Final Report July 2012

Transcription

1 Final Report July 2012 Wildfire Operations Research 1176 Switzer Drive Hinton, AB T7V 1V3 Fire behaviour in simulated mountain pine beetle-killed stands Dave Schroeder Colleen Mooney Introduction The ability of fire managers to predict the onset of crown fire during a wildfire is a key element in fire operations planning and directly affects resource deployment and firefighter safety. The Canadian Forest Fire Behaviour Prediction (FBP) System (Forestry Canada Fire Danger Group 1992) is used by all fire management agencies in Canada to provide fire behaviour predictions for 16 fuel types. Two of the 16 fuel types in the FBP System describe stands that have been attacked by spruce budworm (Stocks 1987), but these are not representative of stands that have been killed by mountain pine beetle. This presents a serious limitation for fire managers in Western Canada responsible for developing suppression strategies for wildfires burning in mountain pine beetle-killed stands. In British Columbia, Canada, several consecutive mild winters and large continuous tracts of mature pine have contributed to the largest outbreak of mountain pine beetle (MPB) (Dendroctonus ponderosae) in North American history 1. The beetle is now present in Alberta s Lodgepole pine forests at increased levels and poses a threat to the Jack pine stands of Canada s northern boreal forest (Cullingham et al. 2011). The extensive tree mortality that typically follows a widespread forest insect epidemic can significantly alter both the quantity and spatial distribution of live and dead fuels across the landscape. These altered fuels can lead to changes in the behaviour of subsequent wildfires (Graham et al. 2004). At the red-needle stage of a mountain pine beetle attack, the greatest impact on fuel condition is a decrease in the moisture content within the needles. These changes in foliar moisture content can affect crown fire initiation and crown fire rate of spread. Anecdotal accounts from forest protection personnel in British Columbia report that crown fire initiation happens more readily, and crown fire rates of spread are greater in MPB-killed stands 1-2 years post-outbreak, when dead trees still retained flammable dead needles. Van Wagner (1977) deemed that foliar moisture content (FMC) is an important factor that could be used to determine a threshold of surface fire intensity needed to initiate crowning. This concept is built into the Canadian FBP System 2. While live foliar moisture content ranges from 70 to 130%, moisture content values in red needles may fall to between 7% and 30% (Shore et al. 2006; Jenkins et al. 2008). According to Van Wagner, we expect that the critical surface intensity needed to initiate crown fire within stands of red-needled trees would be less than that for green stands. Foliar moisture content could also play a role in the rate of spread of crown fire. Since drier fuels require less energy to ignite, we can expect less resistance to fire spread within the canopy and higher rates of spread. 1 [Accessed March 2011] 2 The FBP system works with a live foliar moisture content range of 85% to 120%. 1 P a g e

2 In 2007, Alberta Sustainable Resource Development (ASRD) asked FPInnovations Wildfire Operations Research to conduct research to determine the differences in fire behaviour, if any, between live green pine stands and pine stands at the red-needle stage. We focused on the change in moisture content for foliar and surface 3 fuels and the resulting fire behaviour. The objective of this study was to provide a better understanding of potential differences in crown fire initiation, rate of fire spread and fire type between green-needled and red-needled stands. General familiarity with the FBP System (Forestry Canada Fire Danger Group 1992, Hirsch 1996) and the Canadian Forest Fire Weather Index System (FWI) (Van Wagner 1987) on the part of the reader is presumed. Methods Simulated MPB-attacked stands were created in May 2007 by girdling trees. This approach allowed researchers to locate the study site in a remote area where experimental burns could be conducted with minimal suppression effort and with little risk of escape fires. It also allowed researchers to arrange treated (girdled) stands adjacent to control (not girdled) stands which could be burned simultaneously (paired burns). Girdling was thought to be an effective method of cutting off the supply of water and nutrients to the trees, mimicking the effect of mountain pine beetle larvae and its associated fungus. However, it took two years for the treated stands to fully reach the red-needled stage. Experimental fires were conducted in 2008 and 2009 using simultaneous ignitions in control and treated stands (paired burns) over a range of FWI values to determine threshold differences in crown fire initiation, rate of spread and fire type. Study Site The study site was located at Archer Lake in the Waterways District of Alberta, Canada approximately 165 kilometres northeast of the city of Fort McMurray (Figure 1) at 58 o 07 latitude, 110 o 15 longitude. Figure 1. Location of Archer Lake study site in Alberta, Canada. 3 Litter, lichen, moss tips. 2 P a g e

3 At 345m elevation, the site is flat and surrounded by old wildfires, muskeg and lakes. The site is remote with no road access and there are no timber or community values at risk nearby. Study Units Study units were established in May 2007 by outlining six naturally occurring patches of live Jack pine (Pinus banksiana) trees untouched by recent wildfire (Figure 2). Each study unit was divided approximately in half. Trees were girdled in the eastern half to simulate a mountain pine beetle attack with >90% mortality of the overstory trees. N Figure 2. Layout of Archer Lake study units. The western half of each unit represented the control stands where trees remained untreated. The 2008 burn trials were conducted in Unit 1 (1 ha) and Unit 6 (0.12 ha). The 2009 burn trials were conducted in Unit 2 (2 ha); Unit 3 (4 ha) and Unit 4 (0.75 ha). Unit 5 was deemed not suitable for burning in either of these trials. Data Collection Fuels and Fire Weather In May 2007, data were collected to calculate fuel loads. Sampling methods followed a slightly modified version of the protocol described in the Alberta Fire and Vegetation Monitoring Field Manual (Bannerman and McLoughlan 2009). Twenty sampling plots were randomly established through-out the site (a minimum of three plots per unit). Fuel moisture sampling was conducted on each day of burning and typically began one to two hours before each ignition. Surface moisture samples were taken every 5m along the planned ignition lines and included lichen, needle litter, moss tips, and duff. Foliar moisture samples were taken randomly from both the control and treated stands using tree pruners. A Remote Automated Weather Station (RAWS) was placed on the experiment site on May 3, The weather station recorded hourly weather data: temperature; relative humidity; wind speed; wind direction; and precipitation. 3 P a g e

4 Fire Behaviour In-situ fire behaviour data were collected using in-fire video cameras; hand-held video and still-photo cameras; aerial video and still-photo cameras; and observations by fire behaviour specialists. Nine temperature data loggers with thermocouples were placed in a grid pattern within each plot to capture surface temperatures. Data Analysis Fuels and Fire Weather Surface fuels were divided into two broad categories: (1) litter & duff and (2) dead & down woody debris. Forest floor (litter and duff) samples were collected using a 30cm x 30cm square. Oven dry weights of the samples (in grams) were converted to tonnes per hectare. Counts of dead and down woody pieces in each of the six size classes were converted to tonnes per hectare using equations and variables in Nalder et al. (1999) and Delisle and Woodard (1988). The crown 4 fuel load (kg/m 2 ) of Jack pine was calculated using crown biomass equations in Alexander et al. (1991) which were derived from the Darwin Lake Experimental Burn Project (Quintilio et al. 1977). For black spruce, crown fuel load was calculated using crown biomass equations in Alexander et al. (2004). Canopy 5 fuel load, canopy depth and canopy bulk density were calculated using equations in Cruz et al. (2003). Moisture samples were bagged and weighed wet on site at the time of collection, then sent to the Alberta Sustainable Resource Development lab in Edmonton, Alberta where they were oven-dried and gravimetric moisture contents were calculated. In 2008, gravimetric moisture contents were calculated on site; this was a slow and tedious process that severely limited the amount of samples that could be analyzed. The new procedure in 2009 allowed researchers to collect 10 times more samples. The following values were calculated using the Canadian Forest Fire Weather Index System and the RAWS weather data: hourly Fine Fuel Moisture Code (HFFMC) hourly Initial Spread Index (HISI) hourly Fire Weather Index (HFWI) Values for the Duff Moisture Code (DMC), the Drought Code (DC) and the Build-Up Index (BUI) were calculated daily at 13:00 HRS (daylight savings time). Fire Behaviour Van Wagner (1977) and the FBP system (Forestry Canada Fire Danger Group 1992) each use categories to describe different classes, stages or types of fire (Table 1). Both use surface fire as their first category and then, as crown fire begins, they use the terms passive crown (Van Wagner) and intermittent crown (FBP). For both classification systems, this phase is characterized by a threshold surface fire intensity (CSI) needed for a surface fire to reach into the crown fuels (Van Wagner 1989): Critical Surface Intensity (kw/m) = 0.001(CBH) 1.5 x ( FMC) 1.5 where, CBH = crown base height FMC = foliar moisture content 4 Crown refers to the aerial fuels of individual trees (Cruz et al. 2003). 5 Canopy refers to the aerial fuels at the stand level (Cruz et al. 2003). 4 P a g e

5 To determine whether a surface fire has become a passive/intermittent crown fire, observed fire intensity must exceed CSI. Unfortunately, researchers could not collect the data required to calculate observed fire intensity due to limited resources and time. Instead, researchers estimated observed fire intensities by comparing photos and video footage from each burn to colour plates of known fire intensities provided in Stocks and Hartley (1995) and Alexander and De Groot (1988). Researchers also used a conversion of Van Wagner s CSI formula to determine a critical flame length (L o ) that could be used instead of CSI (Alexander and Cruz 2012). Critical flame length (m) = (0.01 x CBH x ( (FMC)) 0.69 where, CBH = canopy base height (m) FMC = foliar moisture content (%) Higher intensity and faster moving crown fires are defined as active crown (Van Wagner) and continuous crown (FBP). Active crown fires are defined by Van Wagner as those which exceed a critical rate of spread that is based on canopy bulk density. Critical Rate of Spread for active crown fire (m/min) = 3.0 / canopy bulk density (kg/m 3 ) Observed fire rates of spread were calculated using data collected from the temperature data loggers and estimates by on-site fire behaviour specialists. Continuous crown fires are defined in the FBP as those where canopy fuel consumption, or crown fraction burned (CFB), exceeds 90%. Van Wagner has a fourth fire type, independent crown fire, which could not occur during conditions under which these test burns were conducted. Table 1. Fire type categories used by Van Wagner and the FBP System. Van Wagner Surface Passive Crown Active Crown FBP System Surface Intermittent Crown Continuous Crown Independent Crown - Each burn was classified according to the categories in Table 1 by fire behaviour specialists based on real-time on-site assessments and post-fire review of photos and video footage. Burn Procedures Burn procedures and ignition patterns for the 2009 burn trials were based on experience gained from the 2008 burn trials (Schroeder and Mooney 2009). For 2009, each control burn was separated from the treated burn by approximately 100 m to reduce potential interaction between the fires. Also in 2009, a series of smaller paired burns were conducted within each unit rather than igniting an entire unit for one large paired burn as in This arrangement allowed for several paired burns to be conducted within each study unit, greatly increasing the opportunities to observe fire behaviour. Ignition lines of 30 m were used for all burns, with the exception of the first set which was ignited with a 10m line. Ignitions in each paired burn were made at the same time and 5 P a g e

6 in the same direction using drip torches. Burns were allowed to run approximately m before extinguishment. The location and direction of the burns were determined on-site each day, based on the prevailing wind direction to ensure that each fire would burn into non-fuels (i.e., muskeg; old burn; lake). This reduced the chance of escape fires and spot fires in the other study units and only a small fire crew was required to monitor the fire perimeter and extinguish the fires. Because crown fires developed rapidly in the 2008 burn trials, researchers determined that the 2009 burn prescription should have lower FFMC and BUI values than in 2008 (Table 2). The first paired burn was ignited during conditions that would not likely result in crowning with subsequent paired burns ignited at increasing FFMC values to determine whether there was a threshold at which crowning would occur in the treated stands but not in the control stands. Table 2. Actual fire weather conditions for 2008 and prescription for Fire Weather Variable 2008 Actual (Plot 6) 2008 Actual (Plot 1) 2009 Prescription Temp ( o C) Relative Humidity (%) FFMC BUI ISI Wind Speed (km/hr) Results Nine paired experimental burns were conducted between July 26 and July 29, We were able to conduct 2-3 paired burns each burning day at slightly increasing FWI values. Fuels Fuel Type The stand density averaged 1700 stems/ha with 90% Jack pine (Pinus banksiana) and 10% black spruce (Picea mariana). There was a nearly continuous lichen layer (70-80% cover) with sparse to moderate feather moss throughout (10-25% cover) (Figure 3). The organic layer was generally shallow, but deepened moderately beneath larger patches of moss. Sparse to moderate herbs and shrubs consisted of primarily blueberry (12-25% cover) and kinnikinnick (5-18% cover). The scattered understory had the same composition as the overstory. Ladder fuels were not extensive, but did exist in scattered areas. There was flaky bark present on the Jack pine stems which has been shown to act as an effective ladder fuel (Quintilio et al. 1977; Schroeder and Mooney 2009). 6 P a g e

7 Fuel Load Figure 3. Typical Archer Lake stand structure showing extensive lichen ground cover. There was no significant difference (p < 0.05) between the fuel loads of individual units or between the treated and control stands (Table 3). Table 3. Fuel load data for the Archer Lake study area. Fuel Characteristic Value Forest Floor 6 Depth (cm) 6.8 Forest Floor Load (kg/m 2 ) 2.4 Forest Floor Bulk Density (kg/m 3 ) 35.4 Surface Fuel 7 Loads (kg/m 2 ) 0.75 Canopy Height (m) 8.7 Live Crown Base Height (m) 4.6 Live Crown Depth (m) 4.2 Canopy Fuel Load (kg/m 2 ) 0.65 Canopy Bulk Density (kg/m 3 ) 0.16 Fuel Moisture Although the surface fuel moisture results were highly variable, there was no significant difference in the moisture content of lichen, needle litter and moss tips between the control and treated stands. The foliar moisture content of red needles in treated stands averaged 16.10% (min 5.93%; max 24.63%). Unfortunately, green-needle samples spoiled en-route to the laboratory and moisture contents could not be established. 6 Refers to the litter (needles), moss tips, lichen and duff layers. 7 Refers to dead and down woody pieces. 7 P a g e

8 However, the few foliar moisture samples taken from control stands in 2007 and 2008 suggest that greenneedle MC is approximately %. There was also no relationship between the observed moisture content of the fine fuels and the Fine Fuel Moisture Code. Mean values for the moisture content of the fine fuels are listed in Table 4. Table 4. Moisture content (%) for fine fuels sampled in Fuel Type N Mean SD Lichen Moss Tips Litter Red Needles There was a significant difference in the moisture content of duff between the control and the treated stands and there was also a significant correlation with the Duff Moisture Code (Figure 4). Fire Weather Figure 4. Differences in duff moisture content between control and treated stands. Error bars represent +/- 1 SD. The fire weather variables recorded on-site for each experimental fire, and the FWI System codes and indices calculated from those conditions, are outlined in Table 5. The HFFMC ranged from 85.6 to 89.4 (92 in 2008), the HISI ranged from 3.1 to 6.6 (10 in 2008), and the HFWI ranged from 9.7 to 17.5 (32 in 2008). 8 P a g e

9 Table 5. Fire weather variables and FWI indices for the 2008 and 2009 burns. Burn # Burn Date Ignition Length Ignition Time Temp ( o C) Relative Humidity (%) Wind (km/h) DMC DC BUI HFFMC HISI HFWI Jul 100m 14: Jul 10m 13: Jul 30m 14: Jul 30m 16: Jul 30m 11: Jul 30m 15: Jul 30m 12: Jul 30m 16: Jul 30m 13: Jul 30m 17: Fire Behaviour The critical surface intensity (CSI) was calculated using a canopy base height of 4.6 m and foliar moisture content of 24% (treated) and 120% (control). Recall that this was the intensity required for surface fire to become a passive/intermittent crown fire. CSI = 350 kw/m (treated) CSI = 2100 kw/m (control) The critical flame length (L o ) was also calculated using a canopy base height of 4.6 m and a foliar moisture content of 24% (treated) and 120% (control). Recall that this was the flame length required for surface fire to become a passive/intermittent crown fire. L o = 1.1 m (treated) L o = 2.6 m (control) The critical rate of spread for active crown fire was calculated using the canopy bulk density of 0.16 kg/m 3. Recall that canopy bulk density was calculated in 2007, at which time there was no significant difference between control and treated stands. This spread rate was required for a passive/intermittent crown fire to become an active/continuous crown fire. ROS = m/min Rates of spread for Burns 1 through 4 were estimated by a fire behaviour specialist at ground level. Data from temperature data loggers deployed in Burn 5, 6, 7, 8, and 9 were used to calculate fire rates of spread. Several data loggers failed in the control stand of Burn 8 and in the treated stand of Burn 9 so no rates of spread could be calculated for those two burns. 9 P a g e

10 Fire behaviour specialists classified each fire (Table 6) according to its estimated fire intensity, flame length and rate of spread. Table 7 presents three examples of fires observed at Archer Lake and the data used to classify them. Table 6. Fire classifications and rates of spread for Archer Lake burn trials. Control Stand Treated Stand Burn Date HFFMC HISI HFWI Van Wagner FBP ROS (m/min) Van Wagner FBP ROS (m/min) Jul Active Continuous Active Continuous Jul Surface Surface 3.0 Surface Surface Jul Passive Intermittent - Passive Intermittent Jul Passive Intermittent 4.0 Passive Intermittent Jul Surface Surface 3.0 Surface Surface Jul Surface Surface 3.1 Surface Surface Jul Passive Intermittent 8.8 Passive Intermittent Jul Passive Intermittent 3.2 Passive Continuous Jul Passive Continuous - Passive Continuous Jul Passive Continuous 3.9 Passive Continuous - Except for Burn 7, there were no differences in fire classification between the control and treated stands and no operationally significant differences in fire rates of spread. Only the 2008 burns produced rates of spread fast enough to be classified as active/continuous crown fires (>18.75 m/min); however, the crown consumption in the treated stand of Burn 7 and in the control and treated stands of Burn 8 and 9 was >90% (based on visual estimation). By the FBP definition, these fires can be classified as continuous crown fires. As the FWI value increased each burning day, fire behaviour also increased. These results suggest that an FWI value of may be the threshold value at which crown fire occurs in this region; however, there was no difference in the threshold FWI value between control and treated stands. 10 P a g e

11 Table 7. Three examples of fire classifications observed at Archer Lake. Control Burn 1 Treated low to moderate intensity surface fire ROS 3.0 m/min; flame length <2m EST Intensity = kw/m Control Burn 3 low to moderate intensity surface fire ROS 3.0 m/min; flame length <2m EST Intensity = kw/m Treated high intensity surface fire/intermittent crown ROS 4.0 m/min; flame length >2m EST Intensity = kw/m Control Burn 7 high intensity surface fire/intermittent crown ROS 4.0 m/min; flame length >2m EST Intensity = kw/m Treated intermittent crown ROS 3.2 m/min; flame length >3m EST Intensity = kw/m developing active crown ROS 7.6 m/min; flame length > 3m EST Intensity = kw/m 11 P a g e

12 Discussion Based on the anecdotal evidence from wildfire personnel in British Columbia, we expected to see greater differences in fire behaviour between red-needled (treated) and green-needled (control) stands. Our results showed no differences in either crown fire initiation or rates of spread between green-needled and redneedled stands. Fuel Moisture and Fire Behaviour We expected crown fire initiation to occur earlier in treated stands because lower foliar moisture content (FMC) should require less surface fire intensity to initiate crowning. We also expected that crown involvement would occur in treated stands at lower FWI values. Our results showed that at a given FWI value, crown involvement occurred at the same time in the control and treated stands. However, both the Van Wagner and the FBP classification systems allow for a broad range of crown involvement, intensity and rate of spread at the passive/intermittent phase and in these trials we did observe greater crown involvement in the treated stands (Figure 5). Figure 5. Intermittent/passive crown fire showing more crown involvement in the red-needled stand. The lack of transpiration in the treated stands did appear to cause increased duff moisture, but this increase in duff moisture did not affect the moisture content in the surface fuel components (lichen, needles, moss tips). This may help to explain why rates of spread and fire intensities were similar between the control and treated stands. Fuel Characteristics and Fire Behaviour The 2007 statistical analysis of the surface and canopy fuel load indicated no significant differences between the control and treated stands. However, by 2009 trees in the treated stands had dropped a noticeable amount of their needles (Figure 6).8 A lower canopy fuel load would inhibit crown fire initiation and crown fire rates of spread. Jolly et al. (2011) conducted single tree ignition tests and found that candling was inhibited after notable needle loss had occurred. Sparser canopy in the treated stands may help explain why the expected crown fire activity did not occur. 8 Approximately 25% - visual estimate made by D. Schroeder. 12 P a g e

13 Figure 6. Differences in canopy needle retention by 2009 between treated (left) and control (right) stands. The increase of dry needles on the forest floor did not appear to increase surface fire intensity in the treated stands nor did the increased consumption potential of dry twigs remaining in the trees appear to compensate for needle loss to affect crown fire behaviour. Archer Lake Fire Behaviour vs. Anecdotal Observations The fire behaviour results at Archer Lake seem counter to wildfire observations from British Columbia where fires in red-needled stands were reported to spread much more quickly and at higher intensity, relative to green-needled stands. In BC, the general caution for fire crews was at FFMC 91, a red-needled stand was to be viewed as if it was standing cured grass 20m tall (Harvey and Duffy 2008). The 2008 Archer Lake burns did not show a difference in fire type or ROS between red-needled and green-needled stands at FFMC 91; both control and treated stands exhibited active crown fire behaviour. Van Wagner s (1977) criterion for active crowning is based on canopy bulk density and explicitly states that foliar moisture is not a factor. There was no needle loss in 2008 so the same rate of spread would have been needed for the onset of active crowning in both the control and treated stands. And although many of the girdled tree needles had not yet turned red in 2008, Jolly et al. (2011) state that this would not have limited their ignitability. It was unexpected that the ROS in 2008 was not different after active crown fire began. Perhaps the difference in energy needed to evaporate moisture out of green needles relative to dead needles is small in comparison to the overall energy output of an active crowning fire. Wildfire personnel from BC had also reported higher ignition probability from long-range flying embers. The burn plots at Archer Lake were too small to capture effects of long-range spotting (<100m); however, since there were no differences in surface fuel moisture, a difference in ignition probability between the control and treated stands would not be expected. 13 P a g e

14 Archer Lake vs. FBP Fuel Types The FBP C-3 fuel type best describes the types of stands that are typically attacked by mountain pine beetle. The stands at Archer Lake approximated the C-3 fuel type; the stand density averaged 1700 stems/ha and there was a lack of ladder fuels with sparse understory and shrubs. However, some important forest fuel characteristics at Archer Lake did not match the C-3 FBP fuel type; the low crown base height of 4.6m was more like C-4; the low canopy fuel load of 0.65 kg/m 2 was about half of what it typically is for other pine types (C-3: 1.15 kg/m 2 and C-4: 1.2 kg/m 2 ); and the nearly continuous lichen layer was more like C-1. Consequently, the fire behaviour exhibited by the control and treated stands did not match that predicted for a C-3 FBP fuel type prior to a MPB attack (Figure 7). At high FFMCs (>90), abundant reindeer lichen can result in greater rates of spread and higher fire intensities than what is predicted to occur in typical C-3 stands (McRae et al. 2005, Schroeder 2010). Coupled with a lower canopy base height, the potential for crown fire is greater in the pine stands at Archer Lake regardless of foliar moisture content. Figure 7. Comparison of Archer Lake ROS/ISI relationship with other experimental burns. Porter (Alexander et al. 1991); Darwin (Quintillio et al. 1977); ICFME (Stocks et al. 2004) Figure 7 suggests that the 2009 Archer Lake burns followed a trend similar to the C4 fuel type. However, using the C-4 fuel type to predict fire behaviour in stands similar to Archer Lake should be done with caution and only when ISI <10, until more data becomes available. The Archer Lake data set is small and only has FWI values <90. As well, the two fuel types have only a few similarities (canopy base height, canopy bulk density), but many differences (surface fuel characteristics, stand density, vertical fuel continuity, and canopy fuel load). 14 P a g e

15 Although the differences between the Archer Lake fuel type and a typical C-3 fuel type may have confounded the analysis for this study, the results nevertheless increase our fire behaviour knowledge for fuel types that do not neatly match one of the 16 FBP fuel types. Conclusion This study attempted to isolate the impact of tree mortality and associated moisture loss on fire behaviour to gain insight into the effect a mountain pine beetle attack might have on fire hazard. Fuel load, fuel structure and fine fuel moisture were not different between control and treated stands for nine paired burns; however, foliar moisture content was lower and needle cast was greater in the treated stands. The low foliar moisture content in treated stands resulted in greater crown involvement at the passive/intermittent phase. There was no difference in fire rates of spread between treated and control stands. There was no difference in the FWI threshold for crown involvement between control and treated stands. Needle loss may have inhibited crown fire initiation and crown fire rates of spread in treated plots. The FBP System with a C-3 fuel type under-predicted the rate of spread and fire type for the Archer Lake stands. Final Thoughts Although the Archer Lake site was different from typical lodgepole pine sites, it did provide researchers the ability to conduct paired burns with control stands and to conduct crown fires in pine stands with a low risk of fire escape. The concern over potentially extreme fire behaviour in red-needled stands is declining in western Canada as mountain pine beetle stands enter the grey phase; however, it remains an important concern for the rest of Canada as recent evidence indicates the potential for mountain pine beetle to spread through Jack pine forests. The results from this study can be applied to improve wildfire behaviour predictions in stands similar to Archer Lake. Fire behaviour in the grey phase has now the concern in western Canada as the standing dead stem shed bark that could increase spot fire occurrences and as dead trees fall to create major fuel loads. The grey phase lasts longer than the red phase and is not represented by current fire behaviour prediction models. Acknowledgements Thanks to Alberta Sustainable Resource Development - Wildfire Management Branch, in particular the Waterways Fire Management Area, for providing logistical, operational, planning and financial support for this project. We appreciate reviews of earlier drafts by B. Mazurik (Alberta SRD), D. Hicks (BC Ministry of Forest, Lands and Natural Resource Operations) and B. Hawkes (Canadian Forest Service) and M. Alexander (formerly Canadian Forest Service). 15 P a g e

16 References Alexander, M.E.; de Groot, W.J Fire behavior in Jack Pine stands as related to the Canadian Forest Fire Weather Index (FWI) System. Government of Canada. Canadian Forestry Service. Northern Forestry Centre. Edmonton, AB. Poster Alexander, M.E.; Stocks, B.J.; Lawson, B.D Fire behaviour in black spruce-lichen woodland: the Porter Lake Project. Forestry Canada, Northern Forestry Centre, Edmonton, AB. Information Report NOR-X-310. Alexander, M.E.; Stefner, C.N.; Mason, J.A.; Stocks, B.J.; Hartley, G.R.; Maffey, M.E.; Wotton, M.E.; Taylor, S.W.; Lavoie, N.; Calrymple, G.N Characterizing the jack pine-black spruce fuel complex of the International Crown Fire Modeling Experiment (ICFME). Natural Resources Canada. Canadian Forest Service, Northern Forestry Centre, Edmonton, AB. Information Report-X-393. Alexander, M.E.; Cruz, M.G Interdependencies between flame length and fireline intensity in predicting crown fire initiation and crown scorch height. International Journal of Wildland Fire. 21: Bannerman, B.A.; McLoughlan, N.R Alberta Fire and Vegetation Monitoring Program Field Sampling Manual. Wildfire Prevention Section, Wildfire Management Branch, Forestry Division, Sustainable Resource Development. Edmonton, Alberta. Cullingham, C.I.; Cooke, J.E.K.; Dang, C.S.; Davis, B.J.; Cooke, D.; Coltman, W Mountain pine beetle hostrange expansion threatens the boreal forest. Molecular Ecology 20: Cruz, M.G.; Alexander, M.E.; Wakimoto, R.H Assessing canopy fuel stratum characteristics in crown fire prone fuel types of western North America. International Journal of Wildland Fire 12: Delisle, G.P.; Woodard, P.M Constants for calculating fuel loads in Alberta. Natural Resources Canada. Canadian Forestry Service. Northern Forestry Centre, Edmonton, AB. Forest Management Note 45. Forestry Canada Fire Danger Group Development and structure of the Canadian Forest Fire Behavior Prediction System. For. Can., Ottawa, ON. Inf. Rep. ST-X-3. 63p. Graham, R.T.; McCaffrey, S.; Jain, T.B Science basis for changing forest structure to modify wildfire behaviour and severity. General Technical Report RMRS-GTR-120. Fort Collins, CO: US Department of Agriculture, Forest Service, Rocky Mountain Research Station. 43 p. Harvey, S.; Duffy, C Mountain pine beetle fire operations & fuel management. Canadian Interagency Forest Fire Centre, National Conversation. Internet-based presentation. March 27, Hirsch, K.G Canadian Forest Fire Behaviour Prediction (FBP) System: user s guide. Natural Resources Canada. Canadian Forest Service, Northern Forestry Centre, Edmonton, AB. Special Report p. Jenkins, M.J.; Hebertson, E.; Page, W.; Jorgensen, C.A Bark beetles, fuels, fires and implications for forest management in the intermountain west. Forest Ecology and Management 254: Jolly, M.; Parsons, R; Hadlow, A; Cohn, G Mountain Pine Beetle-Induced changes in Lodgepole pine needle flammability. 16 P a g e

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