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

Roshan, Ajmal; Biswas, Ashis Kumer

doi:10.1016/j.scitotenv.2023.161714

Cited by 15 publications

(7 citation statements)

References 181 publications

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“…The measured temperatures were representative of a high intensity wildfire. 59 No wood was burned on top of the UB1, UB2, or UB3 pyrocosms. The morning after the burns (referred to as "Day 0"), a soil density core (6 cm diameter, 10 cm height) was inserted into each of the six pyrocosms.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

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Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability

VanderRoest,

Fowler,

Rhoades

et al. 2024

Environ. Sci. Technol.

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Global wildfire activity has increased since the 1970s and is projected to intensify throughout the 21st century. Wildfires change the composition and biodegradability of soil organic matter (SOM) which contains nutrients that fuel microbial metabolism. Though persistent forms of SOM often increase postfire, the response of more biodegradable SOM remains unclear. Here we simulated severe wildfires through a controlled "pyrocosm" approach to identify biodegradable sources of SOM and characterize the soil metabolome immediately postfire. Using microbial amplicon (16S/ITS) sequencing and gas chromatography−mass spectrometry, heterotrophic microbes (Actinobacteria, Firmicutes, and Protobacteria) and specific metabolites (glycine, protocatechuate, citric cycle intermediates) were enriched in burned soils, indicating that burned soils contain a variety of substrates that support microbial metabolism. Molecular formulas assigned by 21 T Fourier transform ion cyclotron resonance mass spectrometry showed that SOM in burned soil was lower in molecular weight and featured 20 to 43% more nitrogen-containing molecular formulas than unburned soil. We also measured higher water extractable organic carbon concentrations and higher CO 2 efflux in burned soils. The observed enrichment of biodegradable SOM and microbial heterotrophs demonstrates the resilience of these soils to severe burning, providing important implications for postfire soil microbial and plant recolonization and ecosystem recovery.

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Section: ■ Materials and Methodsmentioning

confidence: 99%

“…Approximately 21 kg of lodgepole pine wood was burned on each of the B1, B2, and B3 pyrocosms (Figure S2), and soil temperature was monitored during burning (Figure S3). The measured temperatures were representative of a high intensity wildfire . No wood was burned on top of the UB1, UB2, or UB3 pyrocosms.…”

Section: Materials and Methodsmentioning

confidence: 99%

Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability

VanderRoest,

Fowler,

Rhoades

et al. 2024

Environ. Sci. Technol.

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“…Soil heating is locally heterogeneous, influenced by the micrometre-scale characteristics of soil (including moisture, organic matter, mineralogy and texture) and the overlying fire conditions (including fuel type, temperature and duration) 20,22,33,34 (Fig. 2).…”

Section: Factors Influencing Fire-induced Reactionsmentioning

confidence: 99%

Molecular insights and impacts of wildfire-induced soil chemical changes

Lopez,

Avila,

VanderRoest

et al. 2024

Nat Rev Earth Environ

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Wildfires act as important ecosystem controls and can benefit fire-adapted biomes by promoting habitat heterogeneity, seed germination and disease control. However, the frequency of highseverity fires and the extent of total burn area have increased since the 1970s, transforming both the organic and inorganic composition of soil. In this Review, we outline the molecular-scale transformations and biogeochemical interactions of soil organic matter (SOM) and metals induced by wildfires and explore their impacts on post-fire human health and ecosystem recovery. Wildfires enhance organic matter solubility and increase the number of nitrogen-containing SOM molecules by up to 32%. Additionally, wildfires can double the concentration of toxic polycyclic aromatic hydrocarbons (PAHs) in soil and induce the formation of toxic metal species such as As(III) and Cr(VI) through redox reactions. In post-fire environments, pyrogenic organic matter is susceptible to microbial degradation and can interact with soil minerals to influence metal redox cycling. Moreover, post-fire products such as karrikins and PAHs promote and inhibit revegetation, respectively, influencing ecosystem recovery. Improved techniques to monitor changes in the soil and the surrounding ecosystem are needed to better understand and mitigate the negative effects of wildfires. Key points• Wildfires increase water solubility and enrich nitrogen in soil organic matter while also generating toxic polycyclic aromatic hydrocarbons.• Wildfires can alter the oxidation state of metals, such as Cr, Hg and As, influencing their toxicity and mobility.• Laboratory measurements indicate that pyrogenic organic matter (PyOM) can be microbially degraded within weeks, suggesting that PyOM could have an important role in post-fire soil biogeochemical cycling.• The presence of growth-promoting organic molecules and growthinhibiting metal and organic species in post-fire soils can determine the success of revegetation efforts.• Future work should include organic and inorganic speciation measures to better estimate human and ecosystem impacts from wildfires.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author selfarchiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

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“…Large wildfires would have a broadly regional-scale impact which, given the close proximity of our two lakes, could theoretically produce a measurable Hg signal in both systems. However, more frequent and/or intense regional fires could also yield measurably different sedimentary Hg signals by their capacity to: (1) enhance surface run off without a corresponding increase in erosion and effectively reduce transport of catchment sourced, mineral-hosted Hg (Mataix-Solera et al, 2011;Shakesby, 2011); (2) enhance downstream transport of Hg released from burned soils and bound to fine and coarse particulate matter (Burke et al, 2010;Takenaka et al, 2021); and/or (3) release large quantities of Hg into the atmosphere following biomass combustion (Howard et al, 2019;Melendez-Perez et al, 2014;Roshan and Biswas, 2023). All three combine to generate impacts that may vary in significance owing to lake-specific differences in sedimentation, accumulation, and flux of materials to/from the lake.…”

Section: Holocene (12-0 Ka; Mis1)mentioning

confidence: 99%

Mercury records covering the past 90 kyr from lakes Prespa and Ohrid, SE Europe

Paine

Fendley

Frieling

et al. 2023

Preprint

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Abstract. The element mercury (Hg) is a key pollutant, and much insight has been gained by studying the present-day Hg cycle. However, many important processes within this cycle operate on timescales responsive to centennial to millennial-scale environmental variability, highlighting the importance of also investigating the longer-term Hg records in sedimentary archives. To this end, we here explore the timing, magnitude, and expression of Hg signals retained in sediments over the past ~90 ka from two lakes, linked by a subterranean karst system: Lake Prespa (Greece/North Macedonia/Albania) and Lake Ohrid (North Macedonia/Albania). Results suggest that Hg fluctuates largely independent of variability in common host phases in each lake, and the recorded sedimentary Hg signals show distinct differences first during the late Pleistocene (Marine Isotope Stages 2–5). The Hg signals in Lake Prespa sediments highlights an abrupt, short-lived, peak in Hg accumulation coinciding with local deglaciation. In contrast, Lake Ohrid shows a broader interval with enhanced Hg accumulation, and, superimposed, a series of low-amplitude oscillations in Hg concentration peaking during the Last Glacial Maximum, that may result from elevated clastic inputs. Divergent Hg signals are also recorded during the early and middle Holocene (Marine Isotope Stage 1). Here, Lake Prespa sediments show a series of large Hg peaks; while Lake Ohrid sediments show a progression to lower Hg values. Around 3 ka, anthropogenic influences overwhelm local fluxes in both lakes. The lack of coherence in Hg accumulation between the two lakes suggests that, in the absence of an exceptional perturbation, local differences in sediment composition, lake structure, and water balance all influence the local Hg cycle, and determine the extent to which Hg signals reflect local or global-scale environmental changes.

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

Cited by 15 publications

References 181 publications

Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability

Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability

Molecular insights and impacts of wildfire-induced soil chemical changes

Mercury records covering the past 90 kyr from lakes Prespa and Ohrid, SE Europe

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