Low-intensity Burning Research Articles

Smoke Emissions and Buoyant Plumes above Prescribed Burns in the Pinelands National Reserve, New Jersey

Prescribed burning is a cost-effective method for reducing hazardous fuels in pine- and oak-dominated forests, but smoke emissions contribute to atmospheric pollutant loads, and the potential exists for exceeding federal air quality standards designed to protect human health. Fire behavior during prescribed burns influences above-canopy sensible heat flux and turbulent kinetic energy (TKE) in buoyant plumes, affecting the lofting and dispersion of smoke. A more comprehensive understanding of how enhanced energy fluxes and turbulence are related during the passage of flame fronts could improve efforts to mitigate the impacts of smoke emissions. Pre- and post-fire fuel loading measurements taken during 48 operational prescribed burns were used to estimate the combustion completeness factors (CC) and emissions of fine particulates (PM2.5), carbon dioxide (CO2), and carbon monoxide (CO) in pine- and oak-dominated stands in the Pinelands National Reserve of southern New Jersey. During 11 of the prescribed burns, sensible heat flux and turbulence statistics were measured by tower networks above the forest canopy. Fire behavior when fire fronts passed the towers ranged from low-intensity backing fires to high-intensity head fires with some crown torching. Consumption of forest-floor and understory vegetation was a near-linear function of pre-burn loading, and combustion of fine litter on the forest floor was the predominant source of emissions, even during head fires with some crowning activity. Tower measurements indicated that above-canopy sensible heat flux and TKE calculated at 1 min intervals during the passage of fire fronts were strongly influenced by fire behavior. Low-intensity backing fires, regardless of forest type, had weaker enhancement of above-canopy air temperature, vertical and horizontal wind velocities, sensible heat fluxes, and TKE compared to higher-intensity head and flanking fires. Sensible heat flux and TKE in buoyant plumes were unrelated during low-intensity burns but more tightly coupled during higher-intensity burns. The weak coupling during low-intensity backing fires resulted in reduced rates of smoke transport and dispersion, and likely in more prolonged periods of elevated surface concentrations. This research facilitates more accurate estimates of PM2.5, CO, and CO2 emissions from prescribed burns in the Pinelands, and it provides a better understanding of the relationships among fire behavior, sensible heat fluxes and turbulence, and smoke dispersion in pine- and oak-dominated forests.

The legacy of millennial-scale land-use practices on landscape composition, diversity and slope erosion in the subalpine areas of Eastern Carpathians, Romania

We conducted multi-proxy analyses in two subalpine lakes, Lake Gropile, in the Rodna Mountains and Lake Vinderelu in the Maramureș Mountains, the Eastern Carpathians, Romania, to investigate the effect of different land-use practices on landscape composition, diversity and slope erosion. In the case of Lake Gropile, results evidenced a more extended tree and shrub cover and high fire activity between 6400 and 2800 cal yr BP, accompanied by reduced soil erosion, which appeared more strongly regulated by climatic conditions. Anthropogenic impact became evident 2800 years ago, when landscape openness, pasturing, and disturbance of soil cover increased and intensified over the last four centuries. In the case of Lake Vinderelu, intensified burning was followed by grazing around 1200–1100 cal yr BP and continued throughout the last millennium. Results also highlight the site-specific effects of land-use on vegetation composition and landscape diversity. For Lake Vinderelu, a combined effect of local burning and grazing in removing shrub cover appear to be the main drivers of changes in landscape diversity and structure. At Lake Gropile, fire was more connected to shrub cover changes while grazing to herbaceous cover diversity. Moderate to low grazing appeared to benefit both subalpine ecosystems, creating rich grassland-shrub mosaic communities, while overgrazing reduced landscape diversity and exacerbated erosion. Our findings document the millennial-scale legacy of land-use practices on the subalpine landscapes in this region. We propose that these semi-natural ecosystems hold important ecological and cultural value, and recommend their maintenance through controlled, low intensity pasturing and/or burning.

Short-Term Effects of Prescribed Burn Seasonality on the Understory in a Pinus nigra Arnold subsp. salzmannii (Dunal) Franco Mediterranean Forest

Worsening climate change and increasing temperatures generate more sever and extended wildfires, raising concerns about ecosystem services. Prescribed burns (PB) are used to reduce forest fuel loads. Improving knowledge regarding the vegetation response after PB is essential for generating common points for monitoring ecological burning effects and generating a protocol or practice guide. We compared the PB seasonality of low-intensity (spring, summer, and autumn) and unburned areas in a total of 12 plots in Pinus nigra Arnold ssp. salzmannii Mediterranean forest. Our vegetation analysis was short term (one year after each PB). We analyzed vegetation coverage, α-diversity (Pielou, Simpson, and Shannon’s index), life forms, and fire-adapted traits using the Canfield transect method, followed by statistical analyses such as non-metric multidimensional scaling (NMDS) and two-way ANOVA. α-diversity was significantly decreased (>55% of dissimilarity) in the burned plots during each season, with the lowest values after summer PB (69% of dissimilarity) when comparing the burned and unburned plots. There was a significant increase in hemicryptophytes (15−20%) and geophyte coverage (from 6% to 14%, or from 4% to 8% in certain cases) in the burned plots after PB seasonality; however, the phanerophytes were reduced (from 13% to 5%). Resprouters were more dominant after PB (an increase of 15–20%), which indicates that resprouters have a faster recovery and generate a fuel load quickly for highly flammable species such as Bromus after low-intensity burning. This suggests that low-intensity prescribed burning may not be the best methodology for these resprouting species. This study helps to understand how burning in the early season can affect inflammable vegetation and the change in fuel that is available in semi-arid landscapes. This is key to achieving the basis for the development of a standardized system that allows for the efficient management of forest services in order to reduce wildfire risks. One objective of this line of research is to observe the effects of recurrent burning in different seasons on vegetation, as well as plant−soil interaction using the microbial and enzyme soil activity.

Short-term arthropod recovery in Eucalyptus plantations after harvesting is not affected by different residue management practices

To sustainably manage soils, we need to understand the impact of management practices on soil biota. A major disturbance in commercial tree plantations is the management of the woody residue that remains in situ after harvesting. We examine the impact of different harvest residue management practices on soil biota in a forestry landscape in KwaZulu-Natal, South Africa on nutrient-rich clay soils. We assess four different management practices and unmanaged grassland at three time periods: prior to implementation of residue management, directly after implementation, and six months after implementation. Management practices are 1) on-site retention of unburned harvest residue, 2) residue removal off site, 3) high-intensity burning and 4) low-intensity burning of residue. We examine the response of ant and springtail taxonomic and functional diversity, assemblage composition, and soil biological activity. We also assess whether soil biological activity at different soil depths differs among treatments. Across all sites, all biotic responses declined in the post-treatment, but recovery of the focal arthropods after six months was low regardless of the type of residue management practice. At each time period, ant and springtail taxonomic and functional diversity showed no difference among management practices. Soil biological activity showed minor differences between practices after implementation overall, and at different soil depths, and recovery was similar between residue management practices after six months. After six months, soil biological activity recovered to ∼ 50 % in all sites. Thus, in the short term, soil biota in this region are not differentially impacted by different residue management practices, despite major variations in conditions. We recommend further assessments in different soil types and over a longer period to assess the full impact of slash management on these functionally important soil arthropods.

Influence of burning and mechanical clearing on the provision of Gentiana lutea L. in the Iberian Peninsula

Overexploitation, land-use change, and climate warming are compromising the conservation of many plant species across the globe, as well as the benefits they provide to people. The yellow gentian (Gentiana lutea L.) is a hemicryptophyte used for pharmacological and food industries harvested in the mountain systems of Southern Europe, which may be subject of management measures. Here we identify the influence of two common management strategies, burning and clearing, on G. lutea populations, and provide insights on the role of burning on seed germination by analyzing the effect of thermal shocks from a populational approach. To achieve these goals, we selected areas affected by low intensity burning and mechanical clearing over the short term (1–2 years) and over the medium term (6–8 years) in the Cantabrian Mountains (NW Iberian Peninsula), where we sampled the number of basal rosettes, fertile stems and cover of G. lutea, and the total cover of woody species. Likewise, we collected seeds from three populations, which were used to quantify several seed traits and to analyze the germination dynamics after heat shocks alone and combined with a dormancy break treatment (gibberellic acid). Results showed decreases in G. lutea population variables immediately after burning and a full recovery over the medium term. On the contrary, clearing did not show effects over the short-term but largely increased all population variables over the medium term. Among other factors, management effects are mediated by their influence on woody species cover, which constrains G. lutea populational growth. Thermal shocks did not break the dormancy of G. lutea seeds, and thermal shocks combined with forced dormancy break revealed no clear effects of heating. Populational differences in the germinative response were detected, as heavier and less moist seeds require longer time to germinate. Based on our results, we propose mechanical clearing as a suitable management strategy to sustain G. lutea populations in NW Iberian Peninsula, but we recommend further analysis to extrapolate our advice to sites with distinct environmental conditions.

Time burnt away: The impact of heat-induced changes on skeletal age-at-death diagnostic features

This paper investigates the established notion that bone calcination has a major impact on age estimation while low-intensity burns have a mere negligible impact. Few systematic researches have been carried out so far about this topic so the true impact of heat-induced changes on diagnostic age features is mostly unknown.The agreement between pre-burning and post-burning observations of age features was investigated on 51 human skeletons (22 males and 29 females with ages-at-death ranging from 61 to 93 years old) subjected to experimental burns. These skeletons belong to the 21st Century Identified Skeletal Collection housed at the Laboratory of Forensic Anthropology of the Department of Life Sciences, University of Coimbra, Portugal. The Suchey-Brooks method based on the pubic symphysis and the method developed on the auricular surface by Buckberry and Chamberlain (2002) were scrutinized.The Suchey-Brooks method provided better agreement between pre- and post-burn observations than the method from Buckberry and Chamberlain (2002). However, it became clear that heat-induced changes affected both methods regardless of heat intensity since both calcined bones and bones burnt at lower intensities often showed less than perfect agreement. Therefore, this research demonstrates that the analysis of age-at-death can be impaired in burnt bones, even those not subjected to calcination, with clear impact for forensic and archaeological investigations.

Variability in pyrogenic carbon properties generated by different burning temperatures and peatland plant litters: implication for identifying fire intensity and fuel types

Pyrogenic carbon (PyC), generated by fire, acts as a stable carbon deposit in natural ecosystems and is widely used to reconstruct fire history. Fuel type and burning temperature are the two major factors that influence PyC properties and exert variable effects on soil carbon pools, especially for peatlands. However, whether analysis of PyC can identify these two factors remains unclear. To address this knowledge gap, we selected typical peatland plant litters of seven shrub and seven herb plants in the Great Khingan Mountains, China. The properties of PyC produced at 250°C (low-intensity burning) and 600°C (high-intensity burning) without oxygen were evaluated. The results showed that the effects of burning temperature and plant type on δ13C-PyC were not significant. The differences in the initial compositions of herbs and shrubs led to more aromatic and carboxylic compounds in shrub PyC than in herb PyC. A high burning temperature led to less labile components (e.g. aliphatic compounds and acids) and higher thermal stability of high-temperature PyC compared to that of low-temperature PyC. Our results also indicate that several typical PyC chemical composition indicators (e.g. Fourier-transform infrared spectroscopy 1515/1050 ratio and 1720/1050 ratio) can potentially identify PyC sources.

The Ethnobotany and Ethnomedicine of Zanthoxylum acanthopodium in Lake Toba, North Sumatra, Indonesia

Zanthoxylum acanthopodium is a nutritional plant utilized for both culinary and medicinal purposes. The herb, popularly known as andalimanis found in sloppy, barren, cultivated lands and secondary forests in Lake Toba, North Sumatra. This study aimed to provide an ethnobotanical description, productivity and propagation, essential oil of andaliman and the application as traditional medicine in Lake Toba. Botanical characters were collected by observing phenology and distilling essential oils. The ethnomedicine information was collected through in-depth interviews with farmers and herbal practitioners, meanwhile, phytochemical content was identified based on various primary literature. Results showed flowering period occurs from March until April and followed by fruiting in May to September. Fruits were widely processed as cooking spices for various cuisines. It played an important role in local people’s diet by supplying carbohydrate, minerals and vitamins. This ingredient was favoured for its citrus-colored oil content and a spicy taste with an appetizing aroma. This spice was also utilized in traditional medicine. Both dry and fresh fruits were used for gums and dental disorders as dyspepsia or lotion for scabies. Fresh roots were also used to cure dental problems. All plant plants contain essential oil with a higher concentration in fruits (4.89%). The local wisdom also reveals the essential oil utilization as an antimicrobial ingredient that could be further processed as a food preservative. To increase generative propagation, seed dormancy breaking treatment through a low-intensity burning can increase the germination rate.

Apparent Resilience to Fire of Native Bee (Hymenoptera: Apoidea) Communities from Upland Longleaf Pine Forests in Louisiana and Mississippi

Controlled burning is an essential tool for restoration and management of Pinus palustris (Longleaf Pine) habitats, yet effects of controlled burning on insect species, including pollinators, are rarely considered in conservation planning. We used blue vane traps to sample native bees (Hymenoptera: Apoidea) at recently burned and unburned sites in 2 Longleaf Pine upland forests in Mississippi and Louisiana. Our objective was to quantify short-term effects of controlled burns given fire-return intervals of 1–2 years are now regularly employed to manage Longleaf Pine woodlands. We sampled during 2016 and 2017 and collected 1777 native bees, representing 43 species. Recent fire was found to have no clear effect on species composition, richness, or community structure. Overall, bee communities from burned and unburned sites were similar. Even the community collected from a site that had remained unburned for 8 years was only marginally different from the others. These results suggest that native bee communities may be resilient to low intensity burns.

Vulnerability of soil organic matter to microbial decomposition as a consequence of burning

Ecosystem fires are stochastic and anthropogenic phenomena that affect critical soil processes. Nevertheless, environmental managers, policy-makers, and even scientists have often overlooked the induced transformations that fire does to soil organic matter (SOM), which sustains an ecosystem’s overall health. Here, we investigated the effects of simulated fire conditions on bulk SOM, water-extractable organic matter (WEOM), and vulnerability to microbial degradation. Sequential thermal decomposition experiments were carried out to investigate the effect of increasing temperature on C, N, δ13C, and δ15N of bulk SOM and WEOM. A microbial decomposition experiment was also done to determine the effects of burning on SOM degradability. Intermediate-intensity burns caused significant decreases in C and N concentrations in soils, as well as alterations in bulk SOM and WEOM properties. Conversely, the effects of low-intensity burns were less apparent in terms of bulk SOM content and stable C and N isotope composition. However, the results of the microbial decomposition experiment revealed that low-intensity burning resulted in elevated CO2 emission that were significantly correlated with C concentration, δ13C values, and the C/N ratio of WEOM. These results provide evidence that low-intensity burning can have important consequences for soils, altering its organic components and releasing significant amounts of greenhouse gases. Thus, particular focus must be given to managing ecosystem fires and evaluating their impacts, especially because fire is still widely used in agriculture and forest management with frequency projected to increase in the coming years.

Microbial communities of upland peat swamps were no different 1 year after a hazard reduction burn

Fire in wetlands is poorly understood, yet hazard reduction burns are a common management practice and bushfires are becoming increasingly prevalent because of climate change. Fire may have long-lasting implications for the microbial component of these wetland ecosystems that regulate carbon and nutrient cycling. The extremely fire-prone Blue Mountains World Heritage Area in south-eastern Australia contains hundreds of endangered peat-forming upland swamps that regularly experience both bushfires and hazard reduction burns. In a before–after control–­impact study, we surveyed the sediment microbial community of these swamps to test the impact of a low-intensity hazard reduction burn. Along with sediment pH, moisture and organic content, we measured gene abundances including those relating to carbon cycling (quantitative PCR (qPCR) of pmoA, mcrA, bacterial 16S rRNA and archaeal 16S rRNA), and bacteria community fingerprint (terminal restriction fragment length polymorphism (T-RFLP)). One year after the hazard reduction burn, there were no significant differences in the gene abundances or microbial community fingerprint that could be attributed to the fire, suggesting that the hazard reduction burn did not have a long-term impact on these microbial communities.

Immediate Effects of Prescribed Burning on Chemical Properties of the Cerrado Soil

The Cerrado biome increasingly suffers from the environmental impacts of human action. Burning is known as an action used to destroy native vegetation and to clean areas mainly with the purpose of growing soybeans, corn, or raising cattle. In this study we aimed to investigate the influence of low-intensity burning on the chemical composition of a Red-Yellow Latosol in a region characterized as Cerrado sensu stricto. A total of 14 parcels of land were demarcated. In order to analyze the effects of fire on the soil chemical properties, soil samples were collected before and within 24 hours of the burning by means of the same methodology. An increase in organic matter and in the levels of Ca2+, Mg2+, K+, Mn2+, Zn2+, B+, S, as well in the ratios characterizing the soil (CECt, SB, Ca+/T, Ca+/Mg+, V, and Ca+/K+), was observed. Variables that determine the acidity of the soil, such as pH and H + Al, presented changes, although not significant (p > 0.05).

Response by Three Plant Indicator Groups of Upland Habitat to Manipulation of a Black Oak (Quercus velutina) Sand Barren

In the absence of a disturbance regime, flora at historical oak sand barrens change as leaf litter builds up and increasing canopy cover shades bare soils. Over time, black oak sand barrens become more mesic, and other trees including Acer rubrum, Fraxinus sp., Prunus serotina, and Sassafras albidum often mix with oaks in the canopy. Three different restoration techniques were applied to recreate disturbance across 10 sites within degraded black oak (Quercus velutina) glacial kames, which are mounds of sand and gravel deposited by melting ice sheets: select canopy tree thinning favoring 5–30% tree canopy cover, forest floor leaf litter removal, and prescribed fire. Ground layer richness and abundance 1 and 3 y after treatment were assessed within modified North Carolina Vegetation Survey plots and compared against both temporally and spatially equivalent control sites. Thinning the canopy induced the greatest vegetation response in species diversity, whether as xeric-tolerant indicator species, graminoid species, as a taxonomic group, or pooling all plants. Leaf litter removal produced a modest pulse response from a few select species released from the shade-creating effects of accumulating leaf litter. Prescribed burns did not create a disturbance sufficient for any significant plant response, presumably because low-intensity burning minimally reduced leaf litter cover. Thus, manipulations that opened the canopy and reduced soil moisture more directly induced barren-species recovery than did efforts to recreate historical disturbance processes.

Simulation Comparisons of Particulate Emissions from Fires under Marginal and Critical Conditions

Using a particulate emissions model developed for FIRETEC, we explore differences in particle emission profiles between high-intensity fires under critical conditions and low-intensity fires under marginal conditions. Simulations were performed in a chaparral shrubland and a coniferous pine forest representative of the southeast United States. In each case, simulations were carried out under marginal and critical fire conditions. Marginal fire conditions include high moisture levels and low winds, often desired for prescribed fires as these conditions produce a low-intensity burn with slower spread rates. Critical fire conditions include low moisture levels and high winds, which easily lead to uncontrollable wildfires which produce a high-intensity burn with faster spread rates. These simulations’ resultant particle emission profiles show critical fire conditions generate larger particle emission factors, higher total mass emissions, and a higher lofting potential of particles into the atmosphere when compared against marginal fire conditions but similar particle size distrubtions. In addition, a sensitivity analysis of the emissions model was performed to evaluate key parameters which govern particle emission factor and particle size.

Breeding bird response to season of burn in an upland hardwood forest

Upland hardwood forest managers are increasingly burning during the growing-season in hopes of improving wildlife habitat and attaining or accelerating other restoration goals, highlighting the need for research addressing how season of burning affects wildlife, including breeding birds. We used 1-ha strip transects in nine units before (2011) and after (2013–2016) treatments to experimentally assess how breeding birds respond to early growing-season (26 April 2013; GSB) and dormant-season (5 March 2014; DSB) burns, and controls (C). Burn effects on forest structure were minor and transitory, regardless of burn season. Burns did not affect overstory or midstory tree basal area or density; shrub cover did not significantly differ among treatments, but within GSB and DSB it decreased for 1–2 years post-burn. A trend of reduced leaf litter depth immediately following both burn treatments was apparent, and recovery was rapid. Percent canopy cover decreased slightly in GSB within four years post-burn. Total bird species richness and density did not differ among treatments or years, and no treatment × year interaction effects were detected. A treatment effect was detected for one of the 10 species tested; Red-bellied woodpecker density was greater in GSB than C in 2013 and 2015. No treatment × year interaction effect was detected for any tested species. Density of birds within the tree-, cavity-, and shrub and midstory-nesting guilds were not detectably affected by either burn treatment, but ground-nester density was lower in GSB and DSB than C in 2014. Our results indicate that single, low-intensity burns, regardless of burn season, are not an effective tool in creating suitable forest structure for disturbance-dependent breeding bird species, or changing breeding bird community composition. In the short-term, substantial forest overstory reduction by timber harvests or high-severity burns will likely be required to improve forest conditions for disturbance-dependent species, and to increase species richness and abundance of breeding birds.

Assessing the role of native herbaceous legumes in the nitrogen cycle of regularly burned loblolly pine forests

Prescribed burning is one of the most commonly used management practices in pine (Pinus spp.) forests of the southeastern United States. There is concern, however, that burning may lead to excessive losses of nitrogen (N), thereby decreasing forest productivity. The N losses due to burning may be potentially countered via symbiotic N2-fixation by native and naturalized herbaceous legumes that may thrive in burned forests. However, the rates and controls of N input via legume N2-fixation in these ecosystems are poorly understood. The objectives of this study were to measure legume abundance, biomass, N2-fixation, substrate quality, and associated environmental controls in regularly burned loblolly pine (P. taeda) forests. The study sites were located in four management blocks at the Piedmont National Wildlife Refuge. This assessment revealed a total of 23 legume species in 9 genera. Legume abundance averaged 12.95 ± 2.30 individuals m−2, and collectively Centrosema virginianum, Chamaecrista nictitans, Desmodium marilandicum, Galactia volubilis, and Lespedeza procumbens constituted 70.8% of the total legume abundance. Legumes comprised 17.1% of the understory aboveground biomass, and legume foliage, stem, and total (foliage + stem) biomass estimates averaged 15.38 ± 3.18, 20.88 ± 4.01, 36.26 ± 6.95 g m−2, respectively. Legume foliar N concentration averaged 2.22 ± 0.06% (ranging from 1.42−2.83%), and all legume foliar N concentrations were significantly higher than the average foliar values for blackberry (Rubus spp., 1.10 ± 0.05%) and the aggregate of non-leguminous forbs (1.03 ± 0.08%) that grew concurrently with the legumes in the study sites. N2-fixation assessments, based on the differential between legume and non-N2-fixing reference plant foliar N concentrations, indicated that approximately 50% of legume N was derived from the atmosphere. Legume foliage tissues exhibited relatively high substrate quality indices such as high N concentrations, low lignin concentrations (average of 14.3 ± 1.9%), and correspondingly low lignin:N ratios (average of 6.7 ± 0.9) indicative of tissues that exhibit rapid mass loss and N mineralization rates during decomposition. Canopy openness was the environmental variable that was most strongly correlated with foliar N and areal biomass among the dominant legume species. The estimated N input of 0.14 g m−2 yr−1 via N2-fixation may compensate for N losses due to relatively low intensity and infrequent understory burns during a stand rotation. Additional studies are needed to more comprehensively assess legume N2-fixation inputs, associated environmental constraints, and practical field applications which may increase N input via symbiotic N2-fixation in regularly burned pine forest ecosystems.

Effect of fire on insectivorous bat activity in northern Australia: does fire intensity matter on a local scale?

Fire is notably becoming more intense, frequent and widespread due to climate change. In northern Australia, inappropriate fire regimes have been implicated in mammal declines, yet nothing is known about how different aspects of fire regimes affect bats in this region. This study aimed to determine how fire intensity, associated with seasonality, affects insectivorous bats on a local scale. An experimental M BACI approach was used on five site replicates across Cape York Peninsula, where ultrasonic detectors were used to determine the activity of insectivorous bats in response to low intensity burns (LIBs) and high intensity burns (HIBs) on a local scale. Total bat activity increased due to LIBs, but showed no response to HIBs. Activity of edge-open guild bats also increased due to LIBs but decreased in response to HIBs. Activity of open guild bats was unaffected by LIBs, but exhibited a strong positive response to HIBs. Activity of closed guild bats showed no response to fire, or fire intensity. Responses were likely derived from changes in habitat structure and prey availability. Given that each bat guild responded differently to each fire intensity, this lends support to the ‘pyrodiversity begets biodiversity’ concept, which is currently the basis for many fire management practices for conservation in northern Australia.

Endocrine stress response of Eastern Fence Lizards in fire-disturbed landscapes.

Landscape disturbances can alter habitat structure and resource availability, often inducing physiological responses by organisms to cope with the changing conditions. Quantifying the endocrine stress response through measurement of glucocorticoids has become an increasingly common method for determining how organisms physiologically respond to challenges imposed by their environment. We tested the hypothesis that Eastern Fence Lizards cope with fire disturbance effects by modulating their secretion of corticosterone (CORT). We measured the baseline and stress-induced plasma CORT of male Eastern Fence Lizards in a chronosequence of fire-altered habitats (recently burned, recovering from burn, and unburned). Although habitat use by lizards differed among burn treatments, including differences in use of canopy cover, leaf litter, and vegetation composition, we did not detect a significant effect of fire-induced habitat alteration on plasma CORT concentration or on body condition. In addition, we found no effect of blood draw treatment (baseline or stress-induced), body temperature, body condition, or time taken to collect blood samples on concentration of plasma CORT. Low intensity burns, which are typical of prescribed fire, may not be a sufficient stressor to alter CORT secretion in Eastern Fence Lizards (at least during the breeding season). Instead, lizards may avoid allostatic overload using behavioral responses and by selecting microsites within their environment that permit thermoregulatory opportunities necessary for optimal performance and energy assimilation.

Vulnerability of Physically Protected Soil Organic Carbon to Loss Under Low Severity Fires

Soil aggregate degradation during medium and high severity fires is often identified as the main mechanism that leads to loss of soil organic matter due to fire. Low severity fires, however, are considered not to cause aggregate degradation assuming that temperatures <250o C, as occurring during low-severity burns, have only limited effects on the stability of the soil organic binding agents. Recent studies suggest that low severity burns may cause soil aggregate degradation due to rapid vaporization of soil pore water that can induce pressure on the soil aggregates beyond their yield stress. Such pressure-driven degradation of soil aggregates may expose physically protected organic carbon to decomposition. Our study investigated the effect of a low-severity fire on soil organic matter, water extractable organic C and N as well as respiration for two initial soil moisture conditions undergoing three heating regimes using aggregates from a California forest and Nevada shrubland soil. We found that initially moist soil aggregates that were rapidly heated up degraded the most, showing increased cumulative carbon mineralization when compared to aggregates that were not heated, aggregates that were dry before being heated , and initially moist soil aggregates that were slowly heated. Our results suggest that exposure of previously physically protected organic carbon within the soil aggregates to oxidative conditions was the most likely cause of increased rates of decomposition of organic matter after low-intensity burns. Additionally, we show that for a shrubland soil, aggregates with relatively low organic carbon content, low severity burns increased cumulative carbon mineralization. We hypothesized that this was due to decomposition of cytoplasmic material from lysed microbes. Our results suggest that low severity burns can accelerate decomposition of soil organic carbon protected in soil aggregates.

Scientific support to prescribed underburning in southern Europe: What do we know?

Prescribed burning is a technically demanding and usually highly scrutinized and debated practice. Barriers of various natures have constrained the development of prescribed burning in forests (PUB) in southern Europe, with insufficient research and outreach among the contributing factors. This paper synthesizes PUB knowledge in the region and identifies research needs. PUB research in the western Mediterranean basin was fostered by international cooperative projects that studied the ecological and management ramifications of low-intensity burning for fire hazard mitigation. Effects of PUB on soil and vegetation are minor and short-lived and regulated through forest floor moisture content, fire intensity, tree resistance to fire, and ignition patterns. Generic burn prescriptions are available and specific burn windows targeting site-specific burn objectives can be developed with the existing software tools. However, the need to increase the depth and breadth of PUB research is apparent. Current knowledge is based upon pine forests, particularly Pinus pinaster, as past research has overlooked hardwoods; was obtained across a limited number of research teams and study sites; and essentially reflects short-term treatments. Fuel consumption by PUB effectively decreases fire potential, but post-treatment fuel dynamics and effects on wildfire spread and severity warrant further study. Future work should devote more attention to the socioeconomic, biodiversity and carbon storage implications of PUB and should expand to encompass cumulative effects and the whole PUB regime and its variation; long-term experiments and monitored management programs are crucial to this end.