Fire season precipitation variability influences fire extent and severity in a large southwestern wilderness area, United States

Holden, Zachary A.; Morgan, Penelope; Crimmins, Michael A.; Steinhorst, R. Kirk; Smith, Alistair M. S.

doi:10.1029/2007gl030804

Cited by 78 publications

(56 citation statements)

References 22 publications

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“…At that point, fuels have presumably become dry enough to carry fire, and the probability of severe fire increases and stays high as temperatures increase. Similarly, the probability of high severity increases sharply in all Southwest ecoregions when precipitation during the previous month or spring drops below average, consistent with the suggestion from Holden et al (2007) that the likelihood of high severity in the Gila Wilderness, New Mexico increases with longer rain-free periods. In our three Northwest ecoregions, where the maritime influence on climate changes from west to east, the direct effects of weather and climate on severity are more variable and difficult to interpret.…”

Section: Discussionsupporting

confidence: 73%

“…Alternatively, the non-linear relationships may be due to the multi-modal distribution of some topographic variables. For climate variables, our observation of thresholds is consistent with the notion that critical shifts in fuel moisture conditions can directly influence fire occurrence and behavior (Holden et al 2007), evident in climatologically-based fire danger rating indices used in predicting the probability of fire occurrence (Andrews et al 2003).…”

Section: Discussionsupporting

confidence: 62%

“…First, drier conditions generally increase the net energy released from fuel during burning. In New Mexico, for example, area burned severely was correlated with the duration of rain-free periods in the spring preceding the fire (Holden et al 2007). Second, more fuel, including logs, duff, and tree crowns, is likely to be consumed if fuels are dry than if they are not (Pyne et al 1996), and significant consumption of crown fuels can lead to severe fire effects.…”

Section: Topography and Climate Are Likely Important Drivers Of Burn mentioning

confidence: 99%

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Both topography and climate affected forest and woodland burn severity in two regions of the western US, 1984 to 2006

et al. 2011

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Fire is a keystone process in many ecosystems of western North America. Severe fires kill and consume large amounts of above‐ and belowground biomass and affect soils, resulting in long‐lasting consequences for vegetation, aquatic ecosystem productivity and diversity, and other ecosystem properties. We analyzed the occurrence of, and trends in, satellite‐derived burn severity across six ecoregions in the Southwest and Northwest regions of the United States from 1984 to 2006 using data from the Monitoring Trends in Burn Severity project. Using 1,024 fires from the Northwest (4,311,871 ha) and 497 fires from the Southwest (1,434,670 ha), we examined the relative influence of fine‐scale topography and coarse‐scale weather and climate on burn severity (the degree of change from before the fire to one year after) using the Random Forest machine learning algorithm. Together, topography, climate, and weather explained severe fire occurrence with classification accuracies ranging from 68% to 84%. Topographic variables were relatively more important predictors of severe fire occurrence than either climate or weather variables. Predictability of severe fire was consistently lower during years with widespread fires, suggesting that local control exerted by topography may be overwhelmed by regional climatic controls when fires burn in dry conditions. Annually, area burned severely was strongly correlated with area burned in all ecoregions (Pearson's correlation 0.86–0.97; p < 0.001), while the proportion of area burned severely was significantly correlated with area burned only in two ecoregions (p ≤ 0.037). During our short time series, only ecoregions in the Southwest showed evidence of a significant increase (p ≤ 0.036) in annual area burned and area burned severely, and annual proportion burned severely increased in just one of the three Southwest ecoregions. We suggest that predictive mapping of the potential for severe fire is possible, and will be improved with climate data at the scale of the topographic and Landsat‐derived burn severity data. Although severity is a value‐laden term implying negative ecosystem effects, we stress that severity can be objectively measured and recognize that high severity fire is an important ecological process within the historical range of variability in some ecosystems.

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Section: Discussionsupporting

confidence: 73%

Section: Discussionsupporting

confidence: 62%

Section: Topography and Climate Are Likely Important Drivers Of Burn mentioning

confidence: 99%

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Both topography and climate affected forest and woodland burn severity in two regions of the western US, 1984 to 2006

et al. 2011

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“…These fire severity estimates are based on the relative differenced Normalized Burn Ratio, which is computed from Landsat TM imagery (see Thode 2007, Miller et al 2009a). This index has been used extensively to characterize contemporary fires and fire regimes (Holden et al 2007, van Wagtendonk and Lutz 2007, Collins et al 2009, Miller et al 2009b). We used three fire severity classes: low, moderate, and high, which were based on the classification thresholds reported by Miller and Thode (2007), to broadly represent the extent of fire-caused change in burned lots.…”

Section: Fire Informationmentioning

confidence: 99%

Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests

2011

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Abstract. We re-sampled areas included in an unbiased 1911 timber inventory conducted by the U.S.Forest Service over a 4000 ha study area. Over half of the re-sampled area burned in relatively recent management-and lightning-ignited fires. This allowed for comparisons of both areas that have experienced recent fire and areas with no recent fire, to the same areas historically based on early forest inventories. Our results indicate substantially altered present forest conditions, relative to the 1911 data, and can largely be attributed to the disruption of the key ecosystem process for these forests, fire. For areas that burned recently there was a noticeable difference in forest structure based on fire severity. Current tree density and canopy cover in areas burned recently with moderate severity did not differ from 1911 estimates, while areas that burned recently with low severity or were unburned had higher tree density and canopy cover relative to the 1911 estimates. This emphasizes an important distinction with regard to using fire to restore forests, resting primarily on whether fires kill trees in the lower and intermediate canopy strata. Our results also demonstrate nearly a doubling of live tree carbon stocks in the present forest compared to the historical forest. The findings presented here can be used by managers and ecologists interested in restoring Sierra Nevada mixed conifer systems.

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“…A growing literature has made use of these records to evaluate broad-scale fire-climate patterns (e.g. Westerling et al , 2006Gillett et al 2004;Keeley 2004;McKenzie et al 2004;Collins et al 2006;Crimmins 2006;Holden et al 2007;Morgan et al in press).…”

Section: Modern Fire Climatology From Documentary Recordsmentioning

confidence: 99%

Fire Climatology in the western United States: introduction to special issue

Swetnam¹,

Anderson²

2008

Int. J. Wildland Fire

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Abstract. Advances in fire climatology have derived from recent studies of modern and paleoecological records. We convened a series of workshops and a conference session to report and review regional-scale findings, and these meetings led to the 10 papers in this special issue. Two papers focus on fire and climate patterns in the modern era using documentary records, four papers utilise tree rings to evaluate recent centuries of change, and four papers evaluate charcoal and pollen in lake, bog, and alluvial sediments over the Holocene. Here we summarise some of the key findings from these papers in the context of other recent fire climatology literature. These studies illustrate the value of long-term perspectives and spatial networks of fire and climate data in discovering the patterns and modes of past fire regime and climate variations.Warming temperatures and increasing drought occurrence in many regions of the world are resulting in widespread ecosystem impacts (ACIA 2005; IPCC 2007). One of the most dramatic ecological responses to climate change is wildfire. The importance of climate in driving past, present, and future fire regimes has greatly increased the need for better understanding of fire climatology. As distinct from fire meteorology, which addresses relatively fine-scale spatial processes over short time periods (i.e. days to weeks), fire climatology addresses broad-scale spatial and temporal processes (i.e. seasons to millennia).Advances in fire climatology

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Fire season precipitation variability influences fire extent and severity in a large southwestern wilderness area, United States

Cited by 78 publications

References 22 publications

Both topography and climate affected forest and woodland burn severity in two regions of the western US, 1984 to 2006

Both topography and climate affected forest and woodland burn severity in two regions of the western US, 1984 to 2006

Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests

Fire Climatology in the western United States: introduction to special issue

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