Northern Rockies Pyrogeography: an Example of Fire Atlas UtilitySpringer Science and Business Media LLC - Tập 10 - Trang 14-30 - 2014
Penelope Morgan, Emily K. Heyerdahl, Carol Miller, Aaron M. Wilson, Carly E. Gibson
We demonstrated the utility of digital fire atlases by analyzing forest fire extent across cold, dry, and mesic forests, within and outside federally designated wilderness areas during three different fire management periods: 1900 to 1934, 1935 to 1973, and 1974 to 2008. We updated an existing atlas with a 12 070 086 ha recording area in Idaho and Montana, USA, west of the Continental Divide, 81 % of which is forested. This updated atlas was derived from records maintained locally by 12 national forests and Glacier National Park. Within the cold, dry, and mesic forests that encompass 45 %, 44 %, and 11 % of the fire atlas recording area, respectively, we analyzed 3228 fire polygons (those ≥20 ha in extent and ≥75 % forested). We discovered that both fire extent and the number of fire polygons were greater in the north during the early period and greater in the south during the late period, but in all cases burned in proportion to land area. Over the 9 731 691 ha forested fire-atlas recording area, 36 % of 10 000 randomly located points burned at least once, 7 % burned twice, and fewer than 1 % burned three or more times. Of these same points, disproportionately more burned inside wilderness than outside. These points burned in proportion to land area by forest type and generally by slope, aspect, and elevation. Analysis revealed that despite extensive fires early and late in the twentieth century, area burned was likely still low relative to prior centuries, especially at low elevations and outside large wilderness areas. The fire atlas includes few fires <40 ha, and its perimeter accuracy is uncertain and likely historically inconsistent; even so, the perimeters are georeferenced and, because they include the entire twentieth century, can serve to bridge past and future fire regimes. Fire atlases are necessarily imperfect, but they remain useful for exploring the pyrogeography of modern fire regimes, including how the spatial distribution of fire varied through time with respect to landscape controls, fire management, and climate.
Tree regeneration following wildfires in the western US: a reviewSpringer Science and Business Media LLC - Tập 15 - Trang 1-17 - 2019
Camille S. Stevens-Rumann, Penelope Morgan
Wildfires, like many disturbances, can be catalysts for ecosystem change. Given projected climate change, tree regeneration declines and ecosystem shifts following severe wildfires are predicted. We reviewed scientific literature on post-fire tree regeneration to understand where and why no or few trees established. We wished to distinguish sites that won’t regenerate to trees because of changing climate from sites where trees could grow post fire if they had a seed source or were planted, thus supporting forest ecosystem services for society and nature, such as timber supply, habitat, watershed protection, and carbon storage. Our literature review showed that little to no post-fire tree regeneration was more common in low-elevation, dry forest types than in high-elevation forest types. However, depending on the region and species, low tree regeneration was also observed in high elevation, moist forests. Regeneration densities varied by species and seedling densities were attributed to distances to a seed source, water stress or precipitation, elevation, slope, aspect, and plant competition. Our findings provide land managers with two primary considerations to offset low tree regeneration densities. First, we supply a decision support tool of where to plant tree seedling in large high severity burned patches. Second, we recommend possibilities for mitigating and limiting large high severity burned patches to increase survival of trees to be sources of seed for natural regeneration. Few or no tree seedlings are establishing on some areas of the 150+ forest fires sampled across western US, suggesting that forests may be replaced by shrublands and grasslands, especially where few seed source trees survived the wildfires. Key information gaps on how species will respond to continued climate change, repeated disturbances, and other site factors following wildfires currently limit our ability to determine future trends in forest regeneration. We provide a decision tree to assist managers in prioritizing post-fire reforestation. We emphasize prioritizing the interior of large burned patches and considering current and future climate in deciding what, when, and where to plant trees. Finally, managing fires and forests for more seed-source tree survival will reduce large, non-forested areas following wildfires where post-fire management may be necessary.
Vai trò của khoảng thời gian lửa quay trở lại và mùa đốt trong động lực học cây chết đứng tại rừng thông chẻ Florida phía Nam Dịch bởi AI Springer Science and Business Media LLC - Tập 8 Số 3 - Trang 18-31
John D. Lloyd, Gary W. Slater, James R. Snyder
Tóm tắtCác cây chết đứng, hay còn gọi là cây snag, là một yếu tố habitat quan trọng cho nhiều loài động vật. Trong nhiều hệ sinh thái, lửa là một yếu tố chính điều khiển động lực học quần thể cây snag vì nó có thể tạo ra và tiêu hủy các cây snag. Mục tiêu của nghiên cứu này là xem xét cách mà sự biến đổi của hai thành phần chính trong chế độ lửa—khoảng thời gian quay trở lại của lửa và mùa đốt—ảnh hưởng đến động lực học quần thể cây snag. Sử dụng thiết kế nhân tố, chúng tôi đã phơi bày các ô 1 ha, nằm trong các đơn vị đốt lớn hơn ở rừng thông chẻ Florida phía Nam (Pinus elliottii var. densa Little và Dorman), với việc đốt theo quy định được áp dụng ở hai khoảng thời gian (khoảng 3 năm vs. khoảng 6 năm) và trong hai mùa (mùa ẩm vs. mùa khô) trong khoảng thời gian 12 đến 13 năm. Chúng tôi không tìm thấy sự ảnh hưởng nhất quán của mùa đốt hoặc tần suất đến mật độ của các cây snag nhẹ đến vừa bị phân hủy hoặc nặng bị phân hủy, điều này cho thấy rằng sự biến đổi của các yếu tố này trong chế độ lửa ở quy mô mà chúng tôi xem xét là tương đối không quan trọng trong động lực học quần thể cây snag. Tuy nhiên, sự tự tin của chúng tôi về những phát hiện này bị giới hạn bởi kích thước mẫu nhỏ, sự ảnh hưởng có thể gây nhầm lẫn của biến đổi không được đo lường trong hành vi và hiệu ứng của lửa (ví dụ: cường độ, mức độ nghiêm trọng, sự tương tác với chu kỳ hạn hán) và sự biến đổi lớn trong các phản ứng trong một mức độ điều trị. Việc tổng quát những phát hiện của chúng tôi cũng bị giới hạn bởi phạm vi hẹp của các mức độ điều trị được xem xét. Các thí nghiệm trong tương lai kết hợp một phạm vi rộng hơn của các chế độ lửa và định lượng trực tiếp cường độ lửa sẽ hữu ích trong việc xác định rõ hơn vai trò của lửa trong việc định hình động lực học quần thể cây snag.
Fuel types misrepresent forest structure and composition in interior British Columbia: a way forwardSpringer Science and Business Media LLC - Tập 20 - Trang 1-21 - 2024
Jennifer N. Baron, Paul F. Hessburg, Marc-André Parisien, Gregory A. Greene, Sarah. E. Gergel, Lori D. Daniels
A clear understanding of the connectivity, structure, and composition of wildland fuels is essential for effective wildfire management. However, fuel typing and mapping are challenging owing to a broad diversity of fuel conditions and their spatial and temporal heterogeneity. In Canada, fuel types and potential fire behavior are characterized using the Fire Behavior Prediction (FBP) System, which uses an association approach to categorize vegetation into 16 fuel types based on stand structure and composition. In British Columbia (BC), provincial and national FBP System fuel type maps are derived from remotely sensed forest inventory data and are widely used for wildfire operations, fuel management, and scientific research. Despite their widespread usage, the accuracy and applicability of these fuel type maps have not been formally assessed. To address this knowledge gap, we quantified the agreement between on-site assessments and provincial and national fuel type maps in interior BC. We consistently found poor correspondence between field assessment data and both provincial and national fuel types. Mismatches were particularly frequent for (i) dry interior ecosystems, (ii) mixedwood and deciduous fuel types, and (iii) post-harvesting conditions. For 58% of field plots, there was no suitable match to the extant fuel structure and composition. Mismatches were driven by the accuracy and availability of forest inventory data and low applicability of the Canadian FBP System to interior BC fuels. The fuel typing mismatches we identified can limit scientific research, but also challenge wildfire operations and fuel management decisions. Improving fuel typing accuracy will require a significant effort in fuel inventory data and system upgrades to adequately represent the diversity of extant fuels. To more effectively link conditions to expected fire behavior outcomes, we recommend a fuel classification approach and emphasis on observed fuels and measured fire behavior data for the systems we seek to represent.
Impacts of increasing fine fuel loads on acorn germination and early growth of oak seedlingsSpringer Science and Business Media LLC - Tập 17 Số 1
Rachel E. Nation, Heather D. Alexander, Geoff Denny, Jennifer K. McDaniel, Alison K. Paulson
Abstract
Background
Prescribed fire is increasingly used to restore and maintain upland oak (Quercus L. spp.) ecosystems in the central and eastern US. However, little is known about how prescribed fire affects recently fallen acorns under different fine fuel loads, which can vary with stand composition and basal area, burn season, and fire frequency. We conducted plot-level (1 m2) burns in an upland oak stand in northern Mississippi, USA, during December 2018, using single (i.e., ambient), double, and triple fine fuel loads, representative of those in nearby unburned and recently fire-treated, closed-canopy stands. Pre burn, we placed 30 acorns each of white oak (Quercus alba L.) and Shumard oak (Quercus shumardii Buckley) ~1 cm below the litter surface in five plots of each fuel treatment. Immediately post burn, we planted unburned and burned acorns in a greenhouse. After ~50% of each species’ unburned acorns germinated, we measured percent germination and height, basal diameter, and leaf number of germinating seedlings weekly for 11 weeks. Then, we harvested seedlings to determine above- and belowground biomass.
Results
The single fuel treatment reduced acorn germination rates of both species to ~40% compared to ~88% in unburned acorns. When burned in double and triple fuel loads, acorns of both species had a <5% germination rate. There was no difference in basal diameter, leaf number, or biomass of seedlings from burned versus unburned acorns for either species. However, seedlings originating from burned acorns of both species were ~11% shorter than those from unburned acorns. Thus, both species responded similarly to fuel load treatments.
Conclusions
Acorns of both species exhibited greater survival with lower fine fuel loads, and consequently lower percent fuel consumption. Acorns germinating post fire generally produced seedlings with growth patterns similar to seedlings originating from unburned acorns. These findings indicate that regular, repeated prescribed fires or canopy reductions that limit fine fuel accumulation and create heterogeneous fuel beds are likely to increase acorn germination rates relative to unburned sites or those with recently introduced fire.
Impacts of Fire on Microbial Carbon Cycling in Subtropical WetlandsSpringer Science and Business Media LLC - Tập 9 - Trang 21-37 - 2013
Cassandra A. Medvedeff, Kanika S. Inglett, Leda N. Kobziar, Patrick W. Inglett
Fire is a major determinant of the global carbon (C) balance. While it is known that C is lost through organic matter combustion, the effect fire has on soil C biogeochemistry is unclear. Studies investigating the role of fire on C greenhouse gas production (CO2 and CH4) have been conducted in forested and grassland ecosystems, yet research in wetlands has been limited. With their high potential for C storage, wetland ecosystems are important in C cycling while simultaneously serving as the largest single CH4 source in the world. Wildfires typically consume a majority of the above-water biomass in wetland systems that result in direct C losses, but the subsequent implications for C processing are unknown. Thus, understanding C cycling in wetlands regularly maintained or influenced by fire is critical to meeting C sequestration management objectives. This study focused on a fire-adapted wetland ecosystem undergoing restoration from agricultural impacts within the Everglades National Park, Florida, USA. Within the site, the effects of prescribed fire on C cycling (organic C, extractable organic C, enzyme activity, CO2, and CH4 production) were monitored in a restored (high-phosphorus [P]) and reference (low-P) wetland at both high and low elevations. Because fire can affect both C and P forms and availability, the objective of this study was to investigate the short- (two-day) and long-term (one-year) effect of fire on C cycling in subtropical wetlands soils of varying soil nutrient concentrations. Initially (two days post fire), C cycling was stimulated in both soils. However, stimulation of CO2 and CH4 production was observed only at the reference (low-P) site. This result suggests that fire may have an adverse effect on C cycling in low-P soils, initially augmenting C greenhouse gas production. Minimal heat transfer coupled with constant microbial biomass suggests that nutrients may have been a regulating factor in this process. After one year, no fire effect was distinguishable on C parameters from reference sites, yet variable effects were observed in restored soils. This suggests that C cycling in reference sites may recover more quickly than restored sites. The ultimate consequences of fire on C cycling in these wetlands systems are dependent on time and are strongly influenced by pre-fire site conditions.
The impact of UAS aerial ignition on prescribed fire: a case study in multiple ecoregions of Texas and LouisianaSpringer Science and Business Media LLC - Tập 19 - Trang 1-15 - 2023
Brett L. Lawrence, Kevin Mundorff, Eric Keith
Small Unmanned Aerial System (UAS) technologies and their applications have expanded in recent years, to include aerial ignition support in prescribed fire and wildland fire settings. In 2019, we incorporated the use of UAS aerial ignition into our existing prescribed fire program of over 20 years. To assess its impact, comparisons of UAS and non-UAS burns were performed on burn data from 2012 to 2021, with 58 total UAS burns conducted from 2019 to 2021. A subset of these burns conducted at Cook’s Branch Conservancy in Montgomery County, TX, included post-burn assessment data, which we used to compare UAS and non-UAS fire effects. Non-parametric significance tests were used to analyze and compare non-UAS burning before (2012–2018) and after (2019–2021) the incorporation of the UAS, and UAS burning from 2019 to 2021. Response variables included ha day−1 burned and six different post-burn assessment metrics. Principal findings were that from 2019 to 2021, UAS burns were 61 ha day−1 or 129% more efficient than non-UAS burning and required one extra staff member to pilot the UAS on average. This increase enabled a previously unachievable efficiency in terms of hectares burned each year vs days burned each year when using the UAS. While fire effects were less severe for most post-burn assessment metrics during UAS burning, burn results still met fuel management goals when compared to non-UAS burning. A large increase in ha day−1 was previously unachievable, making the UAS a viable tool for accomplishing safer and more effective prescribed burn operations in the limited number of suitable days available. When managed responsibly, UAS aerial ignition is poised to have a positive impact on the safe and effective application of prescribed fire, resulting in more achievable conservation and fuel management goals.
Modeling fuel moisture dynamics under climate change in Spain’s forestsSpringer Science and Business Media LLC -
Rodrigo Balaguer‐Romano, Rubén Díaz‐Sierra, Miquel De Cáceres, Jordi Voltas, Matthias M. Boer, Víctor Resco de Dios
Abstract
Background
Current assessments of the effects of climate change on future wildfire risk are based on either empirical approaches or fire weather indices. No study has yet used process-based models over national scales to understand how and where will increases in climate aridity affect the likelihood of fire activity through changes in the moisture content of live (LFMC) and of dead (DFMC) fuels. Here, we used process-based models to forecast changes in LFMC and DFMC under the 21st century climatic conditions projected from moderate and high greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Predictions were performed across broad productivity gradients in peninsular Spain to understand how productivity mediates the effects of climate change on fuel moisture dynamics.
Results
LFMC and DFMC were predicted to decline under the climatic conditions projected for the coming decades. Increases in the annual frequency of days with fuel moisture content below wildfire occurrence thresholds were predicted to extend fire season lengths by 20 days under RCP4.5 and by 50 days under RCP8.5. The effects of climate change on LFMC and DFMC varied linearly and negatively with productivity (stronger fuel moisture decreases in least productive environments). Although we observed a significant mitigation effect from rising CO2 (via increases in water-use efficiency), it was not enough to offset LFMC declining trends induced by increased temperature and aridity.
Conclusions
We predicted that the warmer and more arid climatic conditions projected for the 21st century will lead to generalized declines in fuel moisture, lengthening fire seasons, and increasing wildfire danger. The use of process-based models to forecast LFMC dynamics allowed the consideration of plant species capabilities to buffer climate change impacts. Significant increases in the fire season length predicted in the most productive environments, currently with large fire return intervals, would pose an increase of fire danger in major Spanish carbon sinks. Finally, the CO2 mitigation effect would not be enough to offset climate change-driven declines in seasonal LFMC levels.
Landscape controls on fuel moisture variability in fire-prone heathland and peatland landscapesSpringer Science and Business Media LLC - - 2024
Kerryn Little, Laura J Graham, Mike Flannigan, Claire M Belcher, Nicholas Kettridge
Cross-landscape fuel moisture content is highly variable but not considered in existing fire danger assessments. Capturing fuel moisture complexity and its associated controls is critical for understanding wildfire behavior and danger in emerging fire-prone environments that are influenced by local heterogeneity. This is particularly true for temperate heathland and peatland landscapes that exhibit spatial differences in the vulnerability of their globally important carbon stores to wildfire. Here we quantified the range of variability in the live and dead fuel moisture of Calluna vulgaris across a temperate fire-prone landscape through an intensive fuel moisture sampling campaign conducted in the North Yorkshire Moors, UK. We also evaluated the landscape (soil texture, canopy age, aspect, and slope) and micrometeorological (temperature, relative humidity, vapor pressure deficit, and windspeed) drivers of landscape fuel moisture variability for temperate heathlands and peatlands for the first time. We observed high cross-landscape fuel moisture variation, which created a spatial discontinuity in the availability of live fuels for wildfire spread (fuel moisture < 65%) and vulnerability of the organic layer to smoldering combustion (fuel moisture < 250%). This heterogeneity was most important in spring, which is also the peak wildfire season in these temperate ecosystems. Landscape and micrometeorological factors explained up to 72% of spatial fuel moisture variation and were season- and fuel-layer-dependent. Landscape factors predominantly controlled spatial fuel moisture content beyond modifying local micrometeorology. Accounting for direct landscape–fuel moisture relationships could improve fuel moisture estimates, as existing estimates derived solely from micrometeorological observations will exclude the underlying influence of landscape characteristics. We hypothesize that differences in soil texture, canopy age, and aspect play important roles across the fuel layers examined, with the main differences in processes arising between live, dead, and surface/ground fuels. We also highlight the critical role of fuel phenology in assessing landscape fuel moisture variations in temperate environments. Understanding the mechanisms driving fuel moisture variability opens opportunities to develop locally robust fuel models for input into wildfire danger rating systems, adding versatility to wildfire danger assessments as a management tool.
