Fire ignition patterns affect production of charcoal in southern forests

Abstract. Although charcoal represents a relatively minor portion of available biomass burned in wildfires and prescribed burns, its recalcitrant properties confer residence times ranging from centuries to millennia, with significance for carbon sequestration in frequently burned forests. Here, we determined whether charcoal formation differed between the two most common prescribed fire spread patterns in southern forests: head (with the wind) and backing (against the wind). Pine wood samples were distributed randomly within a mesic flatwoods burn unit in north-central Florida, and subjected either to a head fire (n ¼ 34) or a backing fire (n ¼ 34). Backing fires formed more than twice as much charcoal as head fires (1.53 v. 0.38% of available biomass), presumably because of differences in residence times, oxygen availability and fire intensity between the two fire spread patterns. These results suggest that the contribution of charcoal to ecosystem carbon sequestration is greater when flatwoods forests are burned against the prevailing wind direction, and that further investigation of these trends is warranted

Fire as a fundamental ecological process: Research advances and frontiers

© 2020 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society Fire is a powerful ecological and evolutionary force that regulates organismal traits, population sizes, species interactions, community composition, carbon and nutrient cycling and ecosystem function. It also presents a rapidly growing societal challenge, due to both increasingly destructive wildfires and fire exclusion in fire-dependent ecosystems. As an ecological process, fire integrates complex feedbacks among biological, social and geophysical processes, requiring coordination across several fields and scales of study. Here, we describe the diversity of ways in which fire operates as a fundamental ecological and evolutionary process on Earth. We explore research priorities in six categories of fire ecology: (a) characteristics of fire regimes, (b) changing fire regimes, (c) fire effects on above-ground ecology, (d) fire effects on below-ground ecology, (e) fire behaviour and (f) fire ecology modelling. We identify three emergent themes: the need to study fire across temporal scales, to assess the mechanisms underlying a variety of ecological feedbacks involving fire and to improve representation of fire in a range of modelling contexts. Synthesis: As fire regimes and our relationships with fire continue to change, prioritizing these research areas will facilitate understanding of the ecological causes and consequences of future fires and rethinking fire management alternatives

Fire as a fundamental ecological process: Research advances and frontiers

© 2020 The Authors.Fire is a powerful ecological and evolutionary force that regulates organismal traits, population sizes, species interactions, community composition, carbon and nutrient cycling and ecosystem function. It also presents a rapidly growing societal challenge, due to both increasingly destructive wildfires and fire exclusion in fire‐dependent ecosystems. As an ecological process, fire integrates complex feedbacks among biological, social and geophysical processes, requiring coordination across several fields and scales of study. Here, we describe the diversity of ways in which fire operates as a fundamental ecological and evolutionary process on Earth. We explore research priorities in six categories of fire ecology: (a) characteristics of fire regimes, (b) changing fire regimes, (c) fire effects on above‐ground ecology, (d) fire effects on below‐ground ecology, (e) fire behaviour and (f) fire ecology modelling. We identify three emergent themes: the need to study fire across temporal scales, to assess the mechanisms underlying a variety of ecological feedbacks involving fire and to improve representation of fire in a range of modelling contexts. Synthesis: As fire regimes and our relationships with fire continue to change, prioritizing these research areas will facilitate understanding of the ecological causes and consequences of future fires and rethinking fire management alternatives.Support was provided by NSF‐DEB‐1743681 to K.K.M. and A.J.T. We thank Shalin Hai‐Jew for helpful discussion of the survey and qualitative methods.Peer reviewe

Wildfire burn patterns and riparian vegetation response along two nor- thern Sierra Nevada streams. Forest Ecology and

Abstract Riparian vegetation plays an integral role in the ecology of the streams it borders, and in many western US forests, is subjected to frequent wildfire disturbances. Many questions concerning the role of natural fire in the dynamics of riparian zone vegetation remain unanswered. This case study explores the relationships between wildfire burn patterns, stream channel topography, and the short-term response of riparian vegetation to fire along two creeks in the northern Sierra Nevada mixed-conifer forest. Post-fire sampling along 60, 3 m wide transects across riparian zones was used to document the topography, species distribution, sprouting response, and seedling recruitment 1 year after the Lookout fire in the Plumas National Forest, CA. Our results indicate that larger riparian zones acted as natural fire breaks, limiting the progression of the predominantly backing fire downhill toward the stream. On Fourth Water creek's steeper first terraces, where crown fires occurred, the percentage of burned plants that sprouted was higher than in the less-severely burned and more extensive first terraces of Third Water creek (93% versus 33%, P < 0.05). Total seedling recruitment was higher along Fourth Water creek (69 versus 35 seedlings, P < 0.05), while plant regeneration along Third Water creek was primarily vegetative. Along Fourth Water creek, the percent of burned hardwoods that sprouted increased with proximity to the water's edge from 33% on the slope above the riparian zone to 95% on the gravel bar, suggesting that moisture content plays a role in riparian species response to fire. An influx of white fir (Abies concolor Gordon & Glend. (Lindl.)) seedlings on the second terraces of Third Water creek may indicate a shift in species composition if future fires are suppressed and regeneration trends do not change significantly in the next few years. These results contribute to the limited research on natural fire in riparian zones, and can inform management strategies designed to restore and maintain riparian vegetation in the fire-prone forests of the Sierra Nevada.

Fire ignition patterns affect production of charcoal in southern forests

Although charcoal represents a relatively minor portion of available biomass burned in wildfires and prescribed burns, its recalcitrant properties confer residence times ranging from centuries to millennia, with significance for carbon sequestration in frequently burned forests. Here, we determined whether charcoal formation differed between the two most common prescribed fire spread patterns in southern forests: head (with the wind) and backing (against the wind). Pine wood samples were distributed randomly within a mesic flatwoods burn unit in north-central Florida, and subjected either to a head fire (n = 34) or a backing fire (n = 34). Backing fires formed more than twice as much charcoal as head fires (1.53 v. 0.38% of available biomass), presumably because of differences in residence times, oxygen availability and fire intensity between the two fire spread patterns. These results suggest that the contribution of charcoal to ecosystem carbon sequestration is greater when flatwoods forests are burned against the prevailing wind direction, and that further investigation of these trends is warranted

Perspectives on Trends, Effectiveness, and Impediments to Prescribed Burning in the Southern U.S.

The southern region of the U.S. uses prescribed fire as a management tool on more of its burnable land than anywhere in the U.S., with ecosystem restoration, wildlife habitat enhancement, and reduction of hazardous fuel loads as typical goals. Although the region performs more than 50,000 prescribed fire treatments each year, evaluation of their effects on wildfire suppression resources or behavior/effects is limited. To better understand trends in the use and effectiveness of prescribed fire, we conducted a region-wide survey of 523 fire use practitioners, working on both public and private lands. A 1–2 year prescribed fire interval was consistently viewed as effective in decreasing wildfire ignitions, behavior, and severity, as well as reducing suppression resources needed where wildfire occurred. Yet fewer than 15% of practitioners viewed burn intervals of 3–4 years as effective in reducing ignitions, underscoring the importance of high-frequency burning in vegetation communities where fuel recovery is rapid. Public lands managers identified limited budget and staffing as major institutional impediments to prescribed fire, in contrast to private individuals, more of whom chose liability as a key challenge. Differences in responses across ownership type, state, and vegetation type call for a broader perspective on how fire managers in the southern U.S. view prescribed fire

Immediate and short-term response of understory fuels following mechanical mastication in a pine flatwoods site of Florida, USA

a b s t r a c t Mechanical fuel hazard reduction treatments are widely implemented in fire-prone ecosystems, but research evaluating their effects on fuel dynamics has focused only on woody-dominated post-treatment fuels. In the southeastern US, one of the most fire-prone regions of the world, mechanical fuels reduction is being increasingly used, yet the resulting fuelbeds have yet to be fully characterized for their fire risk. In order to broaden our understanding of the longevity and effectiveness of these treatments, mechanical mastication (''mowing'') was examined in a common pine ecosystem of the southeastern US Coastal Plain, where the post-mastication fuel environment was dominated by non-woody fuels. Fuel dynamics differed between recently burned mature stands, mature stands that had not burned for several years, and younger pine plantations. Foliar litter dominated (46-69%) the 17.1-23.1 Mg ha À1 of post-mastication surface fuels across these ecosystems, where pre-treatment understories were dominated by palmetto and gallberry shrubs. Although surface fuels compacted over time, the shrub layer recovered quickly, contributing to the result that stand-alone mechanical treatments did not reduce overall fuel loads. Increases in surface fuels followed by rapid shrub recovery may indicate short-term treatment efficacy, with narrow windows of opportunity for post-treatment fuel reduction burns. The fuelbed characteristics and fuel dynamics observed in these treated sites broaden our understanding of mechanical fuels reduction treatments in general, and provide the critical data for fuel model development

Appendix A. Final stress, instability, and r2 values for all ordination diagrams.

Final stress, instability, and r2 values for all ordination diagrams