The national Fire and Fire Surrogate study: effects of fuel reduction methods on forest vegetation structure and fuels

Abstract

Abstract. Changes in vegetation and fuels were evaluated from measurements taken before and after fuel reduction treatments (prescribed fire, mechanical treatments, and the combination of the two) at 12 Fire and Fire Surrogate (FFS) sites located in forests with a surface fire regime across the conterminous United States. To test the relative effectiveness of fuel reduction treatments and their effect on ecological parameters we used an informationtheoretic approach on a suite of 12 variables representing the overstory (basal area and live tree, sapling, and snag density), the understory (seedling density, shrub cover, and native and alien herbaceous species richness), and the most relevant fuel parameters for wildfire damage (height to live crown, total fuel bed mass, forest floor mass, and woody fuel mass).In the short term (one year after treatment), mechanical treatments were more effective at reducing overstory tree density and basal area and at increasing quadratic mean tree diameter. Prescribed fire treatments were more effective at creating snags, killing seedlings, elevating height to live crown, and reducing surface woody fuels. Overall, the response to fuel reduction treatments of the ecological variables presented in this paper was generally maximized by the combined mechanical plus burning treatment. If the management goal is to quickly produce stands with fewer and larger diameter trees, less surface fuel mass, and greater herbaceous species richness, the combined treatment gave the most desirable results. However, because mechanical plus burning treatments also favored alien species invasion at some sites, monitoring and control need to be part of the prescription when using this treatment.

Short-Term Effects of Fire and Fire-Surrogate Treatments on Avian Nest Survival: A National-Scale Analysis

“…However, treatments resulting in an increase in the mean diameter of live trees could enhance long-term habitat quality through the eventual recruitment of larger snags. Across the FFS network, mechanical thinning alone and thinning followed by prescribed fire resulted in the largest increases in the mean diameter of live trees, but also the greatest removal of snags [30] and could explain the lower nest survival estimates we observed for the Red-bellied Woodpecker in these treatment areas.…”

“…Burning treatments tended to reduce overall surface fuels [30] and therefore nest cover for this group. However, the same fire may provide long-term benefits by encouraging greater production of grasses, forbs, and shrubs that provide cover for nests.…”

“…Across the FFS network, thinning treatments resulted in the largest increase in woody surface fuels [30], which could serve as effective cover for ground nesting birds. Thinning treatments that reduce the overstory canopy and leave behind slash may benefit ground-nesting birds by increasing both vegetative and structural diversity.…”

“…The nesting requirements of this guild include a diverse layer of shrubs in which to conceal their nests, so treatments that result in a decline of this vegetative layer could have a negative impact on these species. Implementation of the FFS treatments resulted in initial declines in shrub cover across the entire network, especially in burned areas [30]. These declines were reversed in subsequent years as the understory and shrub layers regained vigor [30].…”

“…Implementation of the FFS treatments resulted in initial declines in shrub cover across the entire network, especially in burned areas [30]. These declines were reversed in subsequent years as the understory and shrub layers regained vigor [30]. Given these habitat changes, one might expect to see an initial decrease in the nest survival of these bird species, followed by an increase as the shrub layer recovers.…”