Fire Effects on Wildlife (Harper)

I. General Context and Goals of Prescribed Fire

• Primary Use: Fire is increasingly prescribed for ecosystem restoration (e.g., oak woodlands and savannas) and managing wildlife habitat in the Central Hardwoods and Appalachian regions.

• Benefits: Reasons for fire use include ecosystem restoration, oak regeneration, fuels reduction, and wildlife habitat management.

• Objectives: A major limitation in management is the failure to articulate precise management objectives. No single fire prescription is optimal for all wildlife species.

• Overarching View: A lack of fire in these regions is viewed as a major limiting factor for increasing landscape heterogeneity and biological diversity, and for increasing the abundance of many wildlife species that benefit from burning.

II. Fire Effects: Direct vs. Indirect

• Indirect Effects (Habitat Change) are Primary: Fire primarily affects wildlife indirectly by impacting cover and food resources. These changes can influence presence, density, survival, movements, and home range size.

• Direct Effects (Mortality) are Rare: Documented direct effects (mortality) on wildlife are rare from prescribed fire in hardwood systems.

• Key Influential Factors: Indirect effects are greatly influenced by light availability, fire frequency, and fire intensity.

III. Fire Factors and Silvicultural Integration

A. Light and Canopy Management (Crucial in Hardwoods)

• Challenge in Closed Canopies: Burning in closed-canopy forests provides little benefit for most wildlife because insufficient sunlight penetrates to elicit an understory response.

• Need for Silviculture: Canopy reduction via silvicultural treatments (e.g., thinnings, regeneration harvests, herbicide application) allows managers to use fire more effectively.

• Light Threshold: At least 20% full sunlight is needed on the forest floor to stimulate extensive groundcover response.

• Synergy: Coupling low-intensity fire with canopy disturbance can result in eight times as much deer forage compared to unthinned and unburned areas.

B. Intensity and Tree Effects

• Intensity Limitation: Fire intensity must be kept low in hardwoods to limit damage to many overstory tree species.

• Benefits of Damage: Wounding or killing trees with fire benefits many wildlife species by increasing sunlight, stimulating understory growth, and leading to snag and subsequent cavity creation.

• Dead Trees/Snags: Injured and dead trees are used by many species, including woodpeckers, secondary cavity users (birds, bats, squirrels), and threatened species like the Indiana bat and northern long-eared bat.

C. Frequency

• General Recommendation: A fire-return interval of 2 years to 7 years benefits a wide variety of wildlife species by diversifying understory structure, increasing forage, browse, and soft mast, and creating snags and cavities.

• Early Successional/Grasslands: Maintaining early successional communities or grasslands often requires more frequent fire (e.g., 1 yr to 3 yr interval).

D. Season (Timing) of Burning

• Historical Prevalence: Historically, dormant-season fire was most common, and it is still when most prescribed fire is implemented in hardwood systems.

• Growing Season Difficulty: Burning from May through mid-August is usually difficult in hardwood stands due to shade and high fuel moisture, limiting opportunities.

• Controlling Woody Composition: Late growing-season burning (August through October) increases the burning window and may offer better control over woody composition than dormant- or early growing-season fire.

• Risk Periods (Vulnerability):

  • Early Growing Season (April): Poses increased risk for herpetofauna recently emerged from hibernation.

  • May to June: Poses increased risk for forest songbirds that nest in the understory.

  • Fawning/Brooding Seasons (e.g., May–July): Concerns exist for white-tailed deer and wild turkey.

• Population Effects: Negative population-level effects are generally unlikely unless the burned area is relatively large and early growing-season fire is used continually.

E. Pattern and Size

• Topography: Topography is diverse and affects burn frequency and intensity; drier, south- and west-facing slopes burn more frequently.

• Salamander Mitigation: Concern over woodland salamanders is alleviated when fire is concentrated on drier, ecologically appropriate aspects and slope gradients where salamanders are less common, rather than forced into moist, mesic environments.

• Landscape Heterogeneity: Applying fire on positions best suited for burning is an effective approach to increase regional landscape heterogeneity and biological diversity.

• Burn Size: Larger burns (e.g., >100 ha) are often necessary to affect the landscape and achieve ecosystem goals like perpetuating oak woodland or savanna, especially given manpower and funding constraints.

IV. Species and Guild-Specific Recommendations (Selected)