Fire effects on soils: the human dimension

Impact of wildfire recurrence on soil properties and organic carbon fractions

The recurrence and severity of wildfire is on the rise due to factors like global warming and human activities. Mediterranean regions are prone to significant wildfire events, which cause extensive damage to ecosystems and soil properties. This study focuses on the municipality of Allande in south-western Asturias (Spain), a region highly affected by recurrent wildfires. In this regard, we sought to examine how the recurrence of such fires influences soil organic carbon fractionation and other soil parameters, such as nitrogen fractionation, pH, and cation exchange capacity. The study involved six sampling plots with between varying fire recurrence levels, from 0 to 4 events between 2005 and 2022. The results revealed some significant effects of wildfires recurrence on soil texture, inorganic elemental composition and CEC, but not on pH and CE. In soil affected by recurrent fires, labile carbon fractions (cold-water extractable & hot-water extractable), and fulvic acid concentrations decreased by up to 36%, 5%, and 45%, respectively in comparison with undisturbed soil. In contrast, humic acid concentration remained stable or increased in soils damaged by fire. Additionally, nitrogen species in soil were observed to decrease significantly in high recurrence scenarios, especially nitrate. On the basis of our findings, we conclude that wildfires impact the distinct fractions of organic carbon and nitrogen in soils and that this effect is aggravated by increasing recurrence.

Spatio-temporal assessment of soil properties immediately and eight months after a high intensity-controlled burn in the south of Spain

In recent years, the use of fire as a means by which to manage forest ecosystems has become more frequent in Europe. Fire has a significant impact on the soil, and it is therefore necessary to understand how controlled burns affect this invaluable resource. The purpose of this study was to evaluate the main alterations in the physical-chemical and biological properties of the soil because of a high intensity-controlled burn in "Los Boquerones" area (Villaviciosa de Córdoba, Spain). Additionally, we assessed the spatial heterogeneity of the alterations of different soil properties. A grid of 12 points was established on a hillside in Sierra Morena (Córdoba). Thermocouples were placed at each point, and soil samples were collected at two depths (0-2 cm and 2-5 cm) before burning, immediately after burning and eight months later. Soil pH, electrical conductivity, nutrient content and/or availability, among others, and their spatio-temporal variations were analysed. Soil pH, increased in the first centimetres of the soil (0-2 cm) immediately after burning up to >2 units, and the increase was maintained eight months following the burn. Additionally, the high-intensity burn had a positive short-term effect on some of the soil properties, such as nutrient availability for plants, which was considerably increased. The magnitude of the alterations in the soil indicators assessed was spatially explained by the behaviour of the fire during the controlled burning. The burn also had both direct and indirect effects on soil microorganisms. In conclusion, the possible immediate and short-term effects of burning on the soil resource should be considered for a more holistic management of fire in forest ecosystems, as its functionality and capacity to provide ecosystem services is largely altered by these events as a function of their intensity.

Short-term responses of ecosystem multifunctionality to fire severity are modulated by fire-induced impacts on plant and soil microbial communities

This study represents a first attempt to shed light into the mechanisms that modulate the response of ecosystem multifunctionality (EMF) to fire severity in post-fire landscapes. We specifically investigated the role played by fire-induced changes on above and belowground communities in the modulation of EMF responses at short-term after fire. For this purpose, we estimated EMF using an averaging approach from three ecosystem functions (carbon regulation, decomposition and soil fertility) and their standardized functional indicators in field plots burned at low and high fire severity 1-year after a wildfire occurred in a Mediterranean ecosystem in the central region of Spain. Plant taxonomic and functional richness, and the bacterial and fungal taxonomic richness, were measured in the plots as community properties with a potential intermediate control over fire severity effects on EMF. The ecological effects of fire severity on above and belowground communities were important in shaping EMF as evidenced by Structural Equation Modeling (SEM). Indeed, the evidenced shrinkage exerted by high fire severity on EMF at short-term after fire was not direct, but modulated by fire-induced effects on the plant functional richness and the microbial taxonomic richness. However, EMF variation was more strongly modulated by indirect effects of fire severity on the biodiversity of soil microbial communities, than by the effects on the plant communities. Particularly, the fungal community exerted the strongest intermediate control (standardized SEM β coefficient = 0.62), which can be linked to the differential response of bacterial (β = -0.36) and fungal (β = -0.84) communities to fire severity evidenced here. Our findings demonstrate that the effects of fire severity on above and belowground communities are important drivers of short-term ecosystem functioning. Efforts tailored to secure the provision of multiple functions should be focused on promoting the recovery on soil microbial communities under high-severity scenarios.

Soil microbial diversity under different types of interference in birch secondary forest in the Greater Khingan Mountains in China

Introduction

Soil microorganisms are an important component of soil ecosystems with an indispensable role in forest ecosystems. We analyzed the soil microbial diversity in birch secondary forest formed by natural restoration or artificial reconstruction after interference by burning, clear cutting, and gradient cutting, and the Betula platyphylla Suk undisturbed forest in the Greater Khingan Mountains in China.

Methods

Illumina high-throughput sequencing technology was used to analyze the characteristics of the soil microbial community during the restoration process of birch secondary forest caused by the different types of interference. The relationships between bacteria and fungi were analyzed. The gene functions of the soil bacterial community and the ecological functions of soil fungi were predicted using PICRUSt and FunGuild, respectively.

Results

At the phylum level, the species and quantity of bacteria were more abundant than that of fungi. At the genus level, no obvious differences in the abundance of bacteria were observed; there were obvious differences in the abundance of fungi. Among the eight sample plots, the artificial larch forest belt had the highest bacterial and fungal alpha diversity, which was slightly higher than undisturbed forest, while the other sample plots were significantly lower. Gradual cutting pure birch forest bacteria and fungi had the highest beta diversity, and artificial larch forest belt bacteria and heavy burn sample plot fungi had the lowest beta diversity. Samples from the cutting and burning sample plots were significantly different from the undisturbed forest at the phylum level of Acidobacteriae, Acidimicrobiia, Mortierellomycetes and Sordariomycetes. We found statistical differences in biomarkers between bacterial and fungal communities in undisturbed forest and artificial larch forest belt and burn sample plots. PICRUSt prediction and FunGuild prediction showed that soil bacterial and fungal communities were rich in gene and ecological functions, respectively. In the microbial network, the stability or anti-interference performance of the fungal community was higher than that of bacteria.

Conclusion

Our data reveal the characteristics of the soil microbial community during the restoration process of Betula platyphylla Suk secondary forest under different types of disturbance, which is of great significance for understanding the role of soil microorganisms in the forest ecological cycle.

Cross-country risk quantification of extreme wildfires in Mediterranean Europe

We estimate the country-level risk of extreme wildfires defined by burned area (BA) for Mediterranean Europe and carry out a cross-country comparison. To this end, we avail of the European Forest Fire Information System (EFFIS) geospatial data from 2006 to 2019 to perform an extreme value analysis. More specifically, we apply a point process characterization of wildfire extremes using maximum likelihood estimation. By modeling covariates, we also evaluate potential trends and correlations with commonly known factors that drive or affect wildfire occurrence, such as the Fire Weather Index as a proxy for meteorological conditions, population density, land cover type, and seasonality. We find that the highest risk of extreme wildfires is in Portugal (PT), followed by Greece (GR), Spain (ES), and Italy (IT) with a 10-year BA return level of 50'338 ha, 33'242 ha, 25'165 ha, and 8'966 ha, respectively. Coupling our results with existing estimates of the monetary impact of large wildfires suggests expected losses of 162-439 million € (PT), 81-219 million € (ES), 41-290 million € (GR), and 18-78 million € (IT) for such 10-year return period events. SUMMARY: We model the risk of extreme wildfires for Italy, Greece, Portugal, and Spain in form of burned area return levels, compare them, and estimate expected losses.

Anthracological study of a Chalcolithic funerary deposit from Perdigões (Alentejo, Portugal): A new analytical methodology to establish the wood burning temperature

Anthracological analyses of charcoal samples retrieved from Pit 16 of Perdigões (Reguengos de Monsaraz, Portugal), a secondary deposition of cremated human remains dated back to the middle of the 3rd millennium BC, enabled the identification of 7 different taxa: Olea europaea, Quercus spp. (evergreen), Pinus pinaster, Fraxinus cf. angustifolia, Arbutus unedo, Cistus sp. and Fabaceae. All taxa are characteristic of both deciduous and evergreen Mediterranean vegetation, and this data might indicate that the gathering of woods employed for the human cremation/s occurred either on site, or in its vicinity. However, considering both the large distribution of the identified taxa and data about human mobility, it is not possible to conclusively determine the origin of the wood used in the cremation(s). Chemometric analysis were carried out to estimate the absolute burning temperature of woods employed for the human cremation/s. An in-lab charcoal reference collection was created by burning sound wood samples of the three main taxa identified from Pit 16, Olea europaea var. sylvestris, Quercus suber (evergreen type) and Pinus pinaster, at temperatures between 350 and 600 °C. The archaeological charcoal samples and the charcoal reference collection were chemically characterized by using mid-infrared (MIR) spectroscopy in the 1800-400 cm-1 range, and Partial Least Squares (PLS) regression method was used to build calibration models to predict the absolute combustion temperature of the archaeological woods. Results showed successful PLS forecasting of burn temperature for each taxon (significant (P <0.05) cross validation coefficients). The anthracological and chemometric analysis evidenced differences between the taxa coming from the two stratigraphic units within the Pit, SUs 72 and 74, suggesting that they may come from two different pyres or two different depositional moments.

Fire-induced geochemical changes in soil: Implication for the element cycling

Soils play an essential role in supporting and sustaining life on this planet. In fire-impacted environments, fire causes considerable changes to the soil, especially in the various elements. The present work provides a comprehensive and up-to-date review of the effect of fire on soil geochemistry, and its impact on the cycling of different biogenic, major, minor, and trace elements in the soil. Results from both natural and experimental fires (field-scale and lab-scale) are considered in this review. The temperature at which mineral transformation occurs in the soil during fires is summarised. The review suggests that fires can significantly alter mobility and hence, the cycling of many elements in fire-affected regions. Change in speciation of elements following fires risks formation and/or increased availability of the toxic forms of elements in the soil. The unique physical, chemical, and biological conditions observed during fires make many unlikely reactions more likely. However, the information available in the literature is often fire, vegetation, and element specific. More studies on this topic by changing these three variables will improve our understanding of changes in the soil caused by fire. Hence, with fires being touted to increase global presence in the coming years, more studies on understanding their effects on soils are recommended.

Effect of fire on characteristics of dissolved organic matter in forested catchments in the Mediterranean biome: A review

Fires in forested catchments pose a water contamination risk from fire-derived dissolved organic matter (DOM). Fire events are expected to increase under a projection of warmer and drier climatic conditions; therefore, understanding the consequences of fire-derived DOM is critical for water supply and management of drinking water and catchments. This paper addresses how fire regime - the intensity, severity and frequency of fires - influences DOM quantity and composition in surface waters in forested catchments, and how long it takes for water quality to recover to pre-fire levels. A review of post-fire studies in Mediterranean regions reporting on DOM related parameters has been conducted. The literature shows that post-fire DOM composition and reactivity is different from DOM generated under processes of biological degradation, and hence our reliance on DOM 'bulk properties' and surrogate DOM bulk parameters may not provide sufficient information to deal with the potential complexity of the organic compounds produced by a catchment fire. Appropriate measures are important to adequately operate conventional water treatment facilities, for example. Critical parameters for the effects of burning include the alteration of DOM composition, aromaticity, and the relative amounts of labile/recalcitrant organic components. The literature shows mixed information for the influence of both burn severity and fire intensity, on these parameters, which indicates DOM response to fire is highly variable. For fire frequency, the evidence is more unequivocal, indicating that frequent fires change the composition of DOM to components that are less bioavailable, and elevate the degree of aromaticity, which may be detrimental to water quality. In addition, and in general terms, the more recent the fire, the more aromatic and humified DOM components are found, and vice versa. The recovery of surface water quality to pre-fire conditions was variable, with no safe temporal thresholds suggested in the literature. In some cases, fire-induced changes in DOM composition were observable up to 16 years post-fire. The lack of clearly observed trends in post-fire DOM with fire regimes could be attributed to numerous factors such as limited long-term and event-based observations, experimental design challenges, and site-specific biological, physical and hydrological factors. The application of terminologies used to describe fire regimes such as burn severity and fire intensity also creates challenges in comparing the outcomes and results from numerous studies.

Beta Diversity of Arbuscular Mycorrhizal Communities Increases in Time after Crop Establishment of Peruvian Sacha Inchi (Plukenetia volubilis)

(1) Background: Beta diversity, i.e., the variance in species compositions across communities, has been pointed out as a main factor for explaining ecosystem functioning. However, few studies have directly tested the effect of crop establishment on beta diversity. We studied beta diversity patterns of arbuscular mycorrhizal (AM) fungal communities associated to sacha inchi (Plukenetia volubilis) after crop establishment. (2) Methods: We molecularly characterized the AM fungal communities associated to roots of sacha inchi in plots after different times of crop establishment, from less than one year to older than three. We analyzed the patterns of alpha, beta, and phylogenetic diversity, and the sources of variation of AM fungal community composition. (3) Results: Beta diversity increased in the older plots, but no temporal effect in alpha or phylogenetic diversity was found. The AM fungal community composition was driven by environmental factors (altitude and soil conditions). A part of this variation could be attributed to differences between sampled locations (expressed as geographic coordinates). Crop age, in turn, affected the composition with no interactions with the environmental conditions or spatial location. (4) Conclusions: These results point out towards a certain recovery of the soil microbiota after sacha inchi establishment. This fact could be attributed to the low-impact management associated to this tropical crop.

Wildfire-induced pollution and its short-term impact on COVID-19 cases and mortality in California

Globally, wildfires have seen remarkable increase in duration and size and have become a health hazard. In addition to vegetation and habitat destruction, rapid release of smoke, dust and gaseous pollutants in the atmosphere contributes to its short and long-term detrimental effects. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has emerged as a public health concern worldwide that primarily target lungs and respiratory tract, akin to air pollutants. Studies from our lab and others have demonstrated association between air pollution and COVID-19 infection and mortality rates. However, current knowledge on the impact of wildfire-mediated sudden outburst of air pollutants on COVID-19 is limited. In this study, we examined the association of air pollutants and COVID-19 during wildfires burned during August-October 2020 in California, United States. We observed an increase in the tropospheric pollutants including aerosols (particulate matter [PM]), carbon monoxide (CO) and nitrogen dioxide (NO₂) by approximately 150%, 100% and 20%, respectively, in 2020 compared to the 2019. Except ozone (O₃), similar proportion of increment was noticed during the peak wildfire period (August 16 - September 15, 2020) in the ground PM_2.5, CO, and NO₂ levels at Fresno, Los Angeles, Sacramento, San Diego and San Francisco, cities with largest active wildfire area. We identified three different spikes in the concentrations of PM_2.5, and CO for the cities examined clearly suggesting wildfire-induced surge in air pollution. Fresno and Sacramento showed increment in the ground PM_2.5, CO and NO₂ levels, while San Diego recorded highest change rate in NO₂ levels. Interestingly, we observed a similar pattern of higher COVID-19 cases and mortalities in the cities with adverse air pollution caused by wildfires. These findings provide a logical rationale to strategize public health policies for future impact of COVID-19 on humans residing in geographic locations susceptible to sudden increase in local air pollution.

Energy dispersive X-ray fluorescence analysis to estimate the maximum temperature reached in burned soils from an Amazonian region

Determining the maximum temperature reached in soil during burning is important when evaluating fire intensity. Forest conversion is an ongoing process in the Amazon ecosystem. It is of utmost importance to predict fire effects on soil properties and avoid damaging environmental systems. Spectroscopic methods combined with multivariate statistics may provide chemical and mineralogical information from soil. This study aims at predicting the maximum temperature reached in Oxisols from an Amazonian region in Brazil. Slash-and-burn and pasture samples collected after fire events and unburned forest soil samples submitted to heating (250-800 °C) were investigated. Energy-dispersive X-ray fluorescence (EDXRF) was used to acquire chemical data. The experimental procedure is rapid and requires minimal sample preparation and no hazardous chemical reagents. The EDXRF data, combined with partial least squares regression, were applied in controlled-heated samples from five different sites of forest, pasture, and slash-and-burn areas. Estimated temperatures for burned samples ranged from 317 to 609 °C. Considering the instrumental advantages and the achieved results, the use of EDXRF combined with multivariate analysis is a feasible alternative technology to evaluate fire effects in soil.

An integrated approach for the restoration of Australian temperate grasslands invaded by Nassella trichotoma

Invasive plants are considered to be one of the biggest threats to environmental assets, and once established, they can be immensely difficult to control. Nassella trichotoma is an aggressive, perennial grass species, and is considered to be one of the most economically damaging weeds to grazing systems due to its unpalatability, as well as being one of the leading causes of biodiversity loss in grassland communities. This species produces high density seedbanks that rapidly respond to disturbance events. Despite control programs being developing in Australia since the 1930s, this species is still widespread throughout south-east Australia, indicating that a new management approach is critical to control this Weed of National Significance at the landscape scale. The present study explored the effect of 12 different combinations of herbicide, fire, a second application of herbicide, grazing exclusion, tillage and broadcasting seeds in order to reduce the above and below-ground density of N. trichotoma. A control treatment was also included. The results were assessed using a Hierarchy analysis, whereby treatments of increasing complexity were compared for their efficacy in reducing N. trichotoma cover and seedbank density, while simultaneously increasing the establishment of the broadcast species. Whilst all integrated treatments effectively reduced N. trichotoma's seedbank, the treatments that included fire performed significantly better at simultaneously reducing N. trichotoma and increasing the establishment of broadcasted seeds. Overall, the integration of herbicide, fire and broadcasting native seeds was observed to provide the most economically feasible management strategy for the landscape scale restoration of a degraded temperate grassland dominated by N. trichotoma.

Evaluation of change in the peat soil properties affected by different fire severities

The tropical peatland ecosystems of Indonesia provide direct economic benefits to local communities and act to maintain local weather patterns. The impact of burning tropical peat swamp forests of land clearing for palm oil plantations can have significant consequences on the change in the characteristics of peat soil. The aim of this study was to determine the physical, chemical, and biological properties of peat soils by field and laboratory testing and analysis to understand changes in the nature and characteristics of peatlands at four locations in the Pelalawan Regency of Riau Province. The results showed that the effect of burning peat swamp forests can lead to a change in the physical, chemical, and biological properties of the peat soils. Soil permeability and the soil microbial population can significantly decrease with increasing fire severity. The effect of different fire severities on the characteristics of peat soil is verified to contribute to advanced management of the tropical peatland in the future.

Post-fire dynamics of the main biogenic nutrients of the Pinus pinaster forest soil of Jijel, Northeastern Algeria

Forest fires are part of the natural dynamics of Mediterranean forest ecosystems. In the Mediterranean regions, the ecosystems are shaped by this disturbance that they have been subjected to for a long time. This work aimed to study the effect of fire on the superficial soil of the Pinus pinaster forest of Jijel, Northeastern Algeria. Soil samples were taken at a depth of 0–5 cm at different dates over a period of 24 months, in a diachronic mode. The following parameters have been tested: total carbon (C), total nitrogen (N), pH, cations exchange capacity (C.E.C.) and main exchangeable bases: calcium (Ca2+), magnesium (Mg2+), sodium (Na+) and potassium (K+). The results of the study showed a significant soil enrichment during the first few months after the fire; this temporary high fertility decreases with time due to ecosystem recovery, which could be interpreted as a return to the pre-fire state.

Crop residue burning in South Asia: A review of the scale, effect, and solutions with a focus on reducing reactive nitrogen losses

This paper reviews the literature on crop residue burning - a widespread practice in many regions in South Asia. Specifically, we examine evidence from studies highlighting the scale of the practice in South Asia, the environmental implications, the drivers of the practice and the remedies to the problem. The studies provide evidence that the Indo-Gangetic Plain (IGP) is a hot-spot for atmospheric pollutants, with seasonal crop residue burning being a major contributor. The burning of crop residue is reported to degrade the soil, increase the risk of erosion, and increase the soil temperature, consequently decimating soil microorganisms. This subsequently impacts the monetary cost involved in recovering the soil fertility and the potential for further pollution through the increased use of fertilizer. The review shows that farmers' reasons for burning crop residues are mainly the high cost of incorporating, collecting, transporting, and processing crop residues in South Asia. Labour shortages, the marketability of the crop residue and the short time interval between harvest and next cropping seasons also influence farmers decision to burn crop residue. To address this problem, there is the need to encourage the use of agricultural machines capable of sowing crops in standing stubble, adopting in-situ practices and changing crop varieties to those with short duration. In addition, education and awareness are needed to change beliefs and perceptions on crop residue burning. Crucially, when promoting alternative sustainable uses of crop residue, the economic benefits should be prioritized, and support towards initial investments that accompany the adoption of alternative practices should be provided.

Fire frequency and type regulate the response of soil carbon cycling and storage to fire across soil depths and ecosystems: A meta-analysis

Fire is a very common disturbance in terrestrial ecosystems and can give rise to significant effects on soil carbon (C) cycling and storage. Here, we conducted a global meta-analysis on the response of soil C cycling and storage across soil profiles (organic layer, 0-5 cm, 0-10 cm, 0-20 cm, and 20-100 cm) to fire reported in 308 studies across 383 sites and examined the role of fire frequency, fire type, soil type, ecosystem type, and post-fire time in regulating the response of soil C dynamics to fire. Overall, we found soil C cycling and storage were more responsive to one fire and wildfire as compared to frequent fire and prescribed fire, respectively. Soil respiration significantly decreased by 22 ± 9% by one fire, but was not significantly affected by frequent fire across ecosystems. One fire significantly reduced soil C content in the organic, 0-10 cm, and 20-100 cm layers by 27 ± 16%, 10 ± 9%, and 33 ± 18%, respectively, while frequent fire significantly reduced soil C content at a depth of 0-5 cm and 0-20 cm by 29 ± 8% and 16 ± 12%, respectively. Soil C cycling and storage showed little response to frequent prescribed fire. In addition, the response of soil C cycling and storage varied among different soil and ecosystem types, with a stronger response being observed in forest than in grassland. Within 20 years post-fire, soil C cycling and storage tended to recover only after one fire but not after frequent fire. We also found that soil physicochemical properties and microbial communities were more responsive to one fire than frequent fire, which could indirectly affect the effects of fire on soil C cycling and storage. The results of our study have filled some critical gaps in previous meta-analyses in fire ecology.

GIS-Based Frequency Ratio and Analytic Hierarchy Process for Forest Fire Susceptibility Mapping in the Western Region of Syria

Forest fires are among the most major causes of global ecosystem degradation. The integration of spatial information from various sources using statistical analyses in the GIS environment is an original tool in managing the spread of forest fires, which is one of the most significant natural hazards in the western region of Syria. Moreover, the western region of Syria is characterized by a significant lack of data to assess forest fire susceptibility as one of the most significant consequences of the current war. This study aimed to conduct a performance comparison of frequency ratio (FR) and analytic hierarchy process (AHP) techniques in delineating the spatial distribution of forest fire susceptibility in the Al-Draikich region, located in the western region of Syria. An inventory map of historical forest fire events was produced by spatially digitizing 32 fire incidents during the summers of 2019, 2020, and 2021. The forest fire events were divided into a training dataset with 70% (22 events) and a test dataset with 30% (10 events). Subsequently, FR and AHP techniques were used to associate the training data set with the 13 driving factors: slope, aspect, curvature, elevation, Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), Topographic Wetness Index (TWI), rainfall, temperature, wind speed, TWI, and distance to settlements, rivers and roads. The accuracy of the maps resulting from the modeling process was checked using the validation dataset and receiver operating characteristics (ROC) curves with the area under the curve (AUC). The FR method with AUC = 0.864 achieved the highest value compared to the AHP method with AUC = 0.838. The outcomes of this assessment provide constructive spatial insights for adopting forest management strategies in the study area, especially in light of the consequences of the current war.

Effect of different soil amendments on soil buffering capacity

The buffering capacity of the soil is a very important property of the soil, which determines the ability of the soil to resist external influences, especially changes in pH and thus create good living conditions for plants and microorganisms in the soil. The buffering capacity thus significantly contributes to maintaining the health and quality of the soil. Buffering capacity is an important indicator of soil quality, because it is related to the overall condition of the soil ecosystem and other soil properties. The goal of this paper is to determine the effect of applying different soil amendments on the soils, 10 years after application. We compared the effect of 6 different treatments in closed plots: Natural conditions (N = control); Bare soil (B); Straw mulching (S); Pine mulch (P); TerraCottem hydroabsorbent polymers (H); Prescribed burn (F); and Sewage sludge (M). Our results have shown that the application of different amedments leads to an effect on the plowing capacity of the soil. While in the case of the control variant (Natural conditions, N) the buffering capacity of the soil was measured at 144.93 ± 0.25, the addition of different amendments decreased the buffering capacity in the following order: Bare soil (B) 142.73±0.21 > TerraCotem hydroaborbent polymer (H) 142.23±.15 > Pine mulch (P) 140.40±0.30, Prescribed burn (F) 138.20±0.30, Sludge (S) 127.47±0.15. In the case of all variants, these are statistically significant differences (p ≤ 0.05). Thus, soil amendments have been shown to have a statistically significant effect on soil buffering capacity.

Prediction, validation, and uncertainties of a nation-wide post-fire soil erosion risk assessment in Portugal

Wildfires are a recurrent and increasing threat in mainland Portugal, where over 4.5 million hectares of forests and scrublands have burned over the last 38 years. These fire-affected landscapes have suffered an intensification of soil erosion processes, which can negatively affect soil carbon storage, reduce fertility and forest productivity, and can become a source of pollutants. The main objective of the present study is to produce a post-fire soil erosion risk map for the forest and shrubland areas in mainland Portugal and assess its reliability. To this end, the semi-empirical Morgan–Morgan–Finney erosion model was used to assess the potential post-fire soil erosion according to distinct burn severity and climate scenarios, and the accuracy of the predictions was verified by an uncertainty analysis and validated against independent field datasets. The proposed approach successfully allowed mapping post-fire soil erosion in Portugal and identified the areas with higher post-fire erosion risk for past and future climate extremes. The outcomes of this study comprise a set of tools to help forest managers in their decision-making for post-fire emergency stabilization, ensuring the adequate selection of areas for mitigation to minimize the economic and environmental losses caused by fire-enhanced soil erosion.

Potentially Toxic Substances and Associated Risks in Soils Affected by Wildfires: A Review

The presence of toxic substances is one of the major causes of degradation of soil quality. Wildfires, besides affecting various chemical, physical, and biological soil properties, produce a mixture of potentially toxic substances which can reach the soil and water bodies and cause harm to these media. This review intends to summarise the current knowledge on the generation by wildfires of potentially toxic substances, their effects on soil organisms, and other associated risks, addressing the effects of fire on metal mobilisation, the pyrolytic production of potentially toxic compounds, and the detoxifying effect of charcoal. Numerous studies ascertained inhibitory effects of ash on seed germination and seedling growth as well as its toxicity to soil and aquatic organisms. Abundant publications addressed the mobilisation of heavy metals and trace elements by fire, including analyses of total concentrations, speciation, availability, and risk of exportation to water bodies. Many publications studied the presence of polycyclic aromatic hydrocarbons (PAH) and other organic pollutants in soils after fire, their composition, decline over time, the risk of contamination of surface and ground waters, and their toxicity to plants, soil, and water organisms. Finally, the review addresses the possible detoxifying role of charcoal in soils affected by fire.

Fire effects on the distribution and bioavailability of potentially toxic elements (PTEs) in agricultural soils

In the last years, uncontrolled fires are frequently occurring in forest and agricultural areas as an indirect effect of the rising aridity and global warming or caused by intentional illegal burnings. In addition, controlled burning is still largely used by farmers as an agricultural practice in many parts of the world. During fire events, soil can reach very high temperatures at the soil surface, causing dramatic changes of soil properties and elements biogeochemistry. Among soil elements, also potentially toxic elements (PTEs) can be affected by fires, becoming more or less mobile and bioavailable, depending on fire severity and soil characteristics. Such transformations could be particularly relevant in agricultural soils used for crop productions since fire events could modify PTEs speciation and uptake by plants and associated (micro)organisms thus endangering the whole food-chain. In this review, after describing the effects of fire on soil minerals and organic matter, the impact of fires on PTEs distribution and speciation in soils is presented, as well as their influence on soil microorganisms and plants uptake. The most common experimental methods used to simulate fires at the laboratory and field scale are briefly illustrated, and finally the impact that traditional and innovative agricultural practices can have on PTEs availability in burned agricultural soils is discussed in a future research perspective.

Short-Term Changes in Erosion Dynamics and Quality of Soils Affected by a Wildfire and Mulched with Straw in a Mediterranean Forest

Wildfire heavily impacts the quality of forest soils, and the precipitation occurring immediately after fire can determine high runoff and erosion rates, which may lead to noticeable soil degradation. Mulching is commonly used to limit the hydrological impacts of wildfire and climate, but this post-fire management technique may alter the erosion–deposition dynamics at the hillslope scale and, consequently, alter soil quality. In order to explore the magnitude and significance of these changes (little was studied in the literature until now), this communication reports the first results of a field activity that evaluated the changes in soil quality in areas affected by a wildfire and subjected to different post-fire treatments in Mediterranean forests. The main properties of sediments eroded from burned and untreated soils, and mulched soils (using a straw dose of 0.2 kg/m2 of dry weight), were measured after the first rainstorm (height of 37 mm and maximum intensity of 11.6 mm h−1) occurring two months after a wildfire (occurred on 30 June 2016) in a pine forest of Castilla-La Mancha (Spain). This event produced a runoff volume of 0.07 ± 0.02 mm in mulched soils and 0.10 ± 0.10 mm in non-mulched soils; soil loss was 0.20 ± 0.06 g/m2 in the mulched area and 0.60 ± 0.60 g/m2 in the non-mulched area. In comparison to burned and non-treated areas, this study showed: (i) increases in salinity, and reductions in organic matter, nutrients, nitrates, and micro-elements in burned and untreated soils; (ii) reductions in runoff (−20%) and in soil erosion (−60%) as a result of mulch cover; (iii) effectiveness of mulching in limiting the declines in soil quality detected in burned and eroded areas; and (iv) transport of low amounts (less than 10–15%) of some compounds (organic matter and nutrients) downstream of the fire-affected areas (both mulched and untreated). Phosphorous runoff toward valley areas and nitrate incorporation into the soil, detected in both mulched and untreated areas, require attention, since these processes may cause eutrophication of water bodies or nitrate pollution in groundwater.

A multi-hazard map-based flooding, gully erosion, forest fires, and earthquakes in Iran

We used three state-of-the-art machine learning techniques (boosted regression tree, random forest, and support vector machine) to produce a multi-hazard (MHR) map illustrating areas susceptible to flooding, gully erosion, forest fires, and earthquakes in Kohgiluyeh and Boyer-Ahmad Province, Iran. The earthquake hazard map was derived from a probabilistic seismic hazard analysis. The mean decrease Gini (MDG) method was implemented to determine the relative importance of effective factors on the spatial occurrence of each of the four hazards. Area under the curve (AUC) plots, based on a validation dataset, were created for the maps generated using the three algorithms to compare the results. The random forest model had the highest predictive accuracy, with AUC values of 0.994, 0.982, and 0.885 for gully erosion, flooding, and forest fires, respectively. Approximately 41%, 40%, 28%, and 3% of the study area are at risk of forest fires, earthquakes, floods, and gully erosion, respectively.

Combined Effect of Laboratory-Simulated Fire and Chromium Pollution on Microbial Communities in an Agricultural Soil

Simple Summary

Soil quality and fertility rely on soil microorganisms which contribute to nutrient cycling and plant nutrition. Accidental or intentional fires can almost completely kill soil microbiota and cause soil sterilization. Fires can also destroy soil organic matter (OM), thus causing the release of potentially toxic elements such as Cr that can further disturb soil recolonization by surviving bacteria. The identification of species able to cope with such altered environments is highly relevant to restore soil life in degraded soils and to remediate polluted sites. In this study, we identified soil microorganisms potentially suitable to colonize fire-affected areas and tolerate high concentrations of bioavailable and toxic Cr, and which therefore could be useful for the above-mentioned purposes.

Abstract

Fire events in agricultural soils can modify not only soil properties but also the structure of soil microbial communities, especially in soils containing high concentrations of potentially toxic elements (PTEs). The recolonization of burned soils can in fact favor the proliferation of certain microorganisms, more adaptable to post-fire soil conditions and higher PTE availability, over others. In this study, we simulated with laboratory experiments the microbial recolonization of an agricultural soil containing high Cr concentrations after heating at 500 °C for 30 min, to mimic the burning of crop residues. Changes in soil properties and Cr speciation were assessed, as well as soil microbial structure by means of 16S rRNA gene sequencing. Both altered soil conditions and increased Cr availability, especially Cr(VI), appeared to be responsible for the reduction in species diversity in heated soils and the proliferation of Firmicutes. Indeed, already after 3 days from the heat treatment, Firmicutes increased from 14% to 60% relative abundance. In particular, Paenibacillus was the most abundant genus identified after the simulation, with an average relative abundance of 40%. These bacteria are known to be good fire-responders and Cr-tolerant. These results could be useful to identify bacterial strains to be used as bioindicators of altered environments and for the recovery of fire-impacted polluted sites.

Fire alters diversity, composition, and structure of dry tropical forests in the Eastern Ghats

Fire is known to have dramatic consequences on forest ecosystems around the world and on the livelihoods of forest-dependent people. While the Eastern Ghats of India have high abundances of fire-prone dry tropical forests, little is known about how fire influences the diversity, composition, and structure of these communities. Our study aimed to fill this knowledge gap by examining the effects of the presence and the absence of recent fire on tropical dry forest communities within the Kadiri watershed, Eastern Ghats. We sampled plots with and without evidence of recent fire in the Eswaramala Reserve Forest in 2008 and 2018. Our results indicate that even though stem density increases in the recently burned areas, species richness is lower because communities become dominated by a few species with fire resistance and tolerance traits, such as thick bark and clonal sprouting. Further, in the presence of fire, the size structure of these fire-tolerant species shifts toward smaller-sized, resprouting individuals. Our results demonstrate that conservation actions are needed to prevent further degradation of forests in this region and the ecosystem services they provide.

Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness

Tyrannosaurids are hypothesized to be gregarious, possibly parasocial carnivores engaging in cooperative hunting and extended parental care. A tyrannosaurid (cf. Teratophoneus curriei) bonebed in the late Campanian age Kaiparowits Formation of southern Utah, nicknamed the Rainbows and Unicorns Quarry (RUQ), provides the first opportunity to investigate possible tyrannosaurid gregariousness in a taxon unique to southern Laramidia. Analyses of the site's sedimentology, fauna, flora, stable isotopes, rare earth elements (REE), charcoal content and taphonomy suggest a complex history starting with the deaths and transport of tyrannosaurids into a peri-fluvial, low-energy lacustrine setting. Isotopic and REE analyses of the fossil material yields a relatively homogeneous signature indicating the assemblage was derived from the same source and represents a fauna living in a single ecospace. Subsequent drying of the lake and fluctuating water tables simultaneously overprinted the bones with pedogenic carbonate and structurally weakened them through wet-dry cycling. Abundant charcoal recovered from the primary bone layer indicate a low temperature fire played a role in the site history, possibly triggering an avulsion that exhumed and reburied skeletal material on the margin of a new channel with minimal transport. Possible causes of mortality and concentration of the tyrannosaurids include cyanobacterial toxicosis, fire, and flooding, the latter being the preferred hypothesis. Comparisons of the RUQ site with other North American tyrannosaur bonebeds (Dry Island-Alberta; Daspletosaurus horneri-Montana) suggest all formed through similar processes. Combined with ichnological evidence, these tyrannosaur mass-burial sites could be part of an emerging pattern throughout Laramidia reflecting innate tyrannosaurid behavior such as habitual gregariousness.

Long-term effects of wildfire on rock weathering and soil stoniness in the Mediterranean landscapes

The severe wildfire at Mt. Carmel, Israel, in 2010, caused massive destruction of carbonate rocks. The thermal shock caused extreme exfoliation, producing large and flat clasts, affecting rocks to a depth of up to 20 cm. A decade after the fire, most flakes and spalls disappeared from the rock outcrops and adjacent soils. From these observations, this study pursued two objectives: (a) to monitor and analyze the spatio-temporal distribution of the disintegrated flakes 10 years after the fire and (b) to test the hypothesis that fires contribute to increased soil stoniness via physical and chemical flake erosion. The studied area included five lithostratigraphic units composed of chalk, limestone, and dolomite. The Schmidt Hammer test showed that after a decade, most of the spalled surface on the burned outcrops was lost, exposing new rock surfaces to atmospheric and weathering processes. The spalls and flakes were broken down and pulverized. The most prominent effects were changes in surface stoniness on the rendzina soils over the chalks, while there was less impact on the dolomite and limestone samples. The stoniness of the non-burned chalk was 23-39% and increased significantly to 69-86% in the burned area. Chalk erosion produced large (>16 mm, median 8-16 mm) and abundant gravel, suggesting fragmentation of large spalls, and particles that lost their bladed shapes becoming oblate and equant. While earlier works suggested that increasing rock fragment cover is often associated with the removal of fine particles, our results showed a substantial increase in rock fragments due to fire-induced exfoliation of rock surfaces, leading to long-term changes in soil properties. We therefore propose that the size, shape, and spatial distribution of rock fragments should be considered when examining the effects of rock fragments on hydrological and geomorphological processes or on post-fire soil rehabilitation.

Assessing the Ecotoxicity of Soil Affected by Wildfire

This study was carried out to assess the ecotoxicity of soil affected by wildfire using two laboratory toxicity tests, and to investigate the possibility of application of selected soil amendment into the burnt soil in order to improve its properties for faster post-fire reclamation. A phytotoxicity test is a fast-indicative test for revealing acute toxicity and was performed on quickly growing plant species Sinapis alba L. and Lepidium sativum L., while a pot experiment is a standardized toxicity test with a longer experiment duration and was carried out with Lolium perenne L., Festuca rubra L., Brassica juncea L. Diatomite, bentonite, compost, and biochar were supplemented to the soil. Regarding the phytotoxicity test only 3% w/w of biochar stimulated the growth of Lepidium sativum L. Pot experiment confirmed that effect of soil application amendments on biomass yield is more significant than the plant species. The average highest biomass yields were achieved in treatments with bentonite and diatomite. Subsequent research should focus on investigating possible combinations of soil amendments for burnt soil reclamation and complementing the experiments with chemical analysis.

Historical survey of research related to fire management and fauna conservation in the world and in Brazil

Abstract: Fire is a key ecological factor affecting biodiversity structure and composition. Fires' effects on biodiversity can be beneficial or harmful depending on how, where, when, and why they occur. The impacts of fire on fauna vary according to species ecology and the fire regime. To understand the research effort relating fire, fauna, and mammals, we surveyed papers published in World and in Brazil. Only 5% of the publications between 1970 and 2019 with fire subject dealt with fauna and 0.5% with mammal. For Brazil, we obtained 7% of papers for fauna and 3% for mammal. The Brazilian Biome with more papers was Cerrado, followed by Atlantic Forest, Amazon, Pampas, Caatinga and Pantanal. The United States of America and Australia stand out as protagonists in their continents with the largest papers number. The volume of research is related to investment in Research and Development and to occurrence of fires. The slope of temporal trend shows the terms related to wildfire have more papers than prescribed burn and there is less interest in fauna and mammal research. It is necessary to form research groups with these themes as research lines and intensify research relating fire ecology and mammals. There is yet no unified understanding of how fire may influence animal diversity and how it influences the vegetative structure and subsequently the resources which wildlife rely on. We consider this information is essential to establish efficient conservation policies.

Topsoil microstructure changes after a shrubland prescribed burn (Central Pyrenees, NE Spain)

The dense thicket Echinospartum horridum (Vahl, Rothm) is expanded in secondary pastures of the Central Pyrenees (NE-Spain). The control of this grassland encroachment is attempted through prescribed burnings, trying to minimize its direct effects on the soil. But the structural changes on the new soil surface, burned and bare, are unknown in the medium-term. To check it, soil aggregate stability (SAS), mean weight diameter of the aggregates (MWD), water repellency (WR), unsaturated hydraulic conductivity (k), and soil organic carbon (SOC) were measured in the surface (at 0-1, 1-2, 2-3, and 3-5 cm) in both unburned and 1-yr burned soils, after verifying that it suffered no direct damage. We also used the digital images of thin sections, obtained from undisturbed and oriented topsoil samples, to detect potential changes in soil microstructure. No significant changes were found in SAS, MWD and SOC for any thickness of soil studied. Nevertheless the WR, which was high before and just after burning, decreased significantly in the upper soil cm after 1-yr burning. WR decrease coincides with the 6-fold increase of the unsaturated hydraulic conductivity (k) and the presence of cappings on the burned topsoil. Cappings are coatings poor in organic matter and composed by fine sand-sized particles of angular quartz, mixed with charcoal, covering irregularly the original topsoil. The formation of cappings seems to derive from the impact of raindrops on the bare soil surface, hence its irregular spatial distribution. Summarizing, removing bushes by means of a low-intensity fast-moving prescribed burning caused the formation of discontinuous cappings without worsening significantly the rest of the measured properties.

Drivers of Fire Anomalies in the Brazilian Amazon: Lessons Learned from the 2019 Fire Crisis

The 2019 fire crisis in Amazonia dominated global news and triggered fundamental questions about the possible causes behind it. Here we performed an in-depth investigation of the drivers of active fire anomalies in the Brazilian Amazon biome. We assessed a 2003–2019 time-series of active fires, deforestation, and water deficit and evaluated potential drivers of active fire occurrence in 2019, at the biome-scale, state level, and local level. Our results revealed abnormally high monthly fire counts in 2019 for the states of Acre, Amazonas, and Roraima. These states also differed from others by exhibiting in this year extreme levels of deforestation. Areas in 2019 with active fire occurrence significantly greater than the average across the biome had, on average, three times more active fires in the three previous years, six times more deforestation in 2019, and five times more deforestation in the five previous years. Approximately one-third of yearly active fires from 2003 to 2019 occurred up to 1 km from deforested areas in the same year, and one-third of deforested areas in a given year were located up to 500 m from deforested areas in the previous year. These findings provide critical information to support strategic decisions for fire prevention policies and fire combat actions.

Forest fire induces short-term shifts in soil food webs with consequences for carbon cycling

We tested for fire-induced (5-6 years post-fire) changes in the structure and functioning of the soil food web along a 3000-km north-south transect across European Russia, spanning all major forest types in the northern hemisphere outside the tropics. The total biomass of the detrital food web, including microbes and invertebrates, was not affected by fire. However, fire reduced the biomass of microfauna and mites, but had no impact on mesofauna or macrofauna. Fire also reduced rates of carbon (C) mobilisation by soil biota. Our results demonstrate that fire-induced shifts in soil food webs have significant short-term effects on forest soil C cycling, but that these effects vary across forest types and geographic locations.

Barbero G, Palma M. Characterization of Biodegraded Ignitable Liquids by Headspace-Ion Mobility Spectrometry

The detection of ignitable liquids (ILs) can be crucial when it comes to determining arson cases. Such identification of ILs is a challenging task that may be affected by a number of factors. Microbial degradation is considered one of three major processes that can alter the composition of IL residues. Since biodegradation is a time related phenomenon, it should be studied at different stages of development. This article presents a method based on ion mobility spectroscopy (IMS) which has been used as an electronic nose. In particular, ion mobility sum spectrum (IMSS) in combination with chemometric techniques (hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA)) has been applied for the characterization of different biodegraded ILs. This method intends to use IMSS to identify a range of ILs regardless of their degree of biodegradation. Three ILs (diesel, gasoline and kerosene) from three different commercial brands were evaluated after remaining in a soil substrate for several lengths of time (0, 2, 5, 13 and 38 days). The HCA results showed the samples’ trend to fall into categories characterized by ILs type and biodegradation time. The LDAs allowed a 99% successful classification of the samples according to the IL type. This is the first time that an HS-IMS technique has been used to detect ILs that have undergone biodegradation processes. The results show that IMS may be a promising alternative to the current standard method based on gas-chromatography for the analysis of biodegraded ILs. Furthermore, no pretreatment of the samples nor the use of a solvent is required.

Effect of Natural Forest Fires on Regional Weather Conditions in Siberia

Effects of forest fires on regional weather conditions were analyzed for Central and Eastern Siberia after warm and dry weather conditions in summer 2019 using COSMO-Ru (COnsortium for Small-scale MOdeling; Ru—Russia) and COSMO-RuART (ART—Aerosols and Reactive Trace gases) model systems. Four series of numerical experiments were conducted (one control experiment and three forest fire experiments assuming total vegetation destruction within the burned areas) to evaluate possible effects of forest fires on surface albedo and vegetation properties as well as their influence on air chemistry and aerosol concentration in the atmosphere. The modeling results showed significant influence of forest fires on regional weather conditions that occurred over large areas situated even away from burnt regions. Decreased surface albedo and reduced latent heat fluxes due to fire-induced destruction of forest cover lead to higher near-surface air temperature and lower air humidity in both burned and surrounding unburned forest areas. On the other hand, reduced incoming solar radiation due to smoke from forest fire plumes decreased land surface temperatures and increased thermal atmospheric stability resulting in reduced regional precipitation.

Low-severity fire as a mechanism of organic matter protection in global peatlands: Thermal alteration slows decomposition

Worldwide, regularly recurring wildfires shape many peatland ecosystems to the extent that fire-adapted species often dominate plant communities, suggesting that wildfire is an integral part of peatland ecology rather than an anomaly. The most destructive blazes are smoldering fires that are usually initiated in periods of drought and can combust entire peatland carbon stores. However, peatland wildfires more typically occur as low-severity surface burns that arise in the dormant season when vegetation is desiccated, and soil moisture is high. In such low-severity fires, surface layers experience flash heating, but there is little loss of underlying peat to combustion. This study examines the potential importance of such processes in several peatlands that span a gradient from hemiboreal to tropical ecozones and experience a wide range of fire return intervals. We show that low-severity fires can increase the pool of stable soil carbon by thermally altering the chemistry of soil organic matter (SOM), thereby reducing rates of microbial respiration. Using X-ray photoelectron spectroscopy and Fourier transform infrared, we demonstrate that low-severity fires significantly increase the degree of carbon condensation and aromatization of SOM functional groups, particularly on the surface of peat aggregates. Laboratory incubations show lower CO₂ emissions from peat subjected to low-severity fire and predict lower cumulative CO₂ emissions from burned peat after 1-3 years. Also, low-severity fires reduce the temperature sensitivity (Q₁₀ ) of peat, indicating that these fires can inhibit microbial access to SOM. The increased stability of thermally altered SOM may allow a greater proportion of organic matter to survive vertical migration into saturated and anaerobic zones of peatlands where environmental conditions physiochemically protect carbon stores from decomposition for thousands of years. Thus, across latitudes, low-severity fire is an overlooked factor influencing carbon cycling in peatlands, which is relevant to global carbon budgets as climate change alters fire regimes worldwide.

Do Fire Regime Attributes Affect Soil Biochemical Properties in the Same Way under Different Environmental Conditions?

Global change is altering fire frequency and severity in many regions across the world. In this work, we studied the impact of different frequency and severity regimes on the soil biochemical properties in burned areas with different environmental conditions. We selected three sites dominated by pine ecosystems along a Mediterranean-Transition-Oceanic climatic gradient, where we determined the fire frequency, and severity of the last wildfire. Four years after the last wildfire, we established 184 4 m2 plots. In each plot, we collected a composed soil sample from a 3 cm depth, and measured several ecological variables potentially affected by the fire frequency and severity (cover of bare soil, cover of fine and coarse plant debris, cover of vegetation, and vegetation height). From each soil sample, we analyzed the enzymatic activities corresponding to the biogeochemical cycles of carbon, nitrogen, and phosphorus (β-glucosidase, urease, and acid-phosphatase, respectively), and the microbial biomass carbon. The results indicated that fire frequency only played a significant role in soil biochemical properties at the Mediterranean and Transition sites. Specifically, we found that increases in frequency contributed to increased urease and phosphatase activities (at the Transition site), as well as microbial biomass carbon (at the Mediterranean and Transition sites). In relation to burn severity, we found opposite patterns when comparing the Mediterranean and Oceanic sites. Specifically, increased severity significantly decreased β-glucosidase, urease, and microbial biomass carbon at the Mediterranean site, whereas at the Oceanic one, severity significantly increased them. Burn severity also decreased microbial biomass carbon at the Transition site. Our results also indicated that, overall, fire frequency determined the studied ecological variables at the Mediterranean and Transition sites, but clear indirect effects on biochemical properties due to changes in ecological variables were not found. This study adds to the knowledge on the impact of shifts in fire regimes on soils in the current context of change.

Soil Microbiota of Dystric Cambisol in the High Tatra Mountains (Slovakia) after Windthrow

There has been much more damage to forests in the Slovak Republic in the second half of the 20th century than to other European countries. Forested mountain massifs have become a filter of industrial and transportation emissions from abroad, as well as from domestic origins. There are not only acidic deposits of sulphur and heavy metals present in forest soils, but other additional environmental problems, such as climate change, storms, fires, floods, droughts, are worsening the situation. Therefore, forest terrestrial ecosystems are becoming more vulnerable due to changes in natural and environmental conditions. In the High Tatra Mountains in Slovakia, which are protected as a national park, four internationally monitored localities were established after the windthrow disaster in 2004 and fire in 2005: REF, with intact forest; EXT, with extracted wood mass; NEX, with non-extracted wood mass; and FIR, the burnt locality. Soils from these localities were microbiologically analysed with special attention to fungi. Bacterial microbiota detected by high-throughput sequencing showed the prevalence of the genera Acidothermus, Mycobacterium, and Nocardia, and a very low presence of the genera Acidibacter, Burkholderia-Paraburkholderia, Optitus and the uncultured genus Desulfurellaceae H16 in the soil sample from the burnt locality when compared with the unburned sites. Additionally, soil mycocoenoses showed a low similarity between the locality with an intact forest ecosystem and the localities with extracted (REF–EXT) and non-extracted (REF–NEX) wood mass. There was no similarity with the burnt locality (FIR), where heat-resistant fungi dominated. It was shown that the windthrow disaster and subsequent extraction or non-extraction of wood mass did not affect the soil microbial communities or their development. On the other hand, the influence of fire was significant.

Fire-Induced Changes in Soil and Implications on Soil Sorption Capacity and Remediation Methods

Vegetation changes caused by fire events are visible instantly but changes in soils are less apparent, and could be short-term, long-term or permanent in nature. Research has shown that soils undergo changes in their mineralogical, geochemical, physico-chemical and biological properties after a fire event that may vary depending on the intensity and duration of the fire, and the properties of the soil. Some of these properties make significant contributions towards soil’s ability to sorb contaminants. Changes in these properties could affect soil sorption complex and the effectiveness of remediation methods used to clean these soils when contaminated. This review synthesizes available information on fire-induced changes in soil properties affecting soil sorption and the factors which dictate these changes. The implications of changes in these properties on the soil’s natural attenuation capacity and choice of remediation method to clean up fire-affected contaminated soils are also discussed.

Temporal changes in magnetic signal of burnt soils - A compelling three years pilot study

Wildfires strongly affect soils, including iron biogeochemical cycling and carbon storage. Thus, it is important to reveal the dynamics of iron oxide synthesis and transformations during and after a wildfire. This study investigates the temporal stability of strongly magnetic minerals appearing after a wildfire. Following a designed experimental fire, samples from vegetation ash and mineral soil were taken immediately after and at progressively longer time intervals. The magnetic susceptibility monitoring of samples during three years period demonstrates an initial increase in magnetic signal of ash-rich material taken immediately after the fire followed by a gradual decrease over time. The behavior of samples collected later after the fire showed only a moderate decrease. It is suggested that the magnetic susceptibility rise during the laboratory storage could be due to the increased availability of nutrients and microbial activity immediately after the fire and related intense redox reactions involving iron oxide particles. The decreasing trend in magnetic susceptibility is ascribed to the oxidation of ultrafine magnetite particles with time. All mineral soil samples from the deeper level showed an initial susceptibility increase, assigned to a similar process. Magnetic susceptibility monitoring was also carried out on samples gathered shortly after natural wildfires. The soil samples affected by strong and long wildfires show a decrease in magnetic susceptibility with time. This effect is more pronounced in the surface black-colored ash layer. The ash material from a site disturbed by a strong short wildfire demonstrates behavior similar to the ash from the experimental fire. It is supposed that the temporal evolution of magnetic susceptibility of the mineral alteration products of wildfires is influenced by the grain size of the produced iron oxide particles, their redox reactions mediated by the heterotrophic bacteria, as well as the amplifying role of pyrogenic carbon for intensification of the redox reactions.

Wildfire and Prescribed Fire Effects on Forest Floor Properties and Erosion Potential in the Central Appalachian Region, USA

Short- and long-term impacts of wildland fires on forest floor properties and erosion potential were examined at three locations in the Central Appalachian region, U.S.A. In 2018, two wildfires were investigated within six months of burning on the George Washington–Jefferson National Forest (GWJNF) in Bland County, Virginia and the Monongahela National Forest (MNF) in Grant County, West Virginia. An additional wildfire was studied eight years post-fire on the Fishburn Forest (FF) in Montgomery County, Virginia. A 2018 prescribed fire was also studied within six months of burning on the MNF in Pendleton County, West Virginia. Litter and duff consumption were examined to evaluate fire severity and char heights were measured to better understand fire intensity. The Universal Soil Loss Equation for forestlands (USLE-Forest) was utilized to estimate potential erosion values. For the 2018 comparisons, litter depth was least as a result of the wildfires on both the MNF and GWJNF (p < 0.001). Wildfire burned duff depths in 2018 did not differ from unburned duff depths on either the MNF or GWJNF. Eight years after the FF wildfire, post-fire litter depth was less than that of an adjacent non-burned forest (p = 0.29) and duff depth was greater than that of an adjacent non-burned forest (p = 0.76). Mean GWJNF wildfire char heights were greatest of all disturbance regimes at 10.0 m, indicating high fire intensity, followed by the MNF wildfire and then the MNF prescribed fire. USLE-Forest potential erosion estimates were greatest on the MNF wildfire at 21.6 Mg soil ha−1 year−1 due to slope steepness. The next largest USLE-Forest value was 6.9 Mg soil ha−1 year−1 on the GWJNF wildfire. Both the prescribed fire and the 2010 wildfire USLE-Forest values were approximately 0.00 Mg soil ha−1 year−1. Implications for potential long-term soil erosion resulting from similar wildfires in Central Appalachian forests appeared to be minimal given the 2010 wildfire results.

Linking fire and the United Nations Sustainable Development Goals

Fire is a ubiquitous natural disturbance that affects 3-4% of the Earth's surface each year. It is a tool used by humans for land clearing and burning of agricultural wastes. The United Nations Sustainable Development Goals (SDGs) do not explicitly mention fire, though many of the Goals are affected by the beneficial and adverse consequences of fires on ecosystem services. There are at least three compelling reasons to include a fire perspective in the implementation of the United Nations Sustainable Development Goals. The first reason relates to the stated vision of the United Nations 2030 Agenda to protect the environment. In order to achieve environmental protection during sustainable development activities, it is necessary to understand and plan for the effects of disturbances, in this case fire, on ecosystem services. The second reason is that fires produce emissions with regional and global impacts on air quality and rainfall patterns. Fires contribute to global warming though the release greenhouse gases, primarily CO₂, and black carbon, identified as a SLCP (short-lived climate pollutant). The third reason is that fire is one of several complex processes that lead to land degradation across the globe. Opportunities exist to incorporate a fire perspective into sustainable development projects or approaches. Two examples are highlighted here. Transdisciplinary communication and collaboration are needed to address the complex issues related to fire, and to climate and land use change.

The importance of fire season when managing threatened plant species: A long-term case-study of a rare Leucopogon species (Ericaceae)

Implemented burns are a primary source of fire in natural systems and occur outside of the wildfire season. However, the impacts of fire season shift on native plant species are rarely studied. Understanding fire season effects are particularly important for managing threatened species, which are often the focus of managed burns. To assess the impacts of fire seasonality and identify potential limiting traits, I studied the threatened Leucopogon exolasius and two common congeners, all of which persist via fire-driven population dynamics. All species were monitored over a 16 year period to assess seedling survival, growth and primary juvenile period after fire. For L. exolasius and the common L. esquamatus, comparisons of survival, growth and maturation were made after winter and summer fires, to assess the effects of season of burn. A key difference was found in primary juvenile period, which was exceptionally long for L. exolasius (>11 years for 80% of the population to flower) compared to the common congeners (3.2-7.57 years). Seasonal seed dormancy mechanisms meant that winter fires delayed emergence, leading to increases in primary juvenile period for both species. A long primary juvenile period may limit L. exolasius population persistence because plants are more likely to be killed by subsequent fire before maturation, while seasonal dormancy cues is a trait that would exacerbate the effects of this interval squeeze. In fire-prone systems, fire frequency is the key factor assumed to drive persistence, however, interactions with fire season can influence recruitment success. There are scant data on recruitment variation in response to fire seasonality, a factor that may have broad implications for rare and common species with seasonal germination requirements.

Translating Fire Impacts in Southwestern Amazonia into Economic Costs

Between 1998 and 2017, climate-related disasters represented 91% of all occurrences worldwide, causing approximately US$ 2.245 billion of direct economic losses. In the Amazon region, fire is used as a widely spread technique for land clearing, agricultural management, hunting, and religious rituals. However, over the past 20 years, severe droughts caused a major amplification of fire occurrences, leading to several socioeconomic and environmental impacts. Particularly in Acre state, located in the southwestern Brazilian Amazon, the occurrence of extensive fires, associated with extreme climatic events, has been reported since 2005. However, fire dynamics, land tenure relationships, and associated impacts are poorly quantified. In this study, we aim to investigate the following: (1) The spatiotemporal variability of fire dynamics during anomalously dry and regular climate conditions; (2) the attribution of fire occurrence and land tenure relationship, and (3) the environmental, social, and economic impacts caused by fires and its consequences for Acre’s economy. We analyzed information on the spatial patterns of fire, its direct impacts on land use and land cover, carbon stocks, CO2 emissions, the indirect impact on human illness, and finally the costs of these impacts from 2008 to 2012. During the studied period, burned areas were concentrated around the major cities and roads, forming polygons up to 0.6 km2. However, in 2010, an extremely dry year, fires spread to remote areas, impacting protected private areas and sustainable-use conservation areas. In 2010, the total area affected by forest fires was approximately 16 times greater than in meteorologically normal years. The total economic loss estimated in 2010 was around US$ 243.36 ± 85.05 million and for the entire period, US$ 307.46 ± 85.41 million. These values represent 7.03 ± 2.45% and 9.07 ± 2.46% of Acre’s gross domestic product (GDP), respectively.

Using artificial neural networks to predict future dryland responses to human and climate disturbances

Land degradation and sediment remobilisation in dryland environments is considered to be a significant global environmental problem. Given the potential for currently stabilised dune systems to reactivate under climate change and increased anthropogenic pressures, identifying the role of external disturbances in driving geomorphic response is vitally important. We developed a novel approach, using artificial neural networks (ANNs) applied to time series of historical reactivation-deposition events from the Nebraska Sandhills, to determine the relationship between historic periods of sand deposition in semi-arid grasslands and external climatic conditions, land use pressures and wildfire occurrence. We show that both vegetation growth and sediment re-deposition episodes can be accurately estimated. Sensitivity testing of individual factors shows that localised forcings (overgrazing and wildfire) have a statistically significant impact when the climate is held at present-day conditions. However, the dominant effect is climate-induced drought. Our approach has great potential for estimating future landscape sensitivity to climate and land use scenarios across a wide range of potentially fragile dryland environments.

Solar UV radiation in a changing world: roles of cryosphere-land-water-atmosphere interfaces in global biogeochemical cycles

Global change influences biogeochemical cycles within and between environmental compartments (i.e., the cryosphere, terrestrial and aquatic ecosystems, and the atmosphere). A major effect of global change on carbon cycling is altered exposure of natural organic matter (NOM) to solar radiation, particularly solar UV radiation. In terrestrial and aquatic ecosystems, NOM is degraded by UV and visible radiation, resulting in the emission of carbon dioxide (CO2) and carbon monoxide, as well as a range of products that can be more easily degraded by microbes (photofacilitation). On land, droughts and land-use change can reduce plant cover causing an increase in exposure of plant litter to solar radiation. The altered transport of soil organic matter from terrestrial to aquatic ecosystems also can enhance exposure of NOM to solar radiation. An increase in emission of CO2 from terrestrial and aquatic ecosystems due to the effects of global warming, such as droughts and thawing of permafrost soils, fuels a positive feedback on global warming. This is also the case for greenhouse gases other than CO2, including methane and nitrous oxide, that are emitted from terrestrial and aquatic ecosystems. These trace gases also have indirect or direct impacts on stratospheric ozone concentrations. The interactive effects of UV radiation and climate change greatly alter the fate of synthetic and biological contaminants. Contaminants are degraded or inactivated by direct and indirect photochemical reactions. The balance between direct and indirect photodegradation or photoinactivation of contaminants is likely to change with future changes in stratospheric ozone, and with changes in runoff of coloured dissolved organic matter due to climate and land-use changes.