Variability in vegetation and surface fuels across mixed-conifer-dominated landscapes with over 40 years of natural fire

Collins, Brandon M.; Lydersen, Jamie M.; Fry, Danny L.; Wilkin, Katherine M.; Moody, Tadashi; Stephens, Scott L.

doi:10.1016/j.foreco.2016.09.010

Cited by 47 publications

(23 citation statements)

References 77 publications

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“…) or describe the natural range of variation in forest structure and composition (e.g., Lydersen and North , Collins et al. ). This assertion is partially based on the fact that, in many of these areas, fire has been reintroduced or restored as a key landscape‐level ecosystem process (Collins and Stephens , Larson et al.…”

Section: Discussionmentioning

confidence: 99%

“…Beyond the actual implementation, moderate severity fire can result in a substantial pulse of woody fuels from fire‐killed trees that increases fire behavior and effects in subsequent fires (Collins et al. ). Low severity fire may be more practical to implement, and can be effective at modifying forest structure relative to un‐manipulated areas.…”

Section: Discussionmentioning

confidence: 99%

“…First, although there are plenty of unlogged fire‐excluded areas (e.g., U.S. National Parks), they tend to occur in somewhat unique biophysical settings relative to logged fire‐excluded areas, i.e., higher elevations, different species composition, and greater discontinuity due to exposed rock (Collins et al. ). This makes comparisons somewhat confounded by fundamental site differences.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…In fire research, various indicators have been adopted to delineate topographic characteristics. The most common topographic indicators used in studies include elevation, slope, aspect, topographic wetness index (TWI), solar radiation index (SRI), topographic position index, elevation relief ratio, heat load index, topographic roughness index and gullies (e.g., [19,[34][35][36][37][38][39][40][41]). Because there is no clear evidence indicating which variables are more effective in delineating topographic characteristics, we tried to adopt indicators that have proven to be effective in capturing the complex topographic characteristics of our study areas in previous studies (e.g., [3,10,30]).…”

Section: Mapping Topographic Characteristicsmentioning

confidence: 99%

Complex Relationships of the Effects of Topographic Characteristics and Susceptible Tree Cover on Burn Severity

2018

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Forest fires and burn severity mosaics have profound impacts on the post-fire dynamics and complexity of forest ecosystems. Numerous studies have investigated the relationship between topographic variables and susceptible tree covers with regard to burn severity. However, these relationships have not been fully elucidated, because most studies have assumed linearity in these relationships. Therefore, we examined the linearity and the nonlinearity in the relationships between topographic variables and susceptible tree covers with burn severity by comparing linear and nonlinear models. The site of the Samcheok fire, the largest recorded forest fire in Korea, was used as the study area. We generated 802 grid cells with a 500-m resolution that encompassed the entire study area and collected a dataset that included the topographic variables and percentage of red pine trees, which are the most susceptible tree cover types in Korea. We used conventional linear models and generalized additive models to estimate the linear and the nonlinear models based on topographic variables and Japanese red pine trees. The results revealed that the percentage of red pine trees had linear effects on burn severity, reinforcing the importance of silviculture and forest management to lower burn severity. Meanwhile, the topographic variables had nonlinear effects on burn severity. Among the topographic variables, elevation had the strongest nonlinear effect on burn severity, possibly by overriding the effects of susceptible fuels over elevation effects or due to the nonlinear effects of topographic characteristics on pre-fire fuel conditions, including the spatial distribution and availability of susceptible tree cover. To validate and generalize the nonlinear effects of elevation and other topographic variables, additional research is required at different fire sites with different tree cover types in different geographic locations.

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“…Lower severity fire patches provide ecosystem‐level benefits by moving overstory structure towards historic density and composition, reducing unnaturally high fuel loads, and creating greater diversity in vegetation patches and wildlife habitat (Collins et al. , , Das et al. , Kane et al.…”

Section: Management Implicationsmentioning

confidence: 99%

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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Variability in vegetation and surface fuels across mixed-conifer-dominated landscapes with over 40 years of natural fire

Cited by 47 publications

References 77 publications

Impacts of different land management histories on forest change

Impacts of different land management histories on forest change

Complex Relationships of the Effects of Topographic Characteristics and Susceptible Tree Cover on Burn Severity

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

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