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Wade A. Wall ERDC-CERLJanet B. Gray Fort Bragg Endangered Species Branch Matthew G. Hohmann ERDC-CERL
NMFWA Annual Meeting14 March 2012Atlanta, GA
Courtesy Beth Evans
Historical (1500 A.D) estimates: 1-3 years
Fire suppression, buildup of fuel loads
Prescribed fire ~ 20 years (red cockaded woodpecker
Benefits: wildfire reduction, improved habitat, species management
Reduced competition
Increased survivorship
Increased productivity
Increased flowering
Increased germination
Reduced seed predation
50% of rare plant species in FL exhibited positive responses (Slapcinsky et al. 2010)• 9 of 18 no
response Climatic
uniqueness of Florida?• Fire history
centerforplantconservation.org
Determine effects of fire on study species• Identify “optimal”
fire return interval• Model population
dynamics Interpret results in
light of the climatic history of the Sandhills region.
Astragalus michauxii• Sandhills milkvetch• “Pea swales”• xeric sandhill scrub• Fort Bragg, Gordon
Pyxidanthera brevifolia• Sandhills pyxie moss• xeric sandhill scrub• Fort Bragg, Dix
Both species SAR, FSC
A. michauxii• Surveyed 87 pops.• Tagged all identified
individuals 2007• Measured
survivorship, growth, reproduction 2007-2010 stem height Counted viable seeds
in 400 fruits
P. brevifolia• Selected 24 pops.
(out of 277 total pops.)
• Tagged 1000 individuals
• Measured survivorship, growth, reproduction 2008-2010 Major, minor axis Estimated percent
coverage Fruit production
Generalized linear models to analyze survivorship, growth, and reproduction.
Matrix modeling to project population growth through time
N
25
50
=
N
(7.5+7.5) = 15
(5+40) = 45
Short-term effect of fire on mortality: A. michauxii
Short-term effect of fire on mortality: P. brevifolia
Fire reduces fruit production in A. michauxii
Fire reduces fruit production in P. brevifolia
Regeneration following fire size is dependent in A. michauxii
Regeneration following fire is size dependent in P. brevifolia
Projected population growth rate lower under annual burning
Vegetation differences during last ice age• Spruce forest• Exposed soil, reduced
biomass Lower competition Adapted to colder
environment? Fire replaced climate
as limiting factor• Necessary for
competition removal• A. michauxii and P.
brevifolia may not be as adapted to fire as other species. rst.gsfc.nasa.gov
Short term consequences of fire• Increases mortality• Decreases seed
production• No increase in seedling
recruitment• Slow regrowth?
Long term consequences of fire• Reduction of
competition, woody growth
• Necessary for long term population persistence “Caught between a rock
and a hard place” Current fire return interval
adequate
Distribution of Astragalus michauxii and Pyxidanthera brevifolia across Fort Bragg
Military Reservation
Rare taxa may have different responses to fire• Different histories
Lack of information on many plant species in fire-dependent ecosystems
412 plant SAR• ~318 dependent on
or influenced by fire• Few have been
studied
Fort Bragg Military InstallationFort Bragg Endangered Species
BranchERDC-CERLNorth Carolina State University