fire ecology of sagebrush steppe - university of idaho · sagebrush steppe vegetation vegetation...
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For 426: Fire Ecology of Sagebrush Steppe
Ecology of Arid and
Semi-arid lands
Source: www.sagebrushsea.org
Sand sagebrush
(Artemisia filifolia)
Silver sagebrush
(Artemisia cana)
NOTE: Silver sagebrush is also found on
dry slopes in southeastern Alaska.
Source: USGS
Black sagebrush
Mountain big sagebrush
Wyoming and basin
big sagebrush
Threetip sagebrush
Wyoming big sagebrush/bluebunch wheatgrass steppe near Boise, Idaho
Wyoming big sagebrush/bluebunch wheatgrass steppe near Arco, Idaho
Big sagebrush steppe and southern shrublands near Lone Pine, California
Stiff sagebrush/Sandberg bluegrass steppe, near Jordan Valley, Oregon
Wyoming big sagebrush steppe-Shortgrass prairie ecotone near Casper, Wyo
Big sagebrush subspecies
Wyoming big sagebrush (A. t. ssp. wyomingensis)
Basin big sagebrush (A. t. ssp. tridentata)
Mountain big sagebrush (A. tridentata ssp. vaseyana)
Foothill big sagebrush (A. tridentata ssp. xericensis)
“Spiked big sagebrush” (A. tridentata ssp. spiciformis)
“Mountain big sagebrush” (A. tridentata ssp. pauciflora)
(Tart and Winward 1996, 2001)
Other common sagebrush vegetation types
Low sagebrush (Artemisia arbuscula)
Threetip sagebrush (Artemisia tripartita)
Black sagebrush (Artemisia nova)
Stiff sagebrush (Artemisia rigida)
Note: Several subspecies have been described
for these Artemisia species.
Range of fire-free-intervals in pristine
sagebrush steppe vegetation
Vegetation type FFI (yrs)
Mtn. Big sagebrush-mtn. Snowberry-fescue
Conifer contact zone (7) 15-25 (70)
Lower valley, mtn. Foothill 15-40
Wyo. big sagebrush/bluebunch wheatgrass 30-60
Wyo. big sagebrush/Sandberg bluegrass 50->100
Stiff sagebrush/Sandberg bluegrass >100
FFI varies greatly due to factors such as ignition sources, topography, landscape
context and fuel continuity.
Function of fire in sagebrush steppe vegetation
• Maintenance of sagebrush as a seral vegetation type(ponderosa pine, Douglas-fir, western juniper, pinyon-juniper)
• Maintenance of seral vegetation types within sagebrush steppe (grasslands)
• Divert the primary productivity of the site from woody species to herbaceous species
• Increase the forb component of the community
• Establish recruitment conditions for a new cohort of a species (i.e. sagebrush, rabbitbrush species, bitterbrush, early seral grasses)
• Nutrient cycling
Bluebunch wheatgrass (Pseudoroegneria spicata)
Moderate to high tolerance to
fire.
Moderate to low seedling
recruitment potential.
First-order fire effects: Fire severity
(Balatsos 1994)
Increasing fire severity
resulted in increased
fire damage.
Fire damage was limited
to tissues in the upper
20 mm of soil.
Bluebunch wheatgrass
Photo by J. Kingery
First-order fire effects: Plant phenology
(Balatsos 1994)
Bluebunch wheatgrass
Heat resistance varied
with phenological stage:
[summer > fall > spring].
Heat resistance varied
within a phenological
stage due to current
climatological conditions.
Effects of increasing soil moisture on heat flow
and plant heat resistance:
- Increases the heat capacity of soil
- Increases the heat conductivity of soil
- Increases the heat movement in soil through
vapor flux
- Increases plant activity
Great Basin wildrye (Leymus cinereus)
One of the most fire tolerant
grasses associated with the
sagebrush steppe.
Low seedling recruitment
potential.
Suspected of increased
recruitment post-burn.
Bottlebrush squirrel-tail (Elymus elymoides)
Very fire tolerant species.
High post-fire seedling
recruitment potential.
Relatively short-lived
plant.
Needlegrasses (Acnatherum, Hesperostipa spp.)
Needle-and-thread
Photo by K. Sedivec & W. Barker
Moderate to high mortality
due to fire.
Moderate to high seedling
recruitment potential except
for Thurber needlegrass.
Often fill gaps created by fire
until other species respond.
Photo by C. Johnson
Sandberg bluegrass (Poa secunda)
Moderate to high mortality rates.
High seedling recruitment
potential.
Persists in community under
high sagebrush coverage and
density.
Lupine species (Lupinus spp.)
High fire tolerance
Increased biomass production
post-fire
Often increased density post-fire
High seed production post-fire
Nitrogen fixer
Silky lupine (L. sericeus)
Perennial forbs
Applegate’s paintbrush
(Castilleja applegatei) Most species respond
favorably to fire, however,
many wild buckwheat
species are fire sensitive.
The paintbrush species are
often parasitic.
Many sagebrush steppe
perennial forbs decline
during juniper woodland
encroachment. Seedling
recruitment following fire is
extremely slow.Mat wild-buckwheat
(Eriogonum caespitosum)
Antelope bitterbrush (Purshia tridentata)
Resprouting antelope bitterbrush (Purshia tridentata)
Antelope bitterbrush (Purshia tridentata) seedlings from rodent cache
Deer mouse, David Cappaert,
www.forestryimages.org
Changes in the environment that have significantly altered
the historical role of fire in sagebrush steppe vegetation
• Introduction of annual grasses (Cheatgrass, medusahead)
Photo by Dale Wade, forestryimages.org
The introduction of
annual grasses has
permanently altered
the former role of fire
in sagebrush steppe.
Changes in the environment that have significantly altered
the historical role of fire in sagebrush steppe vegetation
• Introduction of annual grasses (Cheatgrass, medusahead)
• Changes in levels of herbivory
Pronghorn antelope, William M. Ciesla
forestryimages.org
Changes in the environment that have significantly altered
the historical role of fire in sagebrush steppe vegetation
• Introduction of annual grasses (Cheatgrass, medusahead)
• Changes in levels of herbivory
• Climatic change
World Health Organization (www.who.int/globalchange/climate/summary/en/)
Variations in Earth’s average surface temperature over the past 20,000 years
The number of fires by size class in the study region to include the
Snake River Plain and Northern Basin and Range Ecoregions.
Size-Class
3 years of data
Source: Kuchy 2008
Decade
1st and 2nd half
of data set
Wyoming big sagebrush steppe, southern Idaho
First year post-burn
Fifth year post-burn
Bottlebrush
squirrel-tail
Great Basin
wildrye
Fifteenth year post-burn
Unburned sagebrush island
Green rabbitbrush (Chrysothamnus viscidiflorus)
Burn pattern on landscape
1st year post-burn
3rd year post-burn
Mountain big sagebrush/Idaho fescue steppe, eastern Idaho
Douglas-fir, mountain big sagebrush, eastern Idaho
1st year post-burn
3rd year post-burn
7th year post-burn
Post-burn establishment and recovery of the
sagebrush stand depends upon:
- The taxa of sagebrush involved
- Continuity of the burned area, related to
seed availability
- Post-burn environmental conditions
Mountain big sagebrush/
Idaho fescue ht.
Beaverhead Range, Idaho
7th year post-burn
Mountain big sagebrush/
Idaho fescue ht.
Owyhee Mountains, Idaho
8th year post-burn
The use of prescribed fire is limited by
the following considerations:
• Disagreement on the optimal sagebrush cover
for different multiple-uses
• Disagreement on the appropriate size of sagebrush
burns
• Lack of fine fuels
• Low levels of perennial herbs present in the pre-fire
community
• Short-term effects on some high profile species
(bitterbrush, sage grouse)
• Potential for biological invasions
Prescribed fire in Wyoming big sagebrush/bluebunch wheatgrass
Source:
http://pubs.usgs.gov/of/2008/1214
/pdf/ofr20081214.pdf
Murphy Complex Fire
July 16-Aug. 3, 2007
Total area: 653,100 acres
(1020 square miles)
Ignition source: Lightning
This was actually 3 fires:
Rowland Fire
Elk Mtn. Fire
Scotts Creek Fire
Arrows indicate approximate
fire ignition points.
Source:
http://pubs.usgs.gov/of/2008/1214
/pdf/ofr20081214.pdf
July 18
July 19
July 20
July 21
Burn progression mapJuly 16- August 3, 2007
July 24
Source:
http://pubs.usgs.gov/of/2008/1214
/pdf/ofr20081214.pdf
The highest severity fire
(orange) was associated with
areas that had the highest
coverage of big sagebrush.
The lower severity fire (yellow)
was associated with areas that
had previously burned and were
dominated by herbaceous species.
Cheatgrass was common in the
northern quarter.
Native species and seeded
introduced grasses were common
in the southern three quarters.
Burn severity map based
on remotely sensed data
Wyoming big sagebrush steppe- Pre-burn
Murphy Complex FirePhoto taken August 28, 2007, 3 weeks post-burn
Source: http://pubs.usgs.gov/of/2008/1214/pdf/ofr20081214.pdf
Murphy Complex Fire- Burned/unburned mosaicPhoto taken August 28, 2007
Murphy Complex Fire- Unburned (grazed), Burned (ungrazed)Photo taken August 28, 2007
Source: http://pubs.usgs.gov/of/2008/1214/pdf/ofr20081214.pdf
BehavePlus output: 12% dead fuel moisture
Source: http://pubs.usgs.gov/of/2008/1214/pdf/ofr20081214.pdf
Threshold of fire behavior with
decreasing fine fuel load.
BehavePlus output: 10% dead fuel moisture
Source: http://pubs.usgs.gov/of/2008/1214/pdf/ofr20081214.pdf
At lower dead fuel moistures and higher
wind speeds, fire behavior was increasingly
determined by sagebrush overstory and
less by fine fuel loading.
Murphy Fire- 2 years post-burn, June 2009
Idaho fescue & bluebunch wheatgrass Idaho fescue & bluebunch wheatgrass
Bottlebrush squirrel-tailCrested wheatgrass
Western juniper woodland-mountain big sagebrush steppe
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