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Wildlife, Animals, and Plants |
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FIRE CASE STUDIES
1st CASE STUDY:
Preharvest underburn - Pringle Falls, Oregon REFERENCE: Martin, R. E. 1982 [171] FIRE CASE STUDY AUTHORSHIP: Tirmenstein, D. A. 1990. SEASON/SEVERITY CLASSIFICATION: Initial burn: upper plot - September 27, 1976/ moderate Initial burn: lower plot - October 1, 1976/moderate Reburn: upper plot - October 2, 1979/moderate Reburn: lower plot - June 9, 1980/low STUDY LOCATION: The study was conducted on the east slope of Lookout Mountain in the Pringle Falls Experimental Forest, approximately 30 miles (48 km) south-southwest of Bend, Oregon. PREFIRE VEGETATIVE COMMUNITY: Two distinct units were burned. The lower unit is representative of the ponderosa pine (Ponderosa pine)/bitterbrush (Purshia tridentata)/snowbrush ceanothus (Ceanothus velutinus)/needlegrass (Achnatherum spp.) habitat as described by Volland [276]. The upper unit is identified as a mixed conifer/ceanothus/sedge (Carex spp.) community type. Ponderosa pine basal area ranged from 100 to 140 ft2/acre (23-32 m2/ha). Some white fir (Abies concolor) saplings and seedlings were also present on the upper plot. Common shrubs included snowbrush ceanothus, giant chinkapin (Chrysolepis chrysophylla), bitterbrush, and greenleaf manzanita (Arctostaphylos patula). Needlegrass was also present. TARGET SPECIES PHENOLOGICAL STATE: Initial burn: seed fall Reburn: lower plot - seed fall Reburn: upper plot - leaf growth/flowering SITE DESCRIPTION: elevation: upper plot - 5,000 feet (1,525 m) lower plot - 4,550 feet (1,390 m) precipitation: 30 inches (76 cm) per year, primarily as snow aspect: east FIRE DESCRIPTION: Management objective: To evaluate potential shrub control using preharvest prescribed burning. Weather and fuel conditions were as follows:
Fuel consumption (tonnes/ha) was as follows:
FIRE EFFECTS ON TARGET SPECIES: The 1st fire on upper and lower plots top-killed many snowbrush ceanothus plants, stimulated sprouting, and provided heat scarification, which caused many seeds to germinate. The 2nd fire killed all new seedlings and reduced the sprouts resulting from the 1st burn. From 71 to 100% of the sprouting adult plants were killed. No shrub seedlings were observed on either plot after the 2nd burn. Percent cover of snowbrush ceanothus was as follows:
** % of all old plants burned *** seedlings emerging after 1st burn and "living or killed by the 2nd burn were the only ones counted" FIRE MANAGEMENT IMPLICATIONS: Preliminary evidence suggests that preharvest burns can control snowbrush ceanothus and therefore reduce competition with regenerating conifers. Successive fires may kill most shrub seedlings and increase mortality in older plants. Detrimental effects to snowbrush ceanothus are amplified when additional heat is concentrated near the root crown and roots. Fall burns, conducted when soil moisture levels are low, are particularly damaging. 2nd CASE STUDY:
O'Keefe Creek wildlife habitat improvement burn, southwestern Montana REFERENCE: Noste, N. V. 1982 [205] Noste, N. V. 1985 [206] FIRE CASE STUDY AUTHORSHIP: Tirmenstein, D.A. 1990. SEASON/SEVERITY CLASSIFICATION: spring/not reported fall/high STUDY LOCATION: Study sites are located in northwestern Montana, approximately 9.4 miles (16 km) north of Missoula. PREFIRE VEGETATIVE COMMUNITY: The prefire community was a Douglas-fir (Pseudotsuga menziesii)/ninebark (Physocarpus malvaceus) habitat type. Common shrubs included Saskatoon serviceberry (Amelanchier alnifolia), redstem ceanothus (Ceanothus sanguineus), snowbrush ceanothus (C. velutinus), Douglas hawthorn (Crataegus douglasii), Oregon-grape (Mahonia repens), chokecherry (Prunus virginiana), rose (Rosa spp.), Scouler willow (Salix scouleriana), bearberry (Arctostaphylos uva-ursi), and common snowberry (Symphoricarpos albus). Herbaceous species such as spreading dogbane (Apocynum androsaemifolium), arrowleaf balsamroot (Balsamorhiza sagittata), pinegrass (Calamagrostis rubescens), elk sedge (Carex geyeri), orchard grass (Dactylis glomerata), and timothy (Phleum pratense) were well represented in the prefire community. TARGET SPECIES PHENOLOGICAL STATE: spring: leaf bud burst/ growth fall: seed fall SITE DESCRIPTION: aspect - southeast elevation - less than 4,900 feet (1,500 m) slope - average of 30%; 50% maximum FIRE DESCRIPTION: Management objective: To compare the effects of spring and fall prescribed fire treatments for rejuvenating deteriorating stands of snowbrush ceanothus and improving wildlife browse. Weather conditions during burn:
Fuel loading, fine fuel moisture content, and fire behavior varied by position on the slope and season of burn. Fine fuel moisture content:
Prefire fuel loadings, by size class, were as follows:
Rates of spread ranged from 2,640 to 3,696 feet per hour (805-1,126 m/hr) in fall burns, which had flame lengths of 8 to 10 feet (2.5-3.0 m). Spring burns produced average flame lengths of 3 feet (0.9 m) with rate of spread measured at 659 to 1,188 feet per hour (201-362 m/hr). FIRE EFFECTS ON TARGET SPECIES:Soils and fuels were drier in the fall, and heat transfer downward was presumably greater, thus increasing the likelihood of damage to underground regenerative structures. Portions of all spring-burned plants survived, but 60% of shrubs burned in the fall were killed. Many seedlings emerged on fall-burned plots, but none were observed on plots burned during the spring. Heat generated by the spring burns may not have been adequate to scarify the seeds. Exposed mineral soil, which normally serves as an excellent seedbed, was also lacking. By the fourth growing season, nearly 6,500 snowbrush ceanothus seedlings per acre (16,000/ha) were observed on the fall-burned plots, but none were present on plots burned in spring. Root crown sprouting following spring burns enabled snowbrush ceanothus to recover much more rapidly than after fall burns, where recovery was through seedling establishment. On the spring-burned plot, cover exceeded preburn values by the 1st growing season and had doubled by the 3rd growing season. Cover on fall-burned plots averaged only 0.2% 1 year after fire but increased to approximately one-half of preburn coverage by the 3rd growing season. Comparative cover values for snowbrush ceanothus were:
FIRE MANAGEMENT IMPLICATIONS: Both spring and fall fires can rejuvenate decadent stands of snowbrush ceanothus and produce sufficient stocking to improve wildlife browse. Lighter spring burns, after which shrubs reestablished through sprouting, promoted rapid short-term wildlife browse improvement. Fall burns produced vigorous seedling growth and more long-term benefits to wildlife as succession was delayed. Management programs that include a combination of spring and fall burns can produce both short and long-term benefits to wildlife. Potential for postfire reestablishment of snowbrush ceanothus on south slopes in Douglas-fir habitat types of western Montana is high. 3rd CASE STUDY:
Preharvest burn - Lassen National Forest, California REFERENCE: Weatherspoon, C. P. 1985. [280] FIRE CASE STUDY AUTHORSHIP: Tirmenstein, D. A. 1990. SEASON/SEVERITY CLASSIFICATION: spring/variable fall/variable STUDY LOCATION: The study site is located on the Lassen National Forest in northeastern California. PREFIRE VEGETATIVE COMMUNITY: The stand was dominated by 60- to 70- year-old white fir (Abies concolor), but included a few scattered red fir (Abies magnifica). Basal area ranged from 300 to 350 ft2/acre (67-78 m2/ha) and the overstory canopy cover was described as "nearly complete". Shrubs were "not a significant factor" within the study area prior to treatment. However, a shrubfield dominated by bush chinquapin (Chrysolepis sempervirens) and snowbrush ceanothus (Ceanothus velutinus) bordered the study area to the north and northeast. TARGET SPECIES PHENOLOGICAL STATE: spring: leaf bud burst/ growth fall: seed fall SITE DESCRIPTION: aspect - southeast elevation - 6,200 feet (1,891 m) slope - <10% precipitation - 50 inches (127 cm) per year, primarily as snow between November and April FIRE DESCRIPTION: Management objective: To evaluate potential shrub control and reduction of competition with conifer seedlings using preharvest prescribed burning. Initial preharvest burns were conducted during the spring of 1982. Fires were carried by natural fuels (15-20 tons/acre of downed woody fuels) and 2 to 4 inches (5-10 cm) of the upper forest floor. Stands were commercially thinned in the fall of 1982. Subsequent burns (2nd burns for the twice-burned plots) were carried out during the spring and fall of 1983. Harvested plots burned only once and uncut plots were burned only in 1983. FIRE EFFECTS ON TARGET SPECIES:Because snowbrush ceanothus plants were not "a significant factor" in the study area before treatments began, sprouting was not a factor and only the production of snowbrush ceanothus seedlings from dormant seeds is described here. Seedling densities of snowbrush ceanothus were significantly lower (p<0.01) on plots burned twice than on the once-burned plots. Seedling density (number of seedlings per acre) in relation to treatment was:
Seedling densities were reduced with increasing slash depth. These reductions were particularly noticeable on unburned plots. The density of snowbrush ceanothus after burning increased with moderate burn depth, with density decreasing in response to high burns depth. Results suggest that a deep burn may kill much of the stored seed rather than stimulate germination. Snowbrush ceanothus densities (number of seedlings per acre) in relation to burn depth were as follows:
L - fire burned into, but not deeper than the litter layer F - fire burned into, but not deeper than fermentation layer (moderate severity) H - fire burned into, or completely consumed, humus layer (high severity) FIRE MANAGEMENT IMPLICATIONS: These study results are inconclusive regarding the effectiveness of preharvest prescribed burning to reduce snowbrush ceanothus competition with conifer seedlings. Preharvest burning may reduce the amount of snowbrush ceanothus establishing after treatment. The preharvest fires in this study were relatively low consumption fires that provided insufficient heat scarification for many of the seeds stored in the soil. High consumption preharvest fires would presumably result in a reduction of snowbrush ceanothus seedlings. Fall preharvest fires or spring fires under dry conditions may stimulate more seeds to germinate and could result in greater reductions of snowbrush ceanothus seedlings. Higher severity fires may destroy more of the snowbrush ceanothus seed bank. Multiple preharvest fires may also reduce posttreatment snowbrush ceanothus density.
Related categories for SPECIES: Ceanothus velutinus | Snowbrush Ceanothus |
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