Stefan Doerr

Swansea University | SWAN · Department of Geography

Landscape fires burn 3–5 million km2 of the Earth’s surface annually. They emit 2.2 Pg of carbon per year to the atmosphere, but also convert a significant fraction of the burned vegetation biomass into pyrogenic carbon. Pyrogenic carbon can be stored in terrestrial and marine pools for centuries to millennia and therefore its production can be con...

Deforestation in Indonesia in recent decades has made increasingly large parts of the region vulnerable to fires. Burning is particularly widespread in deforested peatlands, and it leads to globally significant carbon emissions. Here we use satellite-based observations to assess loss and fragmentation of primary forests and associated changes in fi...

The 2019/20 Australian bushfires (or wildfires) burned the largest forested area in Australia's recorded history, with major socio‐economic and environmental consequences. Among the largest fires was the 280,000 ha Green Wattle Creek Fire which burned large forested areas of the Warragamba catchment. This protected catchment provides critical ecosy...

Fire is one of the main disturbances in the world's forested ecosystems and its impacts are projected to increase in many regions due to global change. Fire impacts have been studied for decades, but integrative assessments of its effects on multiple ecosystem services (ES) across scales are rare. We thus conducted a global analysis of persistent (...

Recent wildfire outbreaks around the world have prompted concern that climate change is increasing fire incidence, threatening human livelihood and biodiversity, and perpetuating climate change. Here, we review current understanding of the impacts of climate change on fire weather (weather conditions conducive to the ignition and spread of wildfire...

Soil moisture deficits and water table dynamics are major biophysical controls on peat and non-peat fires in Indonesia. Development of modern fire forecasting models in Indonesia is hampered by the lack of scalable hydrologic datasets or scalable hydrology models that can inform the fire forecasting models on soil hydrologic behaviour. Existing fir...

Biochar is widely used as a soil amendment to improve soil properties and as a tool to absorb net carbon from the atmosphere. In this study we determined the signatures of organic molecular markers in soil following the incorporation of 5 and 10 t/ha biochar in a Fluvisol, cultivated with maize at the experimental field of the ISSAPP “N. Poushkarov...

Humans have raised CO₂ levels in the atmosphere to 50% above what they were before the industrial revolution. As a result, the world has already warmed by 1.1°C over the past century and reports indicate that it could reach 2.7°C of warming by the end of this century. Bouts of severe drought, heat and low humidity are becoming more extreme as the c...

Wildfires can either mediate or endanger forest ecosystem services and ecological processes. If left uncontrolled, wildfires can cause severe damage and negative cascading effects. For example, atmospheric pollution, health issues, soil erosion, landslides, biotic damages, and ecosystem degradation. The undergoing climate changes across Europe and...

Although the Park Grass Experiment is an important international reference soil for temperate grasslands, it still lacks the direct extraction of its metaproteome. The identification of these proteins can be crucial to our understanding of soil ecology and major biogeochemical processes. However, the extraction of protein from soil is a technically...

Recurrent extreme landscape fire episodes associated with drought events in Indonesia pose severe environmental, societal and economic threats. The ability to predict severe fire episodes months in advance would enable relevant agencies and communities to more effectively initiate fire-preventative measures and mitigate fire impacts. While dynamic...

Fires are an important perturbation for the carbon (C) dynamics of boreal forests, especially when they are stand-replacing. In North American boreal forests, crown fires are predominant and, therefore, the most studied. However, surface fires can also lead to major tree mortality with substantial implications for the C balance. Here, we assess the...

Fires affect many landscapes whether ignited by lightning or humans. They can affect soil physical, chemical and biological characteristics directly through heating and combustion, or indirectly through modified biological, pedological and hydrological processes after the fire. Direct effects include changes in organic matter, nutrients, biota, wat...

Fire is a primary disturbance in the world’s forested ecosystems and its impacts are projected to increase in many regions due to global climate change. Fire impacts have been studied for decades, but integrative assessments of its effects on multiple ecosystem services (ES) across scales are rare. We conducted a global analysis of persistent (>1 y...

Fire is an important disturbance in many wetlands, which are key carbon reservoirs at both regional and global scales. However, the effects of fire on wetland vegetation biomass and plant carbon dynamics are poorly understood. We carried out a burn experiment in a Calamagrostis angustifolia wetland in Sanjiang Plain (Northeast China), which is wide...

The Park Grass Experiment, is an international reference soil with an impressive repository of temperate grassland (meta)data, however, it still lacks documentation of its soil metaproteome. The identification of these proteins is crucial to our understanding of soil ecology and their role in major biogeochemical processes. However, protein extract...

Recurrent extreme landscape fire episodes associated with drought events in Indonesia pose severe environmental, societal and economic threats. The ability to predict severe fire episodes months in advance would enable relevant agencies and communities more effectively initiate fire preventative measures and mitigate fire impacts. While dynamic sea...

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-...

Wildfires produce large amounts of pyrogenic carbon (PyC), including charcoal, known for its chemical recalcitrance and sorption affinity for organic molecules. Wildfire-derived PyC can be transported to fluvial networks. Here it may alter the dissolved organic matter (DOM) concentration and composition as well as microbial biofilm functioning. Eff...

Wildfires produce large amounts of pyrogenic carbon (PyC), including charcoal, known for its chemical recalcitrance and sorption affinity for organic molecules. Wildfire-derived PyC can be transported to fluvial networks. Here it may alter dissolved organic matter (DOM) concentration and composition as well as microbial biofilm functioning. Employi...

Wildfires produce large amounts of pyrogenic carbon (PyC), including charcoal, known for its chemical recalcitrance and sorption affinity for organic molecules. Wildfire-derived PyC can be transported to fluvial networks. Here it may alter dissolved organic matter (DOM) concentration and composition as well as microbial biofilm functioning. Employi...

This report provide a detailed synthesis of available evidence on wildfire hazards and assessed the changing risk from present to future in a climate change context

Savannah fires are the largest contributor to global carbon (C) emissions from vegetation fires as a result of their high frequency and the large area burnt each year. Fires not only emit CO2 during the combustion process, they can also lead to enhanced CO2 fluxes from affected soils and vegetation, especially during the initial post-fire recovery...

The extreme 2018 hot drought that affected central and northern Europe led to the worst wildfire season in Sweden in over a century. The Ljusdal fire complex, the largest area burnt that year (8995 ha), offered the rare opportunity to quantify the combined impacts of wildfire and post‐fire management on Scandinavian boreal forests. We present chamb...

Globally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as wel...

Anomalously high water contact angles are often measured for soils or other granular materials when using a goniometer which is designed for use with flat surfaces. For many years such high contact angles have been rationalised in terms of Cassie and Baxter, and/or Wenzel models for contact angles on non-planar surfaces, but it is becoming increasi...

Wildfires produce large amounts of pyrogenic carbon (PyC), including particulate charcoal, known for its chemical recalcitrance and sorption affinity for organic molecules. Wildfire-derived PyC is highly mobile in the landscape and can be transported to fluvial networks where it may impact natural dissolved organic matter (DOM) and microbial biofil...

2020 is the year of wildfire records. California experienced its three largest fires early in its fire season. The Pantanal, the largest wetland on the planet, burned over 20% of its surface. More than 18 million hectares of forest and bushland burned during the 2019–2020 fire season in Australia, killing 33 people, destroying nearly 2500 homes, an...

The spike in carbon dioxide (CO2) observed after rewetting of dry soils, known as the ‘Birch effect’, can contribute substantially to total soil carbon (C) emissions, however, the exact mechanisms and timings underlying this sudden CO2 release remain unclear. The amount of applied water and duration of the previous dry period are considered the mai...

Deforestation in Sumatra and Kalimantan in recent decades has made increasingly large parts of the region vulnerable to fires. Burning is particularly widespread in deforested peatlands, leading to globally significant carbon emissions. Here we assess primary forest cover loss and fragmentation combined with active fire observations between 2001 an...

Vegetation fires play an important role in global and regional carbon cycles. Due to climate warming and land use shifts, fire patterns are changing and fire impacts increasing in many of the world's regions. Reducing uncertainties in carbon budgeting calculations from fires is therefore fundamental to advance our current understanding and forecast...

Reactive nitrogen (Nr, defined as all nitrogen-containing compounds except for N2 and N2O) is one of the most important classes of compounds emitted from wildfire, as Nr impacts both atmospheric oxidation processes and particle formation chemistry. In addition, several Nr compounds can contribute to health impacts from wildfires. Understanding the...

Water repellency (hydrophobicity) of granular materials such as soil is usually assessed on bulk samples or arrays of grains, with their wettability being influenced by the often-variable properties of individual particles. Numerous methods exist to assess the wetting behaviour of granular bulk materials, whereas methods for determining the wettabi...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Black carbon (BC) is a recalcitrant form of organic carbon (OC) produced by landscape fires. BC is an important component of the global carbon cycle because, compared to unburned biogenic OC, it is selectively conserved in terrestrial and oceanic pools. Here we show that the dissolved BC (DBC) content of dissolved OC (DOC) is twice greater in major...

Soil degradation affects more than 20% of agricultural land, forest land and grasslands throughout the world. This manual aims to contribute to the quality of training, and it is therefore initially aimed at trainers and students, although it may also be useful for land managers and environmentalists. The selected case studies illustrate real appli...

Soil water repellency has major implications for surface and subsurface water transport and organic and inorganic contaminant mobilisation. Heavy metal mobility and speciation in solutions from acidic coal ash reclaimed Technosols from a major coal mine region in Eastern Europe were studied with the aim to reveal relationships with soil water repel...

Abstract. Total reactive nitrogen (N_r, defined as all nitrogen-containing compounds except for N₂ and N₂O) was measured by catalytic conversion to NO and detection by NO-O₃ chemiluminescence together with individual N_r species during a series of laboratory fires of fuels characteristic of Weste...

Soil water repellency, that is, the reduced ability of soils to absorb water, is thought to be caused by organic coatings with predominantly non‐polar properties on soil particle surfaces. Given the important role of particle surface polarity in determining soil water repellency, we explored the use of fluorescent probes as a method for the direct...

Carbon dioxide (CO2) efflux from soil represents one of the biggest ecosystem carbon (C) fluxes and high-magnitude pulses caused by rainfall make a substantial contribution to the overall C emissions. It is widely accepted that the drier the soil, the larger the CO2 pulses will be, but this notion has never been tested for water-repellent soils. So...

In 2014, we travelled to the northern boreal forests of Canada to set experimental fires that would help us understand the effect of wildfires on the global carbon cycle. Sadly, we never got the chance to set those fires, because the firefighters enlisted to help us were busy dealing with an area the size of Belgium that was already burning. That w...

Rewetting of dry soil results in a well-known short-term pulse of CO 2 from soil to the atmosphere known as the 'Birch effect'. The displacement of CO 2 in air-filled pores with water during wetting has been recognised as one of the sources of this pulse. The Birch effect has been extensively reported under wettable soil conditions, but some studie...

It is well established in the world’s fire-prone regions that wildfires can considerably change the hydrological dynamics of freshwater catchments. Limited research, however, has focused on the potential impacts of wildfire ash toxicity on aquatic biota. Here, we assess the chemical composition and toxicity of ash generated from wildfires in six co...

This short paper provides the framework and introduction to this special issue of International Journal of Wildland Fire. Its eight papers were selected from those presented at two consecutive conferences held in 2018 in Europe and the USA that focussed on the impacts of wildfire on factors that regulate streamflow, water quality, sediment transpor...

Here, we explore how charcoal formation under different heating regimes and circumstances leads to chars of different physical properties. In order to do this, we have undertaken (1) carefully controlled laboratory experiments that replicate the different heating regimes that might be experienced during a wildfire and (2) two experimental wildfires...

Pyrogenic carbon (PyC, charcoal) is produced during vegetation fires at a rate of ~116–385 Tg C yr−1 globally. It represents one of the most degradation-resistant organic carbon pools, but its long-term fate and the processes leading to its degradation remain subject of debate. A frequently highlighted potential loss mechanism of PyC is its consump...

Public article in The Conversation discussing the future of fire in Mediterranean Europe in view of the recent article of Turco et al. 2018 in Nature Communications: https://www.nature.com/articles/s41467-018-06358-z

Spatial variations at the nanoscale of soil aggregate surfaces and in the spatial organisation of soil organic matter (SOM) are critical to understanding the factors involved in soil composition and turnover. However, soil nanoscience has been hampered by the lack of suitable methods to determine soil biophysical properties at nanometre spatial res...

Open biomass burning affects 3-4.6 million km 2 globally per year, an area comparable to that of India. While the majority of the vegetation carbon stocks affected by fire are emitted as CO 2 and CO, a nontrivial fraction is converted to pyrogenic carbon (PyC) in the form of charcoal. PyC contains highly recalcitrant organic carbon forms which pers...

The surface of a material such as soil, as characterized by its topology and roughness, typically has a profound effect on its functional behavior. While nondestructive imaging techniques such as X-ray computed tomography (CT) have been used extensively in recent years to characterize the internal architecture of soil, less attention has been paid...

Forest fires are known to induce changes in soil water-repellency (SWR), often increasing its severity and persistence. SWR restricts infiltration into soils affecting water distribution patterns. This may result in increased overland flow and runoff after the fire, maintaining soil water content low even after substantial rainfall. Rewetting of dr...

Fires can have severe impacts on water quality. Fires disturb vegetation cover, create an ash layer rich in potential contaminants, and increase contaminant mobilization by enhancing runoff and erosion. This may lead to the contamination of surface and groundwater resources with suspended sediments, metals, organic compounds and nutrients. These co...

Executive summary of a critical review of published work and recommendations for decision makers on impacts of prescribed fire in the UK on three key aspects of ecosystem services: (i) water quality, (ii) carbon dynamics and (iii) habitat composition and structure (biodiversity). The full review (Harper et al., 2018) is part of a special issue on p...

Localized variations at the nanoscale in soil aggregates and in the spatial organisation of soil organic matter (SOM) are critical to understanding the factors involved in soil composition and turnover. However soil nanoscience has been hampered by the lack of suitable methods to determine soil biophysical properties at nanometre spatial resolution...

The impacts of vegetation fires on ecosystems are complex and varied affecting a range of important ecosystem services. Fire has the potential to affect the physicochemical and ecological status of water systems, alter several aspects of the carbon cycle (e.g. above- and below-ground carbon storage) and trigger changes in vegetation type and struct...

CITATION: Worldwide_Wildfire , r/Science , Hi Reddit! We're Stefan Doerr, Is human intervention in putting out natural wildfires playing a significant role in the number and severity of wildfires in your opinion? Growing up in California, wildfires were a fact of life. I always wondered why the areas that didn't put people at risk weren't allowed t...

This study examines the direct impact of a moderate/high-severity prescribed fire on phosphorous (P) stocks and partitioning in oligotrophic soils of a dry eucalypt forest within Sydney's water supply catchments, Australia. We also quantify and characterize the P present in the ash produced in this fire, and explore its relationships with the maxim...

This study delivers new insights into rainfall-induced seal formation through a novel approach in the use of X-ray Computed Tomography (CT). Up to now seal and crust thickness have been directly quantified mainly through visual examination of sealed/crusted surfaces, and there has been no quantitative method to estimate this important property. X-r...

Soil carbon dioxide (CO2) emissions are strongly dependent on pore water distribution, which in turn can be modified by reduced wettability. Many soils around the world are affected by soil water repellency (SWR), which reduces infiltration and results in diverse moisture distribution. SWR is temporally variable and soils can change from wettable t...

The surface of a material such as soil, as characterised by its topology and roughness, typically has a profound effect on its functional behaviour. Whilst non-destructive imaging techniques such as X-ray Computed Tomography (CT) have been extensively employed in recent years to characterise the internal architecture of soil, less attention has bee...

Pyrogenic carbon (PyC), produced naturally (wildfire charcoal) and anthropogenically (biochar), is extensively studied due to its importance in several disciplines, including global climate dynamics, agronomy and paleosciences. Charcoal and biochar are commonly used as analogues for each other to infer respective carbon sequestration potentials, pr...

Post-fire hillslope stabilization treatments aim to reduce runoff-erosion risks following forest fires by counteracting the impact of fire on key soil and hillslope properties. Here we evaluate the effectiveness of wood shred mulch, long-leaved pine needle mulch, and polyacrylamide (PAM) in reducing post-fire runoff and erosion in two volcanic soil...

Nutrient availability can be a limiting factor in the recovery of ecosystems after wildfire. Its evaluation is therefore critical for selecting appropriate restoration strategies in the post-fire period. This study explores, for the first time, the use of thermogravimetry (TG) as a rapid proxy for nutrient availability and soil recovery. Soil sampl...