Hétérogénéité d'une lande haute à Ulex europaeus en relation avec la propagation du feu (Bretagne, France)

1998 ◽  
Vol 76 (5) ◽  
pp. 804-817 ◽  
Author(s):  
Christelle Hely ◽  
Françoise Forgeard
Keyword(s):  
Moisture Content ◽  
Fire Risk ◽  
Soil Surface ◽  
Propagation Models ◽  
Heterogeneous Distribution ◽  
Fuel Distribution ◽  
Ulex Europaeus ◽  
Fire Propagation ◽  
Organic Horizons ◽  
Layered Pattern

This study analyzes plant material in a high Ulex europaeus heath to provide information on the partitioning of this ecosystem for fire propagation models. The aboveground biomass, followed for 15 months, has a spatially heterogeneous distribution that is a result of the layered pattern of the various branches. This pattern creates an internal moisture gradient that decreases from the apex to the base of the plant. This gradient also varies according to the species phenology. New, green branches with a high moisture content are at the top of the plant (upper strata), whereas woody branches with a lower moisture content are found near the ground (lower strata). Dry branches and spines, which produce most of the litter, are homogeneously distributed throughout the plant. Temporally, the layered pattern is homogeneous through the year and thus creates a constant fire risk. Soil organic horizons are temporally, spatially, and compositionally heterogeneous. The L layer is always two to three times thinner and drier than the duff layer (F+H). The total depth, weight, and moisture content of the organic horizons vary considerably across both the plot and square metre scales. The distance from a plant has a significant influence on the depth distribution of the soil organic horizons. Fuel distribution on both the soil surface and the plant must be considered to understand fire behaviour in this ecosystem.Key words: architecture, biomass, fire, fuel, humus, moisture content.

Flame characteristics, temperature - time curves, and rate of spread in fires propagating in a bed of Pinus pinaster needles

2003 ◽  
Vol 12 (1) ◽  
pp. 67 ◽  
Author(s):  
José M. C. Mendes-Lopes ◽  
João M. P. Ventura ◽  
José M. P. Amaral
Keyword(s):  
Wind Speed ◽  
Moisture Content ◽  
Pinus Pinaster ◽  
Flame Height ◽  
Fuel Moisture ◽  
Propagation Models ◽  
Fire Propagation ◽  
Rate Of Spread ◽  
Fuel Moisture Content ◽  
Flame Angle

An extensive set of experiments was carried out in order to collect data to validate fire propagation models being developed in the context of an European research project. The experiments were performed in a dedicated burning tray (2.0 m × 0.70 m working section), where wind velocity, fuel moisture content and slope were varied to study fire propagation in beds of Pinus pinaster needles. All the runs were videotaped and, from the recordings, information on flame geometry (i.e. flame height, flame length and flame angle) and rate of spread was obtained. Temperature measurements were also carried out by a small tower of six thermocouples at different heights above the fuel bed. Results show that headfire rate of spread increases steeply with wind speed for wind-driven fires but does not depend on wind speed for backing fire spread rates. Rate of spread increases slightly with slope for up-hill propagation, and is not slope dependent for down-hill cases. Rate of spread decreases when fuel moisture content increases. Flame angle and flame height are also dependent on wind velocity, slope, and fuel moisture content. The importance of temperature for fire propagation is discussed, emphasizing the role of radiation heat transfer in the process. Correlations between temperature and other indicators of fire behaviour (namely the rate of spread) are presented. Results are discussed and compared. The results obtained provide a good database for the assessment of fire propagation models.

scholarly journals 2-DIMENSIONAL GROUND RESPONSE ANALYSIS: A REVIEW

2020 ◽  
Vol 5 (1) ◽  
pp. 35-40
Author(s):  
Norazah Arjuna ◽  
Azlan Adnan ◽  
Nabilah Abu Bakar ◽  
Nabila Huda Aizon ◽  
Noor Sheena Herayani Harith
Keyword(s):  
Risk Mitigation ◽  
Soil Surface ◽  
Future Research ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Heterogeneous Distribution ◽  
Near Surface ◽  
Ground Shaking ◽  
Seismic Risk Mitigation

Earthquake is one of the natural disasters that is caused by ground shaking in soil. Ground response analysis is conducted to obtain the ground motion acceleration on soil surface. Conventional 1-D ground response analysis often suggests that soils are horizontally layered, with little consideration for heterogeneous distribution of soil properties. In this study, literature on 2-D ground response analysis studies has been study as it covers vertically and horizontally waves. Therefore, researcher works were presented in numerical modelling as substantial parameters for studies in near-surface structure. Besides, aspects for future research in the area 2-Dimensional Ground Response Analysis are included. The paper contributes to the under- standing of 2-Dimensional Ground Response Analysis for the application of seismic risk mitigation.

Short-term fire risk: foliage moisture content estimation from satellite data

1999 ◽  
pp. 17-38 ◽  
Author(s):  
Emilio Chuvieco ◽  
Michel Deshayes ◽  
Nicholas Stach ◽  
David Cocero ◽  
David Riaño
Keyword(s):  
Moisture Content ◽  
Satellite Data ◽  
Fire Risk ◽  
Short Term

Ulex europaeus (gorse).

2021 ◽  
Author(s):  
Julissa Rojas-Sandoval ◽  
Nick Pasiecznik
Keyword(s):  
Fire Risk ◽  
Ecosystem Processes ◽  
Tree Seedlings ◽  
Climatic Zones ◽  
Ulex Europaeus ◽  
The World ◽  
Tall Shrub ◽  
Noxious Weed ◽  
Disturbed Habitats ◽  
Grassland Habitats

Abstract U. europaeus was spread intentionally through most of the world in the 1800s and 1900s as a hedge plant, an ornamental and as a forage, although it is unlikely that it will be distributed to new areas for these purposes in future. It has large seeds and there is a threat from inadvertent introduction, but this is not high. U. europaeus was already declared a noxious weed 100 years ago in Australia and New Zealand, and is now a serious weed in many other countries, and poses a threat elsewhere where it is present but not yet invasive. It is an aggressive colonizer of disturbed habitats, and the risk from continued invasion in suitable climatic zones in countries where present is high. It is a tough, spiny, long-lived, tall shrub with a long-lived seed bank and is difficult to control. Thickets displace vegetation in grassland habitats, and outgrow and supplant tree seedlings in plantation forests. Heavy infestations modify soil and hydrological conditions, and so modify ecosystem processes. This plant poses a serious fire risk for indigenous ecosystems as well as managed habitats and human habitations.

scholarly journals Modeling Indoor Relative Humidity and Wood Moisture Content as a Proxy for Wooden Home Fire Risk

Sensors ◽  
2019 ◽  
Vol 19 (22) ◽  
pp. 5050 ◽  
Author(s):  
Torgrim Log
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Moisture Sorption ◽  
Fire Risk ◽  
Cold Weather ◽  
Indoor Climate ◽  
Ambient Conditions ◽  
Wood Panel ◽  
Fire Disaster ◽  
Strong Winds

Severe wooden home conflagrations have previously been linked to the combination of very dry indoor climate in inhabited buildings during winter time, resulting in rapid fire development and strong winds spreading the fire to neighboring structures. Knowledge about how ambient conditions increase the fire risk associated with dry indoor conditions is, however, lacking. In the present work, the moisture content of indoor wooden home wall panels was modeled based on ambient temperature and relative humidity recorded at meteorological stations as the climatic boundary conditions. The model comprises an air change rate based on ambient and indoor (22 °C) temperatures, indoor moisture sources and wood panel moisture sorption processes; it was tested on four selected homes in Norway during the winter of 2015/2016. The results were compared to values recorded by indoor relative humidity sensors in the homes, which ranged from naturally ventilated early 1900s homes to a modern home with balanced ventilation. The modeled indoor relative humidity levels during cold weather agreed well with recorded values to within 3% relative humidity (RH) root mean square deviation, and thus provided reliable information about expected wood panel moisture content. This information was used to assess historic single home fire risk represented by an estimated time to flashover during the studied period. Based on the modelling, it can be concluded that three days in Haugesund, Norway, in January 2016 were associated with very high conflagration risk due to dry indoor wooden materials and strong winds. In the future, the presented methodology may possibly be based on weather forecasts to predict increased conflagration risk a few days ahead. This could then enable proactive emergency responses for improved fire disaster risk management.

A Method for obtaining Samples of the Population of Collembola (Symphypleona) in Pastures

1933 ◽  
Vol 24 (3) ◽  
pp. 351-352 ◽  
Author(s):  
J. Davidson ◽  
D. C. Swan
Keyword(s):  
Moisture Content ◽  
Total Population ◽  
Surface Soil ◽  
Relative Proportion ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Food Plants ◽  
Simple Method ◽  
Factors Affecting

In our investigations on Smynthurus viridis, L., a study has been made of the population of this species, in an area of lucerne, at intervals of three and four days throughout the season.The density of the population of the species in a favourable pasture is markedly affected by the relative abundance of certain food-plants, especially leguminous species and particularly clovers such as subterranean clover (Trifolium subterraneum) and lucerne (Medicago sativa).The activity of the insect is intimately associated with the moisture of its environment, and the moisture content of the surface soil is one of the most important factors affecting the environmental conditions.Considering the habits of the insect, it was felt that the sweeping method would not give a reliable record of the total population in a given area of pasture. A sample obtained by sweeping with a net does not include individuals on or near to the surface of the soil. The relative proportion of individuals situated on or near the soil surface and those situated further up the plants varies considerably from time to time, according to the meteorological conditions, the growth of the herbage and the moisture content of the surface soil. It was necessary therefore to devise a simple method by means of which a more accurate record of the total population in a given area could be obtained.

Ignition and fire spread thresholds in gorse (Ulex europaeus)

2010 ◽  
Vol 19 (5) ◽  
pp. 589 ◽  
Author(s):  
Stuart A. J. Anderson ◽  
Wendy R. Anderson
Keyword(s):  
Moisture Content ◽  
Field Experiments ◽  
Fire Management ◽  
Fire Spread ◽  
Operational Experience ◽  
Management Planning ◽  
Near Surface ◽  
Ulex Europaeus ◽  
Fuel Layer ◽  
Major Variable

Field experiments were carried out in stands of gorse (Ulex europaeus L.) in New Zealand to determine the conditions under which fires would both ignite and spread. Research and operational experience in shrub fuels suggest that there is a clear difference between conditions that support ignition only (fuel ignites but does not spread beyond a single bush or clump) and conditions that are conducive to fire spread (fuel ignites and develops into a spreading fire). It is important for fire management agencies to be equipped with knowledge of these thresholds, because the different conditions require different levels of preparedness and response. Results indicate that the major variable influencing both fire ignition and fire spread development in gorse is the moisture content of the elevated dead fine fuel layer. Fires were observed to spread successfully in this elevated fuel layer only, independently of the surface fuels and the near-surface fuels. Elevated dead fuels failed to ignite at a moisture content of greater than 36%, and ignition only resulted in a spreading fire at moisture contents below 19%. The results correlate well with field observations and fire practitioners’ experience in these fuels, and provide reliable guidelines for fire management planning.

Evaluation of the magnetite as a magnetic tracer of eroded sediment from ephemeral gullies: conditioning factors of magnetic susceptibility

2020 ◽  
Author(s):  
Elena Zubieta ◽  
Juan Larrasoaña ◽  
Rafael Giménez ◽  
Alaitz Aldaz ◽  
Javier Casalí
Keyword(s):  
Magnetic Susceptibility ◽  
Soil Moisture ◽  
Moisture Content ◽  
Soil Surface ◽  
Field Capacity ◽  
Field Studies ◽  
Silty Clay ◽  
Magnetic Signal ◽  
Conditioning Factors ◽  
Detection Depth

<p>In gully erosion, the soil detached by the action of the erosive flow can be transported over long distances along the drainage network of the watershed. In this long way, the eroded material can be redistributed and/or deposited on the soil surface, and then eventually buried by eroded material from subsequent erosion events. Likewise, the variability of the soil (i.e., in texture and moisture content) over which this material moves can be considerable. The presence of the eroded material could be detected through magnetic tracers attached/mixed with the eroded soil. In this experiment, the degree to which the magnetic signal of the magnetite is conditioned by (i) the burying tracer depth, (ii) the texture and moisture content of the soil covering the tracer and (iii) the tracer concentration was evaluated.</p><p>The study was carried out in the lab in different containers (0.5 x 0.5 x 0.3 m<sup>3</sup>). Each container was filled with a given soil. In the filling process, a 0.5-cm layer of a soil-magnetite mixture of a certain concentration was interspersed in the soil profile at a certain depth. Overall, 3 different soil:tracer concentrations (1000:1, 200:1, 100:1), 4 tracer burying depths (0 cm, 3 cm, 5 cm and 10 cm from soil surface), and  2 contrasting soils (silty clay and sandy clay loam) were used. In each case, the magnetic susceptibility was measured with a magnetometer (MS3 by Bartington Instruments). Experiments were repeated with different soil moisture contents (from field capacity to dry soil).</p><p>If the tracer is located under the soil surface a minimum soil:tracer concentration of 200:1 is required for its correct  detection from the surface using a magnetometer. The intensity of the magnetic signal decreases dramatically with the vertical distance  of the tracer from the soil  surface (burying depth). The maximum detection depth of the tracer magnetic signal is strongly dependent on the natural magnetic susceptibility of the soil which hides the own tracer signal. Variation in soil moisture content does not significantly affect the magnetic signal. For extensive field studies the soil-tracer volume to be handled would be very high. Therefore, it is necessary to explore new tracer application techniques.</p>

Heat-Transfer in the Soil During Very Low-Intensity Experimental Fires - the Role of Duff and Soil-Moisture Content

1994 ◽  
Vol 4 (4) ◽  
pp. 225 ◽  
Author(s):  
JC Valette ◽  
V Gomendy ◽  
J Marechal ◽  
C Houssard ◽  
D Gillon
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Temperature Rise ◽  
Soil Moisture Content ◽  
Soil Surface ◽  
Dry Weight ◽  
Prescribed Burns ◽  
Low Intensity ◽  
Lethal Temperatures ◽  
Maximum Temperatures

The aim of this study was to analyse the effects of duff thickness and moisture content, and of soil moisture content on the transfer of heat in the soil. The experimental design used intact soil blocks with their duff layer, subjected to controlled fires of variable very low intensities of up to 100 kW m-1. The fuel on the surface was composed of needles and twigs of Pinus pinaster. The maximum temperatures measured within the fuel were of the order of 650 degrees C and were independent of the fireline intensities. For fires with fireline intensity of the order of 30 kW m-1, the presence of the duff layer reduced from 330 degrees C the temperature rise at the soil surface. Duff thickness played only a secondary role, but increasing moisture content reinforced its insulating effect, so that the temperature rise was 2.5 times less at 1 cm depth in the duff when the moisture content exceeded 70% dry weight, than when the moisture content was less than 30%. For more intense fires (> 50 kW m-1) that produced longer-lasting surface heating, duff thickness and moisture content played an important role in significantly reducing the temperature rise at the soil surface (range 140 degrees C to 28 degrees C). Because of low soil thermal conductivity, temperature attenuation with increasing depth was noticed. In the case of low intensity fires (< 30 kW m-1) in the absence of a duff layer, the maximum temperatures were reduced from 350 degrees C at the surface to 7 degrees C at 3.5 cm. The temperature rise in the soil decreased with depth according to a negative exponential relation. The rate constant of this relation was greater when the initial surface temperature and the soil moisture content were higher. For the soil studied, and under the moisture conditions encountered (between 7 and 19% of dry weight), the rate constant could be predicted with acceptable precision (r2 = 0.67), if the surface soil temperature rise and the soil moisture content were known. In these experimental fires, which were carried out when the air temperature did not exceed 20 degrees C, lethal temperatures (> 60 degrees C) were measured in the upper few centimetres of the duff layer in very low-intensity fires, and in the upper few centimetres of the soil (where nutrients are most concentrated and biological activity most intense) in the slightly more intense fires. The fire intensities were always very moderate, and of the order of magnitude df those encountered in the prescribed burns conducted on fuel-breaks of the french Mediterranean area. Their impact on the surface of the forest soil, in terms of lethal temperatures transmitted to the horizon rich in organic matter, are not negligible. In contrast, below 3 to 5 cm depth, prescribed burns, conducted under the conditions of the experiments, would not lead to significant change to nutrients or microfaunal or microfloral activity; in particular, root tips would not be subjected to heat stress sufficient to kill them.

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