This transect was thinned with mechanical mastication and was not burned by the wildfire (transect 5B).
Mechanically masticated and burned transect displaying domination by annual grasses (transect 5C).
A hand-cut thinned and pile-burned oak woodland just outside of the Squires fire (transect 6B).
The Buncom Bowl fuel reduction project in the Applegate Valley of Southwest Oregon was burned by the Squires fire (2002) before project completion. Prior plant community mapping, permanent transects, and established photo-points together with post-fire surveys provided an opportunity to view fire interaction with treated and untreated woodland and chaparral stands. Post-fire site and vegetative conditions were compared among handcut-piled-and-burned (HPB), handcut-and-piled only (HP), mechanically masticated (SB), and untreated sites. How is post-fire vegetation survival and structure different between treatments? How does wildfire interact with fuel manipulations to affect soil and seedbanks and determine future vegetation?
Paul Hosten and Eric Pfaff
Ashland Resource Area, Medford District Bureau of Land Management,
Medford, OR
Fuel Reduction Treatments. The primary objective for the Buncom Bown fuel reduction project was to reduce fuel, to provide a strategic low-fuel buffer between homes and wildland, and to restore historic vegetation composition and structure.
Stands were either handcut-piled-and-burned (HPB); handcut-and-piled only (HP); mechanically masticated with a SlashBuster (SB); or untreated. In the handcut-piled-and-burned (HPB) method, shrubs and hardwoods were cut to a 20 – 30 foot spacing between stems. The cut material was piled prior to winter or spring burning. While the piles in the photo at right were burned prior to the Squires fire, piles in handcut-and-piled only (HP) areas remained intact at the time of the wildfire. (Learn more about fuels-reduction methods.)
Comparison of Wildfire Effects on Treated and Untreated Sites. Plant community mapping, permanent transect surveys, and photo-points that had been established prior to the fire were compared with post-fire surveys. Burned sites within the Squires fire perimeter were compared that (1) had not been thinned prior to the wildfire; (2) had been handcut, piled, and burned (HPB) prior to the wildfire; and (3) had been handcut and piled, but piles not burned (HP) prior to the wildfire. Seeding with sterile wheatgrass provided an opportunity to compare seeded and unseeded treatments within the burned area.
Above: Vegetation that has been handcut and piled, waiting for winter or spring burning.
Above: Pre-fire stand structure included large Oregon white oaks surrounded by a younger cohort of oak saplings and manzanita estimated to be 120 years old.
The images below provide a visual tour of patterns in interaction between the Squires wildfire, fuels reduction treatments completed prior to the wildfire, and post-wildfire seeding treatments. Each arrow originates at the location of a transect established as part of monitoring for the Buncom Bowl fuel reduction project. Click on the transect name to see a photo of wildfire effects at that location.
These transects are outside of the fire perimeter, to the northwest
Dense brush in an untreated control transect outside of the perimeter of the fire (transect 5A).
Unthinned, unseeded control burned by the Squires fire (transect 3A).
Thinned, hand-cut, piled, piles burned, then burned by the Squires Fire (transect 3B).
This transect was thinned prior to the wildfire, then seeded with sterile wheatgrass after the wildfire to prevent erosion and yellow starthistle invasion (transect 2B).
Outside the Wildfire Perimeter
These photos show the effects of fuels reduction thinning treatments without the effects of wildfire.
Transect 5A: Untreated and unburned (back to map)
Transect 6B: Hand-cut and pile-burned (back to map)
Transect 5B: Mechanical mastication (back to map)
Fire-dependent Yerba Santa was present in the post-fire photo plot (foreground in photo at left), but not in the pre-fire plot (far left).
3R: Post-fire
Untreated Transect 3R post-wildfire (below) shows widespread flowering response of blue dicks (Dichelostemma congestum). Seeds that were deeply situated in the soil survived, while shallowly
3R: Pre-fire
3R: Pre-fire
3R: Post-fire
Transect 3R: Untreated (no fuels redution), Burned by wildfire (back to map)
buried seeds may have been burned.
Inside the Wildfire
These photos show the interaction of the Squires wildfire with different kinds of fuels reduction treatments.
Transect 3B: Hand-cut and pile-burned (back to map)
Transect 5C: Mechanically masticated (back to map)
Transect 2A: Thinned, unseeded (back to map)
This transect (2A) was also burned by the Squires fire, but was thinned prior to fire. 2A was not seeded with sterile wheat grass, and so provides a comparison for the burnt and seeded transect (2B).
Transect 3A: Unthinned, unseeded (back to map)
Transect 2B: Thinned, seeded with sterile wheatgrass (back to map)
Some areas were seeded with sterile wheatgrass after the wildfire. Seeding is used in an effort to reduce erosion and invasion by exotic species. Seeded and unseeded sites were compared within the burn perimeter.
Blue shading - Thinned, piled, and piles burned prior to wildfire
Peach shading - Thinned, piled, but piles NOT burned prior to wildfire
Blue points - Transect endpoints
Red line - Fire perimeter
Black dashed line - Live tree survey area
Green shading - Live trees
Response of Canopy Species
In the spring following the Squires fire, few oak stems and canopies remained alive within the fire perimeter in either untreated stands or in any of the stand treatment types (handcut-piled-and-burned (HPB); handcut-and-piled only (HP); and mechanically masticated (SB)). However, vigorous sprouting from stem bases and roots was evident throughout the study area. Trees outside of the treated area that did survive were associated with gullies and ridge tops. Surviving individual oaks in (HPB) treated areas appeared scorched on the underside of branches, indicating that combustion of the herbaceous understory and the duff layer produced enough heat to damage trees. Many oak trees in the HPB treated area appeared girdled at the base consequent to duff consumption by fire.
Fuel-reduction prescriptions called for thinning manzanita chaparral to a specified space between stems. Many of the remaining manzanita died from environmental stress following thinning prior to the fire. The rest were killed by the fire regardless of treatment, with many completely consumed by fire at the base.
Right: A few unburned patches of chaparral remained (background) in the adjacent watershed. These areas were located next to grass meadows.
(A) During treatment
Above: Although they were few, patches of oaks with live stems and canopies were found throughout the analysis area (particularly along streams and riverbeds), regardless of treatment.
(B) After wildfire
(C) After wildfire
Photo (A) shows hand-cut piles, and a glimpse of pretreatment structure and fuel-loading. These piles were burned prior to the wildfire. (B) shows that herbaceous understory and duff left after the fuel-reduction treatment were sufficient to cause top-kill of trees during the wildfire. Fire consumption of duff and litter was apparently enough to girdle many oaks and madrones (C). Note that these observations are for an area that showed extreme fire-behavior.
No madrone canopies survived the fire, though most individuals showed heavy basal sprouting. Seedlings of madrone and manzanita were evident throughout the study area the following spring.
Other Interactions between Wildfire and Fuels Reduction Treatments
Vegetation response in an adjacent mechanically masticated and burned area indicates that higher soil temperatures consequent to heavy surface fuels may have impacted the soil seedbank within the mechanically treated area.
Response of Understory Species
In general, the strong response by re-sprouters, fire-dependent seedbank-generated shrubs, and geophytes (bulb plants), as well as the reappearance of shrubs and forbs not previously evident in the study area, are characteristic of chaparral vegetation and its relationship to wildfire.
(A) Blue dicks
Widespread flowering by blue dicks (A, Dichelostemma congestum).Other geophytes evident after fire included cats ears (B, Calochortus) and Tritelia (C). Showy phlox (D, Phlox speciosa) was a common half-shrub. Common annuals included miners lettuce, tarweed, and cleavers.
(B) Cats ears
(C) Tritelia
(D) Showy phlox
Right: Burn piles consumed during the wildfire created patches of bare mineral soil.
Below: Unthinned patches had less herbaceous cover than the surrounding thinning-treated area (hand-cut, piled, and piles burned), while areas sown with sterile wheatgrass showed higher herbaceous cover than treated areas.
Unthinned patch
Seeded with sterile wheatgrass
- Vegetation response to wildfire was characteristic of chaparral and its relationship to wildfire.
- Oak survival following the wildfire was unrelated to whether the area had been treated for fuels reduction or not.
- Resprouting of top-killed trees where some trees also survived wildfire resulted in a multi-aged stand.
- Duff and litter remaining after fuels reduction appears enough to girdle and kill the main boles of many oak and madrone trees.
- The manipulation of fuels (creation of piles, treated versus untreated areas) influences the seedbank and consequent recovery and character of the herbaceous community.
Contact Paul Hosten.
Photos are courtesy of the BLM.
Page by Olivia Duren. Updated 9/2007.
Responses of chaparral and oak woodland plant communities to fuel reduction thinning treatments in SW Oregon
Dr. Pat Muir and Dr. Paul Hosten, Principal Investigators
