Wade A. Wall ERDC-CERL Janet B. Gray Fort Bragg Endangered Species Branch Matthew G. Hohmann...

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