Fuel load, stand structure, and understory species composition following prescribed fire in an old-growth coast redwood (Sequoia sempervirens) forest

Abstract

Background With the prevalence of catastrophic wildfire increasing in response to widespread fire suppression and climate change, land managers have sought methods to increase the resiliency of landscapes to fire. The application of prescribed burning in ecosystems adapted to fire can reduce fuel load and fire potential while minimizing impacts to the ecosystem as a whole. Coast redwood forests have historically experienced fire from both natural and anthropogenic sources, and are likely to respond favorably to its reintroduction. Results Random sampling was conducted in three burned sites and in three unburned sites, in an old-growth coast redwood (Sequoia sempervirens [D. Don] Endl.) forest. Data were collected on fuel, forest structure, and understory species composition and compared between treatments. Downed woody fuel, duff depth, litter depth, and density of live woody fuels were found to be significantly lower on sites treated with fire compared to unburned sites. Density of the dominant overstory canopy species, coast redwood and Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), remained consistent between treatments, and the abundance of herbaceous understory plant species was not significantly altered by burning. In addition, both downed woody fuel and live fuel measures were positively correlated with time since last burn, with the lowest measures on the most recently burned sites. Conclusions Our results indicated that the use of prescribed burning in old-growth redwood forests can provide beneficial reductions in live and dead surface fuels with minimal impacts to overstory trees and understory herbaceous species.

Initial Floristic Response to High Severity Wildfire in an Old-Growth Coast Redwood (Sequoia sempervirens (D. Don) Endl.) Forest

“…The post-fire recovery of understory cover, at approximately 4%, was quite low [35]. Though cover and richness were reduced due to conditions created by the fire, it was encouraging that many of the species commonly associated with coast redwood forests, such as Oxalis oregana, T. ovatum, Viola sempervirens, and Prosartes hookeri were present [36].…”

Prescribed fires effects on actual and modeled fuel loads and forest structure in southern coast redwood (Sequoia sempervirens) forests

“…This is especially the case in regions and settings where standard mechanical silvicultural methods are cost prohibitive and may not necessarily address all aspects of restoration goals (Glebocki 2015;North et al 2015;O'Hara et al 2010). Existing research suggests repeated prescribed burning may gradually improve the overall resilience of redwood stands to wildfire by reducing fuel loads (Finney and Martin 1992b;Biblin 2023) and small tree stand density, without adverse effects on the diversity and cover of understory species (Cowman and Russell 2021;Engber, Teraoka, and Van Mantgem 2016).…”

“…Prescribed burning may gradually improve the overall resilience of redwood stands to wildfire by reducing fuel loads (Finney and Martin 1992b;Biblin 2023) and stand density without necessarily reducing the diversity and cover of understory species (Cowman and Russell 2021;Engber, Teraoka, and Van Mantgem 2016). While prescribed fire can reduce surface fuel loads, fuels dynamics after burn treatments are nuanced.…”

“…While prescribed fire can reduce surface fuel loads, fuels dynamics after burn treatments are nuanced. Fine fuel conditions have been found to return to pre-treatment conditions within seven years after burning (Engber, Teraoka, and Van Mantgem 2016) and post-treatment large woody debris can vary (increase or decrease) due to log consumption and tree fall (Cowman and Russell 2021).…”

“…Low intensity fire appears to have little effect on overstory species composition and structure, with tree mortality concentrated in smaller, understory size classes (roughly <20-30 cm DBH). Moderate to higher intensity fire is likely needed to produce meaningful effects on forest structure (Cowman and Russell 2021;Engber, Teraoka, and Van Mantgem 2016;Woodward, Romme, and Evangelista 2020).…”