Moisture Diffusivity in Forest Fuels

1992 ◽  
Vol 2 (4) ◽  
pp. 161 ◽  
Author(s):  
NR Viney
Keyword(s):  
Field Data ◽  
Lodgepole Pine ◽  
Moisture Diffusivity ◽  
Fuel Moisture ◽  
Litter Layer ◽  
Forest Fuels ◽  
Eucalyptus Leaves ◽  
Square Prism

Abstract. Apracticalmeans of quanmingthe diffusivities of forest fuels from fielddata is presented. The mathematics of this method is explored for four fuel shapes: a litter layer, a hardwood leaf, a twig and a square fuel moisture analogue stick, which are represented geometrically by a semi-infinite solid, a slab, a cylinder and a square prism, respectively. Theresults are presented graphically. Analyses of two published sets of field data indicate defusivities of 4.1 x 10-12m2 s-1 and 1.3 x 10-10m2 s-1 for Eucalyptus leaves and twigs, respectively, and 2.9 x 10-9m2 s-1 for a lodgepole pine litter layer.

scholarly journals A Simple Technique to Estimate the Flammability Index of Moroccan Forest Fuels

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
M'Hamed Hachmi ◽  
Abdessadek Sesbou ◽  
Hassan Benjelloun ◽  
Nesrine El Handouz ◽  
Fadoua Bouanane
Keyword(s):  
Simple Technique ◽  
Ignition Time ◽  
Flame Height ◽  
Fuel Moisture ◽  
Summer Period ◽  
Shrub Species ◽  
Forest Fuels ◽  
Wide Range ◽  
Flammability Parameters ◽  
Threshold Point

A formula to estimate forest fuel flammability index (FI) is proposed, integrating three species flammability parameters: time to ignition, time of combustion, and flame height. Thirty-one (31) Moroccan tree and shrub species were tested within a wide range of fuel moisture contents. Six species flammability classes were identified. An ANOVA of the FI-values was performed and analyzed using four different sample sizes of 12, 24, 36, and 50 flammability tests. Fuel humidity content is inversely correlated to the FI-value, and the linear model appears to be the most adequate equation that may predict the hypothetical threshold-point of humidity of extinction. Most of the Moroccan forest fuels studied are classified as moderately flammable to flammable species based on their average humidity content, calculated for the summer period from July to September.

Sampling Intensity for Estimating Fuel Moisture Content in Lodgepole Pine and White Spruce Trees

1992 ◽  
Vol 2 (1) ◽  
pp. 1 ◽  
Author(s):  
SJ Titus ◽  
PM Woodard ◽  
AF Johnson
Keyword(s):  
Moisture Content ◽  
Coefficient Of Variation ◽  
Lodgepole Pine ◽  
White Spruce ◽  
Size Class ◽  
Fuel Moisture ◽  
Probability Level ◽  
Content Variation ◽  
Live Biomass ◽  
Fuel Moisture Content

The moisture content of live and dead foliage and roundwood on 30 lodgepole pine and 27 white spruce trees was determinedduring the summer of 1987. Sample trees were selectedrandomly throughout Alberta, Canada, without regard for weather. Five sub-samples were taken for each of the five roundwood diameter size classes (< 0.5cm,0.5 - 1 cm, 1.0- .0cm,3.0- 5.0cm, 5.0-7.0cm and 7.0-10.0 cm). Moisture content of live biomass was quite similar between species for the same fuel size class, regardless of when sampling occurred. Moisture content variation within trees was about half of the variation between trees for the same fuel size class. The coefficient of variation in moisture was much less for live material (generally < 0.3) than for dead biomass (always > 0.6). Average fuel moisture content for populations of lodgepole pine and white spruce trees may be estimated to within + 10% at the 68% probability level by sampling less than 20 trees and with only 3 fuel sub-samples per tree.

Forest fuels and potential fire behaviour 12 years after variable-retention harvest in lodgepole pine

2016 ◽  
Vol 25 (6) ◽  
pp. 633 ◽  
Author(s):  
Justin S. Crotteau ◽  
Christopher R. Keyes ◽  
Elaine K. Sutherland ◽  
David K. Wright ◽  
Joel M. Egan
Keyword(s):  
Lodgepole Pine ◽  
Structural Complexity ◽  
Fuel Load ◽  
Fire Behaviour ◽  
Forest Fuels ◽  
Fuel Loads ◽  
Variable Retention ◽  
Harvesting Technique ◽  
Trade Offs ◽  
Variable Retention Harvesting

Variable-retention harvesting in lodgepole pine offers an alternative to conventional, even-aged management. This harvesting technique promotes structural complexity and age-class diversity in residual stands and promotes resilience to disturbance. We examined fuel loads and potential fire behaviour 12 years after two modes of variable-retention harvesting (dispersed and aggregated retention patterns) crossed by post-harvest prescribed fire (burned or unburned) in central Montana. Results characterise 12-year post-treatment fuel loads. We found greater fuel load reduction in treated than untreated stands, namely in the 10- and 100-h classes (P = 0.002 and 0.049 respectively). Reductions in 1-h (P < 0.001), 10-h (P = 0.008) and 1000-h (P = 0.014) classes were greater in magnitude for unburned than burned treatments. Fire behaviour modelling incorporated the regenerating seedling cohort into the surface fuel complex. Our analysis indicates greater surface fireline intensity in treated than untreated stands (P < 0.001), and in unburned over burned stands (P = 0.001) in dry, windy weather. Although potential fire behaviour in treated stands is predicted to be more erratic, within-stand structural variability reduces probability of crown fire spread. Overall, results illustrate trade-offs between potential fire attributes that should be acknowledged with variable-retention harvesting.

Simulated fire behaviour in young, postfire lodgepole pine forests

2017 ◽  
Vol 26 (10) ◽  
pp. 852 ◽  
Author(s):  
Kellen N. Nelson ◽  
Monica G. Turner ◽  
William H. Romme ◽  
Daniel B. Tinker
Keyword(s):  
Pinus Contorta ◽  
Stand Structure ◽  
Lodgepole Pine ◽  
Pine Forests ◽  
Fuel Moisture ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Fire Initiation ◽  
Moisture Conditions ◽  
Simulated Fire

Early-seral forests are expanding throughout western North America as fire frequency and annual area burned increase, yet fire behaviour in young postfire forests is poorly understood. We simulated fire behaviour in 24-year-old lodgepole pine (Pinus contorta var. latifolia) stands in Yellowstone National Park, Wyoming, United States using operational models parameterised with empirical fuel characteristics, 50–99% fuel moisture conditions, and 1–60kmhr−1 open winds to address two questions: [1] How does fireline intensity, and crown fire initiation and spread vary among young, lodgepole pine stands? [2] What are the contributions of fuels, moisture and wind on fire behaviour? Sensitivity analysis indicated the greatest contributors to output variance were stand structure mediated wind attenuation, shrub fuel loads and 1000-h fuel moisture for fireline intensity; crown base height for crown fire initiation; and crown bulk density and 1-h fuel moisture for crown fire spread. Simulation results predicted crown fire (e.g. passive, conditional or active types) in over 90% of stands at 50th percentile moisture conditions and wind speeds greater than 3kmhr−1. We conclude that dense canopy characteristics heighten crown fire potential in young, postfire lodgepole pine forests even under less than extreme wind and fuel moisture conditions.

Fuels and fire at savanna-gallery forest boundaries in southeastern Venezuela

1998 ◽  
Vol 14 (4) ◽  
pp. 445-461 ◽  
Author(s):  
Jason Biddulph ◽  
Martin Kellman
Keyword(s):  
Rain Forest ◽  
Dry Season ◽  
Field Observations ◽  
Litter Layer ◽  
Gallery Forest ◽  
Fuel Type ◽  
Forest Fuels ◽  
Savanna Fires ◽  
Gallery Forests ◽  
Forest Microclimate

ABSTRACT. Factors contributing to the resistance of gallery forests in savannas to the entry of fire were investigated using field observations and manipulation experiments. Mass of savanna fuels did not decrease close to forest boundaries, and in some instances increased, while savanna fuels adjacent to forests were moister than in the savanna beyond for only 1 d after rainfall. A fuel drying experiment conducted in both forest and savanna microclimates indicated that both fuel type and microclimate contributed to the resistance of forests to fire entry, although the former played a larger role. While savanna fuels in a savanna microclimate became ignitable in c. 1 d after rain, forest fuels in a forest microclimate required 4 wk to achieve ignitability. A further experiment juxtaposing forest fuels to burning savanna indicated that fire entry into forests was faciliated by deep root mats and the presence of a superficial litter layer, both of which become attenuated at the forest/savanna contact. It is concluded that fuels in these forests can reach an ignitable state late in the dry season, but that frequent fire entry is probably precluded by the tendency of savanna fires to occur earlier in the dry season and by discontinuities in fuels at the savanna/forest contact.RESUMEN. Se investigaron los factores que contribuyen a la resistencia de la entrada del fuego a los bosques en galería de las savanas mediante observaciones de campo y experimentos de manipulación. La masa de los combustibles de la savana no decrecieron cerca de los bordes del bosque; por el contrario, en algunos casos se incrementaron, mientras que los combustibles de la savana cercanos al bosque eran mas húmedos que en la savana restante, solamente por un día despues de un evento de lluvia. Un experimento de secado de combustible, que fue conducido en los microclimas de bosque y de savana, indica que tanto el tipo de combustible como el microclima contribuyen a la resistencia de los bosques a la entrada del fuego, aunque el primer factor tuvo un papel de mayor importancia. Mientras que los combustibles de la savana en el microclima de la savana se volvieron ‘encendibles’ cerca de un día despues de lluvia, los combustibles del bosque dentro del microlima del bosque tomaron cuatro semanas para llegar a dicho estado. Un experimento que sobrepuso combustibles del bosque a la savana ardiente indicó que la entrada del fuego a los bosques se facilitó por la presencia de mantillos orgánicos profundos y de una capa superficial de hojarasca, presencia que se ve atenuada en la zona de contacto bosque/savana. Se concluye que los combustibles en estos bosques pueden alcanzar un estado de ignición tarde en la estación de sequía, pero que la entrada frecuente del fuego es probablemente evitada por la tendencia que tienen los fuegos de savana a presentarse temprano en la estación seca y por las discontinuidades de combustibles en la zona de contacto savana/bosque.

scholarly journals Firefighter Observations of “Surprising” Fire Behavior in Mountain Pine Beetle-Attacked Lodgepole Pine Forests

Fire ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 34 ◽  
Author(s):  
Kevin Moriarty ◽  
Antony S. Cheng ◽  
Chad M. Hoffman ◽  
Stuart P. Cottrell ◽  
Martin E. Alexander
Keyword(s):  
Mountain Pine Beetle ◽  
Lodgepole Pine ◽  
Fire Behavior ◽  
Pine Forests ◽  
Fuel Moisture ◽  
Crown Fire ◽  
Gray Phase ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Moisture Conditions

The recent mountain pine beetle outbreak affecting lodgepole pine forests in the Rocky Mountains has created a novel fire environment for wildland firefighters. This paper presents results from an examination of firefighters’ observations of fire behavior in post-outbreak lodgepole pine forests, with a focus on what they considered surprising from a fire behavior standpoint and how this in turn affected their suppression tactics. The surprises in fire behavior experienced by firefighters during the red phase of post-outbreak forests included an elevated level of fire spread and intensity under moderate weather and fuel moisture conditions, increased spotting, and faster surface-to-crown fire transitions with limited or no ladder fuels. Unexpectedly, during the gray phase in mountain pine beetle-attacked stands, crown ignition and crown fire propagation was observed for short periods of time. Firefighters are now more likely to expect to see active fire behavior in nearly all fire weather and fuel moisture conditions, not just under critically dry and windy situations, and across all mountain pine beetle attack phases, not just the red phase. Firefighters changed their suppression tactics by adopting indirect methods due to the potential fire behavior and tree-fall hazards associated with mountain pine beetle-attacked lodgepole pine forests.

Relationships between the moisture content of fine woody fuels in lodgepole pine slash and the Fine Fuel Moisture Code of the Canadian Forest Fire Weather Index System

1988 ◽  
Vol 18 (1) ◽  
pp. 128-131 ◽  
Author(s):  
R. Trowbridge ◽  
M. C. Feller
Keyword(s):  
Moisture Content ◽  
Forest Fire ◽  
Index System ◽  
Lodgepole Pine ◽  
Fire Season ◽  
Fire Weather ◽  
Fuel Moisture ◽  
Weather Index ◽  
Fire Weather Index ◽  
Moisture Contents

Unsuccessful attempts to ignite slash resulting from the mechanical knocking down of lodgepole pine in west central British Columbia led to a short-term investigation of the relationship between the Fine Fuel Moisture Code of the Canadian Forest Fire Weather Index System and the moisture content of various fine fuel components <1 cm in diameter. Of the types of fuel sampled, the moisture contents of B.C. Forest Service fuel moisture sticks and aged slash were similar to, and well correlated (r = 0.79 and 0.81, respectively) with, the equivalent moisture content calculated from the Fine Fuel Moisture Code. The Fine Fuel Moisture Code was not designed to relate to the moisture content of uncured fuels. Thus, the moisture contents of fresh living slash (material from knocked down trees still attached to living roots) and of fresh dead slash (material unattached to living trees that had not yet experienced a complete fire season in which to fully cure) were poorly correlated with moisture content (r = 0.16 and 0.42, respectively). The moisture content of the progressively curing, needle-bearing fresh dead slash was relatively high at the beginning of the fire season, but became similar to the moisture content during the first half of July. This suggests that the Fine Fuel Moisture Code can also be used to predict the moisture content of such fine slash after these fuels have cured for approximately 3 months during the snow-free period.

Modeling Mediterranean forest fuels by integrating field data and mapping tools

2011 ◽  
Vol 131 (3) ◽  
pp. 571-582 ◽  
Author(s):  
Francisco Rodríguez y Silva ◽  
Juan Ramón Molina-Martínez
Keyword(s):  
Field Data ◽  
Mediterranean Forest ◽  
Forest Fuels

A process-based model of fine fuel moisture

2006 ◽  
Vol 15 (2) ◽  
pp. 155 ◽  
Author(s):  
Stuart Matthews
Keyword(s):  
Forest Type ◽  
Model Parameters ◽  
Fuel Moisture ◽  
Litter Layer ◽  
Wetting And Drying ◽  
Rainy Period ◽  
Dry Conditions ◽  
Fuel Moisture Content ◽  
Complete Process ◽  
Made In

This paper presents the first complete process-based model for fuel moisture in the litter layer. The model predicts fuel moisture by modelling the energy and water budgets of the litter, intercepted precipitation, and air spaces in the litter. The model was tested against measurements of fuel moisture from two sets of field observations, one made in Eucalyptus mallee-heath under dry conditions and the other during a rainy period in Eucalyptus obliqua forest. The model correctly predicted minimum and maximum fuel moisture content and the timing of minima and maxima in the mallee-heath. Under wet conditions, wetting and drying of the litter profile were correctly predicted but wetting of the surface litter was over-predicted. The structure of the model and the dependence of predictions on model parameters were examined using sensitivity and parameter estimation studies. The results indicated that it should be possible to adapt the model to any forest type by specifying a limited number of parameters. A need for further experimental research on the wetting of litter during rain was also identified.

Conversion of dense lodgepole pine stands in west-central British Columbia into young lodgepole pine plantations using prescribed fire. 1. Biomass consumption during burning treatments

1992 ◽  
Vol 22 (4) ◽  
pp. 572-581 ◽  
Author(s):  
B. Blackwell ◽  
M.C. Feller ◽  
R. Trowbridge
Keyword(s):  
Forest Floor ◽  
Lodgepole Pine ◽  
Fire Severity ◽  
Minor Component ◽  
Understory Vegetation ◽  
Fuel Load ◽  
Fuel Moisture ◽  
Wide Range ◽  
A Minor ◽  
Moisture Conditions

The ecological effects of different treatments used to convert dense Pinuscontorta var. latifolia Engelm. stands into young P. contorta plantations are determined. The treatments used were felling the trees with a bulldozer and either broadcast burning the slash or bulldozing the slash into windrows, which were then burned. Burns were conducted under different fuel moisture conditions and state of fuel curing to achieve four classes of fire severity. The preburn surface fuel load was relatively high due largely to fallen dead woody materials (10−21 kg/m2). The biomass of the forest floor (5−10 kg/m2) was similar to that of the tree slash (5−13 kg/m2), while the understory vegetation was a minor component (0.3−0.5 kg/m2). The quantity of slash and understory vegetation consumed by burning increased with the preburn mass of the same components. Forest floor consumption depended primarily on the preburn forest floor mass for windrow burns and on forest floor moisture content as well as preburn forest floor mass for broadcast burns. Fire severity generally did not have a strong influence on biomass consumption, although it did significantly influence forest floor consumption. There was a general trend, however, of increasing biomass consumption in broadcast burns with increasing fire severity. Windrow burning consumed more biomass than did broadcast burning under similar weather and fuel moisture conditions. Windrow burning resulted in uniformly high biomass consumption that was relatively independent of fuel moisture over the wide range of fuel moistures studied.

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