Fire Effects on Wildlife

18 September 2006

Direct Effects• Few studies, marked re-capture approach ideal

– Body size and mobility, i.e. burrowing, influence direct mortality

• Life cycle stages are impacted differently• Depends on fire regime

– Frequency, intensity, extent, and season– Extent-small area, greater ability to repopulate

• Must look at populations rather than the individual

Indirect Effects

• Fire severity and resulting successional patterns dictate wildlife habitats and the effect on wildlife

• Importance of fire regime

• (+/-) Consumer response is species dependent, must consider mechanisms at work

TTYP: What are the indirect effects of fire on wildlife habitat?

Mechanisms of post-fire population change

• Availability of food resources and changes in cover regulate population response

• Sorting out these mechanisms is a research challenge

Understanding the Consumer Response to Food Resources

• Fire alters production, species availability, and food quality

• Migration and immigration • Short term effects

– Arizona grassland example• Green vegetation declines while seed availability

increase• Differential small mammal response

Understanding the Consumer Response to Food Resources

• Alternatively, shift in food sources– Ex. Australian eucalypt forest

• Bettongs exploit fire adapted fungus

– Ex. Primates in Borneo shifting food sources• Flowers and fruits unavailable→ foliar/herbaceous vegetation

and caterpillars/larvae of wood boring insects

Plant Succession and Animal Response

• Ex. Browsers in N.A. boreal forest– Caribou eat lichen, slow growth, easily burned

• Caribou in late successional – Moose eat woody resprouts (birch, aspen)

• Moose in early successional

Consumer Response and Food Quality

• Pulse of higher quality new growth– Increase in protein (nitrogen content) in new

growth– New tender shoots with greater digestibility– Increase in population growth rates?

• Ex. Domestic grazers

Changes in Cover• Burned vegetation results in drastic change in both

physical and thermal cover– Ex. Cryptic insects, evolutionary response

• Physical protection from predation– Structure provides protective habitat

• Structure effects visibility

• Clearing of structure provides visibility – Ex. Red-cockaded

woodpecker and loblolly pine understory maintenance

Balancing Protective Cover and Food Availability

• Tallgrass prairie example• Bird response

• Increase in seed/insect availability• Decrease in cover, nesting habitat, and predator

protection

• Small mammal response • Some small rodents, i.e. prairie vole, are small

navigate litter layer and find seed• Other larger rodents, prefer burned area with

easier seed access

Structural Diversity• Interspersion of food resources and

cover

• Positive or negative effects depending on the severity and extent and the wildlife considered

• Reduced habitat heterogeneity by large extent, severe fires

Example: Structural Diversity• Habitat diversity

and complexity, each supports a specific faunal community– Ex. Snags

important for birds, mammals, reptiles, amphibians, and invertebrates

Structural Diversity and Patchiness• Refugia for migration

and nucleus for recovery

• Mature cover and adjacent high quality growth

• Mosaics of food resources and cover create structural diversity– Ecotones - boundaries

Landscape Diversity Example: Mississippi Alluvial Valley

• Landscape complexity through burning– Rice and waterfowl management– Mississippi rice fields, interspersion of open

water and emergent vegetation (Kross 2006)