UBC Undergraduate Research

Vaseux Lake Canadian Wildlife Service burn Erasmus, Hans 2014-04

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   Vaseux Lake Canadian Wildlife Service Burn Hans Erasmus FRST 497 April 2014 ii  Table of Contents Abstract ........................................................................................................................................... 1 Introduction ..................................................................................................................................... 1 Methods........................................................................................................................................... 3 Study area .................................................................................................................................... 3 Prescribed burn …………………………………………………………………………………3 Field measurements ..................................................................................................................... 5 Pre-burn ................................................................................................................................... 5 Post-burn .................................................................................................................................. 5 Results ............................................................................................................................................. 7 Fire weather indices .................................................................................................................... 7 Fire temperature .......................................................................................................................... 8 Biomass ....................................................................................................................................... 8 Pre-burn stand conditions .......................................................................................................... 11 Basal area .................................................................................................................................. 11 Tree mortality ............................................................................................................................ 12 Charring and crown scorch ....................................................................................................... 12 Above ground fire severity indicators ....................................................................................... 12 Discussion ..................................................................................................................................... 17 Fire Weather Indices ................................................................................................................. 17 Fire temperature ........................................................................................................................ 17 Biomass ..................................................................................................................................... 18 Conclusion .................................................................................................................................... 19 Acknowledgement ........................................................................................................................ 19 References ..................................................................................................................................... 20    1  Abstract This study was done to quantify the intensity and severity of the Vaseux Lake Canadian Wildlife Service prescribed burn in March 2013. Onsite measurements of fuel moisture content were compared to predicted Fire Weather Indices (FWI) for the Fine Fuel Moisture Code (FFMC) and Drought Moisture Code (DMC). Fire intensity was determined from the thermocouple temperature profiles. Fire severity was quantified through consumption of large woody fuels (diameter ≥ 2.6 cm) and change in basal area, mortality, bole char, uphill char height, and crown scorch on trees. We found that the fire weather indices indicated an FFMC of 85 and a DMC of 116. Peak fire temperatures ranged from 38ºC to 762ºC, and burn times above ambient temperature ranged from 10 to 600 minutes. Fire consumption reduced the fuel load by 41.2%. The 100hr fuels (2.6-7.5cm) made up the largest proportion of woody fuels, of which 29% were totally consumed. Tree mortality was limited to 3 ponderosa pines and 5 Douglas-fir. Tree indicators included 82.5% average charring around the circumference of the base, 193cm average uphill char height, and 32.7% average crown scorch. This imperial data can be used as a baseline for long-term monitoring of the site and to prescribe future fire treatments. Introduction The dry-belt of southern British Columbia (BC) occurs at low elevations (< 1200 m.a.s.l.) along dry valleys of the interior plateau (Lloyd et al. 1990). The Biogeoclimatic Ecosystem Classification (BEC) zones of this region include the Bunchgrass zone, Ponderosa Pine zone, and Interior Douglas-fir zones (Klenner et al. 2008). These ecosystems are classified as Natural Disturbance Type 4 (NDT4), and were historically maintained through periodic wildfires and First Nation peoples (MFLNRO 2013). Ecosystems classified as “fire maintained” were subject to frequent low-severity fires that maintained forest structure and species (Noss et al. 2006).  Plants and animals in ecosystems with frequent low-severity fires have evolved with and depend on periodic burning (Agee 1993, Van Wagner et al. 2006). Since the early 1900s, the BC Forest Service has been aggressively suppressing wildfires (MFLNRO 2013). In many areas, the suppression of wildland fires in fire-maintained ecosystems has changed forest structure and composition (Covington and Moore 1994), shifted grassland-forest ecotones (Barrett and Arno 1982), and increased fuel loading (Wagle and Eakle 1979). In some areas, these changes have increased the risk of high-severity stand-replacing wildfire, resulting in wildlife habitat loss (Tiedemann et al. 2000).  In British Columbia, the last decade has seen a renewed interest in applying prescribed burning as a tool in environmental stewardship for ecosystem restoration projects (MFLNRO 2013). Prescribed fire is being used as a management tool for fire-hazard reduction, silviculture prescriptions, insect and disease control, wildlife habitat enhancement and range burning (Weber and Taylor 1992).  2  The study region west of Vaseux Lake is owned by the Canadian Wildlife Service. This region is in the Ponderosa Pine BEC zone (Lloyd et al. 1990) and is characterized by uneven-aged stands of ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii), a C-7 fuel type (Taylor et al. 1997). High frequency low-severity fires are shown to have been an important component of the historic disturbance regime in many ponderosa pine and mixed-conifer ecosystems (Arno et al. 2000; Heyerdahl et al. 2008, 2012, Daniels and Gedalof 2012, Gayton 2013). Historically, periodic surface fires consumed woody debris, rejuvenated shrub species and thinned out younger regenerating trees. Low-severity fires maintained vegetative species composition, stand structure, and regulated coarse wood in a in a complex system of feedbacks (FRPA 2004). The fire-maintained native plant and shrub species make up critical habitat in the Vaseux Lake area, including the endangered White-headed (Picoides albolarvatus) and Lewis’ woodpeckers (Melanerpes lewis) (Ministry of Environment 2013). Local history of Vaseux Lake included the Twin Bays First Nations village at the south end of the lake which was abandoned c.1860 after smallpox epidemic, a stage coach road upslope from the lake, and the Kettle Valley Railway which was built in the early 1930’s. The ecological effects of fire exclusion around Vaseux Lake include encroachment of ponderosa pine and Douglas-fir trees into the grasslands, increased cover and density of trees, changes in plant species and composition, and loss of critical wildlife habitat. Specifically, changes to habitat include invasion of Douglas-fir trees and mortality of antelope brush (Purshia tridentata) in the area (L. Daniels, personal communication, March 9, 2013).  In March 2013, the Canadian Wildlife Service (CWS), in collaboration with the BC Wildfire Management Branch, implemented a prescribed fire in the Vaseux-Bighorn National Wildlife Area to restore the grassland-woodland ecosystem. The objectives of re-introducing fire as an ecological process were to restore critical wildlife habitat, mitigate fuels build-up to decrease the risk of an uncontrollable severe wildfire, and to increase ecosystem resilience to climate and other environmental changes (Mottishaw 2013).  The burn prescription included objectives for stand, understory, wildlife trees, coarse woody debris, wildlife species at risk, rare plant species and plant communities, and antelope brush objectives (Mottishaw 2013). Stand objectives were to reduce tree density in open range to 20 stems/ha and 150 stems/ha in open forest, while preserving trees >30cm diameter at breast height (dbh).  The understory objective was to increase blue bunch wheat grass (Pseudoroegneria spicata) and regenerate Rosaceae shrubs to increase fire adapted native vegetation and increase forage production.  The wildlife tree objectives were to protect snags and to provide a more open stand of mature cone producing ponderosa pine trees. These objectives address the critical foraging and nesting requirements of the White-headed and Lewis’ woodpeckers. Coarse woody debris (CWD) objectives were to maintain and recruit 6-10m3/ha of CWD >30cm dbh within all decay classes. The wildlife species at risk objective is to maintain or increase the species richness and population density of endemic wildlife species, with emphasis on Schedule 1 of the red and blue listed species. Rare plant species and plant communities’ objective maintains or increases 3  the species richness and population density of endemic plant species with emphasis on red or blue listed communities. The antelope brush objective was to maintain the density and size of antelope brush. This is to account for the threatened Behr’s Hairstreak moth (Satyrium behrii) eggs laid on the antelope brush.  The objectives were to monitor fire severity by measuring temperature and duration using thermocouples, and fire severity by using above ground indicators using measurement of trees, snags, and large woody fuel loads.  To quantify effects measurements were taken both before and after the burn in 4 treatment units, and in one control unit.  Methods This burn was done in March when fire weather indices are suitable to meet the desired fire effects. Desired fire weather indices include temperatures between 10-20ºC, relative humidity (RH) between 25-35%, and wind speed <15kmph. Desired fuel moisture contents include Fine Fuel Moisture Code (FFMC) 85-92, Duff Moisture Code (DMC) 25-40, and Drought Code (DC) 250-350. The desired fire behavior is low vigor surface fire (rank 2) with a Head Fire Intensity (HFI) in the 85-1000 range and flame length of 0.5-1.75m. Occasional rank 3 burn (moderate vigorous surface fire, HFI of 1000-2000, and flame length 1.75-2.5m) was acceptable to meet the desired fire effects.   Study area The study area is located on the west side of Vaseux Lake in the southern Okanagan of British Columbia (49º17’29” N, 119º32’30” W). The study area has a continental climate with the warmest temperatures averaging 21.1ºC in July, and coldest temperatures averaging -2.6ºC in January (Environment Canada 2014). The average daily temperature in March is 5.5ºC, with a daily average maximum of 11.4ºC and average minimum of -0.4ºC. Mean precipitation in March is 22.2mm, 20.8mm of which is rainfall and 1.4cm snowfall. The soils are dominantly Chernozemic (Valentine et al. 1978) with a fine texture and a duff layer > 5cm. The study area is classified as a C-7 fuel type within the Ponderosa Pine biogeoclimatic zone with a xeric hot subzone (PPxh). The dominant forest cover includes ponderosa pine and Douglas-fir (Meidinger and Pojar 1991). Dominant vegetation in this ecosystem includes blue bunch wheatgrass, antelope brush, and arrowleaf balsamroot (Balsamorhiza sagittata) (Meidinger and Pojar 1991).   Prescribed burn  The total area proposed for treatment was 48ha, and was divided into five treatment units (TU), including one control and five units to be burned, four of which we monitored (Fig. 1). The treatment area was located on an east aspect and in a lower slope position, at elevations between 325 and 410m. The slope of the study area varied from 0% to >50% (slope mean = 28%). Fuel 4  loading was considered light, with moderate needle loading under the ponderosa pine. Prior treatments in the area include thinning, prescribed burning, and pile burning. In 2003, thinning was done to achieve a density of 200 trees/ha (Mottishaw 2013).  Cut stems were left as downed wood on site. In 2004, a prescribed burn was done upslope of TU 1 & 2. Treatment unit 1 was thinned in 2006 and pile burned in 2009.  The prescribed burn was done over two days between March 27 and 28, 2013 when fire weather indices were suitable to meet the desired fire effects.  Desired fire weather indices include temperatures between 10-20ºC, relative humidity (RH) between 25-35%, and wind speed <15kmph (Mottishaw 2013). Desired fuel moisture contents include Fine Fuel Moisture Code (FFMC) 85-92, Duff Moisture Code (DMC) 25-40, and Drought Code (DC) 250-350. The desired fire behavior was low vigor surface fire (rank 2) with a Head Fire Intensity (HFI) in the 85-1000 range and flame length of 0.5-1.75m. Occasional rank 3 burn (moderate vigorous surface fire, HFI of 1000-2000, and flame length 1.75-2.5m) was acceptable to meet the desired fire effects.  Prior to ignition, a blackline was burned along the high points of land to create fire boundaries and create a barrier to prevent burning near the gas pipeline.  Lighting was done using drip torches, stripping along contours and working downslope from the highest elevation in each TU.  Lighting strips were 5-10 metres wide and orientated along north to south contours. Treatment units were ignited in the afternoon, starting with TU 2 on the first day, followed by TUs 1, 3, and 4 on the next afternoon.  42.6 ha of land were burned at fire intensity rank 2 and 3.  FWI from the Penticton RS WS was obtained to predict fire weather behaviour in the study area (Table 1).   Table 1. On-site fire weather readings and fire weather indices. Fine Fuels Moisture Code=FFMC, Drought Moisture Code=DMC, and Drought Code=DC.  Weather Readings March 27 – 14:00 March 28 – 14:00 Temperature 15.3 ºC 17.0 ºC Relative Humidity 32.5 36.4 Wind Speed 2.6 km/hr 9.3 km/hr Wind Direction 258º 147º Fire Indices  FFMC 88 DMC 12 DC 301   5  Field measurements Pre-burn  Treatment unit boundaries were assigned based on topographic variation (Fig. 1). Shallow gullies were used to delineate treatment units and to create fire breaks for the prescribed burn. Each TU contained one 100m sampling transect, orientated upslope from Vaseux Lake. To estimate the fuel load, wood fuel biomass was measured using the line intersect method (Van Wagner 1968). Diameters of woody surface material ≥2.6cm were measured with calipers where wood pieces crossed the sampling transect. Steel wire was tied around the intersection points so the wood could be re-measured after the burn. Species, decay class, and whether the wood was cut and elevated off the ground were recorded.  At 15m intervals along each sampling transect, trees were measured using the point-centre-quarter method to estimate tree densities and basal area (Cottam and Curtis 1956). The distance and azimuth to the four closest trees (diameter at breast height [dbh] ≥ 5cm) were measured and species, diameter, live or dead status were recorded.  Each tree was tagged with a numbered brass tag so the trees could be re-measured after the fire and monitored through time.  On the morning of the burn, thermocouples were buried 40cm below the soil surface at 0, 50, and 100m along each transect. Samples from the fine fuels surface litter and duff layer were taken and put into aluminum soil sample tins, as well as foliar samples from the ponderosa pine and Douglas-fir nearest the 50m mark along each transect.  Post-burn  Thermocouples were recovered within 24 hours of the burn. Temperature data were downloaded and analyzed for maximum temperatures, durations of temperature above 60ºC, and the time to return to ambient temperature. Samples from the fine fuel litter and duff layer were weighed on-site to obtain wet sample weights. The samples were then dried in a drying oven at 100ºC for 24 hours. Dried samples were re-weighed to obtain the dry sample weight. The following formula was used to obtain the percent moisture content of the fine fuels and duff layer: Wet weight of sample−dry weight of sampledry sample weight−container tare weight (100) = percent moisture content  6   Figure 1. Vaseux Lake treatment units showing transect lines and thermocouple placement.  7  Each of the fuel transects were re-measured in May 2013.  For the woody fuels, the wires were relocated for each piece of wood. The diameter of each piece of wood was measured again at the location of the wire. Woody fuels were categorized by diameter into 100 hour fuels (2.6-7.5cm), small 1000 hour fuels (7.6-23 cm), and large 1000 hour fuels (>23cm). Specific wood densities (Gonzalez 1990) were used to calculate the biomass of each piece of wood, and to determine the total fuel load for each TU. Pre and post-burn fuel loads with associated percent change were compared among TUs. As well, change in fuel load for 100 hour fuels, small 1000 hour fuels, and large 1000 hour fuels were compared among TUs. Each tree was re-measured for live/dead status, dbh, percentage burned around the base, height of charring on the uphill and downhill sides of the bole, and crown scorch. Crown scorch was estimated through visual analysis of the percentage of tree crown that was red, yellow, or black as a result of convective heat killing the tree’s foliage. Pre and post-burn basal area was calculated for each tree and snag using dbh. Total and species-specific relative values of tree density and basal area were calculated for each transect (Cottam and Curtis 1956). Density and basal area were compared before and after the burn, among TUs and between tree species. Bole char, uphill char height, crown scorch, and tree survival were compared among TUs.  Results Fire weather indices The moisture content of the fine fuel litter and duff layer was obtained from each TU to determine the FFMC and DMC. Field-measured FFMC on the day of the burn was 85±3.5 (average ± standard deviation) and DMC was 116±34.7 (Table 2). Fire weather indices on site were compared to the indices reported by the Penticton RS Weather Station for March 28, 2013, at 14:00. The onsite FFMC (85) was similar to that of the Penticton RS Weather Station (88) (Table 3). However, the DMC on site (116) was higher than the DMC reported by the Penticton RS Weather Station (13).  Table 2. Fine fuel moisture code (FFMC) and Drought moisture code (DMC) as measured by fuel moisture content on site on March 28, 2013, at 14:00. For all sites, the average is followed by the standard deviation. Treatment Unit FFMC DMC TU1 84 124 TU2 82 73 TU3 89 157 TU4 86 112 All 85±3.5 116±34.7  8  Table 3. Penticton RS Weather Station fine fuel moisture code (FFMC) and drought moisture code (DMC) on March 28 at 14:00. Indices Penticton RS  Weather Station FFMC 88 DMC 13  Fire temperature Thermocouple data showed variation in peak temperatures along transects and among TUs (Fig. 2). Peak temperatures were highest at the 0 and 50m sites, ranging from 263 to 762°C. Thermocouples at the 100m sites were placed beyond the crest of the slope and recorded lower temperatures ranging from 38 to 258°C. The highest temperature (762°C) was recorded in TU3 at the 50m site, while the lowest temperature (38°C) was recorded in TU1 at the 100m site. Nine of the twelve thermocouples recorded temperatures above 60ºC. Although temperatures at the three other thermocouples did not exceed 60ºC, the recorded temperatures were above ambient temperatures indicating that thermocouples were working, but that fire temperature was low.   Burn times varied among sites ranging from 10 to 600 minutes. The nine sites with temperatures above 60ºC had shorter burn times above ambient temperature, ranging from 5 to 60 minutes, while the three sites with temperatures below 60ºC had longer burn times that ranged from 20 to 600 minutes. All thermocouples at the 0 and 50m sites experienced lethal time-temperature for unprotected plant tissue (60°C for >1 minute) (Agee 1993).   Biomass Pre-burn measurements showed the abundance of 100-hour fuels in each TU (Table 4). Treatment unit 4 had the most number of wood pieces (48), all of which were cut and left as downed wood from the 2003 thinning. Treatment unit 4 also had the largest diameter wood piece (35.2cm), while TU2 had the highest percentage of elevated wood pieces (58.3%).   Of all wood pieces observed, post-burn analysis shows that the 100-hour fuels (2.6-7.5cm) were the most fully consumed diameter class along each transect (Table 4). Treatment units 2 and 3 had the most number of wood pieces consumed (11 pieces each), of which 65.8% were ponderosa pine, 26.3% were Douglas-fir, and 7.9% were antelope brush. Treatment unit 4 had the most number of cut pieces consumed, while TU3 had the most number of naturally broken wood pieces consumed.   9  TU1 TU2 TU3 TU4   Figure 2. Thermocouple data of peak temperature and burn time for each TU at 0, 50, and 100m. In each panel, time 0 represents the starting point for the temperature increase trending above ambient temperature from the approaching fire. Within each panel, the horizontal dashed line indicates 60°C, which is the lethal temperature at which unprotected plant tissue dies if exposed to for more than 1 minute.     10  Table 4. Description of woody fuels observed along each transect and comparison between pre- and post-burn observations.  Post-burn values are in parentheses.  TU 1 TU 2 TU 3 TU 4 Total number of wood pieces observed 27 (23) 36 (25) 26 (17) 48 (36) Number of 100 hour fuels (2.6-7.5cm) 17 (14) 25 (16) 17 (6) 29 (21) Number of small 1000 hour fuels (7.6-23 cm) 9 (8) 11 (9) 8 (8) 18 (14) Number of large 1000 hour fuels (>23cm) 1 (1) 0 (0) 1 (1) 1 (1) Number of ponderosa pine wood pieces 12 (10) 25 (16) 23 (13) 10 (6) Number of Douglas-fir wood pieces 12 (12) 9 (7) 0 (0) 38 (30) Number of antelope brush wood pieces 3 (1) 2 (2) 3 (2) 0 (0) Largest wood diameter in transect (cm) 25.5 21.2 23.3 35.2 Number of cut wood pieces 7 (7) 17 (11) 10 (7) 48 (36) Naturally broken wood pieces 20 (16) 19 (14) 16 (10) 0 (0) Number of elevated wood pieces  7 (5) 21 (14) 7 (3) 13 (7) Number of wood pieces on the ground 20 (18) 15 (11) 19 (14) 35 (29)   Each of the burned TUs showed a reduction in fuel load (Table 5). The average biomass before the burn was 1.87±0.67kg∙m-2 and after the burn was 1.08±0.27kg∙m-2. This represented an average biomass reduction of 41.2±5.55%. Treatment units 3 and 4 had the biggest change in biomass (-45.9%). Treatment unit 4 had the largest fuel loads before burning due to the thinning treatment in 2006 and the largest fuel loads after the prescribed burn as well.   Table 5. Fuel load for the combined 100- and 1,000-hour fuels pre-and post-burn in each TU with the associated percent change in fuel load. Treatment area Fuel load pre-burn Fuel load post-burn % Change (kg∙m-2) (kg∙m-2) TU1 1.52 0.99 -35.1 TU2 1.40 0.87 -37.9 TU3 1.84 1.00 -45.9 TU4 2.72 1.47 -45.9 Average 1.87±0.67 1.08±0.27 -41.2±5.55  11  Pre-burn stand conditions The composition of the forest before the burn was 66±13.2% ponderosa pine and 34±13.2% Douglas-fir (Table 6). The average density of ponderosa pine was 183.5 ±7.2 stems/ha, whereas Douglas-fir was 71.8 ±19.3 stems/ha. The average basal area for ponderosa pine was 11.6±1.0 m2/ha and Douglas-fir was 6.8±3.3m2/ha. Treatment unit 1 had one dead Douglas-fir and two dead ponderosa pine, TU2 had one dead ponderosa pine, and TU4 had four dead Douglas-fir trees. The diameter of the sampled trees ranged from 5.0 to 89.cm. Treatment units 3 and 4 had the smallest trees and highest overall densities of trees. Table 6. Description of trees pre-burn for each TU.  Average values are followed by standard deviations.  TU 1 TU 2 TU 3 TU 4 Average Percentage of Douglas-fir 52% 26% 23% 37% 34±13.2% Percentage of ponderosa pine 48% 74% 77% 63% 66±13.2% Number of dead Douglas-fir 1 0 0 4 1.25±1.9 Number of dead ponderosa pine 2 1 0 0 0.75±0.9 Density of Douglas-fir  (stems/ha) 95 48 74 70 71.8±19.3 Density of ponderosa pine 95 143 255 241 183.5±77.2 Basal area of Douglas-fir (m2/ha) 6.9 11.3 5.4 3.6 6.8±3.3 Basal area of ponderosa pine (m2/ha) 11 11 13 11.3 11.6 ± 1.0 Range of tree sizes (dbh) 5.0-55.2cm 23.1-89.1cm 6.7-40.8cm 5.8-48.0cm - Maximum tree size (dbh) 55.2cm 89.1cm 40.8cm 48.0 - Average tree size (dbh) 33.3±9.9 35.8±14.6 25.2±8.9 23.3±9.2 -  Basal area Each TU showed a reduction in basal area after the burn (Table 7). Treatment unit 4 showed the greatest reduction in basal area from 15.23 m2/ha to 14.33 m2/ha (-5.9%), while TU2 showed the smallest reduction in basal area from 15.27 m2/ha to 15.18 m2/ha (-0.6%).  Table 7. Basal area in each TU before and after the burn with the associated change in basal area.  TU1 TU2 TU3 TU4 Pre-burn basal area (m2/ha) 17.99 15.27 18.4 15.23 Post-burn basal area (m2/ha) 17.11 15.18 18.11 14.33 Change in basal area (%) -4.9 -0.6 -1.6 -5.9  12  Tree mortality Five of the monitored trees died during or immediately after the fire. Three ponderosa pine and two Douglas-fir trees died, all of which were in TU4. The diameter of the dead trees ranged from 6.0 to 27.6cm.   Charring and crown scorch Fire burned at the base of 101 of 117 monitored trees.  Three trees with multiple fire scars that provided critical wildlife habitat were protected during the burn, while the other 13 trees were in microsites to which the fire did not spread. On average, 82.5±6.4% of the circumference of base of the trees burned, with values ranging from 5 to 100% regardless of tree species or size (Table 8). Maximum char height occurred on the uphill side of the tree or on the opposite side from the direction of maximum fire spread. Uphill char height for all the sampled trees averaged 192±82.6 cm, with TU3 and 4 having the highest char height (1060cm). Crown scorch for all sampled trees averaged 32.7 ± 22.8%, with TU4 having the highest average crown scorch. Treatment unit 4 had the highest average uphill char height and crown scorch.   Table 8. Average bole char, uphill char height, and crown scorch summary of trees in each TU.  TU1 TU 2 TU 3 TU 4 Average Bole char (%) 75 80 90 85 82.5 ± 6.4% Uphill char height (cm) 94 154 258 264 193 ± 82.6cm Maximum uphill char height (cm) 260 370 1060 1060 687.5 ± 432.5cm Crown scorch (%) 16.3 9.8 50.6 53.7 32.7 ± 22.8%   Above ground fire severity indicators Fire temperature had variable effects on above-ground fire severity indicators (Fig. 3 to 6). Wood consumption was highest along transects where fire temperature was hottest. Char height also increased relative to fire temperature. Treatment unit 3 had the highest fire temperature (762°C) while TU3 and 4 both had charring height up to 1060cm. Bole char showed similar circumference charring among TUs. Crown scorch was greatest in TU3 and 4.  13   Figure 3. Thermocouple fire temperature profiles at 0, 50, and 100m along TU1 transect with crown scorch, bole char, char height, and wood consumption fire severity indicators. Black bar in shaded area indicates no wood consumption for that piece of wood.  14   Figure 4. Thermocouple fire temperature profiles at 0, 50, and 100m along TU2 transect with crown scorch, bole char, char height, and wood consumption fire severity indicators. Black bar in shaded area indicates no wood consumption for that piece of wood.      15    Figure 5. Thermocouple fire temperature profiles at 0, 50, and 100m along TU3 transect with crown scorch, bole char, char height, and wood consumption fire severity indicators. Black bar in shaded area indicates no wood consumption for that piece of wood.     16   Figure 6. Thermocouple fire temperature profiles at 0, 50, and 100m along TU4 transect with crown scorch, bole char, char height, and wood consumption fire severity indicators. Black bar in shaded area indicates no wood consumption for that piece of wood.    17  Discussion The results from the prescribed burn in the four treatment units provide above ground indicators of fire severity. These data provide empirical support so that prescribed burning can meet the objectives for ecosystem restoration. As well, monitoring the effects of the prescribed burn allow decisions to be made about future treatments to maintain ecosystems within their natural variation. Fire Weather Indices FFMC were similar between the study area and the Penticton RS WS. The FFMC measures the moisture content of litter and cured fine fuels, and indicates the fuel’s flammability and ease of ignition (Canadian Forestry Service 1984). The FFMC represents fast drying fuels and its value changes quickly dependant on temperature, relative humidity, wind, and precipitation. An FFMC >70 will result in spot fires, while an FFMC > 90 will result in severe fire (Taylor et al. 1997). This is consistent with onsite observations of rank 2 and 3 fire and consistent with the predicted fire weather behaviour. We did however find a significant difference in the DMC recorded on site compared to that reported by the Penticton Weather Station. This difference can be attributed to the method of setting the DMC early in the season based on the previous year’s holdover. The DMC represents the moisture content of the loosely compacted organic layers, and its value changes moderately due to the influence of temperature, wind speed, relative humidity, and rain (Canadian Forestry Service 1984). A DMC >40 is unsafe for prescribed fire (Taylor et al. 1997). My analysis indicated the DMC was higher than 40; however, fire weather readings including temperature, relative humidity, wind speed and direction were within acceptable limits for controlled prescribed burning (Mottishaw 2013).  Fire temperature Fire temperatures recorded by the thermocouples varied among sites. Fire intensity varies depending on topography, weather, fuel moisture, and fuel type (Agee 1993). The spatial arrangement and low volume of surface fuels in the treatment area likely caused variations in fire temperature and burn time. Variation in fire temperature may be important for maintaining shrub species diversity and creating openings that break up continuous ground cover (Thaxton et al. 2006).  The ecological impact of fire is directly related to fire intensity (Gedalof 2013). Plants and trees exhibit a wide range of adaptations to fire, and local species richness is strongly influenced by the site’s fire history (Gedalof 2013). Ponderosa pine and Douglas-fir are resisters that have thick bark allowing them to survive low-intensity fire, whereas the dominant vegetation including blue bunch wheatgrass, antelope brush, and arrowleaf balsamroot likely do not survive even low-severity fire. However, spatial variation in fire intensity maintains vegetative biodiversity on the landscape (Gedalof 2013). 18  Biomass We observed the greatest consumption of surface fuels along transects where thermocouples recorded the highest fire temperatures and burn times. Fuel’s effect on fire behaviour is related to the distribution, size, moisture content, arrangement, and volume of available fuels (Agee 1993). Changes to fire fuel elements directly affect fire intensity and fuel consumption. Landscapes with low volumes of fuel loading can result in low-severity fires, while high volumes of fuel loading can lead to high-severity fires and dramatic consumption of wood (Thaxton et al. 2006). Basal area was recorded before the burn and each TU showed a reduction in basal area after the burn. Except in TU4, which experienced tree mortality, these changes can be attributed to re-measurement error as no change in basal area would be expected unless trees were partially or totally consumed during the burn.  Fire severity varied throughout the burn with some fire effects showing strong relations to fire temperature. Fire severity depends on the amount of heat generated from fire but also from the duration of the burn (Agee 1993). Burn duration is a function of rate of fire spread and smolder time (Agee 1993). Rate of fire spread is dependent on fuel type, wind speed, terrain, and slope, with rate of spread most rapid in the direction of wind and upslope (Agee 1993).  Wood consumption was also positively associated with fire temperature. In areas that had high fire temperatures, wood consumption was also high. This is expected because fire temperature describes the amount of heat released per unit time per unit length (Agee 1993).  Bole char showed weak association with fire temperature and varied between 60–100% char. Bole char can be affected by other characteristics such as needle and grass abundance at the base of the tree. As well, slope, temperature, exposure time, moisture content, tree age, and physical adaptations are important in determining bole char (Agee 1993; Gedalof 2013).   Scorch height was positively correlated with fire temperature, which is consistent with Van Wagner (1972). Van Wagner also found scorch height increases as flame length increased with fire intensity.  Intensity can be estimated after the burn from the scorch height on surviving or dead trees (Pomp et al. 2008).Crown scorch showed little correlation with fire temperature and varied throughout the burn. Crown damage results from exposure to heated gas or combustion. These gases can be moved by wind from areas with high fire temperatures to lower temperature areas. The presence of ladder fuels can transmit fire from the ground to the tree crown resulting in combustion. Topography can impact crown damage as flame length and scorch height will increase on slopes. As well, canopy closure affects the amount of heat that is retained casing crown mortality. These factors can explain the low correlation of fire temperature to crown scorch. In general, TU3 and 4 showed the most change to all above ground fire severity indicators. This could be a result from the variation in terrain between the TUs, as well as variations in forest stand characteristics. Treatment unit 3 and 4 were located on steeper terrain, and exposed to the 19  prevailing wind direction from the south sooner than the other treatment units due to their location along the lake. Treatment units 3 and 4 also had smaller average tree sizes and higher tree densities. These attributes affect the fire regime because as tree density increases, the potential for high-severity fire increases (Baker 2009). As well, smaller trees have thinner bark and are therefore less resistant to injury from fire (Baker 2009).   Conclusion Fire was re-introduced in the Vaseux-Bighorn National Wildlife Area to restore critical wildlife habitat, mitigate fuels build-up to decrease the risk of an uncontrollable severe wildfire, and to increase ecosystem resilience to climate and other environmental changes. We observed fire weather indices and fire temperature profiles, and quantitated changes in fuel consumption, basal area, tree mortality, bole char, char height, and crown scorch.  Fire weather indices for FFMC were consistent with those predicted; however, the DMC on site was much higher than predicted. This could be cause for concern when implementing a burn; however, all other fire weather readings were well within acceptable limits for controlled prescribed burning. Fire temperatures and burn times varied over the area, a reflection of the spatial arrangement and low volume of surface fuels. Fuel load reduced considerably, and was correlated with increased fire temperatures. Tree mortality was low, with most of the sampled trees bearing char and crown scorch. The trees that survived can be monitored for fire scars and mortality in the future. This study established a baseline to effectively monitor and prescribe future treatments in the area. Continual monitoring will be necessary to assess the burn’s effectiveness at restoring critical wildlife habitat and ecosystem resilience.   Acknowledgements I wish to thank Dr. Lori Daniels for her guidance, encouragement, and useful critiques during this research project. Thanks to Courtney Albert of the Canadian Wildlife Service for the invitation to be involved with the monitoring of this prescribed burn. Special thanks to Raphael Chavardès for his technical support and constructive recommendations. As well, thanks to Suzie Lavalee, Gregg Greene, Brendan Forge, Mylène Labonté, and Joane Elleouet for their field work.    20  References Agee, J.K. (1993). Fire ecology of Pacific Northwest forests. Washington, DC: Island Press. Arno, S.F., Parsons, D.J., & Keane, R.E. (2000). Mixed-severity fire regimes in the Northern Rocky Mountains: consequences of fire exclusion and options for the future. USDA Forest Service Proceedings, 15(5). 225-232.  Baker, W.L. (2009). Fire ecology in rocky mountain landscapes. Washington, DC: Island Press. Barrett, S.W. & Arno, S.F. (1982). Indian fires as an ecological influence. Journal of Forestry. 80: 647-651. Canadian Forestry Service. (1984). Tables for the Canadian Forest Fire Weather Index System. Forestry Technical Report 25 (4th Ed.), Canadian Forestry Service, Ottawa, ON.  Cottam, G., & Curtis, J.T. (1956). The use of distance measures in phytosociological sampling. Ecology, 37: 451-460. Covington, W.W. & Moore, M.M. (1994). Southwestern ponderosa forest structure. Journal of Forestry. 92: 39-47. Environment Canada (2014). Historical climate data. Retrieved March 3, 2014, from http://climate.weather.gc.ca. Gedalof, Z. (2013). Fire and biodiversity in British Columbia. In Klinkenberg, Brian. (Editor) 2013. Biodiversity of British Columbia [www.biodiversity.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Gonzalez, J.S. (1990). Wood density of Canadian tree species. Forestry Canada, Northwest Region, Northern Forestry Centre, Edmonton, Alberta. Information Report NOR-X-315. Retrieved February 3, 2014, from http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/11744.pdf. Klenner, W., Walton, R., Arsenault, A., & Kremsater, L. (2008). Dry forests in the southern interior of British Columbia: Historic disturbances and implications for restoration and management. Forest Ecology and Management: 256(10)1711-1722.  Lloyd, D., Angove, K., Hope, G., & Thompson, C. (1990). A guide to site identification and interpretation for the Kamloops Forest Region. B.C. Min. For., Victoria, B.C. Land Management Handbook No. 23. Meidinger, D., and Pojar, J. (1991). Ecosystems of British Columbia: Ponderosa Pine Zone. Research Branch Ministry of Forests. Victoria, BC: Research Branch Ministry of Forests. Ministry of Environment (2013) Vaseux protected area. 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Solution of forest health problems with prescribed fire: are forest productivity and wildlife at risk? Forest Ecology and Management, 127, 1–18. Valentine, K.W.G., Sprout, P.N., Baker, T.E., & Lawkulich, L.M. (1978). The soil landscapes of British Columbia. BC Ministry of Environment, Resource Analysis Branch. Retrieved March 3, 2014, from http://www.env.gov.bc.ca/soils/landscape. Van Wagner, C.E. (1968). The line intersects method in forest fuel sampling. Forest Science, 14(1):20-26. Wagle. R.F. and T.W. Eakle. (1979). A controlled burn reduces the impact of a subsequent wildfire in a ponderosa pine vegetation type. Forest Science, 25, 123-129. Weber, M.G. & Taylor, S.W. (1992). The use of prescribed fire in the management of Canada's forested lands. The Forestry Chronicle 68(8):324-334.   

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