Research Project Summary: Revegetation in a subalpine forest after logging and fire in central British Columbia



RESEARCH PROJECT SUMMARY CITATION:
Gucker, Corey L, compiler. 2005. Research Project Summary: Revegetation in a subalpine forest after logging and fire in central British Columbia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ ].

Source:
Unless otherwise indicated, the information in this Research Project Summary comes from the following paper:

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:
Logging and burning occurred in the Clearwater Forest District of south-central British Columbia near Camp Six Creek on the Otter Creek forest road.

SITE DESCRIPTION:
Research sites were on southeast facing slopes at approximately 1,600 m elevation. Soils were described as Morainal tills that remained wet for most of the growing season. The forest floor was approximately 4 to 7 cm deep [3].

PREFIRE PLANT COMMUNITY:
Vegetation in this study area is likely represented by the following vegetation classifications:

FRES23 Fir-spruce [2]
K015 Western spruce-fir forest [4]
SAF 206 Engelmann spruce-subalpine fir [1]

Prior to logging and burning, the vegetation was a subalpine fir/Sitka valerian-oak fern (Abies lasiocarpa/Valeriana sitchensis-Gymnocarpium dryopteris) community. Before logging the area there were approximately 681 stems/ha of subalpine fir and 175 stems/ha of Engelmann spruce (Picea engelmannii) greater than 2 m in height. Predisturbance shrub cover was 50%, of which 80% was dominated by menziesia (Menziesia ferruginea), bristly black currant (Ribes lacustre), Cascade azalea (Rhododendron albiflorum), big huckleberry (Vaccinium membranaceum), and ovalleaf huckleberry (V. ovalifolium). Herb coverage averaged 58%.

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 33 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 PHENOLOGY
The phenology of the prefire vegetation was not described.

FIRE SEASON/SEVERITY CLASSIFICATION:
Spring (1989 June 7)/Low severity
Fall (1989 Sept. 12)/Low severity

FIRE DESCRIPTION:
This study was designed to better understand the rate and method of vegetation recovery after burning logged sites in subalpine forests with typically long fire return intervals (140 to over 500 years). Researchers burned sites in the spring and fall in an attempt to produce fires of different severities and to study differences in the revegetation of these sites.

Before 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/m) 10.7 14.2
Prefire forest floor depth (means x cm) 4.80.7 5.60.6

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/m) 1.6 3.4
% of total fuel (slash) consumed 15 24
% of large fuels (>7 cm) consumed 16 8
Forest floor duff remaining (means x cm) 3.50.5 50.5
Burn depth (means x cm) 1.20.2 0.60.6
% of forest floor (duff) burned 25 10.4
% of pins with depth of burn=0 14.2 47.6

FIRE EFFECTS ON PLANT COMMUNITY:
Researchers monitored the recovery of vegetation 1, 2, 3, 5, and 11 years following the slash fires. Sampling of plots burned in the spring occurred just over 2 months after burning. The mode of recovery or establishment was recorded for many species in the 1st and 2nd postfire samplings. Because of study design considerations, the researchers caution that the potential for extrapolation of their results is limited.

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
bristly black 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
Sitka 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
ovalleaf 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
lady fern Athyrium filix-femina sprouted (rhizomes); no significant differences between treatments from 2nd growing season on
bluejoint reedgrass 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
* Researchers planted Engelmann spruce trees outside of monitoring plots for the 1st three posttreatment years. Coverage
estimates likely included overhanging branches of planted trees.

**Epilobium spp. is independent of other identified Epilobium species in the table.

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:

Coverage table.pdf

Frequency table.pdf

FIRE MANAGEMENT IMPLICATIONS:
This research suggests that subalpine fir forest vegetation tolerates logging and fire, but recovery rates are slow for many species. Multiple disturbances created herb-dominated communities initially, but by the 11th postdisturbance year woody vegetation increased in importance. The coverage of herbaceous species burned in the fall and spring were similar by the 11th postfire year. Species richness increased following fire in this area, suggesting that fire may be important to maintaining diversity in the area. The researchers also note that big huckleberry, an important wildlife food source, dominated shrub regrowth on burned sites. Fire may favor the production of big huckleberries [3].

REFERENCES:


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]

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