Summer Burning Research Articles

Higher absorption enhancement of black carbon in summer shown by 2-year measurements at the high-altitude mountain site of Pic du Midi Observatory in the French Pyrenees

Abstract. Black-carbon-containing particles strongly absorb light, causing substantial radiative heating of the atmosphere. The climate-relevant properties of black carbon (BC) are poorly constrained in high-altitude mountain regions, where many complex interactions between BC, radiation, clouds and snow have important climate implications. This study presents 2-year measurements of BC microphysical and optical properties at the Pic du Midi (PDM) research station, a high-altitude observatory located at 2877 m above sea level in the French Pyrenees. Among the long-term monitoring sites in the world, PDM is subject to limited influence from the planetary boundary layer (PBL), making it a suitable site for characterizing the BC in the free troposphere (FT). The classification of the dominant aerosol type using aerosol spectral optical properties indicates that BC is the predominant aerosol absorption component at PDM and controls the variation in single-scattering albedo (SSA) throughout the 2 years. Single-particle soot photometer (SP2) measurements of refractory BC (rBC) show a mean mass concentration (MrBC) of 35 ng m−3 and a relatively constant rBC core mass-equivalent diameter of about 180 nm, which are typical values for remote mountain sites. Combining the MrBC with in situ absorption measurements, a rBC mass absorption cross-section (MACrBC) of 9.2 ± 3.7 m2 g−1 at λ=880 nm has been obtained, which corresponds to an absorption enhancement (Eabs) of ∼2.2 compared to that of bare rBC particles with equal rBC core size distribution. A significant reduction in the ΔMrBC/ΔCO ratio when precipitation occurred along the air mass transport suggests wet removal of rBC. However we found that the wet removal process did not affect the rBC size, resulting in unchanged Eabs. We observed a large seasonal contrast in rBC properties with higher MrBC and Eabs in summer than in winter. In winter a high diurnal variability in MrBC (Eabs) with higher (lower) values in the middle of the day was linked to the injection of rBC originating from the PBL. On the contrary, in summer, MrBC showed no diurnal variation despite more frequent PBL conditions, implying that MrBC fluctuations are rather dominated by regional and long-range transport in the FT. Combining the ΔMrBC/ΔCO ratio with air mass transport analysis, we observed additional sources from biomass burning in summer leading to an increase in MrBC and Eabs. The diurnal pattern of Eabs in summer was opposite to that observed in winter with maximum values of ∼2.9 observed at midday. We suggest that this daily variation may result from a photochemical process driving the rBC mixing state rather than a change in BC emission sources. Such direct 2-year observations of BC properties provide quantitative constraints for both regional and global climate models and have the potential to close the gap between model-predicted and observed effects of BC on the regional radiation budget and climate. The results demonstrate the complex influence of BC emission sources, transport pathways, atmospheric dynamics and chemical reactivity in driving the light absorption of BC.

Prescribed Fire Case Studies From Wyoming, USA: Diverse Applications and Common Themes at the Great Plains-Rocky Mountains Interface

Prescribed fire is an important management tool for rangelands and forests in North America and globally. However, the application of prescribed fire is a complex endeavor that involves significant planning, partnerships, and risk. Recent evidence suggests that not enough prescribed fire is being applied to reduce wildfires, in part, because risk and bureaucracy continue to hinder application. While common in the eastern and central Great Plains, prescribed fire is less common in the western United States. Therefore, we summarized 11 prescribed fire projects in Wyoming, USA (or immediately adjacent to in one case) across five U.S. Environmental Protection Agency Ecoregions (High Plains, Northwestern Great Plains, Wyoming Basin, Southern Rockies, and Middle Rockies)—a state where the prairies converge with the western mountains. Fires were conducted from 2014 to 2022 and ranged in size from <1 acre to 3,000 acres (a total of 8,795 acres). Fires occurred on a variety of land ownerships including private ranch, university, state trust, Army, Bureau of Land Management, Forest Service, Bureau of Reclamation, and U.S. Department of Agriculture. Crew sizes ranged from 1 to 40 people. Approximately half of the burns were in the spring, a third were in the fall, and two were in the winter; no summer burns were reported. Duration of planning ranged from a few months to 5 years. Drip torches were the most common ignition device used; however, we noted the use of propane torches, terratorches, helitorches, and drones for lighting fires. Weather prescriptions varied across fires with some choosing low humidity to make up for low fuel loads and others choosing moderate humidity to minimize risk. A wide variety of plant communities, purposes, and applications were noted. Weather prescriptions particularly in the spring were consistently challenging and the importance of partnerships with neighbors and other agencies for planning and implementation was noted frequently. Across these unique prescribed fire case studies, we have noted commonalities that can communicate important practicalities of applying fire across complex land types and jurisdictions. Sharing such information is important in a state with the least population density in the country to enhance the professional application of prescribed fire across a diversity of situations.

A Global Perspective of the Functional Trait Responses of Graminoids to the Seasonality of Fire

In fire-prone ecosystems, plant resilience to recurrent fires depends on certain fire-adaptive traits. However, how key functional and reproductive traits of graminoids respond to varying burning seasons is poorly understood. This meta-analysis, therefore, unpacks global perspectives on how resprouting, growth, reproductive, and productivity traits of graminoids (grasses and sedges) respond to different burning seasons. We recorded 569 observations from 80 experimental studies comparing graminoid plant trait responses in unburned vs. burned treatments over different seasons of burn. Weighted log response ratios and 95% confidence intervals (95%CI) were analyzed for each plant trait using random effects models and compared across burning seasons. Summer (0.35 (95%CI = 0.25 to 0.46)) and autumn burns (0.24 (95%CI = 0.16 to 0.31)) increased above-ground biomass m−2, while biomass plant−1 was increased only by spring burns (0.27 (95%CI = 0.22 to 0.32)). Bud production plant−1 and tiller−1 were reduced significantly by fire, especially spring, summer, and autumn burns. The shoot height (0.29 (95%CI = 0.17 to 0.41)), leaf length (0.15 (95%CI = 0.11 to 0.20)), and specific leaf area (0.08 (95%CI = 0.06 to 0.09)) increased only under summer burns, while flowering was enhanced by spring (0.19 (95%CI = 0.00 to 0.38)) and autumn burns [0.34 (95%CI = 0.02 to 0.66)]. However, seed production m−2 was reduced by spring and summer burns and the opposite was true for seed production plant−1. Overall, herbaceous plant trait responses to fire varied by the season of burn, disagreeing with the general principle that early spring burning is the best practice. We suggest that a decision on the season of burn should be informed by the objective of burning.

580 Burn Camp in the Midst of the COVID-19 Pandemic

Abstract Introduction Previous literature has shown that pediatric burn camps provide numerous benefits to childhood burn survivors. Unfortunately, the COVID-19 pandemic resulted in the inability to host camp for fear of viral transmission to burn survivors and camp personnel alike. A comprehensive burn center, with assistance from the firefighter community, hosted its first burn camp since the onset of the COVID pandemic in August of 2022. A camp staff of 54 volunteers modified the previous camp processes to ensure camp was safe, fun and accessible to 20 pediatric burn survivors. Methods This is an academic short report that reviews the process changes necessary to host a safe pediatric burn camp in the midst of the COVID pandemic. All attendees and staff were required to show a negative PCR test result 48 hours prior to arrival at camp. COVID vaccination was encouraged in all participants, however, staff and patients were not required to be vaccinated. Daily symptom tracking was implemented immediately upon arrival to camp. All participants were assigned a thermometer, and daily temperatures and symptom monitoring was performed by the camp director. Masks were mandated when indoors or within close proximity or group activities. There was a quarantine plan in place in the case a camper or staff member became symptomatic, or tested positive for COVID. Lastly, the number of people per cabin decreased from 12 to 8. Results In the early planning phase of camp, it was discovered that some of the participants and staff were unable to obtain a PCR test prior to camp. Therefore, onsite testing was implemented to allow testing as the participants and camp staff arrived to camp. The onsite testing facility was available for the entirety of camp in the case anyone became symptomatic. Implementation of additional camp processes resulted in a successful and safe camp. There were no reported cases of COVID during or after camp. Conclusions As the Public Health Emergency from COVID-19 continues, group activities, such as summer burn camps, with medically vulnerable populations must be altered to protect all stakeholders. We described the steps taken by one burn-center-run camp that enabled children and firefighter volunteers to participate in the full burn camp experience. Plans for the 2023 burn camp are already in process, and the processes implemented in 2022 will be implemented in all upcoming camps to ensure the children and staff are safe from the transmission of COVID. Applicability of Research to Practice N/A

Patch Burning Improves Nutritional Quality of Two Gulf Coast Grasses—And Winter Burning Is Better than Summer Burning

Gulf cordgrass (Spartina spartinae [Trin.] Merr. ex Hitchc.) and seacoast bluestem (Schizachyrium scoparium [Michx.] Nash var. littorale [Nash] Gould) are dominant native warm season grasses in the Texas Coastal Prairies and Marshes ecoregion. Mature Gulf cordgrass nutritive value is considered poor for grazing animals, while seacoast bluestem nutritive value is considered fair to good in spring and early summer. We compared season of burn effects on crude protein (CP) and neutral detergent fiber (NDF) of these grasses. Our study employed four patches (200–305 ha) burned in a patch-burn grazing system (two winter, two summer 2016). Forage samples were collected before burning and every 3 d for 40 d after burning, then weekly for 50 d. Regardless of season of burning, CP was adequate for maintaining a lactating beef cow 90 d post-burning. Although peak CP in Gulf cordgrass following burning did not differ between seasons, CP increased more quickly following winter burning, when it rose abruptly for ~6.4 d and then increased more slowly to its peak at ~30 d post burn, after which it declined. After summer burning, CP of Gulf cordgrass did not increase significantly, and then declined after reaching its peak at ~29 d post burn. Gulf cordgrass NDF declined more rapidly following summer burning than winter burning but remained low for a longer period after winter burning. In seacoast bluestem, CP increased following winter burning, peaking at ~11 d after burning, but there was little change following summer burning, which did not peak until 31 d post burn. NDF of seacoast bluestem declined similarly in both seasons. This study indicates that prescribed fire during winter is more beneficial for improving the nutritive value of Gulf cordgrass and seacoast bluestem than summer burning.

Life History Traits of Exotic and Native Species Determine Grassland Management Outcomes Following Prescribed Fire

<h3>ABSTRACT</h3> Disturbance regimes, including the historical timing of disturbance, are important components of natural ecosystems and greatly influence ecosystem structure and functioning. Consequently, disturbance timing can be an important component of biodiversity management. We evaluated the effect of prescribed fires ignited during the warm and cool seasons (summer and spring, respectively) on the plant community of a calcareous grassland in northern Mississippi (USA). We found that fire season influenced plant community composition by having differential impacts on species with different life history traits. Differences among species were primarily driven by the dichotomy between cool-season (C₃) and warm-season (C₄) plants, independent of species native status. Spring burns reduced the cover of cool-season C₃ graminoids, but had the opposite effect on C₄ graminoids, which likely benefited from increases in resource availability due to the reduction of C₃ species. However, summer burns decreased the abundance of C₄ graminoids, as summer burns were ignited during the active growing and reproductive period for the C₄ species. We found the same patterns for the number of inflorescences of the most abundant C₃ and C₄ graminoids. Summer burns also increased overall species diversity and the abundance of native C₃ graminoids, forbs, and vines, resulting in significant differences in plant community composition between spring- and summer-burned areas. Programs that aim to restore native grassland communities in the short-term using prescribed fire should consider the life history traits of target plants (including invasive species) to determine the best time for prescribed fire implementation.

Diversity and Resilience of Seed-Removing Ant Species in Longleaf Sandhill to Frequent Fire

Prescribed fire is used globally as a habitat restoration tool and is widely accepted as supporting biotic diversity. However, in fire-prone ecosystems, research has sometimes documented post-fire reduction in ant diversity and accompanying changes in seed removal behavior. This is concerning because ants provide important ecosystem services that can aid in restoration efforts, including seed dispersal. In this study, we examined the immediate impacts of fire in the well-studied ant community of longleaf pine forests (LLP) in the SE USA. We surveyed seed-removing ant species in a LLP sandhill ecosystem to investigate the effects of prescribed fire and coarse woody debris (CWD), a nesting and foraging resource, on ant community composition and ant–seed interactions. Seed-removing ants comprised a significant portion of detected ant species (20 of 45); eight of these species are documented removing seeds for the first time. Following an experimentally applied low-intensity summer burn, decreases in seed remover detection were observed, along with reductions in the number of seeds removed, across both burned and unburned areas; neither prescribed fire nor proximity to CWD significantly influenced these factors. Together, these results show that seed-removing ant species constitute a substantial proportion of the LLP sandhill ant community and are relatively robust to habitat changes mediated by low-intensity prescribed burning during the growing season. Considering ant community resiliency to fire, we can infer that using prescribed fire aligns with the goals of restoring and maintaining biotic diversity in this fire-prone ecosystem.

Prescribed fire reduces insect infestation in Karuk and Yurok acorn resource systems

Prescribed fire is used extensively as a management tool in fire-adapted landscapes of the American West to maintain ecosystem structure and function while reducing wildfire risk. Seasonally specific prescribed fire is used by many Indigenous groups to increase the quality and quantity of cultural resources and promote desired patterns of habitat diversity. Traditionally, the Karuk and Yurok Tribes of California applied fire in tanoak (Notholithocarpus densiflorus, Fagaceae) acorn gathering areas during the fall to reduce infestation in acorns by larvae of the filbertworm (Cydia latiferreana, Tortricidae) and filbert weevil (Curculio occidentalis, Curculionidae). It has become increasingly difficult to select culturally appropriate times in which to apply fire as a resource management tool due to changing environmental conditions and associated political considerations. To assess the effect of non-traditional management on tribal acorn resource systems, we investigated the effects of early summer burning on rates of larval infestation in tanoak acorns. We also studied how competing frugivores affected the availability of edible acorns to human consumers. We found that non-traditional early summer prescribed fire significantly reduced rates of larval infestation during the burn year (36.7%) but no difference between treatments was detected one year-post fire. Selective vertebrate frugivory significantly reduced the density of edible acorns by 39%. Our results highlight the importance of seasonally-specific prescribed fire in managing Karuk and Yurok resource systems and supporting tribal eco-cultural revitalization.

Spring fires in Russia: results from participatory burned area mapping with Sentinel-2 imagery

Human-induced fires play a crucial role in transforming landscapes and contributing to greenhouse gas emissions. Russia is a country where human-induced fires are widespread and form distinctive spring and summer burning cycles. However, spring fires are not well documented and it is unclear which land-cover types are associated with the spread of spring fires. Using Sentinel-2 optical satellite imagery, a wall-to-wall spring burned area data set for 1 January to 15 May 2020 was created for Russia (excluding the Arctic) using a participatory crowdsourcing digitizing approach on an online platform developed specifically for this application. The 2020 spring fire product had a producer accuracy of 85% and user accuracy of 92%. Approximately 13.38 million ha, comprising 1.8% of the study area, were mapped as burned, with the majority of the 2020 spring burned areas in Siberia. Our spring-fire product revealed five times more burned area estimates compared to the burned area estimates from the moderate resolution imaging spectroradiometer (MODIS) MCD64 product. We also found high variability of burned area per active fire pixel across regions of Russia, when compared to MODIS and visible infrared imaging radiometer suite active fire data. Spring fires started to increase from the end of February and reached their maximum by the end of March through the middle of April. Spring fires were associated with arable lands and grasslands as land-cover types, except Siberia, where spring fires were most common in deciduous and needle-leaved forests, followed by arable lands. While spring fires were associated with croplands and grasslands, an estimate for Central Russia showed approximately 75% of spring fires occurred on abandoned agricultural lands. Our study demonstrated the suitability of optical Sentinel-2 imagery for spring fire mapping and the great utility of a participatory mapping approach for fast and accurate mapping as well as engagement of the community.

Longleaf pine seedling growth and survival: Effects of season and intensity of simulated prescribed burning

Restoration of longleaf pine (Pinus palustris Mill.) forests is an important land management goal in the southern United States. To achieve this goal, longleaf pine is increasingly being planted across its range. Fire is an important ecological factor that has historically shaped and sustained longleaf pine forests. However, we have limited information on how fire impacts longleaf pine seedlings in newly established plantations. We conducted this study in Northwest Florida to examine the effects of fire intensity (low intensity ((LI), ∼100 °C), medium intensity ((MI), ∼300 °C), high intensity ((HI), ∼500 °C), and an untreated control) on survival, growth (root collar diameter (RCD) and height), physiological processes (net assimilation (A), stomatal conductance (gsw), and intrinsic water use efficiency (iWUE)), and biomass allocation of longleaf pine seedlings over a period of six months after fire was applied in four seasons (summer, fall, winter, spring). Within a given season, the survival of seedlings did not significantly differ at different fire intensities, except in the summer (α = 0.05). For the summer application, survival was lower (18%) in the HI treatment compared to the MI (98%), LI (93%), and control (93%) (p = 0.003). RCD growth was significantly affected by fire intensity treatment only for the summer application. For the summer application, RCD growth six months after treatment (MAT) was highest (7.3 mm) in the control compared to the LI (2.7 mm), MI (2.7 mm), and HI (2.0 mm) (p = 0.021). The height growth of seedlings did not significantly differ at different fire intensities, though their values were greater at 6 months compared to 3 months. The effect of fire temperature on percent biomass allocation was only significant for the fall foliage (p = 0.004). Neither root, stem, nor total shoot percent biomass significantly differed for any other season. Largely, A, gsw, and iWUE were not significantly affected by fire temperature. iWUE did differ for MAT (p = 0.003), however, no pattern could be discerned. Overall, our observations suggest that longleaf pine seedlings are highly resistant and resilient to fire intensity in different seasons, with some vulnerability to high-intensity summer fires which can adversely affect their survival and growth. Summer burning is still a viable option for seedling survival provided conditions on the ground favor low/medium intensity fire.

Season of prescribed fire determines grassland restoration outcomes after fire exclusion and overgrazing

AbstractFire exclusion and mismanaged grazing are globally important drivers of environmental change in mesic C4 grasslands and savannas. Although interest is growing in prescribed fire for grassland restoration, we have little long‐term experimental evidence of the influence of burn season on the recovery of herbaceous plant communities, encroachment by trees and shrubs, and invasion by exotic grasses. We conducted a prescribed fire experiment (seven burns between 2001 and 2019) in historically fire‐excluded and overgrazed grasslands of central Texas. Sites were assigned to one of four experimental treatments: summer burns (warm season, lightning season), fall burns (early cool season), winter burns (late cool season), or unburned (fire exclusion). To assess restoration outcomes of the experiment, in 2019, we identified old‐growth grasslands to serve as reference sites. Herbaceous‐layer plant communities in all experimental sites were compositionally and functionally distinct from old‐growth grasslands, with little recovery of perennial C4 grasses and long‐lived forbs. Unburned sites were characterized by several species of tree, shrub, and vine; summer sites were characterized by certain C3 grasses and forbs; and fall and winter sites were intermediate in composition to the unburned and summer sites. Despite compositional differences, all treatments had comparable plot‐level plant species richness (range 89–95 species/1000 m2). At the local‐scale, summer sites (23 species/m2) and old‐growth grasslands (20 species/m2) supported greater richness than unburned sites (15 species/m2), but did not differ significantly from fall or winter sites. Among fire treatments, summer and winter burns most consistently produced the vegetation structure of old‐growth grasslands (e.g., mean woody canopy cover of 9%). But whereas winter burns promoted the invasive grass Bothriochloa ischaemum by maintaining areas with low canopy cover, summer burns simultaneously limited woody encroachment and controlled B. ischaemum invasion. Our results support a growing body of literature that shows that prescribed fire alone, without the introduction of plant propagules, cannot necessarily restore old‐growth grassland community composition. Nonetheless, this long‐term experiment demonstrates that prescribed burns implemented in the summer can benefit restoration by preventing woody encroachment while also controlling an invasive grass. We suggest that fire season deserves greater attention in grassland restoration planning and ecological research.

Seasonal Cycle of Isotope‐Based Source Apportionment of Elemental Carbon in Airborne Particulate Matter and Snow at Alert, Canada

AbstractElemental carbon (EC) is a major light‐absorbing component of atmospheric aerosol particles. Here, we report the seasonal variation in EC concentrations and sources in airborne particulate matter (PM) and snow at Alert, Canada, from March 2014 to June 2015. We isolated the EC fraction with the EnCan‐Total‐900 (ECT9) protocol and quantified its stable carbon isotope composition (δ13C) and radiocarbon content (∆14C) to apportion EC into contributions from fossil fuel combustion and biomass burning (wildfires and biofuel combustion). Ten‐day backward trajectories show EC aerosols reaching Alert by traveling over the Arctic Ocean from the Russian Arctic during winter and from North America (&gt;40°N) during summer. EC concentrations range from 1.8–135.3 ng C m−3 air (1.9–41.2% of total carbon [TC], n = 48), with lowest values in summer (1.8–44.5 ng C m−3 air, n = 9). EC in PM (Δ14C = ‐532 ± 114‰ [ave. ± SD, n = 20]) and snow (−257 ± 131‰, n = 7) was depleted in 14C relative to current ambient CO2 year‐round. EC in PM mainly originated from liquid and solid fossil fuels from fall to spring (47–70% fossil), but had greater contributions from biomass burning in summer (48–80% modern carbon). EC in snow was mostly from biomass burning (53–88%). Our data show that biomass burning EC is preferentially incorporated into snow because of scavenging processes within the Arctic atmosphere or long‐range transport in storm systems. This work provides a comprehensive view of EC particles captured in the High Arctic through wet and dry deposition and demonstrates that surface stations monitoring EC in PM might underestimate biomass burning and transport.

How stable is the tuft structure of a mesic Drakensberg grassland under various burning regimes?

Management options to maintain the stability of Drakensberg grasslands need to incorporate their dynamic nature in response to fire. This study addressed the lack of information on the spatial and temporal changes of these grasslands at a small (tuft) scale. The basal area of every tuft in three 0.25 m2 quadrats per replicate (3) of four burning treatments was mapped over two years in a long-term burning trial using a pantograph. The extent of change in size and shape of tufts indicated the dynamic nature of these grasslands from year to year. Basal cover of Themeda triandra was high in the annual winter (62.5%) and biennial spring (50.5%) burns, lower in the five-year burn (36.1%) and low in the biennial summer burn (11.5%). The bare area in the biennial summer burn increased by 5.6%, remained the same in the annual winter, and decreased in the biennial spring (6.1%) and five-year (7.8%) burns. The disappearance of Stiburus alopecuroides from the summer burn and increase in basal cover of Tristachya leucothrix indicates a directional change in composition that is likely to be irreversible. The biennial spring burn, where the three dominant species were in a state of equilibrium, is recommended for stability.

Frequent burning maintained a stable grassland over four decades in the Drakensberg, South Africa

The mesic montane grasslands of the uKhahlamba-Drakensberg, which produce cured flammable fuel, have evolved under and are sustained by recurrent fires. The Brotherton burning trial (12 replicated treatments) was established at Cathedral Peak (1 890 m asl) in 1980 to understand how burn season and frequency control the composition and diversity of the montane catchment grassland. Multivariate methods were used to examine the long-term (almost 40 years). compositional stability under different burning regimes. The species composition deviated steadily and markedly from the initial state (Bray–Curtis dissimilarity) by 43.4 ± 9.32% with quinquennial burning (alternating autumn/spring) and by 64.6 ± 2.24% with attempted fire exclusion (three unplanned burns). Composition was rapidly transformed (by 53.1 ± 4.6%) by biennial summer burning (discontinued in 1991). Dominance shifted from Themeda triandra to other grasses (Stiburus alopecuroides, Tristachya leucothrix, Harpochloa falx) with biennial summer and infrequent burning. In contrast, regular dormant season burning annually or biennially (in autumn, winter, or spring) maintained a stable grassland close to the original composition (mean deviation 23.08%). Burning homogenised the composition, overriding the initial extant small-scale spatial variation. Results support the current practice to burn biennially in the dormant season to maintain stable grassland in the Drakensberg catchments.

Fire Behaviour Observation in Shrublands in Nova Scotia, Canada and Assessment of Aids to Operational Fire Behaviour Prediction

Parks Canada, in collaboration with Nova Scotia Lands and Forests and Natural Resources Canada, documented shrub fire behaviour in multiple plots burned over two periods: a spring period in June 2014 and a summer period in July 2017. The study area, located within Cape Breton Highlands National Park, comprised fifteen burn units (20 m by 20 m in size). Each unit was ignited by line ignition and burned under a wide range of conditions. Pre-burn fuel characteristics were measured across the site and used to estimate pre-fire fuel load and post-fire fuel consumption. This fuel complex was similar to many flammable shrub types around the world, results show that this shrub fuel type had high elevated fuel loads (3.17 ± 0.84 kg/m2) composed of exposed live and dead stunted black spruce as well as ericaceous shrubs, mainly Kalmia angustifolia (evergreen) and Rhodora canadensis (deciduous). Data show that the dead moisture content in this fuel complex is systematically lower than expected from the traditional relationship between FFMC and moisture content in the Canadian Fire Weather Index System but was statistically correlated with Equilibrium Moisture Content. A significant inverse relationship between bulk density and fire rate of spread was observed as well as a clear seasonal effect between the spring burns and the summer burns, which is likely attributable to the increase in bulk density in the summer. Unlike most shrub research, wind and dead moisture content did not have a statistically significant association with fire spread rates. However, we believe this to be due to noise in wind data and small dataset. Rate of spread as high as 14 m/min and flame lengths over 4 m were recorded under Initial Spread Index values of 6.4 and relative humidity of 54%. A comparison with a number of well-known shrubland spread rate prediction models was made. An aid to operational fire prediction behaviour is proposed, using a fuel type from the Canadian Fire Prediction System (O-1b) and a modified estimate of fuel moisture of the elevated fuel in the fuel complex.

Personal

Personal James Davis (bio) Give me a faggot, fashion mags evenly fannedacross his coffee table, who serves drinksin snifters, tumblers, flutes, and says behind, not to euphemize ass, but to signal his nearing,e.g. on a bike. Give me a man like an otter,svelte swimmer with claws to tear flesh from pink varicellate shells, fur matted with saltwater.I want a mouth wet with philosophy,lips slick with persuasion, a beard like my father’s. I want him to cook Sunday brunches for me:eggs Benedict, Bloody Marys, metaphorsfor the morning, for the health of our country. Let us zinc our noses and tube down a riveron psilocybin. Let the summer burn us blondright down to the pubes. Let desire italicize our somberest sentiments: there’s sanddown my swimsuit. And when the green dayages into night, give a patch of damp ground under the viscid flow of the Milky Way—some plot of earth that does not care how we have sinned—and we will be more than cocksucker implies. [End Page 108] James Davis James Davis’s poems have appeared in 32 Poems, Best New Poets, Copper Nickel, Hobart, and elsewhere. He received a residency from The Mastheads and an MFA from the University of Florida. Dorothea Lasky selected him as a finalist for Inverted Syntax’s inaugural Sublingua Prize for Poetry. He lives in Denver. Copyright © 2019 University of Wisconsin Board of Regents

Characteristics of atmospheric volatile organic compounds (VOCs) at a mountainous forest site and two urban sites in the southeast of China

Volatile organic compounds (VOCs) are important trace gases in the atmosphere, affecting air quality (e.g. ozone and secondary organic aerosol formation) and human health. To understand the emission, transport and chemistry of VOCs in the southeast of China (Fujian Province), a campaign was conducted in summer and winter of 2016 at three contrasting sites in close proximity. One measurement site (Mt. Wuyi) is a mountainous forest site (1139 m a.s.l.) located in a natural reserve, while the other two sites (Fuzhou, Xiamen) are coastal urban sites with high population and vehicle density. Comparison of VOCs at these three sites provides a valuable perspective on regional air pollution and transport. Many of the measured alkanes, alkenes and aromatics exhibited clear seasonal and diurnal patterns, driven by variations of hydroxyl (OH) radicals, which is the predominant oxidant of VOCs in the atmosphere. By examining tracer-tracer correlations for VOCs, variability-lifetime analysis and 36 h backward trajectories, strong emissions from vehicular exhaust, liquefied petroleum gas (LPG) and solvent usage were identified as key sources in Fuzhou and Xiamen, whereas at Mt. Wuyi the main emission sources were local emissions (e.g. biomass burning) in summer and long-range transport in winter. The results indicate that natural sites could be impacted strongly by surrounding urbanization. Isoprene and propylene in summer and propylene in winter contributed the most to ozone formation at the three sites. The data in this study provides a useful benchmark for future research on air quality monitoring and emission sources in the region.

Effects of 34 Years of Experimentally Manipulated Burn Seasons and Frequencies on Prairie Plant Composition

Historically, tallgrass prairie burns occurred at many seasons and frequencies. Currently, tallgrass prescribed burns often occur annually in the spring, usually for cattle forage production. Altering burning season and frequency is known to affect plant composition and biomass production, but researchers are still uncertain how burning season and frequency interact. We present the long-term effects of a factorial combination of different burn seasons (spring, summer, autumn, or variable [rotated through seasons]) and frequencies (annual or quadrennial) on the plant composition and biomass production of an ungrazed, restored tallgrass prairie in eastern Nebraska, United States. The experimental plots were established in 1978 and visually surveyed for baseline data in 1979 and 1981. Experimental burn treatments were begun in 1982. Plots were visually surveyed until 2011 with the following results: 1) annual spring and summer burns increased C4 graminoid abundance; 2) annual autumn burns increased forb abundance; 3) burn season had little effect on plant composition for quadrennial burns; and 4) variable season burns generally led to plant composition that was intermediate between annual spring/summer and annual autumn burns. We also clipped biomass to estimate aboveground annual net primary production (ANPP) in 2015, a year in which both annual and quadrennial burns occurred. Total ANPP did not differ significantly between burn frequencies nor between spring and autumn burns (772 g m−2 average) but was lower in summer burns (541 g m−2). ANPP results were similar to visual surveys, with significantly higher C4 graminoid ANPP in spring than autumn burns and significantly lower forb and C3 graminoid ANPP in spring than autumn burns. Overall, these results suggest autumn burns can increase forb and C3 graminoid abundance, without strongly affecting total ANPP relative to spring burns. Future studies should compare plant and livestock production between spring and autumn burns in grazed fields.

Analysis of Seasonal Variations in Chemical Characteristics and Sources of PM2.5 During Summer and Winter in Ji'nan City

To investigate seasonal variations in the chemical compositions of aerosols in Ji'nan City, PM2.5 samples were collected during summer and winter in 2015. The sampling period lasted one month during each season. PM2.5 samples were analyzed for the composition, concentration, and sources of water-soluble inorganic ions, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC). Results showed that mass concentrations of PM2.5 in winter were about twice those in summer, and concentration levels varied between fine and excellent. The concentrations of total water-soluble inorganic ions were also higher in winter than in summer, with SO42-, NO3-, and NH4+ being the dominant species and well correlated with each other. NH4+ in PM2.5 mostly existed in the form of (NH4)2SO4 and NH4NO3 in both summer and winter. There was strong secondary oxidation of SO2 and NO2. The sulfate oxidizing rate (SOR) was higher in summer than in winter, while the nitrate oxidizing rate (NOR) showed the opposite trend. The ratio of anions to cations in both summer and winter were less than one, suggesting that PM2.5 were slightly alkaline. The ISORROPIA-Ⅱ mode showed that acidity in winter was stronger than in summer. Concentations of OC and EC were both higher in winter than in summer. The ratios of OC to EC and WSOC to OC and estimated concentrations of secondary organic carbon (SOC) showed that secondary pollution was more serious in winter than in summer. Principal component analysis(PCA)indicated that the major sources contributing to inorganic ions were secondary oxidation and biomass burning in summer, and coal combustion and secondary pollutants formed by chemical oxidation of precursors emitted from coal combustion in winter.

Seasonal cycles of secondary organic aerosol tracers in rural Guangzhou, Southern China: The importance of atmospheric oxidants

Thirteen secondary organic aerosol (SOA) tracers of isoprene (SOAI), monoterpenes (SOAM), sesquiterpenes (SOAS) and aromatics (SOAA) in fine particulate matter (PM2.5) were measured at a Pearl River Delta (PRD) regional site for one year. The characteristics including their seasonal cycles and the factors influencing their formation in this region were studied. The seasonal patterns of SOAI, SOAM and SOAS tracers were characterized over three enhancement periods in summer (I), autumn (II) and winter (III), while the elevations of SOAA tracer (i.e., 2,3-dihydroxy-4-oxopentanoic acid, DHOPA) were observed in Periods II and III. We found that SOA formed from different biogenic precursors could be driven by several factors during a one-year seasonal cycle. Isoprene emission controlled SOAI formation throughout the year, while monoterpene and sesquiterpene emissions facilitated SOAM and SOAS formation in summer rather than in other seasons. The influence of atmospheric oxidants (Ox) was found to be an important factor of the formation of SOAM tracers during the enhancement periods in autumn and winter. The formation of SOAS tracer was influenced by the precursor emissions in summer, atmospheric oxidation in autumn and probably also by biomass burning in both summer and winter. In this study, we could not see the strong contribution of biomass burning to DHOPA as suggested by previous studies in this region. Instead, good correlations between observed DHOPA and Ox as well as [NO2][O3] suggest the involvement of both ozone (O3) and nitrogen dioxide (NO2) in the formation of DHOPA. The results showed that regional air pollution may not only increase the emissions of aromatic precursors but also can greatly promote the formation processes.