Wildlife Management- Dead Wood Management

Dead Wood Management

• Trees (snags) continually decay

• Different age trees and snags provide habitat elements for different species

• Continuous supply of “new” snags must be available

• Up to 40% of bird species in forests are cavity nesters

3 Broad Types of Dead Wood “Users”

• Primary Cavity Users

• Secondary Cavity Users

• Log Users

Primary Cavity Users

Excavators, create cavities

• Almost always excavate fungi softened areas of trees

• Generally excavate in ≥ 10cm/4in dbh

• Generally excavate new nest cavity each year

• May excavate cavities for roost/rest

• Most feed on woodboring insect larvae

• Biggest/most important group in MI is woodpeckers

Secondary Cavity Users

Cavities from natural decay or primary excavators

• Opportunistic Cavity Users- benefit from cavities

  • Ex. Black bears, raccoons, peromyscus, invertebrates, some bat spp

• Obligate Cavity Users- require cavities as a resource for something (reproduction, thermal cover through winter, etc.)

  • Ex. Wood duck, tufted titmouse, flying squirrels

Log Users

Cavities, space underneath & between bark and wood in logs provide cover, nesting, foraging, display sites

• Interior of hollow logs and area under them provide stable, moist microclimate (important for herps)

• Importance of Log Size

  • Area/Volume available (4in min)

  • Persistence

  • Size of cavities/spaces beneath

Number of Cavities Used

• Number used by individual varies widely by spp

  • Most bird species use new cavity for each clutch/brood

  • Mammals often use multiple cavities in a breeding season or year

  • Cavity may be used by multiple individuals at diff times

Other Factors Influencing Value of Logs to Wildlife

• Piece Size and Decay State

  • Wildlife species prefer different sizes & decay states

  • Longer pieces provide connectivity

• Successional Stage in Which Log Occurs

  • More valuable when scarce

  • Suppression mortality → most dead trees 50% (but similar length) dbh of dominant trees

Dead Wood Recruitment

Driven by:

• Suppression Mortality (Competition)

  • Increases after stand initiation, then declines

• Disturbance

  • Big pulse, drop off then slight recovery as trees age

Species of Tree Influences Density of Snags and Rate of Decay

• Conifer stands → more snags than hardwood

• Hardwoods (generally) decay slower than conifers

  • Aspen may live 125 years, stand as a snag for 35, exist as log for 35

  • Oak may live for 300 years, stand as a snag for 75, exist as log for 75

• Fall rates vary- 10 year fall rates for some species of snag >50%

Management of Cavities and Dead Wood

Two approaches:

• Maintain Conditions Within Historical Range of Variability (HRV)

  • Density, size, decay conditions, etc. of snags, logs, etc. maintained at “normal” levels

  • Conduct at larger scale than stand level- at least forest compartment level

• Establish/Estimate functional relationships between animals and dead wood → manage for levels that meet wildlife needs

Steps in Management Process

(Don’t need to memorize)

Live Tree Cavity Management

• Managing for primary cavity users generally doesn’t provide enough cavities for secondary cavity users

  • Some larger than primary users

  • More species → often occur at higher density

  • Nest boxes offer short term (expensive) solution

• Managing live tree cavity abundance is more challenging than dead wood

  • Harder to inventory

  • Rate of gain/loss unpredictable

  • Generally larger trees with signs of injury (limb loss) more likely to have cavities

• Arrangement/Distribution of dead wood/cavity trees should also be considered

  • May not mesh with most efficient harvest methods

• Monitoring should be conducted just like in any other aspect of management