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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