Fires Of Different Severity Research Articles

Fostering biodiversity research in post-fire biology

The impacts of wildfire on vegetation and soil erosion have been studied for decades aiming to bring back ecosystems after fire perturbance. However, the influence of fires on above and belowground biodiversity remains far less understood. Biodiversity is critical for supporting ecosystem function, and this data scarcity is hampering managers in adopting effective practices for a proper restoration of burned ecosystems. This limitation could be overcome by future research that should focus post-fire diversity of plants and soil biota, by (i) analysing the environmental factors driving post-fire evolutionary trends; (ii) exploring their interrelations across different spatial and temporal scales; (iii) identifying the variability across fires of different severities and frequency; (iv) ascertaining the post-fire response of individual plant species and soil taxa to fire with or without application of post-fire restoration actions.

Post-fire soil greenhouse gas fluxes in boreal Scots pine forests–Are they affected by surface fires with different severities?

Although forest fires are one of the main natural disturbance types in boreal forests, there is limited information regarding surface fires (dominant in Northern Europe), and how surface fires of different severities could affect post-fire soil greenhouse gas emissions. The results of our study show that fire severity, time since fire and post-fire changes in soil temperature were the main factors driving soil carbon dioxide (CO2) flux (forest floor ecosystem respiration) from burned boreal forest soils. Approximately two hours after the fire, soil CO2 emissions from burned areas were significantly higher compared to pre-fire conditions, and areas with high-severity fires had significantly higher soil CO2 emissions compared to those with low-severity fires. Later (days, months) after the fire, the unburned control areas always had higher soil CO2 emission values compared to burned areas. In the case of methane (CH4), time since fire and post-fire changes in soil temperatures were the main factors driving soil CH4 fluxes. Unburned study areas were sinks of CH4 through the entire measurement period, while immediately after the fire, the burned areas turned from CH4 sink to CH4 source. For nitrous oxide (N2O) measurements, time since fire was the only factor that significantly affected soil N2O fluxes. Shortly after the fire, N2O emissions increased significantly from both low- and high-intensity study plots. Two days after the fire, post-fire soil C and N content decreased in the O-horizon and increased within the first 5 cm of the soil mineral layer, and the trend was visible both in low- and high-severity fire plots. Samples collected four months after the fire, showed similar total soil C and N content as there was before the fire.

Assessment of carbon emissions due to landscape fires in Ukraine during war in 2022

The russian military aggression and the related socio-economic and environmental consequences have significantly affected the climate and production of ecosystem services through damage to forests, ecosystems, landscape fires and emissions of gases into the atmosphere. The study aims to estimate carbon dioxide emissions due to landscape fires in Ukraine during the year 2022. The OroraTech wildfire monitoring technology was used to detect fires, while perimeters of burned areas were delineated with Sentinel 2 time series. The Copernicus Dynamic Land Cover map was used to extract burned land covers. Emissions were calculated based on the intensity of fires (dNBR) with the share of burned biomass in different types of land cover. Biomass models were selected considering the dominant tree species within a specific region and the species structure of the sown areas of croplands. The volume of biomass losses was estimated as a result of fires of different severities. It was estimated that during in 2022, landscape fires burned 749.5 thousand hectares thereof: croplands – 419.1 thousand hectares; other natural vegetation – 273.8 thousand hectares; conifer forests – 31.1 thousand hectares; other forests – 25.5 thousand hectares. The impact of the war on landscape fires is confirmed by the large proportion of fires in the 60-kilometre buffer zone along the frontline – 68.9% of the total area of fire. Among all fires, 42.5% of fires occurred in the occupied territory. Total CO2 emissions from all types of landscape fires reached 5.20 million tons and other greenhouse gases – 0.28 million tons. It is the first detailed mapping of landscape fires with an analysis of each polygon for the whole territory of Ukraine. The results provide important information for assessing the loss of ecosystem services and estimating carbon dioxide emissions as well as for confirming the impact of hostilities on landscape fires

Combining remote sensing and field data to assess recovery of the Chilean Mediterranean vegetation after fire: Effect of time elapsed and burn severity

It has been debated if Chilean sclerophyllous vegetation can recover after fire of different severity and short and long term. We evaluated the resiliency of this vegetation type after single-occurrence fires of different severities that occurred 30, 20 and 10 years in Central Chile before the study. Two approaches were followed: satellite image analysis and vegetation sampling. Wildfires that occurred between 1985 and 2015 were identified based on Landsat images. We selected 30 sites burned by a single fire in either 1985, 1995 or 2005, and that was not converted to another land use by 2015, then determined the percentage cover by vegetation type. We recorded or estimated the independent variables of burn severity, slope, altitude, pre-fire vegetation type and latitude of the sites. Composition, richness, and abundance of adult and regeneration of woody vegetation and herbaceous cover were sampled. Generalized linear models were used to evaluate the effect of the independent variables and the time elapsed since the fire on vegetation recovery. The proportion of dense vegetation forest cover was significantly higher with more time elapsed since the fire, while semi-dense forest/shrubland and open shrubland vegetation cover returned to pre-fire levels more quickly. The richness and abundance of regenerated woody species was significantly greater with more time elapsed since the fire. However, no relationship was found between species richness and abundance of adult woody species and time elapsed post-fire. We found that vegetative recovery over time was not related to burn severity. Forested and mixed forest/shrubland cover is reached 10–20 years after the fire, if no further intervention occurs. Richness and species abundance was similar to that of unburned sites after 20 or more years post-fire. This study provided evidence thatforestvegetation in the Chilean Mediterranean ecosystem is resilient to fires of at least low and medium intensities.

Spatio‐temporal changes in the understory heterogeneity, diversity, and composition after fires of different severities in a semiarid oak (Quercus brantii Lindl.) forest

AbstractIn arid and semiarid forests and rangelands, native ranchers and farmers frequently use fire as a tool to improve soil fertility and vegetation composition, and to facilitate soil tilling. Investigating changes in ecosystem characteristics after these measures is of great importance for establishing management and recovery strategies. This study aimed to investigate spatial–temporal changes in the understory heterogeneity, diversity and composition after fires of different severities in a Brant's oak (Quercus brantii Lindl.) forest. Vegetation sampling was monitored in 14 patches including unburned sites (UBN), burned sites with low fire severity after 1, 5, and 10 years (LFSO, LFSF, and LFST, respectively), and burned sites with high fire severity after 1, 5, and 10 years (HFSO, HFSF, and HFST, respectively). Fire severity and time since fire significantly affected diversity indices with the lowest values of richness, evenness and diversity in high‐severity fires, while the highest values were observed in low‐severity fires. Time since fire did not significantly affect the understory evenness in both fire severities. However, species diversity and richness in low‐severity fires decreased with time since fire while the reverse was observed in high‐severity fires. The results of a detrended correspondence analysis indicated that the severity and time since fire significantly changed vegetation composition. The largest changes in vegetation composition compared to control sites were observed in HFSO, and then in HFSF and HFST. Both fire severity and time since fire caused changes in the heterogeneity of plant communities. We concluded that the use of low‐severity fires can be suitable for maintaining and increasing the heterogeneity of understory vegetation in semiarid forest ecosystems. However, low‐severity fires have also slightly, while not significantly, increased evenness and can therefore potentially reduce the ecosystem functions of dominant species in such semiarid regions. This could mitigate the positive effect of fire on vegetation heterogeneity and necessitate further investigations.

Distributive features of soil carbon and nutrients in permafrost regions affected by forest fires in northern Da Xing’anling (Hinggan) Mountains, NE China

In permafrost regions, forest fires actively affect physical and chemical properties of soils. Many studies have been conducted on the effects of forest fires on physical and chemical properties of topsoil, while the research on the fire-induced changes in carbon and other nutrients of soils has received much less attention, particularly that of soils in the active layer and near-surface permafrost. Here, using soil samples from two representative areas (Mangui and Alongshan), we investigated the effects of fires on soil nutrients of larch forest soils in the discontinuous permafrost zone in the northern Da Xing’anling (Hinggan) Mountains, Northeast China. The results showed that soil pH increased with fire severity due to the burning of soil organic matter by more severe fires and leaching of base elements in the residual ash into the soil, and; forest fires resulted in a weakly acidic post-fire soil environment. Soil total organic carbon, total nitrogen, and total phosphorus declined with increasing fire severity. A severe burn led to a substantial reduction of soil carbon and nitrogen, which were not recovered seven years after fire. However, there was no substantial change in the C/N ratio. For the two chosen areas, soil C/N ratios decreased with depth. In the first post-fire year, total potassium content increased and were similar at the sites affected by fires of different severity in the area burned seven years ago. There was no significant change in available phosphorus and available potassium. These changes were notable in the active layer and/or organic layers, but not so in the near-surface permafrost layer. Our results suggest that, in permafrost regions, forest fires have important effects on the distribution of soil carbon and other nutrients. This study on the feedback mechanisms between forest fires and nutrients in discontinuous permafrost regions in the northern Da Xing’anling Mountains is of importance for understanding the boreal carbon pool and cycling.

THE INFLUENCE OF FIRES ON THE BIOLOGICAL ACTIVITY OF FOREST SOILS IN VRANCEA, ROMANIA

Soils are influenced by stand composition and hydrological regime as well as by stress abiotic factors, including forest fires. As such, this study analyzed three stands affected by fires of different severities. Soil samples were gathered during the spring of 2017 from three sample areas in Vrancea County, eastern part of Romania. For each area studied, soil profiles were studied in 3 areas affected by fires and in control areas located close to each other. The soil respiration was determined by monitoring CO2 fluxes with an EGMEnvironmental Gas Monitor, PP systems. The microbial measures (mesophilic heterotrophic bacteria, fungi and nitrogen fixing bacteria from genus Azotobacter) were achieved through the plate count method. The results were statistically interpreted with the ANOVA classical- univariate analysis. The fires affected the humus and total nitrogen quantities at a certain time interval from their apparition, but only for the first 10 centimetres of the soil depth and in the case of low intensity fires. The correlation between high temperatures and CO2 fluxes was also established. The fires also affected the abundance of fungi. After six years from their apparition, the unseen effects of fires on forest soils characteristics are still detected, such as the decrease of soil respiration and bacteria amount, a pH increase and a decrease of humus and total nitrogen.

Uso de herramientas de teledetección para el análisis de la severidad y estimación de gases de efecto invernadero (GEI) en incendios forestales de gran magnitud. Estudio de caso incendio La Rufina, VI Región del L. G. B. O’Higgins, Chile

<p>Wildfires destroy thousands of hectares of vegetation every year in Chile, a phenomenon that has steadily increased over time, both in terms of the number of fires and the area affected. Since 1985 until 2016 have occurred 1,476 wildfires severe in intensity (> 200 ha), that burned a total of about 1,243,407 ha of vegetation, and an average of 40,000 ha affected per year. Depending on the type and intensity of the fire, there are different levels of severity with which the fire affects the vegetation, a variation that is crucial for the estimation GEI in the event. The purpose of this research was to analyze the burn severity of Rufina wildfires occurred in 1999, in the VI Region of L. G. B. O’Higgins in Chile, south of the capital Santiago, using Landsat 5 TM and Landsat 7 ETM+ imagery, including in the analysis the estimated greenhouse gases emitted in relation to with the vegetation and burn severity. Burn severity was estimated through the Normalized Burn Ratio (dNBR) and GEI with the equation proposed by IPCC in 2006, which was adjusted with the combustion efficiency coefficients proposed by De Santis et al. (2010). The results show that around 16,783 ha were affected by fires of different severity and the native forest and tree plantations were affected by high severity. The ton of GEI for each level of burn severity and type of vegetation was estimated, being carbon dioxide (CO<sub>2 </sub>) the main GEI emitted to the atmosphere in the fire. The highest emissions occurred in the areas of grasslands and scrublands, with high severity, with values ranging between 186 and 170 t/ha respectively</p>

Impact of thermal shock on forest soils affected by fires of different severity and recurrence

Thermal treatments in the laboratory were conducted using </span><span style="font-size: small;">unburned and burned samples of two soils affected by low- or high severity fires</span><span style="font-size: small;"> in order to study their impact on forests ecosystems with different fire regimes (severity, recurrence). Soils samples were heated in a furnace for 15 minutes at </span><span style="font-size: small;">50 ºC, 75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC and 300 ºC to simulate different fire intensities; the process was repeated after a 1 month incubation of the burned, rewetted samples in order to simulate fire recurrence. The soil temperature was measured with thermocouples at the surface and 1 cm depth. The maximum temperature reached (Tmax) and the amount of heat supplied to the samples (degree-hour, DH) were calculated from the temperature-time curves. </span><span style="font-size: small;">A total of 128 temperature-time curves (4 soil field samples x 8 heating temperatures x 2 depths x 2 successive heat treatments) were analyzed and the estimation of several soil physical and chemical properties (color, moisture content, pH, total C, total N, soluble C) was carried out in the different soil treatments. H</span><span style="font-size: small;">igh-severity burning provoked significant changes on these physical and chemical properties, whereas slight modifications or even no changes were due to low-severity burning or soil heating under laboratory conditions. The thermal properties exhibited a higher sensitivity for the detection of the fire regime impact than the physical and chemical properties. The results showed that the </span><span style="font-size: small;">temperature-time curves and derived parameters (slope, Tmax, DH) can be successfully used to quantify the impact of thermal shocks at low and high temperatures and to evaluate the effect of fire/heating recurrence on forests ecosystems.

Forest fire as a potential environmental threat in recent years in Sikkim, Eastern Himalayas, India

Forest fires of short to medium return intervals are quite common during the winter seasons in the state of Sikkim, Eastern Himalayas, India. The forest fires of different intensities were reported from various locations of three districts of Sikkim in the years 2009 to 2011. This paper discusses and analyses the causes of occurrence of forest fires of different severity, in terms of forest area burnt by the formation of conducive atmosphere by the climatic variables such as rainfall, temperature, sunshine hours and humidity during the fire season from 2009 to 2011. These variables were analysed from the forest fire prone months November to April of the years 2009 to 2011. It further highlights that the forest fire disaster is a potential environmental threat in recent years and suggests certain short-term and long-term strategies for mitigation of forest fire in the state.

Biomass dynamics of central Siberian Scots pine forests following surface fires of varying severity

In 2000–2002 nine 4-ha prescribed fires of various severities were conducted on experimental plots in mature Scots pine forest in the central Siberian taiga, Russia. Total above-ground living biomass decreased after low- and moderate-severity fires by 10 and 15%, whereas high-severity fire reduced living above-ground biomass by 83%. We monitored changes in fuel structure and biomass for 6–8 years following these fires. By 6–8 years after burning the ground fuel loading had recovered to 101, 96 and 82% of pre-fire levels after fires of low-, moderate- and high-severity. Down woody fuel loading increased by 0.18±0.04kgm–2year–1. We developed regressions relating time since fire to changes in above-ground biomass components for fires of different severity for feather moss–lichen Scots pine forest of Siberia. Our results demonstrate the importance of both burn severity and composition of pre-fire surface vegetation in determining rates and patterns of post-fire vegetation recovery on dry Scots pine sites in central Siberia.

Stochastic processes dominate during boreal bryophyte community assembly

Why are plant species found in certain locations and not in others? The study of community assembly rules has attempted to answer this question, and many studies articulate the historic dichotomy of deterministic (predictable niches) vs. stochastic (random or semi-random processes). The study of successional sequences to determine whether they converge, as would be expected by deterministic theory, or diverge, as stochastic theory would suggest, has been one method used to investigate this question. In this article we ask the question: Do similar boreal bryophyte communities develop in the similar habitat created by convergent succession after fires of different severities? Or do the stochastic processes generated by fires of different severity lead to different communities? Specifically we predict that deterministic structure will be more important for large forest-floor species than stochastic processes, and that the inverse will be true for small bryophyte species. We used multivariate regression trees and model selection to determine the relative weight of structure (forest structure, substrates, soil structure) and processes (fire severity) for two groups of bryophyte species sampled in 12 sites (seven high-severity and five low-severity fires). Contrary to our first hypothesis, processes were as important for large forest-floor bryophytes as for small pocket species. Fire severity, its interaction with the quality of available habitat, and its impact on the creation of biological legacies played dominant roles in determining community structure. In this study, sites with nearly identical forest structure, generated via convergent succession after high- and low-severity fire, were compared to see whether these sites supported similar bryophyte communities. While similar to some degree, both the large forest-floor species and the pocket species differed after high-severity fire compared to low-severity fire. This result suggests that the "how," or process of habitat generation, influences community composition in this system and that a snapshot of habitat conditions taken at only one point in time is insufficient to explain species distribution.

不同强度火干扰下盘古林场天然落叶松林的空间结构

Fire is the most common disturbance in natural forested ecosystems and plays a significant role in ecological succession of forest communities.Fires often burn in the Da Hinggan Mountains(also known as the Greater Khingan Mountains) where frequent high-intensity fires rapidly transform the landscape.These fires have extensive and long term effects on the spatial distribution of natural Larix gmelinii forest.This study looks mainly at gaps formed by fires of different severity in natural L.gmelinii forest and is based on data from records collected at the Pangu Farm,Tahe Forest Bureau,Da Hinggan Mountains in July 2011.We describe the dynamic processes which create tree spatial distribution patterns of natural L.gmelinii forest in Pangu farm.Our research looked at how fires of varying severity influenced the spatial distribution patterns of natural L.gmelinii forests by analyzing gaps in plots.We selected suitable class parameters at a landscape scale and combined with the state of tree spatial distribution patterns.We defined three phases,the gaps phase,immature phase and mature phase.The results show stands which suffered moderate fire disturbance are moved into the gaps phase of the forest cycle;these stands retain only a small amount of medium and large diameter live trees of L.gmelinii.Pioneer species reveal aggregative distribution in the newly created patchwork of gaps of different sizes;the distance between the patches was the shortest of the three phases and the shapes of the patches themselves are very complicated since moderately intense fire leaves a significant and irregular accumulation of gaps within any particular plot.The research plot,in a stand that was burned with low intensity fire,retained most of its L.gmelinii,and continued to develop along the normal lines of forest succession.Low intensity fire allowed L.gmelinii to continue to maintain its aggregative distribution.A large number of pioneer species invaded into the area burned with low intensity fire.The low intensity burn area had the smallest gap patches of the three phases studied.The shape of these small gap patches was the most uniform and the separation between the gap patches was the largest of the three phases.The unburned plot with no known history of fire disturbance was a mature phase forest and included a complex patchwork or network of gaps of different sizes.The unburned L.gmelinii community had changed from an aggregative distribution into a uniform distribution.Because fires burn with different levels of intensity,the undergrowth was transformed into gap patches.The spatial distribution pattern had changed with fire distribution.As the level of fire disturbance declined in a particular stand the area moved from the gaps phase,to the immature phase and then the mature phase in the forest cycle.

The fire pulse: wildfire stimulates flux of aquatic prey to terrestrial habitats driving increases in riparian consumers

We investigated the midterm effects of wildfire (in this case, five years after the fire) of varying severity on periphyton, benthic invertebrates, emerging adult aquatic insects, spiders, and bats by comparing unburned sites with those exposed to low severity (riparian vegetation burned but canopy intact) and high severity (canopy completely removed) wildfire. We observed no difference in periphyton chlorophyll a or ash-free dry mass among different burn categories but did observe significantly greater biomass of benthic invertebrates in both high severity burned and unburned reaches versus low severity burned reaches. Moreover, a significantly greater flux of adult aquatic insect emergence occurred at sites that experienced high severity fire versus low severity burned and unburned sites. The greatest number of spiders and bat echolocation calls were also observed at sites of high severity fire. Our results suggest that fires of different severity may have very different affects on stream-riparian food webs and that high severity wildfire may lead to an extended “fire pulse” that stimulates aquatic productivity and flux of prey to terrestrial habitats, driving local increases in riparian consumers.

Climate‐vegetation‐fire interactions and their impact on long‐term carbon dynamics in a boreal peatland landscape in northern Manitoba, Canada

Climate warming may increase the size and frequency of fires in the boreal biome, possibly causing greater carbon release that amplifies warming. However, in peatlands, vegetation change may also control long‐term fire and carbon accumulation, confounding simple relationships between climate, fire, and carbon accumulation. Using 17 peat cores dating to 8000 cal years B.P. from northern Manitoba, Canada, we addressed the following questions: (1) Do past climate changes correlate with shifts in peatland vegetation? (2) What is the relationship between peatland vegetation and fire severity? (3) What is the mean return interval for boreal peat fires, and how does it change across fires of different severities? (4) How does fire severity affect carbon accumulation rates? (5) Do fire and long‐term carbon accumulation change directly in response to climate or indirectly though climate‐driven changes in vegetation? We measured carbon accumulation rates, fire severity, and return intervals using macroscopic charcoal and changes in vegetation using macrofossils. Climate and vegetation changes covaried, with shifts from wetter fen to drier, forested bog communities during the Holocene Thermal Maximum (HTM). Fires became more severe following the shift to forested bogs, with fire severity peaking after 4000 cal years B.P. rather than during the HTM. Rising fire severity, in turn, was correlated with a significant decrease in carbon accumulation from ∼6000 to 2000 cal years B.P. The Medieval Warm Period and Little Ice Age affected vegetation composition and permafrost, further impacting fire and carbon accumulation. Our results indicate that long‐term changes in fire and carbon dynamics are mediated by climate‐driven changes in vegetation.

Remote Sensing of Fire Severity: Assessing the Performance of the Normalized Burn Ratio

Several studies have used satellite data to map different levels of fire severity present within burned areas. Increasingly, fire severity has been estimated using a spectral index called the normalized burn ratio (NBR). This letter assesses the performance of the NBR against ideal requirements of a spectral index designed to measure fire severity. According to index theory, the NBR would be optimal for quantifying fire severity if the trajectory in spectral feature space caused by different levels of severity occurred perpendicular to the NBR isolines. We assess how well NBR meets this condition using reflectance data sensed before and shortly after fires in the South African savanna, Australian savanna, Russian Federation boreal forest, and South American tropical forest. Although previous studies report high correlation between fire severity measured in the field- and satellite-derived NBR, our results do not provide evidence that the performance of the NBR is optimal in describing fire severity shortly after fire occurrence. Spectral displacements due to burning occur in numerous directions relative to the NBR index isolines, suggesting that the NBR may not be primarily and consistently sensitive to fire severity. Findings suggest that the development of the next generation of methods to estimate fire severity remotely should incorporate knowledge of how fires of different severity displace the position of prefire vegetation in multispectral space.

A new approach to modeling heat transfer in compartment fires

Abstract Heat transfer models most often used in fire engineering practice to predict the temperature of structural elements exposed to fires in compartments adopt a radiation component which assumes that the fire is separated from the surrounding surfaces by perfectly transparent media. As a result the predicted temperatures usually differ significantly from the measured values. This paper describes a relatively simple heat transfer model which accounts for the emission and absorption of radiation by some of the combustion products of simulated real fires using wood as fuel. The model is validated by comparing the predicted results with published data of experimentally observed temperatures of unprotected structures with different sizes exposed to fires of different severities in a compartment. Good correlation between calculated and observed temperatures are obtained for the majority of cases under consideration. Notation A area, m2 E total emissive power, W/m2 F transfer factor, dimensionless F i-k shape (view)factor for radiation from surface i to surface k, dimensionless P perimeter of a structural element exposed to fire, m P/A s massivity, m-1 T temperature, K V volume, m3 a/f air-to-fuel ratio c p specific heat at constant pressure, J/kg K h coefficient of convective heat transfer, W/m2 K q heat flux, W/m2 t time, s x mass fraction of a chemical constituent in liquid or solid fuels Greek letters α total absorptivity e total emissivity θ temperature, °C ρ density, kg/m3 σ Stefan–Boltzmann constant, W/m2 K4 Subscripts and superscripts b black body c carbon, convective g gas h hydrogen i surface i k surface k o oxygen s enclosure inner surface, steel, stoichiometric v volumetric