Search

This paper uses the scaling laws obtained from a Froude Modeling perspective to analyze the variations experienced in the rate of spread of wind-aided and up-slope laboratory fires when changing the size of a scale model. The results have shown that the rate of spread scaling law is no longer verified when working at laboratory scale in steep slopes and high wind speed conditions. The paper also provides a framework for scaling and scale issues in forest fire research.

Zusammenfassung Bei Ziegen wurden die Kontraktionen des Labmagenkorpers und des Pylorusteiles des Labmagens mit Dehnungsmesstreifen registriert. Die Kontraktionen des Pylorus wurden mit Induktionsspulen gemessen. Auserdem wurden die Bewegungsvorgange des Labmagens rontgenologisch untersucht. 1. Am Labmagenfundus und -korper erwachsener Ziegen waren bei der rontgenologischen Untersuchung in der Regel keine Kontraktionen zu erkennen. Labmagenfundus und Labmagenkorper werden jedoch bei jeder Haubenkontraktion nach kranial und dorsal gezogen. 2. Am Pylorusteil des Labmagens ist eine fortwahrende Peristaltik vorhanden, die nur hin und wieder fur wenige Minuten gehemmt wird. Die Bewegungsvorgange entsprechen dabei weitgehend der Motorik des gefullten einhohligen Magens wahrend der Entleerung. 3. Die mittlere Frequenz der Labmagenperistaltik betragt 5,6 ± 0,3 Kontraktionen/Minute. 4. Die Ausbreitungsgeschwindigkeit der peristaltischen Wellen betragt im distalen Abschnitt der Pars pylorica des Labmagens 10 ± 2 mm/Sekunde. 5. Der Pylorus der Ziege offnet und schliest sich im Rhythmus der Labmagenperistaltik; die Kontraktion des Pylorus kann dabei als Fortsetzung der peristaltischen Welle angesehen werden. 6. Der Vorgang der Magenentleerung weicht von den Befunden am einhohligen Magen insofern ab, als bei erwachsenen Ziegen keine sog. “terminal antral contraction” auftritt und der am Ende einer peristaltischen Welle vor dem Pylorus befindliche Chymus nicht in den Darm ausgetrieben, sondern in den Labmagen zuruckgeprest wird. Die Ursache hierfur wird in dem andersartigen anatomischen Bau des Pylorus und der Pars pylorica des Labmagens gesehen. 7. Durch Infusion von Sympathikomimetika oder Parasympathikolytika wird die Motorik der Vormagen und des Labmagens (Pars pylorica) verringert, wahrend am Pylorus die Tendenz zur Kontraktion zunimmt. Summary Studies on the molity of the abomasum of the goat Contractions of the body and pyloric part of the abomasum of the goat were recorded by the strain gauge technique. Contractions of the pylorus were measured with induction coils. In addition, the movements of the abomasum were studied radiologically: 1. In the fundus and body of the abomasum of adult goats, no contractions were usually recognisable radiologically but the fundus and body of the organ were nevertheless thrust cranially and dorsally at each rumen contraction. 2. The pyloric part of the abomasum shows continuing peristaltic movements which from time to time are inhibited for periods of a few minutes. These movements correspond closely with the movements of the filled single stomach during emptying. 3. The average frequency of abomasal peristalsis is 5.6 ± 0.3 contractions per minute. 4. The rate of spread of the peristaltic waves in the distal part of the pyloric area of the abomasum is 10 ± 2 mm. per second. 5. The pylorus of the goat opens annd shuts in rhythm with the abomasal peristalsis: contractionns of the pylorus can be seen, therefore, as continuations of the peristaltic waves. 6. The process of gastric emptying differs from that in the single stomach so far as, in adult goats, no so-called “terminal antral contraction” occurs and the chyme present near the pylorus at the end of a peristaltic wave is not carried over into the gut but is pressed back into the abomasum. The reason for this may be the different anatomical structure of the pylorus and the pyloric part of the abomasum. 7. Infusion of sympathico-mimetic or para-sympathico-lytic agents reduces the motility of the fore-stomachs and the pyloric part of the abomasum, whereas the pylorus shows a tendency to increased contraction. Resume Recherches sur la motricite de la caillette de la chevre, en considerant plus particulierement le pylore On enregistre a l'aide de jauges de contrainte les contractions du corps de la caillette et de la partie pylorique de la caillette des chevres. On mesure les contractions du pylore a l'aide de bobines d'induction. De plus, on examine aux rayons X le developpement des mouvements de la caillette. 1. L'examen aux rayons X ne revele en general pas de contractions du fond et du corps de la caillette chez les chevres adultes. Mais ceux-ci sont pourtant etires en direction craniale et dorsale a chaque contraction du bonnet. 2. La partie pylorique de la caillette subit un mouvement peristaltique continuel, qui est inhibe de temps en temps pendant quelques minutes. Les processus moteurs rappellent alors en grande partie la motricite d'un estomac plein a cavite unique pendant la phase d'evacuation. 3. La frequence moyenne du peristaltisme de la caillette est de 5,6 ± 0,3 contractions/minute. 4. La vitesse de propagation des ondes peristaltiques est de 10 ± 2 mm/seconde dans la partie distale de la portion pylorique de la caillette. 5. Le pylore de la chevre s'ouvre et se ferme au rythme du peristaltisme de la caillette; la contraction du pylore peut etre consideree comme un prolongement de l'onde peristaltique. 6. Le processus de l'evacuation stomacale differe des observations faites sur l'estomac a cavite unique, parce qu'on n'observe pas de contraction dite »terminale antrale« chez les chevres adultes et que le chyme, qui se trouve a l'entree du pylore a la fin d'une onde peristaltique, ne passe pas dans l'intestin, mais est refoule dans la caillette. La cause de ce phenomene doit etre recherchee dans la construction anatomique differente du pylore et de la partie pylorique de la caillette. 7. Par infusion de sympathicomimetiques ou de parasympathicolytiques, la motricit ede les preestomacs et de la caillette (partie pylorique) diminue, alors que du cote pylore la tendance aux contractions augmente. Resumen Estudios sobre la fuerza motriz del cuajar de la cabra bajo la consideracion especial del piloro Se registraron en cabras las contracciones del cuerpo del cuajar y de la parte pilorica del cuajar con tiras extensimetras. Las contracciones del piloro se midieron con bobinas de induccion. Ademas se examinaron roentgen-ologicamente los procesos motores del cuajar. 1. En el fondo y cuerpo del cuajar de cabras adultas no se solian reconocer contracciones algunas en el examen roentgenologico. Sin embargo, el fondo y el cuerpo del cuajar son estirados en direccion craneal y dorsal con cada contraccion del bonete. 2. En la parte pilorica del cuajar se halla presente un peristaltismo continuo, que solo es inhibido de vez en vez durante algunos minutos. Los procesos motores corresponden aqui, a grandes rasgos, a la fuerza motriz de la cavidad monogastrica llena durante el vaciamiento. 3. La frecuencia media del peristaltismo del cuajar es de 5,6 ± 0,3 contracciones/min. 4. La velocidad de propagacion de las ondas peristalticas alcanza en el tramo distal de la parte pilorica del cuajar 10 ± 2 mm./seg. 5. El piloro de la cabra se abre y cierra en el ritmo del peristaltismo del cuajar; la contraccion del piloro se puede aceptar asi como continuacion de la onda peristaltica. 6. El proceso de vaciamiento gastrico difiere de los ***hallazgos en el estomago monocavitario, en cuanto que en la cabra adulta no se registra ninguna »contraccion terminal antral« y que el quimo que se halla al final de una onda peristaltica ante el piloro no es exprimido en el intestino, sino que resulta prensado hacia atras al cuajar. La causa de esto se ve en la estructura anatomica diferente del piloro y de la parte pilorica del cuajar. 7. Mediante infusion de simpaticomimeticos y parasimpaticoliticos se disminuye la fuerza motriz de los preestomagos y del cuajar (parte pilorica), mientras que en el piloro aumenta la tendencia a la contraccion.

Measuring rates of spread during biological invasions is important for predicting where and when invading organisms will spread in the future as well as for quantifying the influence of environmental conditions on invasion speed. While several methods have been proposed in the literature to measure spread rates, a comprehensive comparison of their accuracy when applied to empirical data would be problematic because true rates of spread are never known. This study compares the performances of several spread rate measurement methods using a set of simulated invasions with known theoretical spread rates over a hypothetical region where a set of sampling points are distributed. We vary the density and distribution (aggregative, random, and regular) of the sampling points as well as the shape of the invaded area and then compare how different spread rate measurement methods accommodate these varying conditions. We find that the method of regressing distance to the point of origin of the invasion as a function of time of first detection provides the most reliable method over adverse conditions (low sampling density, aggregated distribution of sampling points, irregular invaded area). The boundary displacement method appears to be a useful complementary method when sampling density is sufficiently high, as it provides an instantaneous measure of spread rate, and does not require long time series of data.

Wildfires create a risk to pedestrians traveling through rural areas, because they might not be aware of the presence of a wildfire or its direction and rate of spread until is too late to successfully evacuate. In wildland areas of southern San Diego County, immigrants crossing the U.S.–Mexico border and border security agents are particularly at risk to wildfires. The objective of this study is to develop a framework of analysis and associated tools for examining the combined behavior of wildfires and pedestrian mobility to assess the potential threat of fire to pedestrians in wildland areas. Outputs from a geographic information system (GIS) overlay model for determining potentially dangerous fire zones, the Wildland–Urban Interface Evacuation (WUIVAC) model, and a model of pedestrian mobility in wildland areas were combined to generate wildfire risk to pedestrian maps. The key technical contributions of the study are the development and testing of the pedestrian mobility model and the framework and lo...

Aim of study: To reconcile the effects of live fuel moisture content (FMC) on fire rate of spread (ROS) derived from laboratory and field fires.Methods: The analysis builds on evidence from previous fire-spread experimental studies and on a comparison between two functions for the FMC damping effect: one derived from field burns, based on dead FMC, and another derived from laboratory trials, based on a weighted FMC (dead and live fuels).Main results: In a typical Mediterranean shrubland, laboratory and field-derived FMC damping functions are linearly related, which is explained by the correlation between monthly average live and dead FMC variation throughout the year. This clarifies why the effect of live FMC on real-world fires ROS has remained elusive.Research highlights: By providing evidence that the most significant effect of FMC on ROS is independent of vegetation phenology (dead or live condition), and explaining why in specific situations dead FMC is sufficient to provide satisfactory ROS predictions, our results can assist future modelling efforts.

During a wildfire, a sharp wind change can lead to an abrupt increase in fire activity and change the rate of spread, endangering firefighters working on what had been the flank of the fire. In southeastern Australia, routine forecast of cold-frontal wind change arrival times is a critical component of the fire weather forecasting service, and mesoscale NWP model predictions are integral to this forecast process. An event-based verification method has been developed in order to verify these mesoscale NWP model forecasts of wind changes. The approach is based on fuzzy-rule techniques and objectively determines the timing of significant (fire weather) wind changes from time series of observations at a single surface station. In this paper these rules are applied to observational and NWP model forecast time series at observation locations over five fire seasons to determine objective “observed wind change times” and “forecast wind change times” for significant frontal wind changes in southeastern Australia. These forecast wind change times are compared with those observed, and also with those determined subjectively by forecasters at the Victorian Regional Forecast Centre. This provides an objective verification of NWP wind change forecasts and a measure of contemporary NWP model skill against which future model improvements may be measured. Case studies of two wind change events at selected stations are also presented to demonstrate some of the strengths, weaknesses, and characteristics of this verification technique.

Managers masticate fuels to reduce extreme fire hazards, but the effect on fire behaviour within the resulting compact fuelbeds is poorly understood. We burned 54 masticated fuelbeds in laboratory experiments one and two growing seasons after mastication and 75 masticated fuelbeds in prescribed fire experiments one growing season after treatment in three replicate Pinus ponderosa stands. Mastication treatments reduced density of trees >5 cm diameter by 30–72% resulting in total fuel depth of 6.9–13.7 cm and surface woody fuel loading of 1.0–16.0 kg m−2. Flame length and rate of spread were low and similar for coarse and fine mastication treatments and controls. Smouldering combustion lasted 6–22 h in prescribed fire experiments where fuelbeds included duff and were well mixed by machinery, compared with

The effect of grass fuel load on fire behaviour and fire danger has been a contentious issue for some time in Australia. Existing operational models have placed different emphases on the effect of fuel load on model outputs, which has created uncertainty in the operational assessment of fire potential and has led to end-user and public distrust of model outcomes. A field-based experimental burning program was conducted to quantify the effect of fuel load on headfire rate of spread and other fire behaviour characteristics in grasslands. A total of 58 experimental fires conducted at six sites across eastern Australia were analysed. We found an inverse relationship between fuel load and the rate of spread in grasslands, which is contrary to current, untested, modelling assumptions. This result is valid for grasslands where fuel load is not a limiting factor for fire propagation. We discuss the reasons for this effect and model it to produce a fuel load effect function that can be applied to operational grassfire spread models used in Australia. We also analyse the effect of fuel load on flame characteristics and develop a model for flame height as a function of rate of fire spread and fuel load.

We have developed a transient pyrolysis model based on the modified mass transfer number determined from experiments on the steady-state burning rate of vertical PMMA slabs. It allowed satisfactory concordance with experiments on upward flame spread. A good agreement for the rate of spread was also observed for inclination angles below the critical angle. © 2009 The Combustion Institute.

Population-specific preferences involved in premating isolation may be based on several different types of mating cues. Here, we compare the rates of spread of 12 different mating preferences that reflect preferences for local adaptation, male condition, and reinforcement. We introduce methods to dissect the components of the rate of spread to determine why certain mating preferences spread more quickly than others. We confirm the result that female preferences based on population-specific markers alone always spread faster than female preferences based only on a single local adaptation locus, regardless of the strength of natural selection on hybrid incompatibility. However, we find that this occurs for different reasons depending on the strength of selection against hybrids. Female preferences based on total male condition also achieved high rates of spread, suggesting that preferences for condition-dependent male displays may evolve under reinforcement scenarios.

Stomodeal trophallaxis plays a major role in ant colony nutrition and communication. While the rate of food distribution at the individual level (worker to worker) is rapid, factors affecting the rate of food distribution at the colony level remain poorly understood. We used the odorous house ant, Tapinoma sessile (Say), as a model species to investigate the factors affecting the rate of spread of liquid carbohydrate food throughout a colony. To track the movement of the food we used protein marking and double antibody sandwich enzyme-linked immunosorbent assay, DAS-ELISA. Increasing colony size while keeping the number of donor workers constant significantly decreased the number of individuals testing positive for the marker. After 8 h of trophallactic interactions with ten donors, 92 ± 5% of recipient workers tested positive in a colony of 125 and 38 ± 5% tested positive in a colony of 1,000. Interestingly, as colony size increased and the percentage of workers testing positive decreased, the proportion of workers actually receiving food increased. Food originating from a single donor fed approximately 12 individuals in colonies comprised of 125 recipients and approximately 38 individuals in colonies comprised of 1,000 recipients. Thus, the per capita consumption of food decreased as colony size increased, most likely because the amount of food reaching the colony was limited. Increasing the number of donors while keeping colony size constant significantly increased the number of recipient ants testing positive for the marker. As the number of donor workers doubled, the percentage of recipients testing positive more than doubled suggesting that the number of individuals receiving food increases with increasing colony size, while the per capita amount of food decreases. When food was available ad libitum and in close proximity to the nest, numerous workers fed directly at the food source. This dramatically increased the rate and the extent of food distribution to both the workers and the queens and colony size had no significant effect on the spread of the marker in the workers or the queens. The rate and the extent of food distribution at the colony level may depend on a number of factors including the number of successful foragers, the size and density of the recipient colony, and the recipient caste.

Ligustrum lucidum Aiton (Oleaceae) is one of the most planted species in urban sarborization and in highways at the South and the Southeastern region of Brazil. It's a fast growth rustic tree, with wide and dense crown, extensively used in fences. These characteristics, besides the low inflammability, are very important fuelbreaks. The objective of this research was to evaluate the characteristics of Ligustrum luci- dum inflammability to use in fuelbreaks on urban area/forest area interface and on the edges of highways with high fire risk. The evaluation of inflammability was made through the observations of the rate of spread and the intensity of fire in experimental burnings of 1 m2 parcels made of L. lucidum leaves and branches in two levels of humidity: humidity of the material just collected of the tree and humidity of the dry material oven dried at 75 °C for 48 hours. Results indicate that the inflammability of the studied species is low, even in reduced conditions of humidity, although it would be necessary more investigati- ons about the inflammability characteristics of the species in conditions of high intensity fire.

Summary 1 Biological invasions are characterized by occasional long-distance, human-assisted dispersal. Centres of human transportation that are connected by trade to a wide range of other locations (‘transport hubs’) may be important catalysts of the rate at which new populations of an invader are established. 2 We developed a spatially explicit stochastic model to simulate the spread of a hypothetical marine invader by hull fouling. The model was based on classic ‘Susceptible–Infected–Resistant’ models used in medical epidemiology. It was parameterized using empirical data on the colonization of vessel hulls by fouling organisms, and on maintenance and travel patterns of ~1300 domestic and international yachts around New Zealand. Thirty-six marinas were grouped into three categories that represented a gradient in the number of other transport nodes each marina was ‘connected’ to and the frequencies of yacht movements between them. Invasions were seeded in three locations from each category. Simulations were run over 10 years to determine differences in the trajectory of invasions originating from busy and less frequented transport nodes. 3 Busy ‘hub’ locations were 75% more likely to become infected by an invader than quieter locations. Infection of hub nodes occurred at an earlier average stage in the invasion sequence. This occurred irrespective of whether the initial source of the invasion was associated with low or high traffic volume and connectivity. 4 Biotic invasions originating from hub locations did not consistently result in faster spread, or a larger number of secondary infestations. However, the rate of spread from hubs was less variable than from quieter nodes and was less often preceded by a prolonged lag period. 5 Synthesis and applications. Rapid spread of invasive organisms can occur from busy and from seemingly unimportant transport nodes. Busy locations were consistently more likely to become infested by an invader and to accelerate spread to secondary locations faster. Busy transport hubs should be considered a priority for the allocation of preventative and management efforts, such as regular baseline or target surveys and the development of incursion response plans that minimize the risk of spread within the transport network.

The effectiveness of long-term retardants used in forest fire fighting has been studied at three different scales. In this paper, retardant effectiveness experiments conducted since 1965 are examined and reviewed. These experiments include studies carried out with analytical instrumentation as well as studies involving laboratory and field flame-spread tests. Special attention is paid to the work performed with diammonium phosphate (DAP) and ammonium sulfate (AS). The experimental methodologies and the results obtained are reviewed in detail. A lack of effort in the modeling of fire behavior under the effect of these products is evidenced and recommendations for further work are made.

This work proposes a new method for determining the fire front positions for optically thin flames and the rate of spread (ROS) of forest or vegetation fires. It is based on an application for linear flame fronts that are generated in a fire tunnel with known dimensions using Quercus coccifera shrubs as vegetal fuel. In the first step of the method, the heat fluxes coming from the flame are measured by a specific thermal sensor in four horizontal directions. In the second, these heat fluxes are calculated theoretically using an approximate resolution of the radiative transfer equation. Subsequently, the positions of the fire front and the flame characteristics are determined by applying an inverse method. The rate of spread is deduced by applying a least-square regression on the position values. An extrapolation of this new method to more complex experimental scenarios such as prescribed burnings is proposed.

Work to date on biological invasions and the spread of biological control agents has been focused on the explicitly spatial aspects, such as rate of spread and shape of the wave front. There has been relatively little attention paid to the influence of dispersal on the rate of increase of local populations. We use a simple general model for logistic local growth and one-dimensional diffusive dispersal to show that dispersal can act as a substantial drain on local populations. Local increase at a site of introduction is always slower than would be expected in the absence of dispersal, while the rate of increase of other populations is initially enhanced, then reduced by dispersal. This may have an important effect when estimating population parameters for invading organisms or biological control agents during the initial stages of their spread, and helps explain the “latent period” typically observed in biological invasions.

The tempo and mode of the initial human colonisation of terra incognita has long been a controversial topic in archaeology. Two opposing models have been used to explain the earliest evidence for human occupation of 'Sahul' (a eustatically enlarged Pleistocene landmass that incorporated Tasmania and New Guinea): that people adapted quickly to new environments and hence spread rapidly over the region, or that they found adaptation to new conditions difficult and hence spread slowly, initially around the coast. The assumption that the rate of adaptation to new conditions determines the rate of spread underlies both hypotheses. We present here an alternative model of colonisation that reconsiders these issues. We suggest that initial human movement through Sahul would have been inherently fast. However, this rate of spread would not have been a consequence of rapid adaptation, but of maladapted subsistence strategies that resulted in inefficient extractive methods and hence low carrying capacities. Thus, we reverse the normal argument and posit that minimising adaptiveness, as long as human survival is possible, will maximise the rate of human spread over an empty landmass.

In the 1930s and 1940s, little was known about viruses, and information on plant diseases caused by viruses was just beginning to appear in the scientific literature. Problems with grapevines in California, first referred to as “red leaf,” were initially attributed to inexperience in viticultural techniques and poor growing conditions. However, the problem was later identified as leafroll disease, which causes red leaves, and poor yields and fruit quality. We evaluated its rate of spread for 5 years in a Napa Valley vineyard, and found an average rate of more than 10% per year. Leafroll disease can be vectored by low-level populations of grape mealybugs, and is now spreading rapidly in at least one Napa Valley vineyard for unknown reasons. Using stock for planting vines that is certified as virus-free is a key strategy in preventing the spread of grapevine leafroll disease.

Understanding and being able to predict forest fire occurrence, fire growth and fire intensity are important aspects of forest fire management. In Canada fire management agencies use the Canadian Forest Fire Danger Rating System (CFFDRS) to help predict these elements of forest fire activity. In this paper a review of the CFFDRS is presented with the main focus on understanding and interpreting Canadian Fire Weather Index (FWI) System outputs. The need to interpret the outputs of the FWI System with consideration to regional differences is emphasized and examples are shown of how the relationship between actual fuel moisture and the FWI System’s moisture codes vary from region to region. Examples are then shown of the relationship between fuel moisture and fire occurrence for both human- and lightning-caused fire for regions with different forest composition. The relationship between rate of spread, fuel consumption and the relative fire behaviour indices of the FWI System for different forest types is also discussed. The outputs of the CFFDRS are used every day across Canada by fire managers in every district, regional and provincial fire management office. The purpose of this review is to provide modellers with an understanding of this system and how its outputs can be interpreted. It is hoped that this review will expose statistical modellers and other researchers to some of the models used currently in forest fire management and encourage further research and development of models useful for understanding and managing forest fire activity.

The long-term rate of spread of myrtle wilt disease was monitored in plots within undisturbed forests at six localities in Tasmania representing a range of rainforest types containing myrtle, Nothofagus cunninghamii. The incidence of myrtle wilt, indicated by trees showing evidence of attack by the mountain pinhole borer Platypus subgranosus, at the start of the monitoring period was 15.8-45.4% of standing trees across the range of sites. After 12-18 y, the incidence was 16.8-50.9%, representing an increase in myrtle wilt of 0.08-0.67% per year. There was a significant effect of rainforest type on both disease incidence and the level of physical damage to myrtle trees (broken limbs and stem wounds), callidendrous rainforests having higher disease and damage levels than thamnic and implicate stands. The effect of altitude on disease incidence was also significant, with myrtle wilt levels being lower at higher altitudes. The factors affecting the levels of myrtle wilt and the current significance of the disease in Tasmanian rainforests are discussed; disease levels recorded over the sampling period indicate a currently stable situation.

A serious disease of black raspberry (Rubus occidentalis) was observed in Oregon in the last decade. Plants showing mosaic symptoms declined rapidly and in many cases died over a period of several years. Double-stranded RNA extraction from symptomatic black raspberry revealed the presence of two high molecular weight bands, which were cloned and partially sequenced. Sequence analysis disclosed the presence of Black raspberry virus (BRV). A newly planted field of black raspberries in Oregon was studied to assess the rate of spread of BRV. The timing of BRV infection as it relates to aphid populations and flights was also determined. Testing of nearby vegetation identified several symptomless Rubus hosts of BRV. It was determined that BRV spreads rapidly with a low aphid threshold and was associated with symptoms of decline in black raspberries in Oregon.

Fire behaviour data from Project Vesta experimental fires were used to evaluate the fire behaviour relationship on the Forest Fire Danger Meter (FFDM), the Forest Fire Behaviour Tables (FFBT) for Western Australia and the fire spread model of Burrows (1999) for predicting the rate of spread of fires in jarrah (Eucalyptus marginata) forest under dry summer conditions. Experimental fires were conducted at two sites in southwestern Australia under conditions of moderate to high forest fire danger with fine fuel moisture contents of 6-9% oven dry weight and wind speeds up to 20 km h-1 (at 10 m in the open). Fuels ranged in age from 2 to 22 y since the last fire and had understorey shrub layers from 0.5 to 2.0 m tall. Mean rates of spread for experimental fires were 392 m h-1 and 405 m h-1 at the low and tall shrub sites respectively, with the fastest fires spreading at close to 1200 m h-1. Fires spread two to three times faster than predicted by the FFDM and FFBT fire spread models, and up to five times faster than predicted by the spread model of Burrows. Both the FFDM and FFBT models predicted fire spread better at the low shrub fuel site and when wind speeds were 12.5 km h-1. We argue that existing fire behaviour models under-predict because they were developed using data from fires that had not achieved a quasi-steady rate of spread, whereas the line ignition technique used during Project Vesta experiments resulted in fires travelling at a speed closer to their potential rate of spread for the prevailing conditions. Existing guides remain valid for predicting spread during the early stages of fire growth when fires are developing from a point ignition and the headfire remains narrow.

Understanding the mechanisms and patterns that govern the invasion of species is essential for coping with global change of the biological world. A recent study highlights the possibility, based on data from a wide range of different taxa, that the invasion speed of species could be governed by a regulatory process. In principle, it is possible that mechanisms such as Allee effects could cause the invasion fronts to be regulated, such that the change in the rate of spread is negatively related to the current rate. This is very similar to how some populations are regulated around an equilibrium size, and finding the regulation structure if true, is of both pure and applied interest. However, here we will argue that the methods used so far are incomplete, thus even though there is a theoretical possibility that the speed of species invasions are regulated, more scrutiny is needed for its detection. Analysing changes of the ratio of current and past rate of spread against current ratios may give the impression of regulation in null models that are in fact unregulated. In addition we show that the apparent pattern is highly influenced by the spatial scale of investigation. Our results show that detecting regulatory patterns in species invasions is similarly non-trivial as is detecting density-dependence per se, but necessary, given the importance of this problem.

Tracking macroalgal invasions relies on a variety of approaches and techniques, including random sampling, active tracking near sources of introduction, and identification of alien species and their vectors of introduction using both classical means (based on taxonomical and biogeographical knowledge) and molecular tools. To identify the invaded ecosystems, and to describe the rate of spread and invasion dynamics, other approaches must be used, including mapping techniques and public awareness campaigns. In these endeavours, standardisation of geographical and density data is important. The tracking of alien species before eradication or control measures are instigated requires special cartographic techniques. This paper provides a general overview of these different approaches and the specific strategies adapted to the biological and ecological characteristics of particular species.

Grazing is most effective at treating smaller diameter live fuels that can greatly impact the rate of spread of a fire along with the flame height. DOI:10.2458/azu_rangelands_v29i5_nader

Yersinia pestis invaded the continental United States in 1900 and subsequently became established in wild rodent populations in several western states, traversing 2,250 km in approximately 40 years. However, the specific path of the eastward expansion of plague into the United States is poorly understood. We directly calculated velocities of disease spread and performed trend-surface analyses on spatio-temporally unique plague cases to clarify the route and speed of the initial spread of plague eastward. Velocities of disease spread were then analyzed using multiple linear regression models to identify environmental features that significantly impacted the rate of spread. Between one and three introductions of plague along the Pacific coast were observed, after which plague traveled from 45 to 87 km/year. In all regression models, the coast ranges of California were associated with slower spread, and the Southern Rockies were associated with a significant increase in the rate of disease spread. Additional climatic and environmental factors affecting the velocity of plague's spread varied among the models. Maps were developed to graphically represent the traveling waves of plague over the United States landscape. These analyses identify important large-scale trends regarding the eastward invasion of plague into the continental United States that can be used to better understand the historical spread of plague, as well as how to manage threats from new or re-emerging diseases that might operate under similar spatio-temporal dynamics.

Results of tests conducted with the psyllid Arytainilla spartiophila before it was introduced into New Zealand for biological control of broom, Cytisus scoparius (L.) Link, indicate that it is highly host specific, and unlikely to feed and develop on alternative host plants. Psyllids were reared under containment conditions and in the laboratory between 1991 and 1994 and first released in the field in New Zealand in 1993. From all releases made under a user-funded technology transfer programme, psyllids have established at 28% of sites, have been recovered from a further 7%, have failed at 3% of sites, and their fate at the remaining 62% of sites is unknown. From these releases psyllids are known to have established at 33 sites between Tapanui in Southland and Rotorua in the central North Island. The recorded rate of spread has generally been slow, but from one 1999 release psyllids spread 300-500 m from the original release point in 2 years.

A subset of experimental fires, conducted in the Northern Territory, Australia, in July and August 1986, was analysed to examine the role of the convective Froude number and Byram’s energy criterion (Pw/Pf) in the behaviour of grassland fires. Forms of these dimensionless numbers were obtained from the literature as were functions relating independent variables in these formulations to measured quantities. It was found that Byram’s energy criterion is simply the inverse cube of the convective Froude number and thus, was not examined in detail. It was found that the convective Froude number is not reflected in the observed behaviour of fires, as previous authors have suggested, despite the range of experimental conditions (wind speed 1.5–7.5 ms−1, rate of spread 0.05–2.82 ms−1).

A mathematical method for estimating the endemic status of bovine tuberculosis (bTB) in cattle in England and Wales has been developed. 6.25 km2 hexagonal cells were used as the base resolution. Maps were produced for overlapping two-year periods spanning 2001/03 to 2009/11. Distance from a farm to the ten nearest ‘Officially Tuberculosis Free status – Withdrawn’ incidents within the same time period was measured. Endemic areas were defined as those hexagons containing farms where the 3rd nearest incident occurred within 7 km. Temporal spread of endemic bTB was estimated by creating a contour map displaying the spread of endemic bTB over the two-year periods, and using boundary displacement to calculate the rate of spread across each hexagon. A rate was obtained for ∼2300 cells and varied between 0.04 km and 15.9 km per year (median = 3.3 km per year). This work will enable further analysis of the factors associated with this expansion.

Physical and geometrical characteristics of flame propagation are very important to better understand the forest fire spread behaviour and to improve risk management tools. Having a tool to predict these characteristics is of practical and theoretical interest for a better understanding of the complex chemical and physical mechanisms which occur during forest fire phenomena. A metamodel is presented based on Artificial Neural Networks (ANNs) for estimating physical and geometrical parameters of the forest fire front, namely the rate of spread (ROS), flame height ( H f ) and flame tilt angle ( α f ). The ANN was developed using literature data obtained from experiments of fire propagation in beds of Pinus pinaster needles. The optimal feedforward ANN architecture with error backpropagation (BPNN) was determined by the cross validation method. The ANN architecture having 5 hidden neurons proved to be the best choice. Comparing the modelled values by the ANN with the experimental data indicates that neural network model provide accurate results. The performance of the ANN model was compared with a metamodelling method using a multilinear regression approximation.

Land managers responsible for invasive species removal in the USA require tools to prevent the Asian longhorned beetle (Anoplophora glabripennis) (ALB) from decimating the maple-dominant hardwood forests of Massachusetts and New England. Species distribution models (SDMs) and spread models have been applied individually to predict the invasion distribution and rate of spread, but the combination of both models can increase the accuracy of predictions of species spread over time when habitat suitability is heterogeneous across landscapes. First, a SDM was fit to 2008 ALB presence-only locations. Then, a stratified spread model was generated to measure the probability of spread due to natural and human causes. Finally, the SDM and spread models were combined to evaluate the risk of ALB spread in Central Massachusetts in 2008–2009. The SDM predicted many urban locations in Central Massachusetts as having suitable environments for species establishment. The combined model shows the greatest risk of spread and establishment in suitable locations immediately surrounding the epicentre of the ALB outbreak in Northern Worcester with lower risk areas in suitable locations only accessible through long-range dispersal from access to human transportation networks. The risk map achieved an accuracy of 67% using 2009 ALB locations for model validation. This model framework can effectively provide risk managers with valuable information concerning the timing and spatial extent of spread/establishment risk of ALB and potential strategies needed for effective future risk management efforts.

We review and synthesize recent developments in the study of the invasion of communities in heterogeneous environments, considering both the invasibility of the community and impacts to the community. We consider both empirical and theoretical studies. For each of three major kinds of environmental heterogeneity (temporal, spatial and invader-driven), we find evidence that heterogeneity is critical to the invasibility of the community, the rate of spread, and the impacts on the community following invasion. We propose an environmental heterogeneity hypothesis of invasions, whereby heterogeneity both increases invasion success and reduces the impact to native species in the community, because it promotes invasion and coexistence mechanisms that are not possible in homogeneous environments. This hypothesis could help to explain recent findings that diversity is often increased as a result of biological invasions. It could also explain the scale dependence of the diversity-invasibility relationship. Despite the undoubted importance of heterogeneity to the invasion of communities, it has been studied remarkably little and new research is needed that simultaneously considers invasion, environmental heterogeneity and community characteristics. As a young field, there is an unrivalled opportunity for theoreticians and experimenters to work together to build a tractable theory informed by data.

An evacuation trigger is a point on the landscape that, once crossed by a wildfire, triggers an evacuation for a community. The Wildland-Urban Interface Evacuation (WUIVAC) model can be used to create evacuation trigger buffers around a community using fuels, weather, and topographic inputs. A strategic, community-scale application of WUIVAC for the town of Julian, California was investigated. Eight years of wind measurements were used to determine the worst-case (strongest) winds in 16 directions. Surface fire rate of spread was used to calculate evacuation trigger buffers for the communities of Julian and nearby Whispering Pines, and for three potential evacuation routes. Multiple trigger buffers were combined to create fire planning areas, and trigger buffers that predict the closure of all evacuation routes were explored. WUIVAC trigger buffers offer several potential benefits for strategic evacuation planning, including determination of when to evacuate and locating potential evacuation routes.

We evaluated the predictive capacity of a rate of spread model for active crown fires (M.G. Cruz, M.E. Alexander, and R.H. Wakimoto. 2005. Can. J. For. Res. 35: 1626–1639) using a relatively large (n = 57) independent data set originating from wildfire observations undertaken in Canada and the United States. The assembled wildfire data were characterized by more severe burning conditions and fire behavior in terms of rate of spread and the degree of crowning activity than the data set used to parameterize the crown fire rate of spread model. The statistics used to evaluate model adequacy showed good fit and a level of uncertainty considered acceptable for a wide variety of fire management and fire research applications. The crown fire rate of spread model predicted 42% of the data with an error lower then ±25%. Mean absolute percent errors of 51% and 60% were obtained for Canadian and American wildfires, respectively. The characteristics of the data set did not allow us to determine where model performance was weaker and consequently identify its shortcomings and areas of future improvement. The level of uncertainty observed suggests that the model can be readily utilized in support of operational fire management decision making and for simulations in fire research studies.

et al., This work proposes a new thermal image processing method for computing the rate of spread (ROS) of forest fires. It is based on an application for linear flame fronts that are generated on flat surfaces with known dimensions. In the first step of the method, the correspondence between the points of the thermal image obtained and the real plane is calculated by means of a direct linear transformation (DLT). Subsequently, the position of the flame front is determined by applying a threshold-value-searching criterion within the temperature matrix of the target surface. The design principles for the implementation of this method in the laboratory are described in depth, as well as the considerations that must be taken into account if the method is to be correctly extrapolated to more complex experimental scenarios, such as prescribed burnings or real forest fire emergencies., This work was supported by the project 'Integration of robust perception, learning, and navigation systems in mobile robotics' (J-0929)., This research is supported by the Spanish Ministry of Education and Science under projects DPI 2004-5414, TIC 2003-09291, and a Juan de la Cierva Post doctoral Fellow ship to JAC. It is also supported by the Department of Universities, Research and the Information Society (DURSI) of the Catalan government, the European Social Fund and the Polytechnic University of Catalonia (UPC).

The invasive terrestrial planarian Bipalium kewense is found worldwide in tropical and warm temperate zones. The rate of spread and ecological impact of the flatworm will depend in part on its reproductive strategies. Members of this species reproduce primarily by fission of posterior body fragments. Herein we report, for only the second time in over 120 years of international study, the production of a fertile egg capsule by B. kewense. The capsule was produced by a flatworm from Texas, hatched in 21 days, and it contained 7 juveniles. Although the capsule structure, incubation period, and litter size were similar to those characteristic of the sexual species, B. adventitium, the B. kewense capsule was larger (112 mg) and produced larger offspring.

In fire fighting, the time and effort required to control a fire increase if the beginning of the fire containment effort is delayed. Several demand-covering models have been proposed for the deployment of available fire-fighting resources so that a forest fire is attacked within a specified time limit. This paper considers the problem of scheduling a single fire-fighting resource when there are several existing fires to be controlled using a model specific to the fire's rate of spread. The problem is tackled using the concept of deteriorating jobs, that is, the model represents increasing value loss as fires remain unsuppressed and increasing time for fire suppression.

Quantifying the potential spread and density of an invading organism enables decision-makers to determine the most appropriate response to incursions. We present two linked models that estimate the spread of Solenopsis invicta Buren (red imported fire ant) in Australia based on limited data gathered after its discovery in Brisbane in 2001. A stochastic cellular automaton determines spread within a location (100 km by 100 km) and this is coupled with a model that simulates human-mediated movement of S. invicta to new locations. In the absence of any control measures, the models predict that S. invicta could cover 763 000–4 066 000 km2 by the year 2035 and be found at 200 separate locations around Australia by 2017–2027, depending on the rate of spread. These estimated rates of expansion (assuming no control efforts were in place) are higher than those experienced in the USA in the 1940s during the early invasion phases in that country. Active control efforts and quarantine controls in the USA (including a concerted eradication attempt in the 1960s) may have slowed spread. Further, milder winters, the presence of the polygynous social form, increased trade and human mobility in Australia in 2000s compared with the USA in 1940s could contribute to faster range expansion.

The rate of spread of crown fires advancing over level to gently undulating terrain was modeled through nonlinear regression analysis based on an experimental data set pertaining primarily to boreal forest fuel types. The data set covered a significant spectrum of fuel complex and fire behavior characteristics. Crown fire rate of spread was modeled separately for fires spreading in active and passive crown fire regimes. The active crown fire rate of spread model encompassing the effects of 10-m open wind speed, estimated fine fuel moisture content, and canopy bulk density explained 61% of the variability in the data set. Passive crown fire spread was modeled through a correction factor based on a criterion for active crowning related to canopy bulk density. The models were evaluated against independent data sets originating from experimental fires. The active crown fire rate of spread model predicted 42% of the independent experimental crown fire data with an error lower then 25% and a mean absolute percent error of 26%. While the models have some shortcomings and areas in need of improvement, they can be readily utilized in support of fire management decision making and other fire research studies.

Human transport hubs, such as shipping ports, airports and mail centers are important foci for the spread of non-indigenous species. High relative abundance in a transport hub has been proposed as a correlate of invasion success, since abundant species are thought more likely to colonize vectors and to be transported more frequently. We here evaluate the relative importance of vector characteristics and local source assemblages in determining the pool of species that is transported by hull fouling on recreational boats. We compared the resident fouling communities of three recreational boat harbors in Australia with the assemblages on the hulls of boats that travel between them. We used data on the recent travel and maintenance history of the boats to evaluate correlates of transport probability and the potential for intra-coastal spread of fouling organisms. Invertebrate assemblages on heavily fouled vessels reflected the composition of biotic assemblages within the marina in which they were moored, but by itself, relative abundance in the source port was not a reliable predictor of transport probability. More important was the age of the antifouling paint on the vessels’ hulls, which acted selectively on some groups of organisms. Movements of vessels were characterized by “fidelity” (vessels remaining close to homeport) interspersed with “promiscuity” (vessels traveling to a diverse pool of destinations). In an infested harbor, measures taken to increase the resistance of vectors to colonization by the invader should be effective in slowing the rate of spread to other locations, by decreasing the overall frequency of transport.

Summary ‘Flammability’ means different things to different people. Scientifically, it can be defined through three component variables that describe how well the fuel ignites (ignitibility), how well it burns (combustibility) and how long it burns (sustainability). The ‘fuel’ may be a plant organ, a whole plant or a plant community. While the terms ignitibility, combustibility and sustainability have been developed for laboratory studies, there are conceptual equivalents suited to the field; these are rate of spread, intensity and residence times. Another variable is added for field circumstances—probability of burning at a point. Eucalypt forests can be highly ‘flammable’ even considering all criteria and scales, while Australian forests in general show the whole range of variation from low (‘closed forests’ or ‘rainforests’) to high (e.g. relatively short stringy-barked open forests of Eucalyptus with abundant wiregrass). The expression of flammability depends on the local circumstances. In the field th...

The rates and patterns of spread of 63 species in the Czech Republic and seven in Britain and Ireland were determined from quadrat records, mapovaci pole (11- ¥ 12-km mapping zones in the Czech Republic), and 10- ¥ 10-km hectads in Britain and Ireland. Species that have straight sections on logarithmic, square root, and arithmetic plots were found; the last group (10 of them) are generally casuals. Straight square root plots (52 found) are expected from Fisher-Skellam reaction diffusion models, logarithmic equivalents (36 found) where the dispersal kernel has a thicker tail or where spread involves scattered colonies. The greater frequency of the straight square root plots is unexpected. The straightness of so many plots shows that there is no significant variation in recorder bias. About a third of the species showed lags, and many species showed a later slowing of the rate of spread, called here bends. Lags may indicate an initial casual phase as well as slower growth; bends, a lack of further areas to spread to. Typically, with much variation, areas of occupancy double in about 10 y (logarithmic mode) or spread at about 2 km·y-1 (square root mode). Both speeds indicate that most spread is from human activity. The reasons for the major phenomena (the occurrence of the two types of spread predicted by models, their distinctness, and the distribution in rates) may reflect economic and landscape features as well as biological ones. The straightness, speed, and patterns found are all new results for invasion biology.

The short-term (2 years) influence of fire burning with the wind (head fire) and against the wind (back fire) on the productivity (above-ground phytomass and litter) and fire behaviour were determined over seven growing seasons (1995/96–2001/02) in a semi-arid rangeland. The results showed that head fires had significantly greater flame height and rate of spread than back fires. Fire caused a decrease of 40.5% and 22.5% in basal cover for the first and second seasons after burning respectively. The seasonal above-ground phytomass production and litter were significantly decreased by fire over all growing seasons. Seasonal production losses due to fire varied between 225 and 430 kg ha−1. The relation between above-ground phytomass production loss due to fire, and two independent variables namely seasonal rainfall and fuel load (above-ground phytomass plus litter) before burning, were investigated. The multiple linear regression equations obtained for one (r=0.89) and 2 years (r=0.86) after a fire, can be used with great success in estimating seasonal production losses due to fire in semi-arid rangeland.

Rapid reaction in the face of an epidemic is a key element in effective and efficient control; this is especially important when the disease has severe public health or economic consequences. Determining an appropriate level of response requires rapid estimation of the rate of spread of infection from limited disease distribution data. Generally, the techniques used to estimate such spatial parameters require detailed spatial data at multiple time points; such data are often time-consuming and expensive to collect. Here we present an alternative approach that is computationally efficient and only requires spatial data from a single time point, hence saving valuable time at the start of the epidemic. By assuming that fundamental spatial statistics are near equilibrium, parameters can be estimated by minimizing the expected rate of change of these statistics, hence conserving the general spatial pattern. Although applicable to both ecological and epidemiological data, here we focus on disease data from computer simulations and real epidemics to show that this method produces reliable results that could be used in practical situations.

Mobile systemic signal molecules (salicylic and jasmonic acids) enhance and accelerate the spread of the systemic immunizing effect of elicitors (arachidonic acid and chitosan) over potato tuber tissues (Solanum tuberosum L.).

Aims This study aimed to document and describe the current range expansion of the great-tailed grackle (Quiscalus mexicanus Gmelin) into the USA. By examining the habitat associations and pattern of spread of this species, I intended to determine the factors responsible for this remarkable expansion by a tropical species into a temperate environment. Location This study focused on the spread of the great-tailed grackle in the continental USA, Canada and Baja California. Methods I used published records, museum specimens, and egg collections to document this range expansion from 1880 through 2002. In addition I surveyed large portions of Arizona, Nevada, southern Utah and southern California for great-tailed grackles during 2000 and 2001. The data gathered was used to create maps in order to quantify the rate of spread of this species. Results Between 1880 and 2000 the great-tailed grackle expanded its breeding range in the USA from c. 64,000 km2 to more than 3,561,000 km2, an increase of 5530%. The average annual rate of increase is 3.4%, but has lessened during the past 20 years. Northward movement in the eastern portion of the range has slowed down, reflecting this decrease. However, in the central and western portion of the species range, the rate of northward movement is still accelerating. During this expansion, the average time between first sighting in a state and first breeding was 5.8 years. The species has become less migratory during its range expansion, wintering in 17 of the 20 states where it breeds. Main conclusions This range expansion has been marked by great-tailed grackles preferring human-modified environments as breeding grounds, especially in the western states. This association appears to benefit the species in two ways; nest predation is lessened in such areas compared with natural conditions, whereas human activities tend to generate an abundant and consistent food supply for feeding offspring. Wintering birds are often associated with cattle feed lots and large-scale dairies, where abundant waste grain provides them with a reliable food supply. Given the continued human population increase throughout large areas of the western USA, the great-tailed grackle will continue its range expansion. Resumen Objetivo Este estudio tiene como objetivo documentar y describir la extencion de su expansion actual del Zanate Mayor (Quiscalus mexicanus Gmelin) dentro de Estados Unidos (USA). Examinando las asociaciones de habitat y patrones de desplazamiento de la especie, se intento determinar los factores responsables de la extraordinaria expansion de una especie subtropical dentro de un ambiente templado. Localizacion Este estudio se concentro en la expansion del Zanate Mayor en Estados Unidos continental, Canada y Baja California. Metodos Se uso registros publicados, especimenes de museo, y colecciones de huevos para documentar esta expansion en su distribucion desde 1880 hasta el 2000. Ademas durante el 2000 y 2001 se hicieron censos de una gran extension en Arizona, Nevada, el sur de Utah y el sur de California para ubicar individuos de Zanate Mayor. La informacion obtenida se uso para crear mapas para asi cuantificar el indice de expansion de la especie. Resultados Desde 1880, el Zanate Mayor ha expandido su extencion de nidificacion en USA desde aproximadamente 64,0000 Km2 a mas de 3,561,000 Km2 un crecimiento de 5,530%. El indice de promedio anual de crecimiento es 3.4% pero ha disminuido en los ultimos 20 anos. Hacia el norte y en la porcion este de su distribucion ha disminuido lo que se reflecta en esta disminucion. Si embargo en el centro y la parte oeste de su distribucion su movimiento hacia el norte sigue en crecimiento. Durante esta expansion en algun Estado, el promedio de tiempo entre el primer avistamiento y nidificacion fue 5.8 anos. La especie se a puesto mas sedentaria durante su expansion de rango, invernando en 17 de los 20 Estados donde nidifica. Conclusiones principales Esta expansion de distribucion del Zanate Mayor ha sido marcada por la preferencia de ambientes modificados por humanos como lugares de nidificacion especialmente en los estados del oeste. Esta asociacion aparentemente beneficia la especie en dos formas: la depredacion de nidos es menor en esas areas comparado con condiciones naturales, y ademas las diferentes actividades humanas tienden a producir una abundante y consistente fuente de alimento para alimentar a los pichones. Consistentemente en invierno los individuos estan asociados con corrales de vacuno y lecherias de gran envergadura, donde hay una abundante perdida de granos lo cual les permite una alimentacion segura y continua. Debido al gran crecimiento de la poblacion humana en grandes areas de los estados del oeste de USA, el Zanate Mayor probablemente continuara su expansion de distribucion.

Using a fuel model which characterizes stand fuel properties, the paper quantifies and explains the effects of stand development and silvicultural interventions on fire behavior. It also presents and explains that all fire behavior properties are strongly related to fuel characteristics. Results showed that rate of spread (ROS) was relatively high when crown fuels were becoming more involved and the crown base was low. Fuel consumption was related to the quantity of fuel available. Fire behavior in thinned stands followed the same pattern as in the unthinned stands except for sharp changes brought about by the periodic rearrangements in fuel from the thinnings. ROS, fuel consumption and fire intensity all increased abruptly with thinning, but declined rapidly with the decomposition and lower availability of thinned fuels, and the reduced probability of crowning.