seedling establishment and survival. A canopy seed bank of unburnt cones from trees killed by the 2012 fire potentially contributed to a strong effect of prior burn severity on regeneration after the 2012 fire despite a lack of serotinous or resprouting tree species, although the influence of this canopy seedbank was likely limited to the year following the fire. Our results suggest that a low- to moderate-severity fire increases forest resilience relative to a high-severity fire even when the next fire burns at high severity.

Citation: Harris, Lucas B.; Drury, Stacy A.; Taylor, Alan H. 2020. Strong legacy effects of prior burn severity on forest resilience to a high-severity fire. Ecosystems online early.
Topic(s): Fire Regime, Fire Intensity / Burn Severity, Recovery after fire, Resilience
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 21927
FRAMES RCS number: 61941
Record updated: Sep 28, 2020