• 1st CASE STUDY:
WY/Sprouting density and elk use after prescribed fire

• 2nd CASE STUDY:
CO/Aspen survival & sprouting after prescribed fire

• 3rd CASE STUDY:
MN/Aspen productivity after harvest & repeat prescribed fire

• 4th CASE STUDY:
Central AB/Overstory mortality after repeat spring prescribed fire

• 5th CASE STUDY:
NM/sprouting after wildfire in spruce-fir/postfire browsing

• 6th CASE STUDY:
AZ/Prescribed fire in a quaking aspen/bunchgrass type

• 7th CASE STUDY:
Central AB/Prescribed fire temperatures & effects in aspen forest

1st CASE STUDY:

• REFERENCES
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

WY/Sprouting density and elk use after prescribed fire

REFERENCES:

Bartos, D. L.; Brown, J. K.; Booth, G. D. 1994 [10]
Bartos, D. L.; Mueggler, W. F. 1979 [12]
Bartos, D. L.; Mueggler, W. F. 1981 [13]
Bartos, D. L.; Mueggler, W. F.; Campbell, R. B., Jr. 1991 [14]
Basile, J. V. 1979 [15]
Brown, J. K.; Debyle, N. V. 1987 [26]

FIRE CASE STUDY AUTHORSHIP:

Howard, Janet L. 1996

SEASON/SEVERITY CLASSIFICATION:

summer (Aug. 29, 1974)/low-severity to severe

STUDY LOCATION:

The study site, Breakneck Ridge, is located on the upper drainage of the Gros Ventre River of the Bridger-Teton National Forest, approximately 29 miles (48 km) northeast of Jackson, Wyoming [12].

PREFIRE VEGETATIVE COMMUNITY:

The landscape was a mosaic of quaking aspen (Populus tremuloides), conifer (mostly subalpine fir [Abies lasiocarpa]), big sagebrush (Artemisia tridentata), and grassland communities. Quaking aspen groves were mostly on southwesterly to northwesterly slopes. Subalpine fir was invading on northerly aspects [10,13]. Some decandent quaking aspen clones were being replaced by big sagebrush/grass. Quaking aspen sucker density was approximately 14,000 per hectare. Suckers were mostly less than 1 meter tall and suppressed by elk and moose browsing [13].

The shrub layer of the quaking aspen groves consisted of shrubby cinquefoil (Pentaphylloides floribunda), Wood's rose (Rosa woodsii), mountain snowberry (Symphoriocarpos oreophilus), and quaking aspen sprouts. Slender wheatgrass (Elymus trachycaulus), fringed brome (Bromus ciliatus), sticky geranium (Geranium viscosissimum), lodgepole lupine (Lupinus parviflorus), woodland strawberry (Fragaria vesca), fireweed (Epilobium angustifolium), and Fendler's meadowrue (Thalictrum fendleri) were common in the herbaceous understory [10,12].

Grazing use: The study site lies along an elk migration route. Elk use of the area is severe in fall, winter, and spring. Cattle graze the area three summers out of four on a rest-rotation system [10].

Plots: Ten quaking aspen clones (0.8 to 2 acres [2-5 ha] each) were selected for study. Nine clones were targeted for burning. A firebreak was established around the most southerly clone for an unburned control. Four permanent 10 X 10-meter macroplots were established in each clone, for a total of 40 macroplots [10,13].

TARGET SPECIES PHENOLOGICAL STATE:

The fire was conducted during the growing season. The flowering period was over and quaking aspen was fully leaved [12].

SITE DESCRIPTION:

Aspect on the study sites is northwest to northeast, with a 14 to 42 percent slope. Elevation is 7,897 to 8,263 feet (2,393-2,504 m). Aspen site index (80 yr) was 40 to 65 [14].

FIRE DESCRIPTION:

The primary purpose of the prescribed fire was to produce more quaking aspen suckers than elk could consume, and thus perpetuate the quaking aspen stands [10]. The area was burned on August 29, 1974. Weather conditions were [13]:

air temperature:  77 degrees Fahrenheit (25 deg C) winds:  7.8-19.2 mi/hr (13-32 km/hr), gusty relative humidity:  18% fuel moisture:  10-45%

The area did not burn uniformly and a patchwork of fire severities resulted. Portions of the nine prescribed burned macroplots did not burn; other portions were lightly, moderately, or severely burned. This was attributed to differences in amount of dry fuel on the ground and differences in moisture content of duff and understory vegetation due to slight differences in exposure [13].

Of the 36 burned macroplots (4 were controls), 11 were lightly burned, 13 were moderately burned, and 12 were severely burned. Light burns were defined as those removing less than 21 percent of litter and duff; moderate burns removed 21 to 80 percent, and severe burns removed 81 to 100 percent of litter and duff [13].

FIRE EFFECTS ON TARGET SPECIES:

More than 90 percent of the quaking aspen overstory was killed on severely burned sites. Top-kill on moderately burned sites was less than 90 percent [12].

Prescribed fire stimulated quaking aspen sucker production relative to the control. Sucker production peaked in postfire year 2. By postfire year 3, suckers on burned sites had thinned to about 30,000 per hectare as opposed to 17,000 per hectare on the control. After 3 years, both moderately and severely burned sites supported approximately the same number of sprouts [12].

Although fire stimulated sucker production, elk use of the suckers was heavy. Quaking aspen sucker densities 6 years after fire ranged from 4,300 to 10,300 per hectare for the three fire severities: approximately the same as before the fire. At postfire year 12, densities ranged from 1,500 to 2,400 suckers per hectare, which was 20 to 38 percent less than prefire densities. The control area had 5,150 suckers per hectare in 1986 compared to 8,500 per hectare that occurred prior to treatment. The 39 percent reduction of suckers on the control was attributed to elk use [1].

Average quaking aspen sprout density for 6 sample years follow. Mean values are on top and standard error of the mean (SEM) are shown below [10].

________________________________________________________________________
Fire
severity        1974     1975     1976     1977     1980     1986
---------------------------------Number/ha------------------------------
Control         8,500   18,625   16,750   18,625   12,250    5,150 
                       3,373    4,023     3,455      2,585    3,099    1,981
Low              4,000    7,727    15,727    8,636    4,318    1,518*
                     1,452     2,322     4,093     2,140    1,995      686
Moderate    5,962   18,692   30,692   20,154    9,654    1,854*
                      1,535    5,121     8,528     5,230    2,376      712
Severe          8,417    7,333* 36,458   21,792  10,292    2,400
                      1,633    2,831     7,114     3,889    2,839      589
__________________________________________________________________
*Fire severity means followed by an asterisk are significantly different
(p<0.10) from the control. 

FIRE MANAGEMENT IMPLICATIONS:

After 12 years, the objective of producing more quaking aspen suckers than elk could consume was not met. Enough suckers were produced initially to reestablish the quaking aspen stands; however, most suckers were eliminated or severely suppressed by heavy elk browsing. (Cattle seldom browsed the quaking aspen suckers and appeared to have little impact on quaking aspen.) Bartos, Brown, and Booth [10] have questioned the use of prescribed fire in areas subject to heavy ungulate use. In this case, rather than rejuvenate the quaking aspen stands, fire may have sped up their deterioration.

Differences in browsing by clone: Postfire browsing varied by clone. Elk browsing in the winter of 1976 - 1977 averaged 44 percent of current growth and reduced average height of suckers by 28 percent. In 1977, height of tagged suckers had increased an average of only 1 percent over the previous year. Growth rates of 20 tagged quaking aspen suckers were [15]:

____________________________________________________
          |                                                   |    Height change from
          |            Winter 1976-1977         |  summer 1976-summer 1977
Clone|______________________|_________________________
         | Mortality | Utilization |  Height         | Unprotected | Protected in
         |                   |   current    | reduction     |                        | exclosures
         |                   |   growth    |from summer|                         |
--------------------------------Percent-------------------------------------------------
  1           5              33                 28                  14
  2           5              46                 33                  -6
  3           0              38                 24                   0
  4          20             68                 49                 -25               16 
  5           5              58                 37                  10  
  6           5              63                 37                 -10
  7           5              17                 15                  10
  8           0              22                 13                    4
  9          10             64                 34                 -20               17
 10*       15             34                 10                  14                 7

Average  7             44                 28                    1                13
____________________________________________________
*unburned control clone

There were no significant differences between sucker density on sites with different burn severities [10]. In theory, moderate-severity fire should produce the greatest amount of suckering, but this does not always occur in practice because factors other than fire severity, such as parent stand vigor, genetic differences in clones, and competition with other vegetation also affect postfire sprouting response [26].

Understory response: Prescribed fire stimulated understory production. Increase in production was still evident 12 years after fire. In 1986, understory production was approximately 2,190 kg/ha on severely burned sites; 2,140 kg/ha on moderately burned sites; and 2,130 kg/ha on sites where fire severity was low. This exceeded prefire production by 42, 46, and 23 percent, respectively [10].

2nd CASE STUDY:

• REFERENCES
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

CO/Aspen survival & sprouting after prescribed fire

REFERENCES:

Smith, J. K. 1983 [180]
Smith, J. K. 1996 [181]
Smith, J. K.; Laven, R. D.; Omi, P. N. 1983 [154]
Smith, J. K.; Laven, R. D.; Omi, P. N. 1985 [155]
Smith, J. K.; Laven, R. D.; Omi, P. N. 1993 [156]

FIRE CASE STUDY AUTHORSHIP:

Smith, Jane Kapler. 1996

SEASON/SEVERITY CLASSIFICATION:

late fall/low

STUDY LOCATION:

The study site was in the Roosevelt National Forest of Colorado, 6 to 8 miles (10-13 km) south of Red Feather Lakes [154,156].

PREFIRE VEGETATIVE COMMUNITY:

Uneven-aged quaking aspen (Populus tremuloides) clones dominated the stand. Lodgepole pine (Pinus contorta), ponderosa pine (P. ponderosa) and limber pine (P. flexilis) were scattered throughout the stand. [154,155,156]. The understory consisted of large clumps of common juniper (Juniperus communis) interspersed with bearberry (Arctostaphylos uva-ursi) and herbs. Common juniper covered about 20 percent of the study site. Dominant herbaceous species included western yarrow (Achillea millefolium var. occidentalis), bluebell bellflower (Campanula rotundifolia), Virginia strawberry (Fragaria virginiana ssp. virginiana), northern bedstraw (Galium boreale), alpine false springparsley (Pseudocymopterus montanus), dandelion (Taraxacum officinale), pine goldenpea (Thermopsis rhombifolia var. divaricarpa), Kentucky bluegrass (Poa pratensis), and Letterman's needlegrass (Stipa lettermanii) [155].

TARGET SPECIES PHENOLOGICAL STATE:

Leaf fall had occurred and quaking aspen was dormant.

SITE DESCRIPTION:

Elevation at the burn site ranges from 8,910 to 9,075 feet (2,700-2750 m). Topography is gentle with slopes averaging 14 percent. Soils are a shallow, well-drained Red Feather sandy loam underlain by granite bedrock at 10 inches (25 cm). Precipitation varies from 15.2 to 20.9 inches (380-510 mm) per year. Mean annual temperature ranges from 40 to 46 degrees Fahrenheit (4.4-7.8 deg C) [154,156].

FIRE DESCRIPTION:

Three sites were burned. Site 1 was burned on Oct. 19, 1981, site 2 on Nov. 4, 1981, and site 3 on Nov. 17, 1981. All fires occurred after leaf fall; the second and third were conducted after a light snow had fallen and then melted. Prefire fuel and moisture conditions were [156]:

___________________________________________________________________________
                                             |            Fuel load                              | Fuel moisture
Burn   Understory  Fuel   |_________(kg/sq m)_________|_____(%)______
site           type        depth  |duff   fine   down woody*   total | duff           fine  
____________   _(cm)__|_________________________|______________
 1        herbaceous   21        1.38   0.25    0.70                   2.34       75           33
 1        juniper          32         3.52   1.01    1.06                   5.58     102           58
 2        herbaceous  29         0.90   0.42    1.31                  2.63       30           23
 2        juniper          46         3.01   1.54    1.88                  6.44       60           25
___________________________________________________________________________
*21% of woody particles measured were < 0.64 cm diameter; 34% were
 0.64-2.54 cm; 31% were 2.55-7.62 cm; 14% were > 7.62 cm.

Because the fire on site 1 spread poorly, strip fires were used. Headfire ignition was used on site 2, and ring-center firing was used on site 3. Weather conditions (median of 9 observations/site) were [180,156]:

________________________________________________________
Study     Burn     Ignition                      Weather
site         date       time             __________________________________
                              (MST)        dry           relative        wind       fuel stick
                                                 bulb          humidity    speed      analogs
                                                 (deg C)     (%)             (km/hr)     (% dry weight)
________________________________________________________
 1        Oct 19      14:35            12             26               4 gusty       10.5
 2        Nov  4      12:00            13             24               6 steady     10.6
 3        Nov 17     13:00            17             15               3 steady       9.6 
_______________________________________________________

Fire behavior: The fires burned with low severity except in some common juniper patches. Average fireline intensity was estimated to be 96 kW/m. Very little temperature change was detected below the soil surface; the maximum temperature recorded at the soil surface was 55 degrees C [154]. Less than half of site 1 burned; sites 2 and 3 burned almost completely [155]. Common juniper plots burned more completely than herbaceous plots. Fire behavior on sites 1 and 2 are described in detail [156]:
________________________________________________________________________
Burn   Understory   Area       Rate of      Flame       Fuel                    Total Heat
Site      Type            Burned   Spread       Length     Consumption    Release
                                  (%)          (m/min)      (cm)         (kg/sq m)            (kcal/sq m)
________________________________________________________________________
 1     herbaceous     32               0.9 (0.8)    13             0.57 (0.48)           2345 (1953)
 1     juniper             89               2.3 (1.7)    86              2.01 (1.03)          8300 (4326)
 2     herbaceous    97               1.6 (1.1)    25              1.19 (0.67)          5037 (2640)
 2     juniper          100               0.4             62              3.34 (0.81)        14021 (3420)
________________________________________________________________________

(Numbers in parentheses are standard deviations.) Flames were significantly (p=0.0006) longer in common juniper than in herbaceous fuels. Fuel consumption and total heat release were significantly (p=0.001) greater in common juniper than herbaceous fuels.

Fuel moisture and availability appeared to control fire spread [180,156]. On common juniper plots, fire removed almost all litter, standing herbs, and common juniper foliage. On herbaceous plots on sites 2 and 3, nearly all fine fuels were consumed by fire. Woody fuels were reduced an average of 18 percent [180]. On many plots, woody fuels were not measurably changed by fire, and on some plots they were increased [156].

FIRE EFFECTS ON TARGET SPECIES:

The spring after burning, site 1 showed very light, patchy effects from fire [155]. The authors did not consider this site "effectively burned" and discontinued sampling on it. Fire effects are described for sites 2 and 3: The burns caused about 10 percent mortality in quaking aspen greater than 5 cm dbh in the first postfire year [181]. All quaking aspen originating after the fires were suckers; no seedlings were observed. Sapling (< 5 cm dbh) densities (per hectare) for the year prior to burning and the first postfire year were [155]:


                                          Treatment
__________________________________________________________________
|                                          |                      Control                         |                    Burn                    |
|__________________|__________________________|_____________________|
| Age   Understory          | 1980            1982                 %           | 1980          1982        %          |
|Class     Type                  |                                             change  |                                  change  |
|__________________|__________________________|_____________________|
|  1       herbaceous          |  114             57                     -50          |  229          5886      +2470      | 
|  1       juniper                  |    0                 0                      ---           |     0           8819         - --        |
|                                         | ___________                    __           | ___________      ____      | 
|  1       both                      |  114             57                     -50           |  229        14705      +6321     |
|                                         |                                                              |                                                |
| >1      herbaceous         | 3981         3162                     -21          | 2971           457           -85     |
| >1      juniper                 |   610           857                    +40          |   648             19           -97     |
|                                         | ___________                    __          | ___________           __      |
| >1     both                      | 4591           401                     -12         | 3619            476           -87      | 
|_________________|___________________________|_____________________|

Sapling densities in unburned areas did not change significantly (p > 0.05) from the year prior to burning (1980) to the first postfire year (1982). Changes in sapling densities on burned areas were statistically significant (p < 0.05). One-year-old saplings increased more than 6,000 percent from 1980 to 1982, while older saplings decreased 87 percent. Suckering was significantly (p < 0.05) greater in common juniper than herbaceous plots [155].

FIRE MANAGEMENT IMPLICATIONS:

The range of conditions favorable for fall burning in quaking aspen is "vary narrow." The authors recommend burning after leaf fall and before snowfall [155]. In this study, common juniper burned readily but comprised only patches in the understory. If common juniper occurs in the understory and if a patchy burn meets management objectives, the acceptable prescription window may be wider.

3rd CASE STUDY:

• REFERENCES
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

MN/Aspen productivity after harvest & repeat prescribed fire

REFERENCES:

Deeming, J. E.; Lancaster, M. A.; Fosberg, R.; [and others]. 1972 [176]
Perala, D. A. 1974 [120]
Perala, D. A. 1974 [121]
Perala, D. A. 1974 [119]
Perala, D. A. 1979 [182]
Perala, D. A. 1995 [124]

FIRE CASE STUDY AUTHORSHIP:

Howard, Janet L. 1996

SEASON/SEVERITY CLASSIFICATION:

spring (May 17, 1967)/severe
spring (May 13, 1969)/low
fall (October 5, 1970)/moderate to severe

STUDY LOCATION:

The study site was in the Chippewa National Forest in Minnesota (47 deg 20 min N, 94 deg 30 min W) [120,121,119,182,124].

PREFIRE VEGETATIVE COMMUNITY:

The stand was commercially harvested 2 years before the first prescribed fire. Before harvest, the stand was dominated by 60-year-old quaking aspen (Populus tremuloides). Site basal area was 30 sq m/ha; basal area of quaking aspen was 22 sq m/ha. The rest of the stocking was mostly hardwoods including basswood (Tilia americana), sugar maple (Acer saccharum), red maple (A. rubrum), paper birch (Betula papyrifera), ironwood (Ostrya virginiana), northern red oak (Quercus rubra), bur oak (Q. macrocarpa), and American elm (Ulmus americana). Some balsam fir (Abies balsamea), white spruce (Picea glauca), and eastern white pine (Pinus strobus) were present. Successional trend was toward sugar maple-basswood. Understory shrubs included pin cherry (Prunus pensylvanica), chokecherry (P. virginiana), Allegheny serviceberry (Amelanchier laevis), alternate-leaf dogwood (Cornus alternifolia), red-osier dogwood (C. sericea), willows (Salix spp.), downy arrowwood (Viburnum rafinesquianum), and eastern leatherwood (Dirca palustris) [121,119].

About 74 t/ha of quaking aspen averaging 7.6 inches (19 cm) dbh was harvested. Associated hardwoods were not harvested: with an average dbh of 5.6 inches (14 cm), they were not considered merchantable. Conifers were harvested. After harvest, slash fuels covered 47 percent of the area at a mean depth of 10.8 inches (27 cm), with a few accumulations up to 5 feet (1.5 m) [121,119].

Plots: Twelve 1-hectare blocks were established in the harvest area. On three blocks, overstory trees left after harvest were felled, creating a clearcut. The other nine blocks were targeted for prescribed burning [119].

TARGET SPECIES PHENOLOGICAL STATE:

No entry

SITE DESCRIPTION:

The soils are considered good for quaking aspen: a Warba very fine sandy loam with clayey loam subsoil. Elevation is 1,312 to 1,345 feet (400-410 m). Topography is level to gently rolling. Climate is continental with mean annual precipitation of 24.4 inches (610 mm) and mean July temperature of 68 degrees Fahrenheit (20 deg C) [119,124].

FIRE DESCRIPTION:

Burning conditions - 1st prescribed fire: Suitable burning conditions did not occur until 2 years after logging, on May 17, 1967. The cured slash was burned with 50- to 100-foot-strip (15- to 30-m) headfires after backfiring downwind sides. Hardwoods not killed by the fire, and unharvested hardwoods in the control (no burn) area, were then felled [119].

Repeat fires: Two and four years (May 13, 1969, and Oct. 5, 1970) after the first burn, separate parts of the burn area were burned again using 50- to 100-foot-strip (15- to 30-m) headfires after backfiring the downwind side of the burn area [120]. Weather and fire indices for each fire according to the National Fire-Danger Rating System [176] were [120,119]:


-------------------------------------------------------------------------
                                          Date of Fire
                                   -----------------------------------
                                   May 17,   May 13,   Oct.5,
Item                                1967      1969         1970
-------------------------------------------------------------------------
Air temperature (deg F)
     dry bulb                                    20.6       69        84
     wet bulb                                    11.1       53        65
     dew point                                    1.1       37        53
Relative humidity (%)                    29         32        35
Wind speed (m/s)                             5           6          6
1-h time lag (TL) fuel moisture(%)  5          5          5
10-h TL fuel moisture (%)                 6         7          7   
100-h TL fuel moisture (%)             10        12        15   
herbaceous vegetation condition*10       10        20
fine fuel moisture (%)                        6          6          8
Ignition component                         48        48        42
Spread component                             5         0          2
Energy release component            16          7          6
Burning index                                  17          0          3
-------------------------------------------------------------------------
*percent, by volume, of living fine fuels

Fire behavior - 1st fire (1967): The first, slash-fueled fire was intense. At one point it escaped the fireline, burning a treatment block intended as a control. The fire was later estimated to be "nearly uncontrollable." Nearly all fuels less than 3 inches (7.6 cm) in diameter were completely consumed. Few coarse fuels burned. Approximately 25 minutes were required to burn each 1-hectare replicate; rate of fire advance averaged 4.2 cm/s. Fireline intensity in slash was estimated at 138 kW/m. Intensity in litter was not measured but was "minor in comparison." Litter fuels carried fire between slash accumulations so that burn coverage was complete [124].

Repeat fires (1969 and 1970): The spring repeat fire was considered only partially effective, whereas the fall repeat fire was highly effective [124]. The spring fire crept along the layer of litter and herbaceous vegetation matted down by winter snow. Decomposed organic layers were still wet and did not burn. Burn coverage was 76 percent. Flame heights were just a few decimeters, giving a fireline intensity of about 10 kW/m [120,119,124].

In the fall, the forest floor was drier. Standing vegetation carried the fire well and burn coverage was 85 percent. Flame heights were from 1 to 2 feet (0.3-0.6 m), giving a fireline intensity of 20 to 100 kW/m. The forest floor was completely consumed on 10 percent of the area, exposing mineral soil [120,124].

FIRE EFFECTS ON TARGET SPECIES:

Short-term effects - first prescribed fire: The fire top-killed all woody regeneration including quaking aspen sprouts. Seventy-six percent of the hardwood overstory was top-killed: of an average 6.9 sq m/ha basal area of overstory hardwoods standing after harvest, only 1.7 sq m/ha were alive after fire [120,119]. Some quaking aspen roots were killed or injured by intense heat [124].

One year after the fire, quaking aspen sprout density on the burn was 85 percent higher than on the clearcut [2].

Repeat treatments: The spring and fall prescribed fires top-killed quaking aspen. Some quaking aspen roots were killed by the fall fire. Postfire quaking aspen seedling establishment was noted where mineral soil was exposed, although seedling density was not recorded. Quaking aspen sprout densities on the burns were [120,119]:

                          Stem density (number/acre)
----------------------------------------------------------------------------
                            1968     1969     1970     1971     1972    1973
----------------------------------------------------------------------------
1967 single (spring) fire  25,000   18,000   16,000   13,000   11,000   9,500
1969 repeat spring fire     ----    17,500   10,000    8,000    7,000   6,000 
1970 repeat fall fire       ----     ----     ----    13,000   25,000  14,000

Long-term effects: Perala [124] has monitored these study sites for 25 years. He concluded that in the long term, quaking aspen yield was similar with clearcutting, repeat spring fire, or repeat fall fire. The single prescribed fire treatment reduced quaking aspen. Even after 25 years, productivity had not recovered to prefire levels. Repeat burns, however, slowed growth and reduced yield of other hardwood species, enhancing the quaking aspen component of the stand. Repeat fall burning enhanced quaking aspen productivity the most: On repeat fall burn plots, quaking aspen productivity at postfire year 25 was 111 percent of unburned quaking aspen. Modelling productivity, Perala [124] found that standing crop after 25 years was:


-----------------------------------------------------------------------
     Burn                                Age (yrs)
                     --------------------------------------------------
   treatment                    10       15       20       25     
-----------------------------------------------------------------------
                     ------------------------kg/ha---------------------

                                         Quaking aspen

no burn                         18.5     40.0     60.6     76.2
single burn                   14.6     31.7     49.3     59.1
repeat spring burn      14.9     34.7     56.7     70.6
repeat fall burn            19.8     42.7     67.2     84.8

                                        Other hardwoods

no burn                          2.31     5.86    11.3     18.6
single burn                    5.11     8.70    12.7     16.9
repeat spring burn       5.11     8.70    12.7     16.9
repeat fall burn             3.90     6.32     8.9      11.5
------------------------------------------------------------------------ 

FIRE MANAGEMENT IMPLICATIONS:

There is a very narrow window for prescribed burning dormant quaking aspen in northern Minnesota. Perala [119] predicted that the necessary energy release component of 14 to 17 (see prescription in FIRE MANAGEMENT) would occur during only 2.8 days of the dormant season. In this study, two attempts to burn 11 and 17 months after harvest were unsuccessful because of high humidity, low wind speed, or low temperature.

Because of their readily released energy, fuels less than 2.8 inches (7 cm) in diameter were the most important fuel component to fire spread. Postfire quaking aspen sprouting was greatest where cured fuels were evenly distributed. Slash accumulations burned too hot and damaged roots, which reduced sprouting. Areas without slash reduced burn coverage, which favored other hardwood species [119].

This study shows that even on a productive site, long-term quaking aspen productivity can be reduced by an intense fire resulting from burning heavy slash. Repeat fall burning may ameliorate the effects of a single, intense fire by favoring the quaking aspen component of the stand over associated hardwoods [124].

4th CASE STUDY:

• REFERENCE
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

Central AB/Overstory mortality after repeat spring prescribed fire

REFERENCE:

Quintilio, D.; Alexander, M. E.; Ponto, R. L. 1991 [131]

FIRE CASE STUDY AUTHORSHIP:

Howard, Janet L. 1996

SEASON/SEVERITY CLASSIFICATION:

spring, May 9-15, 1972/low to moderate
spring, May 5, 1978/severe

STUDY LOCATION:

The study site is approximately 120 miles (200 km) north of Edmonton, Alberta, and about 3.6 miles (6 km) northwest of Hondo, Alberta (latitude 50 deg 06 min N and longitude 114 deg 08 min W). It is located in NE Section 30, Range 2, Township 70, west of the Fifth Meridian. The study site lies within a fire research reserve in the Slave Lake Forest.

PREFIRE VEGETATIVE COMMUNITY:

The study area is within boreal mixed-wood forest. The site is surrounded by open, grassy muskeg with some black spruce (Picea mariana). The stand was dominated by quaking aspen (Populus tremuloides). Height and dbh of quaking aspen stems averaged 50 feet and 4.4 inches (13 m and 11 cm), respectively. Stand basal area averaged 29.38 sq m/ha (SD = +/- 5.61). Live and dead tree densities averaged 2,802 (SD = +/- 980) and 916 (SD = +/- 581) stems/ha, respectively. Quaking aspen made up 99 percent of the basal area and 98 percent of the stand density. The site also contained scattered white spruce (Picea glauca) and jack pine (Pinus banksiana) and infrequent clumps of paper birch (Betula papyrifera). Tall understory shrubs included American green alder (Alnus viridis spp. crispa), pin cherry (Prunus pensylvanica), and beaked hazel (Corylus cornuta). Dominant herbs were twinflower (Linnaea borealis), cream peavine (Lathyrus ochroleucus), wild sarsaparilla (Aralia nudicaulis), dwarf red blackberry (Rubus pubescens), and bunchberry (Cornus canadensis).

Litter mass averaged 0.30 +/- 0.09 kg/sq m. Woody fuels averaged 0.369 kg/sq m: scant compared to other forest cover types of Alberta. Consequently, downed-dead woody fuels contributed little to behavior or effects of the 1972 fires.

TARGET SPECIES PHENOLOGICAL STATE:

Spring leaf-out had not yet occurred.

SITE DESCRIPTION:

The study site is well drained. Soils are loam underlaid with deep layers of coarse and fine sand. Topography is strongly undulating with a slope of less than 10 percent. Elevation is 1,947 feet (590 m).

Plots: A 12-meter firebreak was bulldozed around eight 45 X 100 meter blocks. The eight blocks were separated by 6- or 12-meter, bulldozed strips. Each block was subdivided into three plots.

FIRE DESCRIPTION:

Thirteen plots were burned in sequence during a 7-day period in spring 1972. The first plot was burned on May 9, which was as soon after snowmelt as fuels could support a slow-moving fire. Burning continued until May 15, utilizing weather variations during that time. For all plots, headfires were ignited from early to mid-afternoon from an established line source. Ranges of weather variables were:


Ranges                   
----------------------------------------------------------
temperature                  57-75 deg F (13.9-23.9 deg C)
relative humidity          20-36%
average wind speed*   0.48-2.5 miles/hr (0.8-4.2 km/hr)
length of time after a significant** rain:  3-9 days
----------------------------------------------------------
*measured 4.6 feet (1.4 m) above ground at time of fires
** > 1.05 mm

Reburning was done on May 5, 1978.  One and one-half plots were
reburned.  Weather conditions were:

----------------------------------------------------------
temperature           60 deg F (15.5 deg C)
relative humidity  20%
wind speed           4.0 miles/hr (6.6 km/hr)
days after rain       6
----------------------------------------------------------

Fire-danger conditions according to the Canadian Fire Weather Index ranged from low to high during the 1972 fires. Most of the range in fire danger was due to variations in wind speed. Test fires ignited on May 7 and 8, 1972, were not sustainable with dead fine fuel moistures of 70 and 85 percent and initial spread indices (ISI) of 0.5 and 2.0 (i.e., with no wind). All remaining fires spread uniformly over the plots, suggesting that an ISI between 2.0 and 2.5 is a threshold condition for sustained fire spread in the leafless quaking aspen fuel type. Rate of headfire spread ranged from 0.28 to 2.51 m/minute. Flame height ranged from 0.3 to 3.3 feet (0.1-1.0 m); fireline intensities were "low to moderate," ranging from 15 to 390 kW/m. All the 1972 prescribed fires had a fairly easy difficulty of control rating (I < 500 kW/m). Fuel consumption averaged 0.35 kg/sq m.

The 1978 fires were intense, mainly due to an increase in surface fuels (mostly dead quaking aspen) after the 1972 fires. Average rate of headfire spread was 4.6 m/minute, nearly double that of the most intense 1972 fires. Fireline intensity was 4,392 kW/m, equal to a high-intensity surface fire or intermittent crown fire in a conifer forest stand. Fuel consumption averaged 3.4 kg/m sq. Fuel consumption and fire behavior data follow.

--------------------------------------------------------------------------------------------------
Experimental       Fuel                      Energy per       Headfire             Fireline
 fire plot               consumption*    unit area           rate of spread    intensity
  number              (kg/sq m)             (kJ/sq m)           (m/min)               (kW/m)
---------------------------------------------------------------------------------------------------
    5c                      0.177                   3,214                   0.28                     15
    6a                     0.122                    2,266                   0.45                     17
    6b                     0.117                    2,298                   0.47                     18
    2b                     0.263                    4,800                   0.75                     60
    5a                     0.307                    5,680                   0.75                     71
    5b                     0.300                    5,532                   0.77                     71
    2a                     0.274                    5,034                   0.87                     73
    3a                     0.305                    5,591                   0.88                     82
    3c                     0.507                    9,319                   1.41                   219 
    4c                     0.535                    9,851                   1.48                   243
    4a                     0.557                 10,259                    1.62                   277
    4b                    0.539                    9,944                   2.13                   353
    3b                    0.507                    9,323                   2.15                   390
  3b&c**            3.402                  57,261                   4.60                 4,392
-------------------------------------------------------------------------------------------------
*Includes downed-dead woody surface fuels, cured surface vegetation,
   leaf litter, and F and H litter layers
**plots reburned in 1978

FIRE EFFECTS ON TARGET SPECIES:

After the 1972 low-intensity fires, mortality in the quaking aspen overstory ranged from 0 to 100 percent, with top-kill averaging 29 percent. After the 1972 moderate-intensity fires, overstory mortality again ranged from 1 to 100 percent. Average top-kill was 56.5 percent. Large-diameter stems (> 7 inches [17.5 cm] dbh) were more likely to survive both low- and moderate-intensity fire. Stems greater than 8 inches (20 cm) dbh were not top-killed. The intense, 1978 reburns top-killed all small- (1 to 4 inches [2.5-10.0 cm] dbh) and medium-sized (4 to 6 inches [10.0-17.5 cm] dbh) stems, and all but a few of the large stems. Quaking aspen stem mortality data are:


----------------------------------------------------------------------------------------------
                                 Stem Mortality (%)
                                 -----------------------------------------
                                 moderate-               low-intensity     1978
dbh size classes     intensity fires        fires                     reburn   
---------------------     -------------------       ------------------    -------------
stem size                 block    block        block                    plots    unburned 
  (cm)                       3c           4               5                           3b&c   controls  
----------------------------------------------------------------------------------------------
 2.5- 5.0                    67             0           100                        100       100
 5.0- 7.5                    91         100             81                        100        54
 7.5-10.0                   73         100             34                        100          3
10.0-12.5                  35           89             17                        100          2
12.5-15.0                  30           68             10                        100          0
15.0-17.5                  14          52               3                         100          0
17.5-20.0                  15          24               3                           95          0
20.0-22.5                    0            0               0                           90          0
22.5+                          0            0               0                          90           0
----------------------------------------------------------------------------------------------
All size classes       45          68            29                           97        15
----------------------------------------------------------------------------------------------

FIRE MANAGEMENT IMPLICATIONS:

There are few data on fire behavior in relation to burning conditions in quaking aspen types. This study provides information on fire behavior including headfire rate of spread, fuel consumption, fireline intensity, and fire effects on quaking aspen forests in the boreal zone. Additionally, prefire fuel moisture conditions and impact of burning on the forest floor (depth of burn and forest floor reduction) are given. Pre- and postfire frequency and cover data for understory species are also presented.

5th CASE STUDY:

• REFERENCE
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

NM/sprouting after wildfire in spruce-fir/postfire browsing

REFERENCE:

Patton, D. R.; Avant, H. D. 1970 [115]

FIRE CASE STUDY AUTHORSHIP:

Howard, Janet L. 1996

SEASON/SEVERITY CLASSIFICATION:

spring (April 1963)/low severity

STUDY LOCATION:

The study site is located in the Santa Fe National Forest of New Mexico.

PREFIRE VEGETATIVE COMMUNITY:

The Walker Fire occurred in a spruce-fir (Picea-Abies spp.) type with an overstory of Engelmann spruce (P. engelmannii), Douglas-fir (Pseudotsuga menziesii), quaking aspen (Populus tremuloides), and ponderosa pine (Pinus ponderosa). Understory vegetation consisted of willows (Salix spp.), Wood's rose (Rosa woodsii), Oregon-grape (Mahonia repens), Geranium spp., strawberries (Fragaria spp.), shrubby cinquefoil (Pentaphylloides floribunda), cutleaf filaree (Erodium cicutarium), sedges (Carex spp.), and nodding brome (Bromus anomalus).

TARGET SPECIES PHENOLOGICAL STATE:

No entry

SITE DESCRIPTION:

No entry

FIRE DESCRIPTION:

Prior to the wildfire, the litter layer was deep. The fire was a moderate-severity surface fire that consumed understory conifers and hardwoods (mainly quaking aspen). Overstory foliage was killed by heat from the surface fire.

FIRE EFFECTS ON TARGET SPECIES:

The Walker Fire top-killed most of the quaking aspen stems. Eighteen months after the fire, 1 acre of the Walker Burn was fenced to exclude deer, elk, and cattle. Ten 0.01-acre plots were established in the exclosure, and ten 0.01-acre plots were established outside the exclosure. Quaking aspen sprouts were counted 5 times, from September 1964 through June 1968.

Wildfire significantly increased the number of quaking aspen sprouts. Five-year average sprout density was 12,960 sprouts per acre on the burn, compared to 100 sprouts per acre in adjacent unburned forest and 200 and 500 sprouts per acre on similar spruce-fir types in Arizona. Densities each year were:


Quaking aspen sprouts/acre on the Walker Burn, Santa Fe NF, NM, compared
     with unburned quaking aspen areas in the spruce-fir type
----------------------------------------------------------------------------------------------------
                            |        Walker Burn        |      Unburned areas           
                            |-------------------------------------------------------------------------------
  Date data         |                 |                 |               |                         |Apache NF,AZ 
were collected   | Inside     | Outside  |Average|Adjacent to   |---------|------------
                             |exclosure|exclosure|               |Walker Burn*|aspen |Willow
                             |                 |                |                |                        |groves| Creek
----------------------------------------------------------------------------------------------------
                  -----------------Number per acre-----------------------
 1964 (Sept.)    | 10,500        | 13,100    | 11,800    |   100               |   --      |   --
 1965 (June)     | 12,600       | 15,100    | 13,850    |     --                 |   --      |   --
 1966 (June)     | 13,700       | 15,400    | 14,550    |     --                 |   --      |   --
 1967 (June)     | 12,100       | 13,400    | 12,750    |     --                 | 200     |  --
 1968 (June)     | 11,200       | 12,500    | 11,850    |     --                 |   --      |   --
 1969 (Aug.)    |    --             |    --         |    --         |     --                  |   --     | 500
                  --------------------------------------------------------------------------------------
      Average       12,020       | 13,900    | 12,960   |   100               | 200     | 500 
----------------------------------------------------------------------------------------------------
*Estimated--no actual counts made     

In 1964, quaking aspen sprouts on the burn were less then 3 feet (0.9 m) tall, so ungulates could browse them easily. By June 1968, sprouts were 8 to 10 feet (2.4-3 m) tall, and getting out of reach as a food supply. Cattle and wildlife use on the burned area did not significantly affect quaking aspen sprout density; the number of sprouts was similar inside and outside the exclosure.

FIRE MANAGEMENT IMPLICATIONS:

The Walker Fire stimulated quaking aspen sprouting. Quaking aspen sprout density increased for 4 years after the wildfire; then the number of stems per acre began to decrease. The sprouts provided quality browse for cattle and wildlife for at least 5 years.

Although the Walker Fire was wild, it illustrates how fire can be used as a management tool for promoting quaking aspen, providing wildlife and livestock browse, and improving wildlife habitat and diversity.

6th CASE STUDY:

• REFERENCE
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

AZ/Prescribed fire in a quaking aspen/bunchgrass type

REFERENCE:

Covington, W. W.; Kurmes, E. A.; Hailey, J. R. 1983 [34]

FIRE CASE STUDY AUTHORSHIP:

Tirmenstein, D. A. 1989

SEASON/SEVERITY CLASSIFICATION:

fall (October, 1981)/low

STUDY LOCATION:

The study site is approximately 20 miles (32 km) northwest of Flagstaff, Arizona, on the Coconino National Forest. The site is between U.S. Highway 180 on the southeast and Kendrick Park to the north, in sections 4, 8, 9, and 18 of Township 23 North and Range 6 East.

PREFIRE VEGETATIVE COMMUNITY:

The study site was in a quaking aspen (Populus tremuloides)/bunchgrass community. The quaking aspen overstory ranged from 45 to 55 years in age, with tree heights of 36 to 48 feet (11-14.6 m). Average dbh was 6 to 9 inches (16.2-21.6 cm). Some larger, older stems were scattered throughout the site. Understory bunchgrasses included Arizona fescue (Festuca arizonica), mountain muhly (Muhlenbergia montana), and bottlebrush squirreltail (Elymus elymoides). Fringed brome (Bromus ciliatus), sedges (Carex spp.), and mutton grass (Poa fendleriana) were also present. Understory forbs included western yarrow (Achillea millefolium var. occidentalis), lupine (Lupinus spp.), fleabane (Erigeron spp.), American vetch (Vicia americana), dandelion (Taraxacum officinale), and Indian paintbrush (Castilleja spp.).

TARGET SPECIES PHENOLOGICAL STATE:

No entry

SITE DESCRIPTION:

elevation - 8,033 ft. (2,450 m)
climate - cool and subhumid
mean annual temperature - 43 degrees Fahrenheit (6 deg C)
   average January temperature - 25 degrees Fahrenheit (-4 deg C)
   average July temperature - 63 degrees Fahrenheit (17 deg C)
average precipitation, July through September - 8 inches (206 mm)
average annual snowfall - 91 inches (2,310 mm)
average growing season - 117 to 160 days
soils - Brolliar stony clay loam of cinder and basaltic parent material
   surface soils - moderately fine textured, dark, cobbly, or stony loam
   subsoils - reddish brown clay loam or clay
grazing history - rest-rotation allotment in use June 1 through September 30

FIRE DESCRIPTION:

Backing fires were used first, then short strip headfires were set.

winds - 3 to 6 mph (5-10 km/hr) from the southwest
temperature - 50 to 59 degrees Fahrenheit (10-15 deg C)
flame length - 6 to 12 inches (15-30 cm)

Prefire fuel characteristics:

wood fuels - (t/ha)                 plot 1     plot 2     plot 3     plot 4
_______________________________________________________________________
        0-2.5 cm diameter            0.23       0.23        0.08        0.11
        2.5-5.0 cm diameter          1.35       2.08        0.37       2.94
        5.0-7.6 cm diameter        10.19       6.04        0.00       9.86
        7.6 cm diameter             16.58       4.30        6.14      27.55
        ____________________________________________________________________
        Total                               28.35      12.65       6.59      40.46

_______________________________________________________________________
herbaceous fuels - (kg/ha)  91.40    370.00    783.00   339.00
moisture content - (%)         45           41          36          36
avg. litter depth - (cm)           2.30        3.30       2.10        1.10
litter moisture content - (%) 31         23         15         13
% of area burned                   61         50         43         10
_______________________________________________________________________
_

FIRE EFFECTS ON TARGET SPECIES:

Fire was of low intensity and did not kill the quaking aspen overstory. Quaking aspen sprouting increased slightly, but "significantly" (p=0.09), on burn plots compared to control (unburned) plots. By the end of the first postfire growing season, sprout density was 2.1 times the prefire level on burn plots but only 1.7 times the prefire level on control plots. Average sprout densities per hectare on each plot and on all plots combined were:

_________________________________________________
          Year      Burn (SE)       Control (SE)
plot 1    1981*       200 (231)       200 (231)
          1982**    1,100 (756)       400 (325)
plot 2    1981        200 (231)     1,600 (1,348)
          1982      1,200 (1,264)   2,000 (1,424)
plot 3    1981      1,900 (1,192)     200 (231)
          1982      3,600 (2,956)     400 (326)
plot 4    1981      1,800 (516)     1,800 (516)
          1982      2,700 (1,740)   2,500 (1,052)
_________________________________________________
treatment           1,025   (953)      800   (711)
mean                2,150 (1,212)    1,325 (1,087)
__________________________________________________
* 1981 values measure prefire sprout density
**1982 values measure postfire sprout density

FIRE MANAGEMENT IMPLICATIONS:

This fire prescription was ineffective in top-killing the quaking aspen overstory. Sprout production increased slightly on burned plots, but long-term survivorship of sprouts may be poor due to the presence of the quaking aspen overstory. More research is suggested for documentation of the effects of fire in southwestern quaking aspen/bunchgrass communities.

7th CASE STUDY:

• REFERENCES
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

Central AB/Prescribed fire temperatures & effects in aspen forest

REFERENCES:

Anderson, M. L.; Bailey, A. W. 1979 [2]
Bailey, A. W.; Anderson, M .L. 1980 [3]

FIRE CASE STUDY AUTHORSHIP:

Tirmenstein, D. A. 1989

SEASON/SEVERITY CLASSIFICATION:

Spring (May 1977)/severity not reported

STUDY LOCATION:

The study area was located at the University of Alberta Ranch, 91 miles (152 km) southeast of Edmonton, Alberta [2].

PREFIRE VEGETATIVE COMMUNITY:

The landscape was a mosaic of quaking aspen (Populus tremuloides) forest, western snowberry (Symphoriocarpos occidentalis) shrubland, and rough fescue-Canadian needlegrass (Festuca scabrella-Stipa curtiseta) grassland. Differences in plant species composition between the three community types were not described in detail. Western snowberry and willows (Salix spp.) were present in the quaking aspen understory and were important fuels. Other shrubs common on the landscape included roses (Rosa acicularis, R. woodsii), grayleaf red raspberry (Rubus idaeus var. strigosus), Canadian gooseberry (Ribes oxyacanthoides), silverberry (Elaegnus commutata), and cherries (Prunus pensylvanica, P. virginiana). In quaking aspen forest, shrubs were most common on the forest edges. Interior portions of the quaking aspen forest understory were dominated by unspecified forbs [2,3].

TARGET SPECIES PHENOLOGICAL STATE:

No entry

SITE DESCRIPTION:

Topography is moderately to strongly rolling. Loamy black and dark brown chernozemic soils overlay glacial till [2].

FIRE DESCRIPTION:

Standing woody fuels were most plentiful near the margins of quaking aspen groves, where small quaking aspen stems were interspersed with western snowberry. Ground fuels were more sparse on forest margins than on the forest floor. The duff layer was either wet or frozen [3].

The quaking aspen, western snowberry, and grassland communities were prescribed burned with backfires and headfires. Quaking aspen forest was the most difficult of the three communities to prescribe burn; only half the quaking aspen forest burned. However, it had the greatest range of fire temperatures. Headfires were hotter than backfires in all three communities; backfires usually went out within a few feet of ignition in quaking aspen forest. Fire temperatures at the soil surface were greatest (in excess of 1,112 degrees Fahrenheit [600 deg C]) on forest margins, where dead willow and quaking aspen branches had accumulated and stands of live western snowberry were dense. Fire temperature and fuel data for the quaking aspen community follow [3].

total available fuel - 11,824 pounds/acre (13,436 kg/ha)
   ground fuel - 10,300 pounds/acre (11,704 kg/ha)
   standing woody fuel - 1,524 pounds/acre (1,732 kg/ha)

fire temperature (mean) at soil surface - 739 degrees Fahrenheit (393 deg C)
   backfire - 442 degrees Fahrenheit (228 deg C)
   headfire- 806 degrees Fahrenheit (430 deg C)
fire temperature (range) at soil surface
   backfire - 119-670 degrees Fahrenheit (93-371 deg C)
   headfire - 500-1,800 degrees Fahrenheit (260-982 deg C)

total area burned (mean) - 53%
   backfire - 29%
   headfire - 65%

FIRE EFFECTS ON TARGET SPECIES:

Backfires had very little effect on quaking aspen since they extinguished within a few feet after entering quaking aspen forest. Effect of headfires on quaking aspen was variable. Some quaking aspen stems were top-killed by headfires; percentage top-kill was not given. All recorded temperatures at the soil surface were in excess of 140 degrees Fahrenheit (60 deg C), the lethal temperature for plant tissues. Duration of high temperatures influences mortality of plant tissues, however, and temperature duration was not measured. Where top-kill approached 100 percent, survivors were usually protected from fire by topographic relief [3].

FIRE MANAGEMENT IMPLICATIONS:

Quaking aspen forest was difficult to burn. Range of fire temperatures was wide depending upon type and distribution of fuels, weather, topography, and method of ignition. Higher temperatures were reached where downed woody fuels (mostly willows and western snowberry) had accumulated or in dense stands of live western snowberry. Backfires were not successful. Headfires produced a wide range of temperatures. Headfires were most successful (produced nearly 100% top-kill of quaking aspen) when surface fuels were very dry, relative humidity was low, and winds were in excess of 3.6 miles per hour (6 km/hour) [3].

Related categories for SPECIES: Populus tremuloides | Quaking Aspen