Modeling fire interval data from the American southwest with the Weibull distribution

1999 ◽  
Vol 9 (1) ◽  
pp. 37 ◽  
Author(s):  
Henri D. Grissino-Mayer
Keyword(s):  
Weibull Distribution ◽  
Environmental Gradients ◽  
Habitat Type ◽  
Fire Regimes ◽  
Interval Data ◽  
American Southwest ◽  
Underlying Structure ◽  
Shift Parameter ◽  
Modal Interval ◽  
Fire Intervals

In this study, the Weibull distribution is tested as a possible model for fire interval data derived from dendrochronologically-dated fire scars from four sites in the American Southwest. Two- and three-parameter Weibull distributions were fit to fire interval data sets, and additional statistical descriptors based on the Weibull were derived to improve our understanding of the range of variability in presettlement fire regimes. The three-parameter models failed to provide improved fits versus the more parsimonious two-parameter models, indicating the Weibull shift parameter may be superfluous for Southwestern fire regimes. The Weibull Modal Interval (MOI) was a superior overall measure of central tendency, and appears to identify a common underlying structure in Southwestern fire regimes independent of habitat type and environmental gradients. Unusually short and long fire intervals were identified by the lower and upper exceedance intervals (LEI and UEI) and the Maximum Hazard Interval (MHI) based on the Weibull hazard function. Model statistics were nearly identical between two pairs of sites that were 260 kilometers distant that differed in topography, vegetation, and land-use history. However, differences were observed between sites only 10 kilometers apart, suggesting the influence of local factors (e.g., topography and substrate) over regional influences (e.g., climate). Although the Weibull models helped quantify the historical range of variability in presettlement fire regimes, ecological interpretations of the Weibull parameters proved difficult.

scholarly journals Fire regimes and environmental gradients shape vertebrate and plant distributions in temperate eucalypt forests

Ecosphere ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Luke T. Kelly ◽  
Angie Haslem ◽  
Greg J. Holland ◽  
Steven W. J. Leonard ◽  
Josephine MacHunter ◽  
...  
Keyword(s):  
Environmental Gradients ◽  
Fire Regimes ◽  
Plant Distributions ◽  
Eucalypt Forests

Responses of lizards to three experiments fires in the savanna forests of Kakadu National Park

1994 ◽  
Vol 21 (2) ◽  
pp. 131 ◽  
Author(s):  
CR Trainor ◽  
JCZ Woinarski
Keyword(s):  
National Park ◽  
Habitat Type ◽  
Detrended Correspondence Analysis ◽  
Fire Regimes ◽  
Direct Effects ◽  
Short Term ◽  
Lizard Species ◽  
Savanna Communities ◽  
Induced Changes ◽  
Term Response

A species-rich lizard community responded variably to a range of experimental fire regimes in a tropical savanna. Heteronotia binoei was the only lizard species that showed a short-term response to fire, decreasing in abundance directly after the early- and late-burns. H. binoei and Diporiphora bilineata were significantly more abundant in early-burn treatments. Carlia amax was more abundant in unburnt and early-burn treatments. C. munda was more abundant in unburnt and early-burn sites. Differences in the relative abundance of species between treatments is attributed to site differences in vegetation structure, and fire-induced changes to the structure of habitat. Early-burn sites were significantly richer in lizard species (P< 0.05); however, overall lizard abundance, Shannon-Wiener diversity and Detrended Correspondence Analysis (DCA) 1 and DCA 2 scores were not significantly different, suggesting that habitat partitioning has a stronger influence than the direct effects of fire. Many lizards were associated with a direct gradient of moisture availability, including a seepage assemblage, with Carlia gracilis and Sphenomorphus darwiniensis correlated with increased moisture, a well-developed canopy and abundant leaf litter. An assemblage associated with the drier end of the gradient included Carlia triacantha, Ctenotus kurnbudj, Diporiphora magna and D. bilineata. The lizard composition of most quadrats was intermediate along the moisture gradient and was associated with typical eucalypt savanna communities. Lizard species that largely are restricted to the moist seepage zones may be particularly sensitive to late dry-season fires which alter this habitat type.

Factors contributory to fire occurrences in two populated areas in the American southwest

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Susanna T.Y. Tong ◽  
Shitian Wan ◽  
Yuhe Gao
Keyword(s):  
Population Growth ◽  
Fire Regimes ◽  
American Southwest ◽  
Arid Areas ◽  
Vegetative Cover ◽  
Content Type ◽  
Clark County ◽  
Temporal Relationships ◽  
Wide Range ◽  
Semi Arid

PurposeThis study aims to further understand the factors contributory to fire occurrences in two semi-arid regions in the American Southwest, Clark County in Nevada and Maricopa and Pinal Counties in Arizona.Design/methodology/approachStatistical and geographic information system analyses were employed to examine the spatial and temporal relationships of various natural and human-caused factors with fire incidences.FindingsAngström fire danger index, average amount of rainfall one month prior, extent of forests and grasslands, and proximities to secondary roads and population centers have significant relationships with fire events.Research limitations/implicationsThe importance of the factors contributory to fire occurrence is site-specific even in areas with similar climatic regimes and varies among different geographic regions; as such, researchers will need to conduct specific investigation of each study area.Practical implicationsThe findings of this study can be instrumental in facilitating fire managers to derive more informed strategies in fire prevention and management.Originality/valueWhile there are many studies on fire, most of them are conducted in wet regions with a lot of vegetative cover; not much work is done on arid areas. This paper considered and compared the spatial and temporal relationships of a wide range of natural and human-caused factors with fire events in two semi-arid areas. The intent was to assess the relative importance of these factors in areas even with similar climatic regimes. As our world is facing unprecedented changes in terms of climate and population growth, it is paramount to have an enhanced understanding of the impacts of these changes on fire regimes. The study areas are hot and dry, and they are located in the wildland–urban interfaces with rapid population growth and urbanization; as such, the research findings may contribute to existing literature.

scholarly journals Resilience of the boreal forest in response to Holocene fire-frequency changes assessed by pollen diversity and population dynamics

2010 ◽  
Vol 19 (8) ◽  
pp. 1026 ◽  
Author(s):  
Christopher Carcaillet ◽  
Pierre J. H. Richard ◽  
Yves Bergeron ◽  
Bianca Fréchette ◽  
Adam A. Ali
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
Frequency Control ◽  
Regional Scale ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Frequency Changes ◽  
Fire Intervals ◽  
In Fire

The hypothesis that changes in fire frequency control the long-term dynamics of boreal forests is tested on the basis of paleodata. Sites with different wildfire histories at the regional scale should exhibit different vegetation trajectories. Mean fire intervals and vegetation reconstructions are based respectively on sedimentary charcoal and pollen from two small lakes, one in the Mixedwood boreal forests and the second in the Coniferous boreal forests. The pollen-inferred vegetation exhibits different trajectories of boreal forest dynamics after afforestation, whereas mean fire intervals have no significant or a delayed impact on the pollen data, either in terms of diversity or trajectories. These boreal forests appear resilient to changes in fire regimes, although subtle modifications can be highlighted. Vegetation compositions have converged during the last 1200 years with the decrease in mean fire intervals, owing to an increasing abundance of boreal species at the southern site (Mixedwood), whereas changes are less pronounced at the northern site (Coniferous). Although wildfire is a natural property of boreal ecosystems, this study does not support the hypothesis that changes in mean fire intervals are the key process controlling long-term vegetation transformation. Fluctuations in mean fire intervals alone do not explain the historical and current distribution of vegetation, but they may have accelerated the climatic process of borealisation, likely resulting from orbital forcing.

scholarly journals Fire Regimes and Environmental Gradients Shape Bird, Mammal and Plant Distributions in Temperate Forests

2017 ◽  
Vol 98 (3) ◽  
pp. 227-230
Author(s):  
Luke T. Kelly ◽  
Angie Haslem ◽  
Greg J. Holland ◽  
Steven W. J. Leonard ◽  
Josephine MacHunter ◽  
...  
Keyword(s):  
Temperate Forests ◽  
Environmental Gradients ◽  
Fire Regimes ◽  
Plant Distributions

Anthropogenic impact on past and present fire regimes in a boreal forest landscape of southeastern Norway

2005 ◽  
Vol 35 (11) ◽  
pp. 2719-2726 ◽  
Author(s):  
Rune Groven ◽  
Mats Niklasson
Keyword(s):  
Fire History ◽  
Nature Reserve ◽  
Fire Regimes ◽  
Mining Activity ◽  
Forest Landscape ◽  
Sample Mean ◽  
History Of ◽  
Mean Fire Interval ◽  
Fire Intervals ◽  
Historical Accounts

Fire-scarred wood samples from 50 stumps, snags, and living trees of Scots pine (Pinus sylvestris L.) were dendrochronologically cross-dated to describe an 800 year long fire history of Eldferdalen Nature Reserve (~6 ha) and its surroundings (~4000 ha) in southeastern Norway. In the western part of the study area, we recorded 55 different fires within a 200 ha area around the reserve between 1511 and 1759 and a mean fire interval in single samples of 24.6 years. The composite mean fire interval for the nature reserve was 10.5 years. Fire intervals were longer in the eastern part of the study area, with a single sample mean fire interval of 49.1 years. Only three fires were detected after 1759, the last one in 1822. Based on historical accounts, we assume that the high number of fires and short fire intervals were influenced by deliberate ignition for agricultural purposes, most likely burning to improve the conditions for cattle grazing and slash-and-burn cultivation. We suggest that the cessation of fires was influenced by the increased value of timber and mining activity, thereby leading to increased interest in conservation of the timber resources.

scholarly journals Seascape genomics of coastal bottlenose dolphins along strong gradients of temperature and salinity

2021 ◽  
Author(s):  
Eleanor Pratt ◽  
Luciano Beheregaray ◽  
Kerstin Bilgmann ◽  
Nikki Zanardo ◽  
Fernando Diaz-Aguirre ◽  
...  
Keyword(s):  
Kidney Development ◽  
Environmental Gradients ◽  
Bottlenose Dolphins ◽  
Large Population ◽  
Habitat Type ◽  
Enrichment Analysis ◽  
Adaptive Divergence ◽  
Nucleotide Polymorphisms ◽  
Natal Philopatry ◽  
Genomic Study

Heterogeneous seascapes and strong environmental gradients in coastal waters are expected to influence adaptive divergence, particularly in species with large population sizes where selection is expected to be highly efficient. However, these influences might also extend to species characterized by strong social structure, natal philopatry and small home ranges. We implemented a seascape genomic study to test this hypothesis in Indo-Pacific bottlenose dolphins (Tursiops aduncus) distributed along the environmentally heterogeneous coast of southern Australia. The datasets included oceanographic and environmental variables thought to be good predictors of local adaptation in dolphins and 8,081 filtered single nucleotide polymorphisms (SNPs) genotyped for individuals sampled from six different bioregions. From a neutral perspective, population structure and connectivity of the dolphins were generally influenced by habitat type and social structuring. Genotype-environment association analysis identified 241 candidate adaptive loci and revealed that sea surface temperature and salinity gradients influenced adaptive divergence in these animals at both large- (1,000s km) and fine-scales (<100 km). Enrichment analysis and annotation of candidate genes revealed functions related to sodium-activated ion transport, kidney development, adipogenesis and thermogenesis. The findings of spatial adaptive divergence and inferences of putative physiological adaptations challenge previous suggestions that marine megafauna is most likely to be affected by environmental and climatic changes via indirect, trophic effects. Our work contributes to conservation management of coastal bottlenose dolphins subjected to anthropogenic disturbance and to efforts of clarifying how seascape heterogeneity influences adaptive diversity and evolution in small cetaceans.

scholarly journals Spatial patterns of functional diversity and composition in marine benthic ciliates along the coast of China

2019 ◽  
Vol 627 ◽  
pp. 49-60 ◽  
Author(s):  
Y Xu ◽  
J Soininen
Keyword(s):  
Functional Diversity ◽  
Large Scale ◽  
Environmental Gradients ◽  
Spatial Scales ◽  
Habitat Type ◽  
Latitudinal Gradients ◽  
Dispersal Ability ◽  
Ciliated Protozoa ◽  
High Dispersal ◽  
Benthic Ciliates

Large-scale patterns of community composition and diversity along environmental gradients have been well studied for macroorganisms. However, the biogeography of microorganisms, especially ciliated protozoa, remains understudied. Here, we analyzed a comprehensive database of marine benthic ciliates found along the coast of China from 1991 to 2018 to examine the geographical patterns in species and trait composition and functional diversity. According to redundancy analysis conducted at large spatial scales, environmental variables, i.e. habitat type and salinity, explained more variance in species composition than latitude. In contrast, trait composition was better explained by spatial and climatic variables. At small spatial scales, both species and trait composition were probably influenced by mass effects due to the high dispersal ability of ciliates at such small scales, resulting in spatially homogenized communities. Several traits, including body size, feeding type and mobility, exhibited significant positive or negative latitudinal gradients. Functional diversity showed a significant positive correlation with latitude between 20 and 40° N, which may be caused by certain groups of ciliates possessing particular traits related to temperature. Our study is the first comprehensive evaluation of how trait composition and functional diversity of marine ciliated protozoa vary at large scales and can thus make a major contribution to the study of microbial biogeography.

scholarly journals Fire and its interaction with ecological processes in box-ironbark forests

2012 ◽  
Vol 124 (1) ◽  
pp. 72 ◽  
Author(s):  
Andrew F. Bennett ◽  
Greg J. Holland ◽  
Anna Flanagan ◽  
Sarah Kelly ◽  
Michael F. Clarke
Keyword(s):  
Fire Ecology ◽  
Scale Effects ◽  
Fire Regimes ◽  
Ecological Processes ◽  
Ecological Attributes ◽  
Before And After ◽  
Different Seasons ◽  
Experimental Management ◽  
The Many ◽  
Fire Intervals

Box-Ironbark forests extend across a swathe of northern Victoria on the inland side of the Great Dividing Range. Although extensively cleared and modified, they support a distinctive suite of plants and animals. Historical fire regimes in this ecosystem are largely unknown, as are the effects of fire on most of the biota. However, knowledge of the ecological attributes of plant species has been used to determine minimum and maximum tolerable fire intervals for this ecosystem to guide current fire management. Here, we consider the potential effects of planned fire in the context of major ecological drivers of the current box-ironbark forests: namely, the climate and physical environment; historical land clearing and fragmentation; and extractive land uses. We outline an experimental management and research project based on application of planned burns in different seasons (autumn, spring) and at different levels of burn cover (patchy, extensive). A range of ecological attributes will be monitored before and after burns to provide better understanding of the landscape-scale effects of fire in box-ironbark forests. Such integration of management and research is essential to address the many knowledge gaps in fire ecology, particularly in the context of massively increased levels of planned burning currently being implemented in Victoria.

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