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Fire Ecology of the Southern Great Plains
Jim AnsleyCharles Taylor
Rangeland Ecology and Management
Texas A&M University
Dave Engle
Natural Resource Ecology and Management
Iowa State University
Sam FuhlendorfJohn Weir
Terry Bidwell
Natural Resource Ecology and Management
Oklahoma State University
http://gisdata.usgs.net/website/MRLC/viewer.php
Southern Great Plains
Southern Great PlainsOutline
1.Fire Sensitive Trees – Ashe Juniper and Eastern Redcedar
2.Resprouting Shrubs and Trees – Shinnery oak, Sand sagebrush, Plum, Sumac, Mesquite, Live Oak, Post Oak
3.Grasslands- Tall-, Mixed- & Short-grass Prairies
4.Controlling factors of fire effects
http://gisdata.usgs.net/website/MRLC/viewer.php
Fire Sensitive Trees
1900 20201950 2000Year
WoodlandGrassland/Savanna
Woody P
lant Cover (%
)
0
40
80
Increasers
Decreasers
Gra
ssla
ndC
ondi
tion
Gra
ssla
ndC
ondi
tion
Gra
ssla
ndC
ondi
tion
Fire
Ani
mal
Uni
ts/S
ectio
n
0
20
40
60
80
100
120
140
160
Historical Stocking Rate DeclineSonora Experiment Station
JuniperSize and Density
SeedDispersal
SeedProduction
Mortality
Mid-Grass
Short-Grass
Grazing
HerbaceousBiomass
FireIntensity
FireFrequency
Landscape Dynamics(Fuhlendorf et al. 1996)
Patch DynamicsWeatherPatterns
Fuhlendorf et al. 1996Fuhlendorf et al. in review
Year0 20 40 60 80 100 120 140H
erba
ceou
s B
iom
ass
(per
cent
of m
axim
um)
0
10
20
30
40
50
60
70
80
90
100
Larg
e Tr
ees/
ha (>
6m d
ia.)
0
10
20
30
40
50
60
Ungrazed and No Fire
Remaining Herb. BiomassTree Density
Potential Herb. Biomass
Ungrazed with a 10 year fire frequency
Remaining Herbaceous BiomassTree Density
Potential Herbaceous Biomass
Year0 20 40 60 80 100 120 140H
erba
ceou
s B
iom
ass
(per
cent
of m
axim
um)
0
10
20
30
40
50
60
70
80
90
100
Larg
e Tr
ees/
ha (>
6m d
ia.)
0
10
20
30
40
50
60
0Year 10 Year 20 Year 30 Year 40
Year of first fire
No Grazing with a 10 year fire frequencyBiomass Remaining after 150 years
XX
X
XBio
mas
s R
emai
ning
(%)
100
50
Timing of the first fire is critical
75
25
Fire-sensitive woody plants Summary
• Ashe Juniper on Low Prod. site (Sonora TX)– Without fire, JUAS dominance in about 60 yr– Without grazing = 15 year fire return interval– Moderate grazing = 5 year fire return interval – Heavy grazing = sell the farm? or extreme fire
• Eastern Redcedar -High Prod. site (Stillwater OK)
– Without fire, JUVI dominance in about 45 yr– Without grazing = 10 year fire return interval– Moderate grazing = 10 year fire return interval – Heavy grazing = 2-3 year fire return interval
• Ashe Juniper on Low Prod. site (Sonora TX)– Without fire, JUAS dominance in about 60 yr– Without grazing = 15 year fire return interval– Moderate grazing = 5 year fire return interval – Heavy grazing = sell the farm? or extreme fire
• Eastern Redcedar -High Prod. site (Stillwater OK)
– Without fire, JUVI dominance in about 45 yr– Without grazing = 10 year fire return interval– Moderate grazing = 10 year fire return interval – Heavy grazing = 2-3 year fire return interval
http://gisdata.usgs.net/website/MRLC/viewer.php
Resprouting shrubs and trees
Oak savanna annual burn
Photo by John Weir
Briggs et al. 2005
Fire Frequency on Tallgrass PrairieRhus glabra, Cornus durmmundii, Prunus americana
Cross Timbers of Texas, Oklahoma & KansasWithout fire
Cross Timbers of Texas, Oklahoma & KansasWithout fire
4-yr fire return interval4-yr fire return interval
2-yr fire return interval2-yr fire return interval 1-yr fire return interval1-yr fire return interval
3-yr fire return interval3-yr fire return interval
Photo by John Weir
2 year burn frequency
No burn- control
5 year burn frequency
Photo by John Weir
Photos by Jim Ansley
Regrowth 10 years after fire
•Temporary increase in herbaceous dominance
•Minimal negative effect (if any) on density
•Management with fire requires high frequency (e.g. 2-5 year return interval).
•Temporary increase in herbaceous dominance
•Minimal negative effect (if any) on density
•Management with fire requires high frequency (e.g. 2-5 year return interval).
Resprouting shrubs and treesSummary
Resprouting shrubs and treesSummary
http://gisdata.usgs.net/website/MRLC/viewer.php
Grasslands
Years since focal disturbance0 1 2 3 4 5A
bove
grou
nd b
iom
ass
(g/0
.1m
2)
0
20
40
60
80 Spring firesSummer and Fall fires
R2=0.72
End
of y
ear s
tand
ing
crop
(g 0
.10
m-2
)Bison Unit of the Tallgrass Prairie Preserve
Blair 1997
Transient Maxima Hypothesis
Ansley et al. 2006
Season has minimal longterm effects in grasslands
• Howe 1994• Engle et al. 2000• Engle and Bidwell 2001• Brockway et al. 2002• Towne and Kemp 2003• Fuhlendorf and Engle 2004• Fuhlendorf et al. 2006• Ansley et al. 2006
Pre-fire ConditionPre-fire Condition
1 Year Post-fire1 Year Post-fire
1 Month Post-fire1 Month Post-fire
Photos by Jim Ansley
Grasslands Summary
1. Reduce woody plant encroachment2. Alter grazing distribution to provide
heterogeneity3. Short term, stochastic effects on
composition– Interaction with weather– Frequency and season have less effect than
time since fire.
Factors that influence fire effects
1. Everything that influences fire intensity– Fuel load, humidity, temperature, Fuel
moisture etc..– Grazing– Season
Photos by Jim Ansley
0
20
40
60
80
100
0 100 200 300 400 500
Mean fuel load (g m-2)
Sco
rch
prop
ortio
n (%
) Fuel Moisture <5%r2= 0.154P = 0.14
Fuel Moisture > 20%r2= 0.876P < 0.01
Effect of Summer Fire
Twidwell, Fuhlendorf & Engle in review
Factors that influence fire effects
1. Everything that influences fire intensity1. Fuel load, humidity, temperature, Fuel
moisture etc..2. Grazing3. Season
2. Fire Frequency / Time Since Fire
Summary and Synthesis
1.Focus on woody-herbaceous interaction2.For Fire Sensitive species
• Fire interval – 5-15 yr• Grazing and initial conditions are critical
3.For Re-sprouting Species• Fire interval – 2-5 yrs
4.For Grasslands• Time since fire
5.Critical issues• Fire intensity• Time since fire
Rx Fire Associations
• Cooperation among landowners
• Rural fire departments• Go beyond ownership
boundaries• Can limit liability• Create a new land ethic• Provide training