Fire and soil microorganisms: where should we focus on?


Gema Bárcenas-Moreno
University of Seville, Sevilla, Spain

Currently, the complexity of soil microbial ecology on soil systems is a hot topic in the environmental sciences, since the scientific community has achieved a deep knowledge of the relevance of microorganisms in soil processes. After several decades of study of the effects of wildfires on soils, one of the main conclusions is that soil microbial populations are very sensitive to fire, which allows us to use them as a tool to assess the impact of fire on ecosystems.

Polysaccharides distribution due to microbial colonization in a soil microaggregate. Credit: Imaggeo/Maria Hernandez-Soriano. Click the image for more information.
Polysaccharides distribution due to microbial colonization in a soil microaggregate. Credit: Imaggeo/María Hernández-Soriano. Click the image for more information.

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Wildfires and soil: Where are we now?


Lorena M. Zavala. University of Seville, Sevilla, Spain
Antonio Jordán. University of Seville, Sevilla, Spain

Jorge Mataix-Solera. University Miguel Hernández, Elche, Spain
Artemi Cerdà. University of Valencia, Valencia, Spain

Are wildfires a natural ecological factor or an environmental problem?

According to official statistics, during the 1990’s, about 1.5 millions ha were burned in Spain. In the first decade of this century, the burned area in Spain also surpassed one million hectares. To put it in conventional TV surface units, the burned area in the past 20 years equals the provinces of Cáceres and Badajoz, or 274,000 soccer fields. The effects caused by the fire on the soil have been studied over the past 20 years by research groups who have made a significant contribution to the advancement and improvement of scientific knowledge.

Area affected by wildfires in Spain between 1991 and 2010.
Area affected by wildfires in Spain between 1991 and 2010. Source: Spanish Ministry of Agrictulture, Food and Environment.

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Monday paper: Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania


Pereira P, Úbeda X, Mataix-Solera J, Oliva M, Novara A: Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania. Solid Earth, 5, 209-225. DOI: 10.5194/se-5-209-2014.

Evidence of earthworm activity (indicated with a red circle) in the burned plot 17 days after the fire.
Evidence of earthworm activity in the burned plot 17 days after the fire.

Abstract

Fire is a natural phenomenon with important implications on soil properties. The degree of this impact depends upon fire severity, the ecosystem affected, topography of the burned area and post-fire meteorological conditions. The study of fire effects on soil properties is fundamental to understand the impacts of this disturbance on ecosystems. The aim of this work was to study the short-term effects immediately after the fire (IAF), 2, 5, 7 and 9 months after a low-severity spring boreal grassland fire on soil colour value (assessed with the Munsell colour chart), soil organic matter content (SOM) and soil water repellency (SWR) in Lithuania. Four days after the fire a 400 m2 plot was delineated in an unburned and burned area with the same topographical characteristics. Soil samples were collected at 0–5 cm depth in a 20 m × 20 m grid, with 5 m space between sampling points. In each plot 25 samples were collected (50 each sampling date) for a total of 250 samples for the whole study. SWR was assessed in fine earth (< 2 mm) and sieve fractions of 2–1, 1–0.5, 0.5–0.25 and < 0.25 mm from the 250 soil samples using the water drop penetration time (WDPT) method. The results showed that significant differences were only identified in the burned area. Fire darkened the soil significantly during the entire study period due to the incorporation of ash/charcoal into the topsoil (significant differences were found among plots for all sampling dates). SOM was only significantly different among samples from the unburned area. The comparison between plots revealed that SOM was significantly higher in the first 2 months after the fire in the burned plot, compared to the unburned plot. SWR of the fine earth was significantly different in the burned and unburned plot among all sampling dates. SWR was significantly more severe only IAF and 2 months after the fire. In the unburned area SWR was significantly higher IAF, 2, 5 and 7 months later after than 9 months later. The comparison between plots showed that SWR was more severe in the burned plot during the first 2 months after the fire in relation to the unburned plot. Considering the different sieve fractions studied, in the burned plot SWR was significantly more severe in the first 7 months after the fire in the coarser fractions (2–1 and 1–0.5 mm) and 9 months after in the finer fractions (0.5–0.25 and < 0.25 mm). In relation to the unburned plot, SWR was significantly more severe in the size fractions 2–1 and < 0.25 mm, IAF, 5 and 7 months after the fire than 2 and 9 months later. In the 1–0.5- and 0.5–0.25 mm-size fractions, SWR was significantly higher IAF, 2, 5 and 7 months after the fire than in the last sampling date. Significant differences in SWR were observed among the different sieve fractions in each plot, with exception of 2 and 9 months after the fire in the unburned plot. In most cases the finer fraction (< 0.25 mm) was more water repellent than the others. The comparison between plots for each sieve fraction showed significant differences in all cases IAF, 2 and 5 months after the fire. Seven months after the fire significant differences were only observed in the finer fractions (0.5–0.25 and < 0.25 mm) and after 9 months no significant differences were identified. The correlations between soil Munsell colour value and SOM were negatively significant in the burned and unburned areas. The correlations between Munsell colour value and SWR were only significant in the burned plot IAF, 2 and 7 months after the fire. In the case of the correlations between SOM and SWR, significant differences were only identified IAF and 2 months after the fire. The partial correlations (controlling for the effect of SOM) revealed that SOM had an important influence on the correlation between soil Munsell colour value and SWR in the burned plot IAF, 2 and 7 months after the fire.

Solid Earth

Solid Earth (SE) is an international scientific journal dedicated to the publication and discussion of multidisciplinary research on the composition, structure and dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. More at Solid Earth homepage.

Monday paper: Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain)


León J, Seeger M, Badía D, Peters P, Echevarría T: Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain). Solid Earth, 5, 131-140. DOI: 10.5194/se-5-131-2014.

Extraction of soil blocks for this study.
Extraction of soil blocks for this study.

Abstract

Fire is a natural factor of landscape evolution in Mediterranean ecosystems. The middle Ebro Valley has extreme aridity, which results in a low plant cover and high soil erodibility, especially on gypseous substrates. The aim of this research is to analyze the effects of moderate heating on physical and chemical soil properties, mineralogical composition and susceptibility to splash erosion. Topsoil samples (15 cm depth) were taken in the Remolinos mountain slopes (Ebro Valley, NE Spain) from two soil types: Leptic Gypsisol (LP) in a convex slope and Haplic Gypsisol (GY) in a concave slope. To assess the heating effects on the mineralogy we burned the soils at 105 and 205 °C in an oven and to assess the splash effects we used a rainfall simulator under laboratory conditions using undisturbed topsoil subsamples (0–5 cm depth of Ah horizon). LP soil has lower soil organic matter (SOM) and soil aggregate stability (SAS) and higher gypsum content than GY soil. Gypsum and dolomite are the main minerals (>80%) in the LP soil, while gypsum, dolomite, calcite and quartz have similar proportions in GY soil. Clay minerals (kaolinite and illite) are scarce in both soils. Heating at 105 °C has no effect on soil mineralogy. However, heating to 205 °C transforms gypsum to bassanite, increases significantly the soil salinity (EC) in both soil units (LP and GY) and decreases pH only in GY soil. Despite differences in the content of organic matter and structural stability, both soils show no significant differences (P < 0.01) in the splash erosion rates. The size of pores is reduced by heating, as derived from variations in soil water retention capacity.

Solid Earth

Solid Earth (SE) is an international scientific journal dedicated to the publication and discussion of multidisciplinary research on the composition, structure and dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. More at Solid Earth homepage.

Soils at Imaggeo: fire watch constellation


Egle Rackauskaite, Xinyan Huang and Guillermo Rein
HazeLab, Imperial College London, UK

Winner of the Best Fire Science Image, 11th IAFSS Symposium, Christchurch, New Zealand, 2014

Click on the image to see the original picture and details at Imaggeo.

Description

This composite shows a constellation of combined visual and infrared imaging of a smouldering combustion front spreading radially over a thin sample of dry peat. The central watch is created by a series of twelve wedges. Each wedge is extracted from a photo taken every 5 min from an elevated view looking down into the sample during the one-hour lab experiment. The circular peat sample (D=22 cm) was ignited on the centre by an electrical heater. The average radial spread rate was 10 cm/h and the peak temperature 600°C. The top figures show the virgin peat (left) and the final residue (right). The bottom figures show the wedges in visual (left) and infrared (right) imaging. Smouldering combustion is the driving phenomenon of wildfires in peatlands, like those causing haze episodes in southeast Asia and Northeast Europe. These are the largest fires on Earth and an extensive source of greenhouse gases, but poorly studied. Our experiments help to understand this emerging research topic in climate-change mitigation by characterizing the dynamics of ignition, spread and extinction, and also measure the yield of carbon emissions.

About Imaggeo

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes.

All the material in this database is copyrighted under a Creative Commons Attribution 3.0 licence, which means that Imaggeo content is owned by the individual creators and that they must always be credited when their content is used. People interested in submitting material to Imaggeo can also choose a more restrictive licence, such as Creative Commons Attribution NonCommercial ShareAlike 3.0 licence. For more information please check the Copyright page.

Environmental Management Centre Research Group


Paulo Pereira
pereiraub@gmail.com
Mykolas Romeris University, Lithuania

The Environmental Management Centre

The Environmental Management Centre (EMC) was founded in 2013 at Mykolas Romeris University, Vilnius, Lithuania. The group is composed by young and proactive researchers from the entire world. The centre has an interdisplinary vision of science and aims to connect environmental, sociological and economical questions, in order to understand environmental questions from a wide perspective. The areas of research of the centre are, land use management and territorial planning, environmental economics, sustainable development, climate change and urban environment. The EMC members have experienced in the organization of international events as the 4th International Meeting of Fire Effects on Soil Properties (FESP4) and in European Geoscience Union Assembly and work with other scientific groups.

Research

In the previous years, the members of the EMC studied the effects of grassland fires on ash thickness, soil properties and vegetation recuperation. From this work, some papers have been published in international conferences and journals. The most important results were that ash thickness decreases rapidly in the first weeks after the fire. The ash produced at high severity (white and light grey) is easily transported by the wind and it is (re)distributed faster than the ash produced at medium (dark grey black) temperatures. The effects of fire on grassland soils are short termed, due the low severity (Pereira et al. 2013a; Pereira et al., 2014a). Grassland vegetation recovers very fast after the fire and it is very adapted to this disturbance (Pereira et al., 2013b; Pereira et al., 2013c). Research was also carried out about prescribed fire effects in a heathland (see the figure below).

Figure_2
Cormorant colony in Curonian Spit (Lithuania).

The results showed that immediately after the fire no significant differences were observed between the burned and the unburned plot (Pereira et al., 2015a; Pereira et al., 2015b). This research was carried out under the project LitFire. Fire effects on Lithuanian soils and ecosystems. 2011-2012. Contract: No. MIP-11387. Currently, we are continuing this research together with Spanish Universities under the project Soil quality, erosion control and plant cover recovery under different post-fire management scenarios (POSTFIRE), funded by the Spanish Ministry of Economy and Competitiveness (CGL2013-47862-C2-1-R). We started to study the public perception about fire impacts in the ecosystems. The first results showed that the vision about the fire depends of the age, but especially of the professional occupation (Mierauskas and Pereira, 2013;  Pereira et al., 2014b).

Figure_1
Prescribed fire applied in Dzukija National Park (Lithuania)

Recently we started cooperation with the Research Group on Antarctic Environments and Climate Change from University of Lisbon (Portugal) in the study of soil temperatures in Iberian mountains (Oliva et al., 2014a) and physical and chemical properties of soils from the Arctic (Oliva et al., 2014b). At the moment we have also started working with soils from Antarctica. Other line of research that we are developing recently is the study of the impacts of land use is soil hydrophobicity, soil erosion in urban environments and impact of a Cormorant colony (Curonian Spit, Lithuania) in soil physical and chemical properties.

More information on the website of EMC.

References

Special issue on geo-environmental effects of wildfires


When fire runs. Credit: A. Jordán. Click to see the original picture and data at Imaggeo.

Noemí Lana-Renault Monreal
noemi-solange.lana-renault@unirioja.es
University of La Rioja, Spain

We are glad to announce that the Special Issue on “Geo-environmental effects of wildfires”, which has been recently published by Cuadernos de Investigación Geográfica (volume 40 (2), 2014). This Special Issue aims at bringing together the key impacts of wildfires on runoff, soil properties and erosion, and plant biomass changes.

Cuadernos de Investigación Geográfica
Cuadernos de Investigación Geográfica.

Some contributions to this Special Issue include field measurements and lab experiments. Keesstra et al. (2014), investigated in the lab the fire effects on a Redzina soil and suggested that water repellency and protection by ash were factors to consider in assessing the erosion susceptibility of a burnt forest soil; Velasco & Úbeda (2014) analyzed soil aggregate stability after a forest fire that occurred in 1994, and Moya et al. (2014), studied the post fire forest management in relation to biomass recovery and carbon stock on burnt areas. Other contributions to this Special Issue synthesized the state-of-the-art in several related topics, especially the effect of fire on soil properties (Zavala et al., 2014), soil erodibility in Galicia (Benito et al., 2014), soil organic matter (de la Rosa et al., 2014) and soil erosion and runoff in Portugal (Prats et al., 2014). Additionally, the contribution by Herrera & Chuvieco (2014) highlights the importance of estimating fuel moisture content by hyperspectral measurements for fire risk assessment. The last contribution of this Special Issue (Domíneguez et al., 2014) assesses media coverage of wildfires and critically discusses the lack of scientific communication about the nature of wildfires in Mediterranean ecosystems.
All the articles are freely accessible here (see the table of contents below).

About the journal

Cuadernos de Investigación Geográfica is issued twice a year and includes original research and review papers on all aspects of physical geography and environmental sciences. All papers are subject to full peer review. This journal has been in publication uninterruptedly since 1975. It is indexed in Scopus since 2009.

Editors of the Special Issue

Artemi Cerdá, Universitat de Valéncia
José Arnáez Vadillo, Universidad de La Rioja
Noemí Lana-Renault, Universidad de La Rioja
José M. García-Ruiz, Instituto Pirenaico de Ecología (CSIC)

Table of contents