This study evaluated the ignition and burning behavior of woody fuels (e.g. stems and branches >6 mm in diameter with all additional stems and foliage removed) for four species: Douglas-fir, ponderosa pine, manzanita, and sagebrush. Samples were held above a burner while the process was recorded with a DSLR camera. Four burning stages were observed: micro-explosions (eruptive jetting and droplet burning), transition, flaming combustion, and smoldering combustion. Micro-explosions caused bursts of flames and ejected volatiles up to 15 cm away from samples, suggesting that adjacent fuels could be heated from this process. Micro-explosions can occur in both live and dead woody fuels; this contrasts with previous results for foliage, where droplet ejection has only been observed for live samples. The amount of moisture present at ignition depends on fuel size and heat flux. Some samples had no moisture remaining at ignition (how wildland fuels have been classically modeled), while others retained some moisture like live fine fuels. The ignition times showed sensitivity to the fuel diameter and fuel moisture content; an increase in either diameter or fuel moisture content increased the ignition time. Woody fuels up to 25 mm in diameter, which are generally thought of as thermally thick fuels, showed ignition behavior consistent with aspects of thermally thin and thick fuels.
CohenJ.The wildland-urban interface fire problem, forest history. Today (Fall 2008). Fremontia2010; 38: 38.
2.
WeiseDRWottonBM.Wildland-urban interface fire behaviour and fire modelling in live fuels. Int J Wildl Fire2010; 19: 149–152.
3.
FinneyMACohenJDMcAllisterSS, et al. On the need for a theory of wildland fire spread. Int J Wildl Fire2013; 22: 25–36.
4.
RothermelR.A mathematical model for predicting fire spread in wildland fuels. Ogden, UT: Intermountain Forest & Range Experiment Station, Forest Service, U.S. Department of Agriculture, 1972.
5.
WeiseDRZhouXSunL, et al. Fire spread in chaparral—“Go or no-go?”Int J Wildl Fire2005; 14: 99–106.
FletcherTHPickettBMSmithSG, et al. Effects of moisture on ignition behavior of moist California Chaparral and Utah leaves. Combust Sci Technol2007; 179: 1183–1203.
8.
ReszkaPCruzJJValdiviaJ, et al. Ignition delay times of live and dead pinus radiata needles. Fire Saf J2020; 112: 102948.
9.
BuntingSCWrightHAWallaceWH.Seasonal variation in the ignition time of redberry Juniper in West Texas. J Range Manag1983; 36(2): 169–171.
10.
GallacherJRLansingerVHansenS, et al. Effects of season and heating mode on ignition and burning behavior of three species of live fuel measured in a flat-flame burner system. In: Spring technical meeting of the western states section of the combustion institute, Pasadena, CA, 24–25 March 2014.
11.
ShotorbanBYashwanthBLMahalingamS, et al. An investigation of pyrolysis and ignition of moist leaf-like fuel subject to convective heating. Combust Flame2018; 190: 25–35.
12.
AnandCShotorbanBMahalingamS, et al. Physics-based modeling of live wildland fuel ignition experiments in the forced ignition and flame spread test apparatus. Combust Sci Technol2017; 189: 1551–1570.
13.
FazeliHJollyWMBlunckDL.Stages and time-scales of ignition and burning of live fuels for different convective heat fluxes. Fuel2022; 324: 124490.
14.
TachajapongWLozanoJMahalingamS, et al. Experimental and numerical modeling of shrub crown fire initiation. Combust Sci Technol2009; 181: 618–640.
15.
KeaneRE.Wildland fuel fundamentals and applications. New York: Springer, 2015.
16.
XanthopoulosGWakimotoRH.A time to ignition–temperature–moisture relationship for branches of three western conifers. Can J For Res1993; 23: 253–258.
17.
WeiseDRFletcherTMahalingamS.Determination of the effects of heating mechanisms and moisture content on ignition of live fuels, 2016, https://www.frames.gov/catalog/21881
18.
McAllisterSGrenfellIHadlowA, et al. Piloted ignition of live forest fuels. Fire Saf J2012; 51: 133–142.
19.
McAllisterSWeiseDR.Effects of season on ignition of live wildland fuels using the forced ignition and flame spread test apparatus. Combust Sci Technol2017; 189: 231–247.
20.
JollyWMButlerBW.Linking photosynthesis and combustion characteristics in live fuels: the role of soluble carbohydrates in fuel, Final Report for JFSP, Funded Project entitled, 2013.
21.
EngstromJDButlerJKSmithSG, et al. Ignition behavior of live California chaparral leaves. Combust Sci Technol2004; 176: 1577–1591.
22.
Darwish AhmadAAbubakerAMSalaimehA, et al. Ignition and burning mechanisms of live spruce needles. Fuel2021; 304: 121371.
23.
ScottJHReinhardtED. Assessing crown fire potential by linking models of surface and crown fire behavior. Research Paper RMRS-RP, USDA Forest Service, 2001.
24.
CallPTAlbiniFA.Aerial and surface fuel consumption in crown fires. Int J Wildl Fire1997; 7: 259–264.
25.
KeaneREReinhardtEDScottJ, et al. Estimating forest canopy bulk density using six indirect methods. Can J For Res2005; 35: 724–739.
26.
ReinhardtEScottJGrayK, et al. Estimating canopy fuel characteristics in five conifer stands in the western United States using tree and stand measurements. Can J For Res2006; 36: 2803–2814.
27.
WagnerCEV. Conditions for the start and spread of crown fire. Can J For Res1977; 7: 23–34.
28.
StocksBJAlexanderMEWottonBM, et al. Crown fire behaviour in a northern jack pine—black spruce forest. Can J For Res2004; 34: 1548–1560.
29.
IncroperaFPDeWittDP.Fundamentals of heat and mass transfer. Chichester: John Wiley, 1996.
30.
BenkoussasBConsalviJLPorterieB, et al. Modelling thermal degradation of woody fuel particles. Int J Therm Sci2007; 46: 319–327.
31.
LamorletteACandelierF.Thermal behavior of solid particles at ignition: theoretical limit between thermally thick and thin solids. Int J Heat Mass Transf2015; 82: 117–122.
32.
FrankmanDWebbBWButlerBBW, et al. Measurements of convective and radiative heating in wildland fires. Int J Wildl Fire2012; 22: 157–167.
33.
ButlerBWCohenJLathamDJ, et al. Measurements of radiant emissive power and temperatures in crown fires. Can J For Res2004; 34: 1577–1587.
34.
CawsonJGBurtonJEPickeringBJ, et al. Quantifying the flammability of living plants at the branch scale: which metrics to use?Int J Wildl Fire2023; 32: 1404–1421.
35.
YashwanthBLShotorbanBMahalingamS, et al. An investigation of the influence of heating modes on ignition and pyrolysis of woody wildland fuel. Combust Sci Technol2015; 187: 780–796.
36.
HollisJJAndersonWRMcCawWL, et al. The effect of fireline intensity on woody fuel consumption in southern Australian eucalypt forest fires. Aust For2011; 74: 81–96.
37.
AlbiniFAReinhardtED. Modeling ignition and burning rate of large woody natural fuels. Int J Wildl Fire1995; 5: 81–91.
38.
BorujerdiPRShotorbanBMahalingamS.A computational study of burning of vertically oriented leaves with various fuel moisture contents by upward convective heating. Fuel2020; 276: 118030.
39.
JollyWMHadlowAM.A comparison of two methods for estimating conifer live foliar moisture content. Int J Wildl Fire2011; 21: 180–185.
40.
MatthewsS.Effect of drying temperature on fuel moisture content measurements. Int J Wildl Fire2010; 19: 800–802.
41.
CarlquistSSchneiderEL.The tracheid-vessel element transition in angiosperms involves multiple independent features: cladistic consequences. Am J Bot2002; 89: 185–195.
42.
KaramGN.Biomechanical model of the xylem vessels in vascular plants. Ann Bot2005; 95: 1179–1186.
43.
JohnsonEAMiyanishiK.Forest fires: Behavior and Ecological Effects. Amsterdam: Elsevier Science, 2001.
44.
FrickerM.Stomata. Cham: Springer, 2012.
45.
GaoWNeliasDLiuZ, et al. Numerical investigation of flow around one finite circular cylinder with two free ends. Ocean Eng2018; 156: 373–380.
PickettBMIsacksonCWunderR, et al. Experimental measurements during combustion of moist individual foliage samples. Int J Wildl Fire2010; 19: 153–162.
48.
LinSHuangXUrbanJ, et al. Piloted ignition of cylindrical wildland fuels under irradiation. Front Mech Eng2019; 5: 1–9.
49.
FinneyMACohenJDForthoferJM, et al. Role of buoyant flame dynamics in wildfire spread. Proc Natl Acad Sci U S A2015; 112: 9833–9838.
50.
CohenJDFinneyMA.Fuel particle heat transfer Part 1: convective cooling of irradiated fuel particles. Combust Sci Technol2022; 195: 3095–3121.
51.
MardiniJ.Experimental and analytical study of heat and mass transfer in wood prior to ignition in fires, 2015.
52.
FinneyMAMcAllisterSGrumstrupTP, et al. Wildland fire behaviour: dynamics, principles and processes. Clayton, VIC, Australia: Csiro Publishing, 2021.
53.
SimmsDLLawM. The ignition of wet and dry wood by radiation. Combust Flame1967; 11: 377–388.
54.
McAllisterS.Critical mass flux for flaming ignition of wet wood. Fire Saf J2013; 61: 200–206.
55.
GardnerNBlunckDL. Ignition and burning behavior of individual and groups of live Douglas-fir needles. In: 13th United States national combustion meeting, College Station, TX, 19–22 March 2023.
56.
NovaesEKirstMChiangV, et al. Lignin and biomass: a negative correlation for wood formation and lignin content in trees. Plant Physiol2010; 154: 555–561.
57.
KanTStrezovVEvansTJ.Lignocellulosic biomass pyrolysis: a review of product properties and effects of pyrolysis parameters. Renew Sustain Energy Rev2016; 57: 1126–1140.
58.
AlizadehMWeiseDRFletcherTH. Gas and Tar species evolved during rapid pyrolysis of California 2 Chaparral. https://ssrn.com/abstract=4678397
59.
MattFJDietenbergerMAWeiseDR.Summative and ultimate analysis of live leaves from Southern U.S. Forest plants for use in fire modeling. Energy Fuels2020; 34: 4703–4720.
60.
PettersenRC. The chemical composition of wood. In: RowellR (ed.) The Chemistry of Solid Wood. Washington, DC: American Chemical Society, 1984, pp. 57–126.
61.
BukwaW.Isolation and characterization of the structural polysaccharides of Artemisia tridentata subsp. vaseyana, 1969, https://scholarworks.umt.edu/etd/6785.
