Pretreatment data on vegetation, soils, and breeding birds were collected in 1995 and results were published in a Forest Service technical report. Low-intensity dormant-season prescribed fires were applied from 1996 to 1999. During that period, frequent burn units were burned annually (4 times) and periodic burn units were burned twice, in 1996 and 1999. Extensive postreatment data were collected during this period on vegetation, belowground processes, and breeding bird populations. Additional fires were conducted from 2003 to 2005, resulting in units that have now been burned 2 to 5 times.
We will continue the study by applying a shelterwood harvest treatment to all four burn units at VFEF after the 2008 growing season. This treatment will reduce tree basal area from ~110 to ~55 ft2/acre. We will continue to monitor overstory and understory tree populations before and after the shelterwood treatment.
- Annual vs. periodic fires. We found that annual fires were operationally feasible but fire intensity increased significantly with two or more fire-free years between burns.
- Forest structure and composition. Repeated low-intensity fires caused virtually no overstory tree mortality but greatly reduced the density of the maple-dominated sapling layer. However, with the persistence of closed-canopy conditions, oak and hickory advanced regeneration generally failed to develop.
- Herbaceous layer vegetation. Both annual and periodic burns resulted in greater small-scale species richness, as fire stimulated the germination of disturbance-adapted species from the seedbank. Fire cause very little direct damage to herbaceous plants because the burns occurred when the great majority of the flora was dormant.
- Soil chemistry and nutrient cycling. Neither annual nor periodic fires altered soil organic matter, available P, or nitrogen cycling rates. In contrast, both fire regimes increased soil pH and exchangeable calcium, compared to unburned controls. Thus fire appears to offset the effect of atmospheric deposition by increasing pH and calcium, although increased nitrate fluxes through the soil from nitrogen deposition may negate this positive effect of fire.
- Soil temperature and root production. During a fire, we found that very little heat was transferred to the mineral soil. However, the postburn blackened litter layer resulted in soils that warmed earlier and to a greater extent in the growing season. This earlier soil warming was accompanied by an earlier increase in root biomass in the soil.
- Decomposer organisms (springtails and mites). These microarthropods play a major role in the decomposition of leaf litter in forests. In the short-term, four annual fires reduced springtail and mite abundance in the soil. However, their abundance on sites burned twice in four years was no different than on unburned control sites.
- Breeding birds. Of 30 bird species monitored, only 6 were affected positively or negatively by fire over a five-year period. Densities of Eastern Wood Pewees and American Robins increased on burned sites. Populations of several species that nest on the forest floor and the low shrub layer decreased in abundance: Ovenbirds, Worm-eating Warblers, and Hooded Warblers.
- Todd Hutchinson, USDA Forest Service- Northern Research Station Ecologist
- Dan Yaussy, USDA Forest Service - Northern Research Station Supervisory Research Forester
- Robert Long, USDA Forest Service- Northern Research Station Research Plant Pathologist
- Joanne Rebbeck, USDAUS Forest Service- Northern Research Station Plant Physiologist
- Ralph Boerner, Ohio State University
- Mike Bowden, Ohio Division of Forestry
- Greg Wilhelm, Forestland Group, LLC
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