H0W DID PREFIRE TREA TMEI" ~ AFFECT THE BISCUIT FIRE? Crystal Raymond; David L Peterson "­ Fire Managemenl Today; Spring 2005; 65, 2; Career and Technical Education pg.18

How DID PREFIRE TREATMENTS AFFECT THE BISCUIT FIRE?

Crystal Raymond and David L. Peterson

ost scient!fic literature supports torest thinning M to reduce the severity of wildland fires, but the effective­ ness of thinning in modifying fire behavior has not been well documented, The Biscuit Fire of 2002 offered a great opportunity to study the effects of mechanical thinning on fire behavior during a megafire.

The Thinning Theory Forest thinning is done to prevent surface fires (rom transitioning to crown fires. Theoretically, reduc­ ing canopy fuels and eliminating ladder fuels will decrease the prob­ ability that a crown fire will initi­ ate and spread (Cron 1969; Omi and Martinson 2002; Pollet and Omi 2002; Scott and Reinhardt 2001; Stephens 1998).

Most studies on fuel treatment efficacy focus on forests with low-severity, high-frequency fire regimes , such as ponderosa pine and Douglas-fir forests in the Interior West. As a result of fire exclusion, these forcsts are dense, producing greater canopy and lad­ der fuel loadings (Agee 1993). Aerial uiew of fire damage on thinned and untreated plots 1 month after the Hiscuit Fire. At the opposite end of the spec­ Thinned plots arc! circled in orange and untreated plots are circled in red. Photo: USDA trum are forests with high -sever­ Forest Service. 2002. ity, low-frequency fire regimes, because weather influences fire Little information exists for forests such as Pacific coastal. subalpine. behavior more than fuels in these with mixed-severity fire regimes, and boreal forests. However, ecosystems (Bessie and Johnson which encompass a wide range of 1995; Turner and others ]994), fire frequencies, extents, and severi­ Crystal Haymond is a graduate student in the Fire and ,\fountain F:colo[J.I.j Laboratory. thinning is less effective in reduc­ ties. The result of this variability College ofPorest Resources, Unil'ersity ing fire severity than it is in for­ makes it more difficult to quantify 0/ Washington, Sf!attle, vL.J; and D(fJ!id est ecosystems with a higher fire the ecological role of fire than in for­ Peterson is a research biologist for the USDA Forest ')C'I1'I',e, Pacific Wildland Fire return frequ ency. ests with low-severity fire regimes. Sciences La!JuratuYI;. Pacific Northwest Research Station. ,~e attle . v~jt

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Biscuit Fire: A Research Opportunity In 1992, scientists from the USDA Forest Service's Pacific Northwest Research Station started the Long­ Term Ecosystem Productivity (LTEP) study on the Siskiyou National rorest in southwestern Oregon, The initial goa l was to assess the effects of plant community composi tion and large woody debris on the processes that affect forest ecosystem produc­ tivity, When the Biscuit Fire roared through the area on August 16, 2002, the goal changed,

The Biscuit rire was Oregon's largest recorded fire and one of the largest ever to occur on national Crown scorch of Ollerstory trees on a thinned plot (left) alld an Ilntreated plot frighl). The thinned plots studied suffered more damage in the Biscuit Fire than the untreated plots. forest land, It burned more than probably because there were more fine woody debris and dcnse hardwoud sprouts, /ilel­ 499,000 acres (202,000 hal. and cost I ~9 a more Intense surface fire. Photo: Crystal Raymond, Fire and Mountain Ecoloqlj Lab. more than $150 million to suppress, untller51ty of vVashillgtol1, Sealtle, vlA, 2003. .. . Although weather contributed to fire severity through high temperatures, sified as a mixed-severity fire regime thinned plots. On eight treatment low nighttime relative humidity, and with a fire return interval of 90 to plots , tree crowns were removed dry east winds, the LTEP sites burned 150 years. together with the last log; on two under more moderate weather condi­ others, crowns were left onsite. In tions, By the time of the Biscuit Fire, the fall of 2001, Siskiyou National the LTEP sites had been ca refull y Forest resource managers conducted studied, with plenty of prefire data prescribed burns in the understorv collected. Awildland fire burning of thinned plots where crowns we~e Data are sparse for through th e area ,>\'as a great oppor­ left onsi te. forests with mixed­ tunity to study the effects of thin­ severity fire regimes ning on fire severity in forests with The Bi sc uit Fire burned through that encompass a wide mixed-severity fire regimes. three thinned plots, one thinned­ range of fire frequencies, und erburned plot. and two untreated Experimenta I plots with minimal torching of over­ extents, and severities. Treatments story trees. Burned plots are from In the winter of 1996. 10 of the 27 2,690 to 3,610 feet (820-1,100 m) in elevation, with southeast and north­ The LTEP sites were on the western LTEP treatment plots, each from 15 to 20 acres (6-8 hal in size, were northeast aspects and slopes of from perimeter of the Biscuit Fire, about Li to 40 percent. 12,5 miles (20 km) inland from mechanically thinned usin g a heli­ copter to remove the logs. The other th e coast. Douglas-fir, with a small Study Tactics amount of sugar pine and knobcone 17 plots were ei ther clearcut or left Before the Biscuit Fire. researchers pine in th e overstor)" dominates the undisturbed to serve as a control. collected extensive fuels and vegeta­ area, The subcanopy is composed of Thinning from below removed most tion data before and after thinning, hardwoods (tanoak, Pacific madrone, of the subcanopy hard\>\'oods and including data on forest structure and chinquapin) and Douglas-fir, co nifers, reducing tree uensity from and dead and down woody debris. These stands, establish ed approxi­ approximately 419 trees per acre rollowing the harvest. researchers mately 100 years earlier following a (1 ,035 trees per ha l to 85 trees per established five permanently marked stand-replacing fir e, have seen little acre (210 trees per hal. Logging and mapped 0.08-acre (0,03-ha) tree active management. The area is clas- slash "vas minimally treated on the

Volume 65 • NO . 2. Sprin g 2005

Reproduced with permission of the copyright owner, Further reproduction prohibited without permission. plots per treatment plot. We tagged How Did Thinning burned plot, unable to spread all live trees and snags and measured Pan Out? through the sparse surface fuels. On diameter, species, crown class, tree the thinned plots, the fire consumed Our study encompassed only a few height, and canopy base height. the subcanopy layer of 5-year-old stands, and the sample size is not Stem mapping of trees in the plots hardwood sprouts and the extensive large enough for rigorous statistical; helped us locate all trees following fine wood that resulted from thi n­ inferences about differences in treat­ the fire. ning. Crowns of overstory trees were ments. Therefore, the data presented nearly 100 percent scorched. In the summer of 2003, 1 year after here should be considered limited and observational rather than statis­ the Biscuit Fire, we again measured On the untreated plots, there was tically based. stand structure and fuels and collect­ no evidence that subcanopy hard­ ed additional data to assess fire dam­ wood and conifer trees served as age to overstory trees. Tree damage ladder fuels. The older, larger hard­ A wildland fire burning measurements included maximum I wood trees were not consumed. The bole char height, maximum crown through a long-term untreated plots and the thinned­ scorch volume height, crown scorch experiment with pre-fire underburned plots had much lower volume (in percent-a visual esti­ data created a great quantities of fine woody debris prior mate), and percent cambium kill. We to the fire and lower consumption of extracted four cores per tree (uphi II, opportunity to study the fuels during the fire. downhill, and two cross-slope sam­ effects of thinning on ples) at 1.6 feet (0.5 m) above the wildland fire severity Lessons Learned ground to assess cambium status. Greater fire damage to trees from We tested each cambium sample radiant and convective heat rather for the presence of peroxidase, an Maximum bole char height and than crowning occurred in the enzyme found in all living plant tis­ maximum crown scorch height thinned plots. Using Rothermel's sue . One dead sample equates to were similar on all treatment plots. (1983) fire prediction models in approximately 25 percent cambium However, there were definite varia­ hypothetical stands, Graham and girdling, two samples to 50 percent tions in crown scorch volume (fig. 1) others (1999) provided a theoretical girdling, and so forth. and some variations in percent cam­ basis for greater surface fire intensity bium girdled (fig. 2). On the thinned resulting from residual slash fuels Trees often take several years to plots, overstory trees with a diam­ and higher windspeeds in thinned succumb to fire damage, so mortal­ eter at breast height of greater than stands. The high level of crown ity data collected a year after a fire 10 inches (24 cm) had the highest scorch within the thinned LTEP do not reflect total tree mortal­ crown scorch volume and cambium plots most likely resulted from con­ ity. However, previous studies of death. On the thinned-underburned vective heat rising from the intense fire-caused Douglas-fir mortality plots, overs tory trees had the least surface fires below. The intensity of show that percent crown scorch crown scorch volume and cambium these surface fires was exacerbated and percent cambium kill are the death. On the untreated plots, over­ in the thinned plots where there was most important damage variables story trees had moderate damage more fuel in the form of fine woody for predicting mortality (Peterson and the most variability in crown debris and dense hardwood sprouts. and Arbaugh 1988) . These variables scorch volume and cambium death. These fuels were not present in the therefore allowed us to predict total untreated plots, and they were con­ fire-caused tree mortality. Crown The Biscuit Fire burned through sumed in the prescribed burning scorch height and bole char he ight the thinned and untreated plots as treatment in the thinned-under­ are more superficial damages and an intense surface fire but stopped burned plot. indicate less about long-term at the edge of the thinned-under­ fire effects.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In forests with mixed-severity fire o '20406080100 regimes (especially where hardwoods . Untreated Thinned underburned 'n are present), removing ladder fuels might actually increase damage to the remaining stand in a subsequent wildland fire. In the Biscuit Fire, the co...., hardwood subcanopy affected fire B behavior in ways other than serving as a ladder fuel. It is possible that a...., c shading by the hardwoods slowed !ll U the desiccation of dead surface fuels L Q) prior to the fire. During the fire. 0.... the hardwoods possibly decreased windspeeds in the untreated stands. In the thinned plots, consumption of hardwood sprouts probably contrib­ o 2040 6080100 o 20 40 60 80100 uted to crown scorch, whereas the Percent crown scorch older hardwoods in the untreated plots might have prevented the Figure I-Percent crown scorch in ouerstory trees on untreated, thinned-underbumed, and upward movement of heat to over­ thinned research plots following the Biscuit Fire of2002. Damage was high on thinned plots, story conifers. mixed on untreated plots. and low on thinned-underbumed plots. Observations suggest a two-step pro­ cess to prevent wildfires from crown­

Thl n d ing in forests with mixed-severity fi re regimes:

l.Thin dense stands to decrease 60 ladder fuels; and ~ ....,o 2.Remove post-thinning slash and '+­ other accumulated surface fuels to o 40 .j..l confine subsequent fire behavior to c Q) a relatively cool surface fire. U L Q) Q. 20 Although this two-step process is more time consuming and costly than thinning or prescribed burning o alone, it appears to be more effective in enhancing suppression efforts and o 25 50 75100 o 25 50 75100 in reducing undesirable damage to overstory trees. Percent cambium girdled

Figure Z·-Percent cambium girdled in Ol'ers{ory trees on untreated, thinned-linderhurned, and thinned research plols following the BisClIil Fire of2002. Damage u'as higher on thinned and untreated plots lhan on Ihinned--lInderburned plots.

Volume 65 • NO.2. Spring 2005

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. similar stand treatments on fire behav­ ior in Western forests . Gen. Tech. Rep. PNW-GTR-463. Portland. OR: USDA Forest Service, Pacific Northwest Research Station. Omi, P.N.; Martinson, E.J. 20(12. Effects of fuel treatment on wildfire severity. Final report to the Joint Fire Science Program. Boise. !D. Peterson, D.L.; Arbaugh, 1\-1.1. 1988. Estimating postfire survival of Douglas-fir in the Cascade Range. Canadian Journal of Forest Research. 19: 530-533. Pollet, J.; Omi, P.N. 2002. Effects of thin­ ning and prescribed burning on crown iire severity in ponderosa pine forests. International Journal of Wildland Fire. 11: 1-10. Rothermel. R.C. 1983. How to predict the spread and intensity of forest and range fires. Res. Pap. INT-143. Ogden, UT: USDA Forest Service. Intermountain Forest and Range Experiment Station. Scott. J.H.; Reinhardt. E.D. 2001. Assessing crown fire potential by linking models of surface and crown tire behavior. Res. Pap. RMRS-RP-29. Ogden, UT: USDA Forest Service . .Rocky Mountain Research Station. Stephens, S.L. 1998. Evaluation of the effects of silvicultural ano fuels treatments on rotential fire behavior in Sierra Nevada mixed-conifer forests. Forest Ecology and ~1anagement. 105: 21-35. Turner. M.G.; Homme, W.H.: GaroneI', R.H. 1994. Landscape disturbance models and long·term dynamtcs of natural areas. Natural Areas Journal. 14: 3-11 . • Fine /uel accumulation be/ore tabol'e) and oller (below) the Biswit Fire. Fine fuels accumu­ lated lo/!owing {/ thinning treatment ofter tree crowns were remol)ed, out the Biscuit Fire almost completeflJ consumed them. Photo: USDA Forest Sen' ice, 2003,

Acknowledgments References The authors thank Bernard Agee. J.K. 1993. fire ecology of Pacific Northwest forests. Covelo. CA: Islano Press. Bormann, Robyn Darbyshire, and 13essie W.D .; Johnson, E.iI, 1995. The relative Colin Edgar for their assistance in importan~e of fuels and weather on the fire all aspects of the study. Research was behavior in subalpine forests. Ecology. 76: 74i-i62. supported by the Forest Service's Cron. R.H . 1969. Thinning as an aid to fire Pacific Northwest Research Station. control. Fire Control Notes. 30: 1. Pacific Wildland Fire Sciences Graham, R.T; Harvey. A.E. ; Jain. T.B.; Tonn, Laboratory, Seattle, WA. .l.R. 1999. The eifects of thinning and

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