The Nexus Between Silviculture The Nexus Between Silviculture and Fire in Sustaining and Fire in Sustaining

Biodiversity:Biodiversity:

R.J. Mitchell, J.K. Hiers, J. OR.J. Mitchell, J.K. Hiers, J. O’’BrienBrien

Take Home Messages

• Natural disturbances and the legacies they leave sustain native biodiversity by creating complexity in forests

• Fire and overstory disturbances have sustained the high levels of diversity of Florida’s forests

• Silviculture and fire need to be inextricably connected if biodiversity is to be sustained in managed landscapes

Variation is Inevitable and Variation is Inevitable and Important: Can we manage? Important: Can we manage?

Variation is Inevitable and Variation is Inevitable and Important: Can we manage?Important: Can we manage?

• Silviculture is connected to fire primarily by regulating the spatial and temporal patterns in fuels and secondarily by influencing microclimate.

• Single tree selection allows for fuels and thus fire to be continuous across space and time, while allowing for perpetual forest structure and regeneration.

• Time is a ecological consideration that needs to be incorporated into silviculture and prescribed burning

• For sustaining biodiversity frequent fire regimes, compliant to objectives, are THE critical disturbances.

Diversity of Coastal Plain Pine Diversity of Coastal Plain Pine WoodlandsWoodlands

• Highest outside of tropics– Species Richness

• Flora• Herps

– Species Rareness• Species of Concern

Disturbance and LegaciesDisturbance and Legacies

• Disturbance Types– Fire

– Among the highest fire return intervals globally– Fire has been intimately connected to climate and to human

activity since longleaf dominance after retreat of Wisconsin Glacier

Disturbance and LegaciesDisturbance and Legacies• Disturbance Types

– Overstory• Chronic

– Single trees– Multiple agents– Mid range of diameter

distribution• Acute

– Variable across space– Small remnant stands

more venerable– Multiaged stands

» Resistant» Resilient

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Overstory Harvesting Connections with Prescribed fire– Fuels

• Pine distribution across space and time

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Overstory Harvesting Connections with Rx fire– Fuels

• Patterns in fire sensitive species and their fuels

– Sandhills/intermediate– Flatwoods/ecotones

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Overstory Harvesting Connections with Prescribed fire– Fuels

• Disturbance to understory

– Wiregrass (other grasses

– Recovery

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Overstory Harvesting Connections with Prescribed fire– Microclimate

• wind

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Single Tree Selection Approaches– Fuel variation to be

gradual rather than abrupt (opposed to gaps).

– Controls Fire sensitive species

• Competition• Fire

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Single Tree Selection Approaches– Allows three stages of

regeneration• High overstory stocking

– No regeneration of pine, • Intermediate

– Establishment of pine but slow/no growth

– Turnover (death/recruitment)

– insurance• Low

– Release of advanced regeneration

1 yr post-planting

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10

3 yr post-planting

log(

seed

ling

biom

ass)

(g)

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Understory intactUnderstory removed

5 yr post-planting

Gap fraction (%)

35 45 55 65 75123456789

Silviculture and Sustaining Silviculture and Sustaining BiodiversityBiodiversity

• Single Tree Selection Approaches– Allows Frequent Fire

– Uninterrupted across space

Silviculture and Sustaining Biodiversity

• Single Tree Selection Approaches– Allows Frequent Fire

– Uninterrupted across time– 1-3 year return interval

» Target lower return interval (Skewed distribution)

» Expect the unexpected (there will always be a future barrier to burning)

– Frequency trumps seasonal

» Burn by objectives results in multiple season burning

– Fire is inherently variable» Never step in the

same river twice (some Greek guy)

From Kirkman et al. (2004)

Take Home MessagesTake Home Messages

•• Natural Disturbances and the legacies Natural Disturbances and the legacies they leave sustain native biodiversitythey leave sustain native biodiversity

•• Overstory Disturbances and Fire have Overstory Disturbances and Fire have sustained the high levels of Diversity of the sustained the high levels of Diversity of the Coastal PlainCoastal Plain

•• Silviculture and Fire need to be connected Silviculture and Fire need to be connected if biodiversity is to be sustained in if biodiversity is to be sustained in managed landscapesmanaged landscapes

Take Home MessagesTake Home Messages• Silviculture is connected to fire

primarily by regulating the spatial and temporal patterns in fuels and secondarily by influencing microclimate.

• Single tree selection allows for fuels and thus fire to be continuous across space and time but allow for regeneration.

Take Home MessagesTake Home Messages• Linking SilvicultureSilviculture and FireFire is vital

to the restoration of fire suppressed old-growth, a critical component of Florida’s biodiversity.

• For sustaining biodiversity frequency trumps season.

• Sustaining fire regime is paramount.

Herbert StoddardHerbert Stoddard Aldo LeopoldAldo LeopoldCourtesy of aldoleopold.comCourtesy of Tall Timbers Research Station