A parametric model of the fire-size distribution

2001 ◽  
Vol 31 (8) ◽  
pp. 1297-1303 ◽  
Author(s):  
S G Cumming
Keyword(s):  
Size Distribution ◽  
Sampling Interval ◽  
Parametric Modelling ◽  
Fire Size ◽  
Disturbance History ◽  
Threshold Size ◽  
Mixedwood Forests ◽  
Large Fires ◽  
Fire Size Distribution ◽  
Burnt Areas

This paper developes statistical models of the size distribution of lightning-caused wildfires in the boreal mixedwood forests of Alberta, Canada, for the intervals 1980––1998 and 1961––1998. Above any minimum threshold size [Formula: see text]3 ha, the logarithm of fire size is approximately exponentially distributed. However, computer simulations using the best-fit distribution would over predict the frequency of large fires, and thus the mean rate of disturbance. A truncated exponential distribution, which places an upper bound on fire size, is more suitable and, according to probability plots, provides an excellent fit to the data. I estimate the maximum fire size in the study area to be [Formula: see text] 650 000 ha. This estimate is insensitive to the choice of lower bound for fire sizes (between 3 and 1000 ha) and to the choice of sampling interval. Parametric modelling of fire sizes using covariates derived from forest inventory data shows that the expected size of a fire is positively related to the abundance of pine forest in the vicinity of the point of detection and negatively related to the abundance of recently logged or burnt areas. This implies that variation in forest structure and disturbance history impose marked spatial variability on the fire size distribution. Other covariates, such as periodic indices of fire weather, could readily be evaluated in this framework.

Global fire size distribution is driven by human impact and climate

2014 ◽  
Vol 24 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Stijn Hantson ◽  
Salvador Pueyo ◽  
Emilio Chuvieco
Keyword(s):  
Size Distribution ◽  
Human Impact ◽  
Fire Size ◽  
Fire Size Distribution

Global fire size distribution: from power law to log-normal

2016 ◽  
Vol 25 (4) ◽  
pp. 403 ◽  
Author(s):  
Stijn Hantson ◽  
Salvador Pueyo ◽  
Emilio Chuvieco
Keyword(s):  
Size Distribution ◽  
Frequency Distribution ◽  
Power Law ◽  
Likelihood Estimation ◽  
Fire Size ◽  
Chi Square ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
Fire Size Distribution ◽  
Log Normal

Wildland fires are one of the main alleged examples of Self-Organised Criticality (SOC), with simple SOC models resulting in the expectation of a power-law fire size frequency distribution. Here, we test whether fire size distributions systematically follow a power law and analyse their spatial variation for eight distinct areas over the globe. For each of the areas, we examine the fire size frequency distribution using two types of plots, maximum likelihood estimation and chi-square tests. Log-normal emerges as a suitable option to fit the fire size distribution in this variety of environments. In only two of eight areas was the power law (which is a particular case of the log-normal) not rejected. Notably, the two parameters of log-normal are related to each other, displaying a general linear relation, which extends to the sites that can be described with a power law. These results do not necessarily refute the SOC hypothesis, but reveal the presence of other processes that are, at least, modulating the outcome of SOC in some areas.

What do we know about forest fire size distribution, and why is this knowledge useful for forest management?

2008 ◽  
Vol 17 (2) ◽  
pp. 234 ◽  
Author(s):  
Wenbin Cui ◽  
Ajith H. Perera
Keyword(s):  
Forest Management ◽  
Size Distribution ◽  
Forest Fire ◽  
Management Practices ◽  
Fire Management ◽  
Future Research ◽  
Research Approach ◽  
Fire Size ◽  
Forest Fire Management ◽  
Fire Size Distribution

Forest fire size distribution (FSD) is one of the suite of indicators of forest fire regimes. It is applied in forest fire management, particularly for planning and evaluating suppression efforts. It is also used in forest management in the context of emulating natural fire disturbances. Given the recent growth in research and applied interest in this topic, we review and synthesise the state of knowledge on FSD, and identify sources of knowledge uncertainties and future research directions. Based on literature, it is common for forest fires to follow the power law probability distribution, particularly the truncated subtype, under a variety of forest types and forest and fire management practices. Other types of FSD are also observed, but under specific circumstances. Although there is evidence that observed FSDs vary both over space and time, the knowledge is too fragmented to generalise the cause–effect relationships for such variation. As well, it is not clear how the various methods of studying FSD and their spatio-temporal scales influence derivations of FSDs. We suggest that a hypothetico-deductive research approach, combining empirical studies with process-based simulations is an effective means to advance the knowledge of FSD. We suggest caution in the use of FSD in forest management because applying different distributions or even different parameters for the same distribution may result in great fire size class differences and thus different implications for forest management.

scholarly journals The history and characteristics of the 1980–2005 Portuguese rural fire database

2011 ◽  
Vol 11 (12) ◽  
pp. 3343-3358 ◽  
Author(s):  
M. G. Pereira ◽  
B. D. Malamud ◽  
R. M. Trigo ◽  
P. I. Alves
Keyword(s):  
Urban Areas ◽  
Unit Area ◽  
Fire Regime ◽  
Minimum Area ◽  
Burnt Area ◽  
Forested Areas ◽  
Large Fires ◽  
Burnt Areas

Abstract. We focus here on a mainland Continental Portuguese Rural Fire Database (PRFD) that includes 450 000 fires, the largest such database in Europe in terms of total number of recorded fires in the 1980–2005 period. In this work, we (a) list the most important factors for triggering and controlling the fire regime in mainland Continental Portugal, (b) describe the dataset's production, (c) discuss procedures adopted to identify and correct different fire data inconsistencies, creating a modified PRFD which we use here and make available as Supplement, (d) explore some basic temporal and completeness properties of the data. We find that the dataset's minimum measured burnt areas have changed with time between AF = 0.1 ha (1980–1990), AF = 0.01 ha (1991–1992), and AF = 0.001 ha (1992–2005), with varying degrees of completeness down to these values. These changes in minimum area measured are responsible for greater numbers of fires being recorded. A relatively small number of large fires in the PRFD are responsible for the majority of the burnt area. For example, fires with AF > 100 ha represent about 1% of all fire records but 75% of total burnt area. Finally, we consider for each Continental Portugal district and for the 26-yr period, the total number of rural fires and area burnt in forests and shrublands, each normalized by district areas. We find that the highest numbers of fires per unit area are in highly populated districts, and that the largest fraction of burnt area is in forested areas, coinciding with large parcels of continuous forests (predominantly rural and moderately urban areas).

scholarly journals Comparison of ice particle characteristics simulated by the Community Atmosphere Model (CAM5) with in-situ observations

2014 ◽  
Vol 14 (6) ◽  
pp. 7637-7681 ◽  
Author(s):  
T. Eidhammer ◽  
H. Morrison ◽  
A. Bansemer ◽  
A. Gettelman ◽  
A. J. Heymsfield
Keyword(s):  
Size Distribution ◽  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Atmospheric Model ◽  
Slope Parameter ◽  
Cloud Radiative Forcing ◽  
Threshold Size ◽  
Cloud Ice

Abstract. Detailed measurements of ice crystals in cirrus clouds were used to compare with results from the Community Atmospheric Model Version 5 (CAM5) global climate model. The observations are from two different field campaigns with contrasting conditions: Atmospheric Radiation Measurements Spring Cloud Intensive Operational Period in 2000 (ARM-IOP), which was characterized primarily by midlatitude frontal clouds and cirrus, and Tropical Composition, Cloud and Climate Coupling (TC4), which was dominated by anvil cirrus. Results show that the model typically overestimates the slope parameter of the exponential size distributions of cloud ice and snow, while the variation with temperature (height) is comparable. The model also overestimates the ice/snow number concentration (0th moment of the size distribution) and underestimates higher moments (2nd through 5th), but compares well with observations for the 1st moment. Overall the model shows better agreement with observations for TC4 than for ARM-IOP in regards to the moments. The mass-weighted terminal fallspeed is lower in the model compared to observations for both ARM-IOP and TC4, which is partly due to the overestimation of the size distribution slope parameter. Sensitivity tests with modification of the threshold size for cloud ice to snow autoconversion (Dcs) do not show noticeable improvement in modeled moments, slope parameter and mass weighed fallspeed compared to observations. Further, there is considerable sensitivity of the cloud radiative forcing to Dcs, consistent with previous studies, but no value of Dcs improves modeled cloud radiative forcing compared to measurements. Since the autoconversion of cloud ice to snow using the threshold size Dcs has little physical basis, future improvement to combine cloud ice and snow into a single category, eliminating the need for autoconversion, is suggested.

Spatial pattern analyses of post-fire residual stands in the black spruce boreal forest of western Quebec

2010 ◽  
Vol 19 (8) ◽  
pp. 1110 ◽  
Author(s):  
Amar Madoui ◽  
Alain Leduc ◽  
Sylvie Gauthier ◽  
Yves Bergeron
Keyword(s):  
Black Spruce ◽  
Weather Conditions ◽  
Spatial Analyses ◽  
Fire Size ◽  
The West ◽  
Forest Patches ◽  
Burned Areas ◽  
Large Fires ◽  
The Many ◽  
Landsat Satellite

In this study, we characterised the composition and configuration of post-fire residual habitats belonging to two physiographic zones of the black spruce–moss domain in western Quebec. Thirty-three large fires (2000–52 000 ha) were selected and extracted on classified Landsat satellite imagery. The results show that a minimum of 2% and a maximum of 22% of burned areas escaped fire, with an overall average of 10.4%. The many forest patches that partially or entirely escaped fire formed residual habitats (RHs). It was found that although the area of RHs follows a linear relationship with fire size, their proportion appears relatively constant. Spatial analyses showed that the fires could be separated into two groups depending on the physiographic zones (East-Canadian Shield v. West-Clay Belt Lowlands). Fires in the west zone generate less RHs and appear to be associated with more extreme weather conditions. In most cases there was no association with water or wetlands; in some fires the presence of RHs is associated with the proximity of water bodies. The failure to find an association between RHs and wetlands suggests that this type of environment is part of the fuel. Coniferous woodland with moss appears particularly overrepresented within RHs. Our results suggest that the local and regional physiographic conditions strongly influence the creation of RHs; therefore, it is important to consider those differences when applying ecosystem-based management.

Factors influencing large wildland fire suppression expenditures

2008 ◽  
Vol 17 (5) ◽  
pp. 650 ◽  
Author(s):  
Jingjing Liang ◽  
Dave E. Calkin ◽  
Krista M. Gebert ◽  
Tyron J. Venn ◽  
Robin P. Silverstein
Keyword(s):  
Wildland Fire ◽  
Fire Suppression ◽  
Burned Area ◽  
Private Land ◽  
Fire Size ◽  
Department Of Agriculture ◽  
Factors Influencing ◽  
The Us ◽  
Large Fires ◽  
Parsimonious Model

There is an urgent and immediate need to address the excessive cost of large fires. Here, we studied large wildland fire suppression expenditures by the US Department of Agriculture Forest Service. Among 16 potential non-managerial factors, which represented fire size and shape, private properties, public land attributes, forest and fuel conditions, and geographic settings, we found only fire size and private land had a strong effect on suppression expenditures. When both were accounted for, all the other variables had no significant effect. A parsimonious model to predict suppression expenditures was suggested, in which fire size and private land explained 58% of variation in expenditures. Other things being equal, suppression expenditures monotonically increased with fire size. For the average fire size, expenditures first increased with the percentage of private land within burned area, but as the percentage exceeded 20%, expenditures slowly declined until they stabilised when private land reached 50% of burned area. The results suggested that efforts to contain federal suppression expenditures need to focus on the highly complex, politically sensitive topic of wildfires on private land.

Distribution of residual vegetation associated with large fires in Alberta

1987 ◽  
Vol 17 (10) ◽  
pp. 1207-1212 ◽  
Author(s):  
Kevin E. Eberhart ◽  
Paul M. Woodard
Keyword(s):  
Shape Index ◽  
Size Class ◽  
Burned Area ◽  
Fire Size ◽  
Size Classes ◽  
Size And Shape ◽  
The Third ◽  
Island Area ◽  
Large Fires

Fire size and shape, number and size of islands of residual vegetation, amount of edge, and distances to residual vegetation were analyzed for 69 fires that burned in Alberta between 1970 and 1983. These fires ranged in size from 21 to 17 770 ha. Distribution of residual vegetation was compared among five fire size classes. Fires in the smallest size class (20–40 ha) did not contain any islands of unburned vegetation. Percent of area within the fire perimeter that was actually disturbed decreased with increasing fire size. The number of unburned islands per 100 ha was highest for the third and fourth largest fire size classes (201–400 and 401–2000 ha). Median island area per fire, fire shape index, and edge index increased with fire size. Percentages of burned area within 100, 200, 300, 400, and 500 m of residual vegetation decreased with increasing fire size. These results indicate decreased potential for natural reforestation and increased benefits to some wildlife habitats as fire size increases.

Sign in / Sign up

Export Citation Format

Share Document