Relating Fire-Caused Change in Forest Structure to Remotely Sensed Estimates of Fire Severity

Lydersen, Jamie M.; Collins, Brandon M.; Miller, Jay D.; Fry, Danny L.; Stephens, Scott L.

doi:10.4996/fireecology.1203099

Cited by 53 publications

(53 citation statements)

References 45 publications

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“…Looking at a portion of the Stanislaus that burned in the Rim Fire, Lydersen et al. () found high‐severity patches had significantly greater densities of small trees, but no significant difference in basal area than areas that burned at lower severity, and in an untreated portion of Yosemite, Harris and Taylor () found that tree species composition varied with fire severity. However in another study in Yosemite, Kane et al.…”

Section: Discussionmentioning

confidence: 99%

“…For wildfires that occur in forested lands of California, there are typically two versions of the RdNBR fire‐severity map available, the initial and extended assessments (Miller and Quayle , Lydersen et al. ). In the initial assessment, RdNBR is calculated by comparing imagery acquired immediately (30–45 d) after fire containment to imagery acquired prior to the fire.…”

Section: Methodsmentioning

confidence: 99%

“…While the extended RdNBR assessment is more commonly used than the initial, the high‐severity category tends to be stable across both assessments (Lydersen et al. ). Therefore the use of the initial assessment over part of the fire should have little impact on the study results.…”

Section: Methodsmentioning

confidence: 99%

“…Previous work in the Rim Fire demonstrated that high‐severity fire was strongly associated with crown fire and exhibited extremely high tree mortality (Lydersen et al. ). Because the historical fire regime consisted of frequent, predominantly low‐severity surface fire (Scholl and Taylor ), areas of high severity within mixed‐conifer forest at our study site, particularly when occurring as larger patches, are outside the historical range of fire effects (Mallek et al.…”

Section: Introductionmentioning

confidence: 99%

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Evidence of fuels management and fire weather influencing fire severity in an extreme fire event

Lydersen

Collins

Brooks

et al. 2017

Ecological Applications

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Following changes in vegetation structure and pattern, along with a changing climate, large wildfire incidence has increased in forests throughout the western United States. Given this increase, there is great interest in whether fuels treatments and previous wildfire can alter fire severity patterns in large wildfires. We assessed the relative influence of previous fuels treatments (including wildfire), fire weather, vegetation, and water balance on fire-severity in the Rim Fire of 2013. We did this at three different spatial scales to investigate whether the influences on fire severity changed across scales. Both fuels treatments and previous low to moderate-severity wildfire reduced the prevalence of high-severity fire. In general, areas without recent fuels treatments and areas that previously burned at high severity tended to have a greater proportion of high-severity fire in the Rim Fire. Areas treated with prescribed fire, especially when combined with thinning, had the lowest proportions of high severity. The proportion of the landscape burned at high severity was most strongly influenced by fire weather and proportional area previously treated for fuels or burned by low to moderate severity wildfire. The proportion treated needed to effectively reduce the amount of high severity fire varied by spatial scale of analysis, with smaller spatial scales requiring a greater proportion treated to see an effect on fire severity. When moderate and high-severity fire encountered a previously treated area, fire severity was significantly reduced in the treated area relative to the adjacent untreated area. Our results show that fuels treatments and low to moderate-severity wildfire can reduce fire severity in a subsequent wildfire, even when burning under fire growth conditions. These results serve as further evidence that both fuels treatments and lower severity wildfire can increase forest resilience.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evidence of fuels management and fire weather influencing fire severity in an extreme fire event

Lydersen

Collins

Brooks

et al. 2017

Ecological Applications

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123

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“…In result, recent occurrences of uncharacteristically large and intense wildfires, that have caused the loss of key ecosystem components, are thought to be clear consequences of such altered forested ecosystems [45,46]. Because ecological restoration techniques aimed at reducing the accumulation of excessive fuels and encouraging understory vegetation growth [47][48][49] are now planned for the region, a detailed understanding of tree distribution patterns is important for restoration managers, planners, and scientists [50]. Few studies have assessed the landscape or regional patterns of structural diversity in coniferous forests of the southwestern USA using remote sensing.…”

Section: Introductionmentioning

confidence: 99%

Mapping Tree Density in Forests of the Southwestern USA Using Landsat 8 Data

Humagain

Portillo-Quintero

Cox

et al. 2017

Forests

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Abstract:The increase of tree density in forests of the American Southwest promotes extreme fire events, understory biodiversity losses, and degraded habitat conditions for many wildlife species. To ameliorate these changes, managers and scientists have begun planning treatments aimed at reducing fuels and increasing understory biodiversity. However, spatial variability in tree density across the landscape is not well-characterized, and if better known, could greatly influence planning efforts. We used reflectance values from individual Landsat 8 bands (bands 2, 3, 4, 5, 6, and 7) and calculated vegetation indices (difference vegetation index, simple ratios, and normalized vegetation indices) to estimate tree density in an area planned for treatment in the Jemez Mountains, New Mexico, characterized by multiple vegetation types and a complex topography. Because different vegetation types have different spectral signatures, we derived models with multiple predictor variables for each vegetation type, rather than using a single model for the entire project area, and compared the model-derived values to values collected from on-the-ground transects. Among conifer-dominated areas (73% of the project area), the best models (as determined by corrected Akaike Information Criteria (AICc)) included Landsat bands 2, 3, 4, and 7 along with simple ratios, normalized vegetation indices, and the difference vegetation index (R 2 values for ponderosa: 0.47, piñon-juniper: 0.52, and spruce-fir: 0.66). On the other hand, in aspen-dominated areas (9% of the project area), the best model included individual bands 4 and 2, simple ratio, and normalized vegetation index (R 2 value: 0.97). Most areas dominated by ponderosa, pinyon-juniper, or spruce-fir had more than 100 trees per hectare. About 54% of the study area has medium to high density of trees (100-1000 trees/hectare), and a small fraction (4.5%) of the area has very high density (>1000 trees/hectare). Our results provide a better understanding of tree density for identifying areas in need of treatment and planning for more effective treatment. Our analysis also provides an integrated method of estimating tree density across complex landscapes that could be useful for further restoration planning.

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Impacts of different land management histories on forest change

Collins

Fry

Lydersen

et al. 2017

Ecological Applications

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Many western North American forest types have experienced considerable changes in ecosystem structure, composition, and function as a result of both fire exclusion and timber harvesting. These two influences co-occurred over a large portion of dry forests, making it difficult to know the strength of either one on its own or the potential for an interaction between the two. In this study, we used contemporary remeasurements of a systematic historical forest inventory to investigate forest change in the Sierra Nevada. The historical data opportunistically spanned a significant land management agency boundary, which protected part of the inventory area from timber harvesting. This allowed for a robust comparison of forest change between logged and unlogged areas. In addition, we assessed the effects of recent management activities aimed at forest restoration relative to the same areas historically, and to other areas without recent management. Based on analyses of 22,007 trees (historical, 9,573; contemporary, 12,434), live basal area and tree density significantly increased from 1911 to the early 2000s in both logged and unlogged areas. Both shrub cover and the proportion of live basal area occupied by pine species declined from 1911 to the early 2000s in both areas, but statistical significance was inconsistent. The most notable difference between logged and unlogged areas was in the density of large trees, which declined significantly in logged areas, but was unchanged in unlogged areas. Recent management activities had a varied impact on the forest structure and composition variables analyzed. In general, areas with no recent management activities experienced the greatest change from 1911 to the early 2000s. If approximating historical forest conditions is a land management goal the documented changes in forest structure and composition from 1911 to the early 2000s indicate that active restoration, including fire use and mechanical thinning, is needed in many areas.

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Relating Fire-Caused Change in Forest Structure to Remotely Sensed Estimates of Fire Severity

Cited by 53 publications

References 45 publications

Evidence of fuels management and fire weather influencing fire severity in an extreme fire event

Evidence of fuels management and fire weather influencing fire severity in an extreme fire event

Mapping Tree Density in Forests of the Southwestern USA Using Landsat 8 Data

Impacts of different land management histories on forest change

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