Using consecutive prescribed fires to reduce shrub encroachment in grassland by increasing shrub mortality

Abstract

Woody plant encroachment into open grasslands occurs worldwide and causes multiple ecological and management impacts. Prescribed fire could be used to conserve grassland habitat but often has limited efficacy because many woody plants resprout after fire and rapidly reestablish abundance. If fire‐induced mortality could be increased, prescribed fire would be a more effective management tool. In California's central coast, shrub encroachment, especially of Baccharis pilularis (coyote brush), is converting coastal prairie into shrub‐dominated communities, with a consequent loss of native herbaceous species and open grassland habitat. B. pilularis has not been successfully controlled with single prescribed fire events because the shrub resprouts and reestablishes cover within a few years. We investigated whether two consecutive annual burns would control B. pilularis by killing resprouting shrubs, without reducing native herbaceous species or encouraging invasive plants. As expected, resprouting did occur; however, 2 years after the second burn, B. pilularis cover on burned plots was only 41% of the cover on unburned plots. Mortality of B. pilularis more than doubled following the second burn, likely maintaining a reduction in B. pilularis cover for longer than a single burn would have. Three native coastal prairie perennial grasses did not appear to be adversely affected by the two burns, nor did the burns result in increased cover of invasive species. Managers wanting to restore coastal prairie following B. pilularis encroachment should consider two consecutive annual burns, especially if moderate fire intensity is achievable.

Nonperiodic grassland restoration management can promote native woody shrub encroachment

“…Furthermore, an assessment of the savanna biome found that the occurrence of African savannas was correlated with areas with regular fire return intervals (Lehmann et al 2011), whereas O'Connor et al (2020 found fire can reduce the dominance of encroaching shrubs into a native grassland. Moreover, similar to our results, singular prescribed fires (disturbance), were found to promote woody invasion (Abella et al 2020;Hopkinson et al 2020).…”

“…Reestablishing historic disturbance regimes is another growing restoration practice, but past evidence indicates that temporally limited restoration actions can promote native and nonnative woody invasion in open grassland habitat (Hobbs & Mooney 1985; Laris et al 2017; Abella et al 2020; Hopkinson et al 2020). Abella et al (2020) and Hopkinson et al (2020) both found that singular prescribed fires without additional maintenance promoted woody invasion. In pampa grasslands, researchers found that singular small‐ and large‐scale experimental disturbances led to increased recruitment of woody tree species in mesic conditions, but not consistently for drier plots (Mazía et al 2019).…”

“…Reestablishing historic disturbance regimes is another growing restoration practice, but past evidence indicates that temporally limited restoration actions can promote native and nonnative woody invasion in open grassland habitat (Hobbs & Mooney 1985; Laris et al 2017; Abella et al 2020; Hopkinson et al 2020). Abella et al (2020) and Hopkinson et al (2020) both found that singular prescribed fires without additional maintenance promoted woody invasion.…”

Taxonomic and Functional Community Composition of Ground Beetles (Coleoptera: Carabidae) Changes with Prescribed Fire Severity

“…Buisson et al 2018;Hopkinson et al 2020), reduce hazardous fuel loads to mitigate the wild re risk to humans(Adams 2013;Kobziar et al 2015), maintain long term ecosystem carbon stores(Clark et al 2018), and reduce disease carrying ticks(Gallagher et al 2022). Even though there is evidence that reintroducing prescribed res back into our landscapes can bene t biodiversity of certain animal and plant taxa, there can still be detrimental effects on richness, abundance, and/or community composition(Eales et al.…”

Manipulating forest structure and ground flora composition for the restoration of oak woodlands and the reconstruction of oak savannas in Central Missouri

“…A fire-free interval is likely essential to the successful establishment of oak savannas (Brose et al, 2014;Frelich et al, 2017). Because a fire-free interval is detrimental to prairie ecosystems by risking increased abundance of invasive plants and woody plants, our study looked at ways to improve oak seedling survival while maintaining a frequent fire regime Hopkinson et al, 2020). Our study looked at ways to reduce fire-induced top kill through species selection, stock type selection, and cultural treatments.…”