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Hamilton, Evelyn; Peterson, Les. 2003. Response of vegetation to burning in a subalpine forest cutblock in central British Columbia: Otter Creek site. Res. Pap. 23. Victoria, BC: British Columbia Ministry of Forestry, Research Branch. 60 p. [3].
STUDY LOCATION:FRES23 Fir-spruce [2]
K015 Western spruce-fir forest [4]
SAF 206 Engelmann spruce-subalpine fir [1]
Researchers established plots in the summer of 1988, before cutblock (clearcut) logging the following winter. At the time of logging, 1 to 2 m of snow covered the area. A total of 14 unburned, 20 spring-burned, and 15 fall-burned plots, each 3×3 m, were monitored. Predisturbance treatment areas were not significantly different with respect to species composition (p=0.15) or prefire forest floor depth (p=0.4).
PLANT PHENOLOGYBefore burning 12 depth-of-burn pins were located in each plot. Researchers recorded the depth of the pin prior to burning and depth of the remaining forest floor after burning. Estimations of prefire fuel loads came from 3 fuel triangles (30 m/side) on each of the burned sites [3].
Fire weather indices: Researchers recorded several Canadian forest fire weather codes and indices. The fine fuel moisture code (FFMC) rates the moisture content of litter and fine fuels. FFMC addresses the ease of ignition and flammability of fuels. The duff moisture content (DMC) rates the likelihood of mid-sized woody fuel and duff layer consumption through measurements of the moisture content of moderately deep organic layers. The drought code (DC) assesses the smoldering potential of deep duff and large wood by moisture measurements in deep, compact organic soil layers. Initial spread index (ISI) attempts to predict the rate of fire spread using wind speed and FFMC. The build up index (BUI) puts a value on the total fuels available for consumption by combining the DMC and DC ratings. Fire weather index (FWI) is a fire intensity estimate that combines the ISI and BUI ratings to assess forest fire danger [5]. Larger numbers for all of the codes and indices suggest greater and/or more severe fire potential. For the complete categorical and numerical rating system of the Canadian forest fire weather codes and indices, see [6].
When the spring and fall fires burned, air temperature and relative humidity were similar. Wind speed was 10 times greater during the fall fire than the spring fire. Prefire fuel (slash) loads were slightly greater on sites burned in the fall, and prefire forest floor depths were similar before both fires. The "fire weather indices suggested that the forest floor and fuels were drier at the time of the spring burn." Below are the conditions at the time of spring and fall burning.
| Spring fire | Fall fire | |
| Date slash burned | 1989 June 7 | 1989 Sep. 12 |
| Air temperature (°C) | 16 | 17 |
| Relative humidity (%) | 40 | 53 |
| Wind speed (km/h) | 1 | 11 |
| FFMC- ignitability and flammability | 91 (extreme) | 85 (moderate) |
| DMC- probability of mid-sized wood and duff consumption | 28 (low) | 8 (low) |
| DC- smoldering potential | 60 (low) | 38 (low) |
| ISI- rate of spread potential | 5 (moderate) | 4 (moderate) |
| BUI- total available fuels index | 28 (low) | 10 (low) |
| FWI- potential fire intensity | 10 (moderate) | 4 (moderate) |
| Prefire fuel (slash) loads (kg/m²) | 10.7 | 14.2 |
| Prefire forest floor depth (mean±s x cm) | 4.8±0.7 | 5.6±0.6 |
While the fall fire consumed more than twice the total fuel of the spring fire, the spring fire consumed double the large woody fuels of the fall fire. The depth of burn was greater on plots burned in the spring. Just 14% of the depth-of-burn pins on the spring fire showed no reduction in the duff layers compared to almost 50% with no visible reduction on the fall burned plots. The postfire and prefire conditions suggest that the spring fire was more severe than the fall fire. The postfire conditions are summarized below.
| Spring burn | Fall burn | |
| Total fuel (slash) consumed (kg/m²) | 1.6 | 3.4 |
| % of total fuel (slash) consumed | 15 | 24 |
| % of large fuels (>7 cm) consumed | 16 | 8 |
| Forest floor duff remaining (mean±s x cm) | 3.5±0.5 | 5±0.5 |
| Burn depth (mean±s x cm) | 1.2±0.2 | 0.6±0.6 |
| % of forest floor (duff) burned | 25 | 10.4 |
| % of pins with depth of burn=0 | 14.2 | 47.6 |
Species richness was similar (27-31 species) for all sites before the disturbances. Eleven years after fire, the fall and spring burned sites had 41 and 42 species, respectively, while the unburned site had just 30 species.
The overall coverage of shrubs decreased following spring and fall fires. Shrub coverage on spring and fall burned plots was below prelogging levels even in the 11th postdisturbance year. However, by the 11th postfire year, shrub coverage was significantly (p=0.05) greater on the fall burn than the spring burn. Shrub recovery was much slower on spring burned sites. Decreases in shrub coverage occurred on unburned plots as well; the decreases, however, were not as substantial as those on the burned plots.
Prior to any disturbances, herb coverage was significantly lower (p=0.02) on the unburned sites than on either burned site. Herb coverage decreased on the spring and fall burned sites the 1st postfire year (see table below). By the 2nd postfire year, herb coverage on both burned sites was greater than prelogging levels. Increases in herb coverage occurred on the unburned sites as well. However, in the 11th postfire year herb coverage on burned sites was significantly (p=0.002) greater than on the unburned site. The overall shrub and herb coverages before being disturbed, and 1, 2, 3, 5, and 11 years after logging and fire are shown below for all treatment sites.
| Before logging | Postfire yr. 1 | Postfire yr. 2 | Postfire yr. 3 | Postfire yr. 5 | Postfire yr. 11 | |
| Unburned (n=14) | ||||||
| Shrubs | 50.1 | 41.8 | 54.4 | 36.9 | 34.4 | 47.6 |
| Herbs | 47 | 69.6 | 82.1 | 66.2 | 72.8 | 49.5 |
| Spring burn (n=20) | ||||||
| Shrubs | 52.7 | 7 | 14.8 | 5.9 | 10.5 | 24.3 |
| Herbs | 62.5 | 23.5 | 68.5 | 55 | 64 | 73.6 |
| Fall burn (n=15) | ||||||
| Shrubs | 48.7 | 11.3 | 20.7 | 13.6 | 15.1 | 37.3 |
| Herbs | 63.7 | 36.7 | 79.3 | 73 | 72 | 71 |
Fire effects, rate of recovery, mode of revegetation, and/or postfire establishment for many subalpine forest species are summarized below [3].
| Common name | Scientific name | Notes |
| Trees | ||
| subalpine fir | Abies lasiocarpa | few stems survived fire; more frequent in unburned than burned plots in all years (p<0.006) |
| Engelmann spruce* | Picea engelmannii | eliminated by burning |
| Shrubs | ||
| menziesia | Menziesia ferruginea | sprouted (stem buds/root crown); coverage much lower on burned sites |
| Cascade azalea | Rhododendron albiflorum | sprouted (stem buds/root crown); spring fire had more severe effect |
| prickly currant | Ribes lacustre | sprouted and established from seed; coverage lower (p<0.04) on unburned than burned plots |
| red elderberry | Sambucus racemosa | fire encouraged seed germination and sprouting (stem sprouts/rhizomes); burned cover greater (p=0.04) than unburned in 2nd posttreatment year |
| western mountain-ash | Sorbus sitchensis | sprouted; present only on burned sites |
| big huckleberry | Vaccinium membranaceum | prolific sprouting (rhizomes/root crowns); no difference (p>0.23) between burned and unburned plots after 2nd postfire year |
| oval-leaf huckleberry | Vaccinium ovalifolium | sprouted (basal buds/rhizomes); no coverage differences (p>0.37) on fall and spring burns in any year |
| Herbs | ||
| pearly pussytoes | Antennaria anaphaloides | present only on burned sites |
| heartleaf arnica | Arnica cordifolia | sprouted (rhizomes); increased following fire |
| common ladyfern | Athyrium filix-femina | sprouted (rhizomes); no significant differences between treatments from 2nd growing season on |
| bluejoint | Calamagrostis canadensis | present only after disturbance on all treated sites |
| dryspike sedge | Carex foenea var. foenea | present only after disturbance and only on spring burned sites |
| sedges | Carex spp. | seed germination encouraged by burning |
| fireweed | Chamerion angustifolium | sexual and vegetative reproduction; greater coverage (p<0.0003) on burned plots that lasted 5 years |
| queencup beadlily | Clintonia uniflora | sprouts (slender rhizome); spring fire caused long-term decreases in coverage; recovery from fall fire by 2nd postfire year |
| spreading woodfern | Dryopteris expansa | sprouted on fall burned sites; eliminated from spring burned sites |
| fringed willowherb | Epilobium ciliatum | increased on burned sites in 2nd postfire year |
| willowherb** | Epilobium spp. | increased on burned sites in 2nd postfire year |
| sweetscented bedstraw | Galium triflorum | absent from spring burned sites pre- and post disturbance; coverage less on fall burned sites than unburned sites |
| oak fern | Gymnocarpium dryopteris | sprouted (delicate rhizomes); cover was significantly (p<0.04) lower on burned sites for all years; decreases greater after spring fire |
| white hawkweed | Hieracium albiflorum | seedlings; present only after site disturbance |
| smallflowered woodrush | Luzula parviflora | seedlings and sprouts; increased frequency and coverage on burned sites |
| Brewer's miterwort | Mitella breweri | sprouts and seedlings; increased coverage on fall burned sites |
| sweetcicely | Osmorhiza berteroi | sprouted (taproot); increased coverage on fall burned sites |
| strawberryleaf raspberry | Rubus pedatus | sprouts; substantial, long-lived decreases following spring fire; little change after fall burning |
| claspleaf twistedstalk | Streptopus amplexifolius | increased on fall burned plots |
| twistedstalk | Streptopus lanceolatus | sprouted; dramatic increases on burned sites by 2nd posttreatment year |
| threeleaf foamflower | Tiarella trifoliata var. trifoliata | decreased on spring burned plots; coverage double in 2nd year after fall fire |
| oneleaf foamflower | Tiarella trifoliata var. unifoliata | sprouted; coverage on burned sites significantly (p<0.05) less than on unburned sites 1, 2, and 3 years after fire |
| Sitka valerian | Valeriana sitchensis | sprouts (thick rhizomes), few seedlings; essentially recovered to predisturbance levels by 2nd postfire year |
| green false hellebore | Veratrum viride | sprouted (taproot); increased coverage on fall burned plots |
| pioneer violet | Viola glabella | increased on burned plots; longer-lived increases on fall burned plots |
The following files provide coverages and frequencies of the above species on burned and unburned plots before any disturbance, and 1, 2, 3, 5, and 11 years following logging and fire:
FIRE MANAGEMENT IMPLICATIONS:1. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]
2. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]
3. Hamilton, Evelyn; Peterson, Les. 2003. Response of vegetation to burning in a subalpine forest cutblock in central British Columbia: Otter Creek site. Research Report 23. Victoria, BC: British Columbia Ministry of Forestry, Research Branch. 60 p. [46111]
4. Kuchler, A. W. 1964. United States [Potential natural vegetation of the conterminous United States]. Special Publication No. 36. New York: American Geographical Society. 1:3,168,000; colored. [3455]
5. Natural Resources Canada. 2005. Canadian forest fire weather index (FWI) system, [Online]. Natural Resources Canada (Producer). Available: http://cwfis,cfs.nrcan.gc.ca/en/background/bi_FWI_summary_e.php [2005, August 10]. [54100]
6. U.S. Department of the Interior, Bureau of Land Management. 2005. Fire weather index graphs, [Online]. Bureau of Land Management (Producer). Available: http://fire.ak.blm.gov/aicc/FwiGraphs.htm [2005, August 10]. [54099]