A note on fire frequency concepts and definitions

2006 ◽  
Vol 36 (7) ◽  
pp. 1884-1888 ◽  
Author(s):  
William J Reed
Keyword(s):  
Random Variable ◽  
Fire Frequency ◽  
Current Form ◽  
Fire Cycle ◽  
Expected Time ◽  
Time Required

The concepts of hazard of burning, fire interval, and fire cycle are considered. It is claimed that the current notion of fire cycle is poorly defined, since the time required to burn a specified area is a random variable. It is shown that the expected time to burn an area equal in size to the study area normally exceeds the fire interval (the average time between fires at any location). In view of this, it is recommended that the notion of fire cycle in its current form be abandoned.

Fire frequency for the transitional mixedwood forest of Timiskaming, Quebec, Canada

2005 ◽  
Vol 35 (3) ◽  
pp. 656-666 ◽  
Author(s):  
Daniel J Grenier ◽  
Yves Bergeron ◽  
Daniel Kneeshaw ◽  
Sylvie Gauthier
Keyword(s):  
Fire History ◽  
Fire Suppression ◽  
Sampling Strategy ◽  
Fire Frequency ◽  
Management Approach ◽  
Land Use Patterns ◽  
Temporal Shift ◽  
Fire Cycle ◽  
Old Growth Forest ◽  
Time Required

Fire history was reconstructed for a 2500-km2 area at the interface between the boreal coniferous and northern hardwood forests of southwestern Quebec. The fire cycle, the time required for an area equal to the study site to burn once over, was described using a random sampling strategy that included dendrochronological techniques in conjunction with provincial and national government archival data. Physiographic elements were not found to spatially influence fire frequency; however, human land-use patterns were observed to significantly affect the fire frequency. A temporal shift in fire frequency was also detected, which coincided with the period of Euro-Canadian colonization and known extreme dry years for the study site. Additionally, a fire-free period was identified in the most recent times that could be associated with fire suppression and climate change. The estimated cycles (approx. 188–314 years) for the southeastern section of the study area were thought to better represent the natural cycles for this transition zone as a result of less anthropogenic influence. The importance of gap-type dynamics becomes evident with the increased presence of old-growth forest, given the derived fire cycle estimations for the region. Even-aged management with short rotations, consequently, is questioned because fire cycle estimations suggest more complex harvest systems using an ecosystem management approach.

Network Model of Urban Taxi Services: Improved Algorithm

1998 ◽  
Vol 1623 (1) ◽  
pp. 27-30 ◽  
Author(s):  
S. C. Wong ◽  
Hai Yang
Keyword(s):  
Mathematical Model ◽  
Logit Model ◽  
Road Network ◽  
Search Time ◽  
Random Variable ◽  
Taxi Driver ◽  
Movement Model ◽  
Transportation Services ◽  
Type Distribution ◽  
Time Required

A mathematical model is proposed to describe how vacant and occupied taxis will cruise in a road network to search for customers and provide transportation services. The model assumes that a taxi driver, once having picked up a customer, will move to the customer’s destination by the shortest path; and that a taxi driver, once having dropped a customer, will try to minimize individual expected search time required to meet the next customer. The probability that a vacant taxi meets a customer in a particular zone is specified by a logit model by assuming that the expected search time in each zone is an identically distributed random variable due to variations in perceptions and the random arrival of customers. The whole movement of all empty and occupied taxis is formulated as an optimization model, from which a gravity-type distribution of empty taxis is derived. Consequently, the taxi movement model can be solved efficiently by the established iterative balancing method and can be incorporated into any standard transportation planning packages.

Analysis of the patterns of large fires in the boreal forest region of Alaska

2002 ◽  
Vol 11 (2) ◽  
pp. 131 ◽  
Author(s):  
Eric S. Kasischke ◽  
David Williams ◽  
Donald Barry
Keyword(s):  
Forest Cover ◽  
Growing Season ◽  
Fire Frequency ◽  
Lightning Strike ◽  
Data Sets ◽  
Fire Cycle ◽  
Area Burned ◽  
Forest Region ◽  
Large Fires ◽  
The 1960S

Analyses of the patterns of fire in Alaska were carried out using three different data sets, including a large-fire database dating back to 1950. Analyses of annual area burned statistics illustrate the episodic nature of fire in Alaska, with most of the area burning during a limited number of high fire years. Over the past 50 years, high fire years occurred once every 4 years. Seasonal fire statistics indicated that high fire years consist of larger fire events that occur later in the growing season. On a decadal basis, average annual area burned has varied little between the 1960s and 1990s. Using a geographic information system (GIS), the spatial distribution of fires (aggregated by ecoregions) was compared with topographic, vegetation cover, and climate features of Alaska. The use of topographic data allows for a more realistic determination of fire cycle by eliminating areas where fires do not occur due to lack of vegetation above the treeline. Geographic analyses show that growing season temperature, precipitation, lightning strike frequency, elevation, aspect, and the level of forest cover interact in a complex fashion to control fire frequency.

Risk Based Strategy for the Development of an Emergency Pipeline Repair System (EPRS)

2016 ◽  
Author(s):  
Ali Alani ◽  
Graham D. Goodfellow ◽  
Dennis Keen
Keyword(s):  
Economic Consequences ◽  
Third Party ◽  
Repair System ◽  
Pipeline Network ◽  
Expected Time ◽  
Emergency Repair ◽  
Offshore Pipeline ◽  
Timely Access ◽  
The Individual ◽  
Time Required

This paper presents an overview of the various components of an emergency pipeline repair system which should be in place in order to act effectively and efficiently during an emergency pipeline repair scenario. The condition of pipelines during operation is typically monitored by means of external and internal inspections. These inspections allow for planned intervention when a pipeline is found to be deteriorating. A failure to inspect adequately for time dependent threats, or randomly occurring events such as third party interaction, could result in a pipeline failure, leading to a requirement to rapidly return to operation and thus the need for an emergency repair. An Emergency Pipeline Repair System (EPRS) is therefore an essential part of a pipeline integrity management system. The primary purpose of the EPRS is to ensure that pipeline operators have the necessary level of readiness to allow an emergency repair to be carried out, thus minimising the economic consequences of having a pipeline out of service, whilst optimising the cost of purchasing and maintaining equipment and spares. In general, pipeline operators will have some emergency repair procedures to cater for unplanned or unexpected incidents. However, to complete an emergency repair efficiently and effectively, the availability of adequate spare materials and timely access to the damage location is required. For a large pipeline network, satisfying these requirements can be challenging. This paper discusses some basic elements of an EPRS and describes a case study of the development of a risk based EPRS strategy for an offshore pipeline operator. This approach involves the identification of credible hazards that can lead to damage requiring an emergency repair, and identification of repair options. The relative importance of the individual pipelines, in terms of their availability requirement, and the expected time required to complete an emergency repair are then taken into account. This enables the pipelines to be ranked based on the consequence of failure. Pipelines with consequence rankings that are considered unacceptable are therefore highlighted, and EPRS readiness related to those pipelines can subsequently be optimised. Recommendations for the development of an EPRS for an onshore or offshore pipeline network are also made.

Changes in forest fire frequency in Kootenay National Park, Canadian Rockies

1990 ◽  
Vol 68 (8) ◽  
pp. 1763-1767 ◽  
Author(s):  
Alan M. Masters
Keyword(s):  
Forest Fire ◽  
Rocky Mountains ◽  
National Park ◽  
Fire History ◽  
Fire Suppression ◽  
Fire Frequency ◽  
Ice Age ◽  
Distribution Analysis ◽  
Fire Cycle ◽  
Time Since Fire

Time-since-fire distribution analysis is used to estimate forest fire frequency for the 1400 km2 Kootenay National Park, British Columbia, located on the west slope of the Rocky Mountains. The time-since-fire distribution indicates three periods of different fire frequency: 1988 to 1928, 1928 to 1788, and before 1788. The fire cycle for the park was > 2700 years for 1988 to 1928, 130 years between 1928 and 1788, and 60 years between 1778 and 1508. Longer fire cycles after 1788 and 1928 may be due, respectively, to cool climate associated with the Little Ice Age and a recent period of higher precipitation. Contrary to some fire history investigations in the region, neither a fire suppression policy since park establishment in 1919, nor the completion of the Windermere Highway through the park in 1923 appear to have changed the fire frequency from levels during pre-European occupation. Spatial partitioning of the time-since-fire distribution was unsuccessful. No relationship was found between elevation or aspect and fire frequency. Key words: fire cycle, Rocky Mountains, climate change.

How does increased fire frequency affect carbon loss from fire? A case study in the northern boreal forest

2011 ◽  
Vol 20 (7) ◽  
pp. 829 ◽  
Author(s):  
C. D. Brown ◽  
J. F. Johnstone
Keyword(s):  
Boreal Forests ◽  
Forest Canopy ◽  
Short Interval ◽  
Fire Frequency ◽  
Fire Return Interval ◽  
Fire Cycle ◽  
Return Interval ◽  
Canopy Soil ◽  
Carbon Stores ◽  
Stand Conditions

Fire frequency is expected to increase due to climate warming in many areas, particularly the boreal forests. An increase in fire frequency may have important effects on the global carbon cycle by decreasing the size of boreal carbon stores. Our objective was to quantify and compare the amount of carbon consumed during and the amount of carbon remaining following fire in black spruce (Picea mariana (Mill.) BSP) forests burned after long v. short intervals. We hypothesised that stands with a shortened fire return interval would have a higher carbon consumption than those experiencing a historically typical fire return interval. Using field measurements of forest canopy, soil organic horizons and adventitious roots, we reconstructed pre-fire stand conditions to estimate the biomass lost in each fire and the effects on post-fire residual carbon stores. We found evidence of a higher loss of carbon following two fire events that recurred after a short interval, resulting in a much greater total reduction in carbon relative to pre-fire or mature stand conditions. Consequently, carbon storage across disturbance intervals was dramatically reduced following short-interval burns. Recovery of these stores would require a subsequent lengthening of the fire cycle, which appears unlikely under future climate scenarios.

The Kelly system maximizes median fortune

2004 ◽  
Vol 41 (04) ◽  
pp. 1230-1236 ◽  
Author(s):  
S. N. Ethier
Keyword(s):  
Desirable Property ◽  
Expected Time ◽  
Rate Of Growth ◽  
Time Required

It is well known that the Kelly system of proportional betting, which maximizes the long-term geometric rate of growth of the gambler's fortune, minimizes the expected time required to reach a specified goal. Less well known is the fact that it maximizes the median of the gambler's fortune. This was pointed out by the author in a 1988 paper, but only under asymptotic assumptions that might cause one to question its applicability. Here we show that the result is true more generally, and argue that this is a desirable property of the Kelly system.

Inequalities for branching processes

1966 ◽  
Vol 3 (01) ◽  
pp. 261-267 ◽  
Author(s):  
C. R. Heathcote ◽  
E. Seneta
Keyword(s):  
Generating Function ◽  
Conditional Distribution ◽  
Branching Process ◽  
Branching Processes ◽  
Probability Generating Function ◽  
Random Variable ◽  
Expected Time ◽  
Time To Extinction ◽  
Explicit Formulae

Summary If F(s) is the probability generating function of a non-negative random variable, the nth functional iterate Fn (s) = Fn– 1 (F(s)) generates the distribution of the size of the nth generation of a simple branching process. In general it is not possible to obtain explicit formulae for many quantities involving Fn (s), and this paper considers certain bounds and approximations. Bounds are found for the Koenigs-type iterates lim n→∞ m −n {1−Fn (s)}, 0 ≦ s ≦ 1 where m = F′ (1) < 1 and F′′ (1) < ∞; for the expected time to extinction and for the limiting conditional-distribution generating function limn→∞{Fn (s) − Fn (0)} [1 – Fn (0)]–1. Particular attention is paid to the case F(s) = exp {m(s − 1)}.

Forest fire cycles and life tables: a case study from interior Alaska

1981 ◽  
Vol 11 (3) ◽  
pp. 554-562 ◽  
Author(s):  
John Yarie
Keyword(s):  
Fire Frequency ◽  
Entire Study ◽  
Fire Cycle ◽  
Survivorship Curve ◽  
Interior Alaska ◽  
Table Analysis ◽  
Negative Exponential ◽  
The Relationship ◽  
Entire Study Area

The negative exponential and Wiebull distributions were used to estimate stand survivorship curves for forested sites in the Porcupine River drainage of interior Alaska. The survivorship curve of Piceaglauca (Moench) Voss sites was best described by a Wiebull function, while both functions adequately described the Piceamariana (Mill.) Britton, Sterns & Poggenburg hardwood and all sites stand survivorship curve. Fire cycles calculated from the Wiebull distribution were 43, 113, 36, and 26 years for the entire study area, P. glauca, P. mariana, and hardwood sites, respectively. Fire frequencies estimated from a life table analysis were 48, 105, 43, and 30 years, respectively. The relationship between fire cycle and fire frequency calculations is discussed and various management implications are given.

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