Propagation probability and spread rates of self-sustained smouldering fires under controlled moisture content and bulk density conditions

The consumption of large areas of peat during wildfires is due to self-sustained smouldering fronts that can remain active for weeks. We studied the effect of peat moisture content and bulk density on the horizontal propagation of smouldering fire in laboratory-scale experiments. We used milled peat with moisture contents between 25 and 250% (mass of water per mass of dry peat) and bulk densities between 50 and 150 kg m–3. An infrared camera monitored ignition, spread and extinction of each smouldering combustion front. Peats with a bulk density below 75 kg m–3 and a moisture content below 150% self-sustained smouldering propagation for more than 12 cm. Peat with a bulk density of 150 kg m–3 could self-sustain smouldering propagation up to a critical moisture content of 115%. A linear model estimated that increasing both moisture content and bulk density significantly reduced the median fire spread rate (which ranged between 1 and 5 cm h–1). Moisture content had a stronger effect size on the spread rate than bulk density. However, the effect of bulk density on spread rate depends upon the moisture content, with the largest effect of bulk density at low moisture contents.

[1]  Guillermo Rein,et al.  Peat consumption and carbon loss due to smouldering wildfire in a temperate peatland , 2013 .

[2]  G. Rein,et al.  Computational study of critical moisture and depth of burn in peat fires , 2015 .

[3]  Guillermo Rein,et al.  Computational smoldering combustion: Predicting the roles of moisture and inert contents in peat wildfires , 2015 .

[4]  William H. Frandsen,et al.  The influence of moisture and mineral soil on the combustion limits of smoldering forest duff , 1987 .

[5]  Y. Bergeron,et al.  Dynamics of moisture content in spruce-feather moss and spruce-Sphagnum organic layers during an extreme fire season and implications for future depths of burn in Clay Belt black spruce forests , 2014 .

[6]  V. Carey,et al.  Mixed-Effects Models in S and S-Plus , 2001 .

[7]  E. Johnson,et al.  Process and patterns of duff consumption in the mixedwood boreal forest , 2002 .

[8]  David R. Anderson,et al.  Model Selection and Multimodel Inference , 2003 .

[9]  P. Moore,et al.  Hydrological controls on deep burning in a northern forested peatland , 2015 .

[10]  Guillermo Rein,et al.  Study of the competing chemical reactions in the initiation and spread of smouldering combustion in peat , 2013 .

[11]  A. McGuire,et al.  Effects of Experimental Water Table and Temperature Manipulations on Ecosystem CO2 Fluxes in an Alaskan Rich Fen , 2009, Ecosystems.

[12]  Korbinian Strimmer,et al.  APE: Analyses of Phylogenetics and Evolution in R language , 2004, Bioinform..

[13]  K. Ryan,et al.  Factors affecting sustained smouldering in organic soils from pocosin and pond pine woodland wetlands , 2007 .

[14]  D. Vitt,et al.  Spatial Patterns and Temporal Trajectories of the Bog Ground Layer Along a Post-Fire Chronosequence , 2008, Ecosystems.

[15]  H. Ingram.  SOIL LAYERS IN MIRES: FUNCTION AND TERMINOLOGY , 1978 .

[16]  M. Turetsky,et al.  Moderate drop in water table increases peatland vulnerability to post-fire regime shift , 2015, Scientific Reports.

[17]  G. Rein,et al.  The severity of smouldering peat fires and damage to the forest soil , 2008 .

[18]  G. Rein,et al.  Smouldering fire signatures in peat and their implications for palaeoenvironmental reconstructions , 2014 .

[19]  Paul J. Morris,et al.  Hydrological feedbacks in northern peatlands , 2015 .

[20]  M. Turetsky,et al.  Sphagnum mosses limit total carbon consumption during fire in Alaskan black spruce forests , 2008 .

[21]  Yoshihiro Hashimoto,et al.  Combustion and thermal characteristics of peat fire in tropical peatland in Central Kalimantan, Indonesia , 2004 .

[22]  D. Wade,et al.  Combustion characteristics and emissions from burning organic soils , 1980 .

[23]  R. Hadden.  Smouldering and self-sustaining reactions in solids: an experimental approach , 2011 .

[24]  Damaris Zurell,et al.  Collinearity: a review of methods to deal with it and a simulation study evaluating their performance , 2013 .

[25]  R. Wieder,et al.  Variability in organic matter lost by combustion in a boreal bog during the 2001 Chisholm fire. , 2003 .

[26]  Dan K. Thompson,et al.  Interactive effects of vegetation, soil moisture and bulk density on depth of burning of thick organic soils , 2011 .

[27]  S. Page,et al.  Global vulnerability of peatlands to fire and carbon loss , 2015 .

[28]  S. Page,et al.  The amount of carbon released from peat and forest fires in Indonesia during 1997 , 2002, Nature.

[29]  A. Zeileis,et al.  Beta Regression in R , 2010 .

[30]  Jose L. Torero,et al.  SFPE handbook of fire protection engineering , 2016 .

[31]  C. E. Van Wagner,et al.  Duff Consumption by Fire in Eastern Pine Stands , 1972 .

[32]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[33]  Dan K. Thompson,et al.  Wildfire effects on vadose zone hydrology in forested boreal peatland microforms , 2013 .

[34]  Jesse K. Kreye,et al.  Pine cones facilitate ignition of forest floor duff , 2013 .

[35]  J. Waddington,et al.  Peat properties and water retention in boreal forested peatlands subject to wildfire , 2013 .

[36]  Michael Smithson,et al.  A better lemon squeezer? Maximum-likelihood regression with beta-distributed dependent variables. , 2006, Psychological methods.

[37]  Guillermo Rein,et al.  Smouldering combustion of peat in wildfires: Inverse modelling of the drying and the thermal and oxidative decomposition kinetics , 2014 .

[38]  W. Frandsen.  Ignition probability of organic soils , 1997 .

[39]  K. Ryan,et al.  Ignition and Burning Characteristics of Organic Soils , 2011 .

[40]  T. Ohlemiller.  Modeling of smoldering combustion propagation , 1985 .

[41]  Christopher R. Keyes,et al.  Influences of moisture content, mineral content and bulk density on smouldering combustion of ponderosa pine duff mounds , 2011 .

[42]  Merritt R. Turetsky,et al.  Current disturbance and the diminishing peatland carbon sink , 2002 .

[43]  Dan K. Thompson,et al.  A Markov chain method for simulating bulk density profiles in boreal peatlands , 2014 .

[44]  Guillermo Rein,et al.  Smouldering Fires and Natural Fuels , 2013 .

[45]  G. Kiely,et al.  Soil organic carbon stocks of afforested peatlands in Ireland , 2011 .

[46]  R. Petrone,et al.  Statistical characterization of the spatial variability of soil moisture in a cutover peatland , 2004 .

[47]  J. Waddington,et al.  Effect of drainage and wildfire on peat hydrophysical properties , 2013 .

[48]  W. Frandsen.  Heat Flow Measurements From Smoldering Porous Fuel , 1998 .

[49]  Jonathan M. Yearsley,et al.  Baseline intrinsic flammability of Earth’s ecosystems estimated from paleoatmospheric oxygen over the past 350 million years , 2010, Proceedings of the National Academy of Sciences.