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Hopkins AJM, Brace AJ, Bruce JL, Hyde J, Fontaine JB, Walden L, Veber W, Ruthrof KX. Drought legacy interacts with wildfire to alter soil microbial communities in a Mediterranean climate-type forest. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 915:170111. [PMID: 38232837 DOI: 10.1016/j.scitotenv.2024.170111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 01/19/2024]
Abstract
Mediterranean forest ecosystems will be increasingly affected by hotter drought and more frequent and severe wildfire events in the future. However, little is known about the longer-term responses of these forests to multiple disturbances and the forests' capacity to maintain ecosystem function. This is particularly so for below-ground organisms, which have received less attention than those above-ground, despite their essential contributions to forest function. We investigated rhizosphere microbial communities in a resprouting Eucalyptus marginata forest, southwestern Australia, that had experienced a severe wildfire four years previously, and a hotter drought eight years previously. Our aim was to understand how microbial communities are affected over longer-term trajectories by hotter drought and wildfire, singularly, and in combination. Fungal and bacterial DNA was extracted from soil samples, amplified, and subjected to high throughput sequencing. Richness, diversity, composition, and putative functional groups were then examined. We found a monotonic decrease in fungal, but not bacterial, richness and diversity with increasing disturbance with the greatest changes resulting from the combination of drought and wildfire. Overall fungal and bacterial community composition reflected a stronger effect of fire than drought, but the combination of both produced the greatest number of indicator taxa for fungi, and a significant negative effect on the abundance of several fungal functional groups. Key mycorrhizal fungi, fungal saprotrophs and fungal pathogens were found at lower proportions in sites affected by drought plus wildfire. Wildfire had a positive effect on bacterial hydrogen and bacterial nitrogen recyclers. Fungal community composition was positively correlated with live tree height. These results suggest that microbial communities, in particular key fungal functional groups, are highly responsive to wildfire following drought. Thus, a legacy of past climate conditions such as hotter drought can be important for mediating the responses of soil microbial communities to subsequent disturbance like wildfire.
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Affiliation(s)
- A J M Hopkins
- Molecular Ecology and Evolution Group, School of Science, Edith Cowan University, Joondalup, WA 6027, Australia.
| | - A J Brace
- Molecular Ecology and Evolution Group, School of Science, Edith Cowan University, Joondalup, WA 6027, Australia
| | - J L Bruce
- Molecular Ecology and Evolution Group, School of Science, Edith Cowan University, Joondalup, WA 6027, Australia
| | - J Hyde
- Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, Kensington, WA 6151, Australia
| | - J B Fontaine
- School of Environmental and Conservation Sciences, Murdoch University, Murdoch, WA 6150, Australia
| | - L Walden
- Soil and Landscape Science, School of Molecular and Life Sciences, Curtin University, Bentley, WA 6102, Australia
| | - W Veber
- School of Environmental and Conservation Sciences, Murdoch University, Murdoch, WA 6150, Australia
| | - K X Ruthrof
- Biodiversity and Conservation Science, Department of Biodiversity, Conservation and Attractions, Kensington, WA 6151, Australia; School of Environmental and Conservation Sciences, Murdoch University, Murdoch, WA 6150, Australia
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2
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VanderRoest JP, Fowler JA, Rhoades CC, Roth HK, Broeckling CD, Fegel TS, McKenna AM, Bechtold EK, Boot CM, Wilkins MJ, Borch T. Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:4167-4180. [PMID: 38385432 DOI: 10.1021/acs.est.3c09797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
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 CO2 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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Affiliation(s)
- Jacob P VanderRoest
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Julie A Fowler
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Charles C Rhoades
- Rocky Mountain Research Station, U.S. Forest Service, Fort Collins, Colorado 80526, United States
| | - Holly K Roth
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Corey D Broeckling
- Bioanalysis and Omics Center, Analytical Resources Core, Colorado State University, Fort Collins, 80521, United States
| | - Timothy S Fegel
- Rocky Mountain Research Station, U.S. Forest Service, Fort Collins, Colorado 80526, United States
| | - Amy M McKenna
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
- National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Dr., Tallahassee, Florida 32310, United States
| | - Emily K Bechtold
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Claudia M Boot
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Michael J Wilkins
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
| | - Thomas Borch
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80521, United States
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80521, United States
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3
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Barbour KM, Martiny JBH. Investigating eco-evolutionary processes of microbial community assembly in the wild using a model leaf litter system. THE ISME JOURNAL 2024; 18:wrae043. [PMID: 38506671 PMCID: PMC11008689 DOI: 10.1093/ismejo/wrae043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/13/2024] [Accepted: 03/19/2024] [Indexed: 03/21/2024]
Abstract
Microbial communities are not the easiest to manipulate experimentally in natural ecosystems. However, leaf litter-topmost layer of surface soil-is uniquely suitable to investigate the complexities of community assembly. Here, we reflect on over a decade of collaborative work to address this topic using leaf litter as a model system in Southern California ecosystems. By leveraging a number of methodological advantages of the system, we have worked to demonstrate how four processes-selection, dispersal, drift, and diversification-contribute to bacterial and fungal community assembly and ultimately impact community functioning. Although many dimensions remain to be investigated, our initial results demonstrate that both ecological and evolutionary processes occur simultaneously to influence microbial community assembly. We propose that the development of additional and experimentally tractable microbial systems will be enormously valuable to test the role of eco-evolutionary processes in natural settings and their implications in the face of rapid global change.
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Affiliation(s)
- Kristin M Barbour
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - Jennifer B H Martiny
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697, United States
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4
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Liu MD, Du Y, Koupaei SK, Kim NR, Fischer MS, Zhang W, Traxler MF. Surface-active antibiotic production as a multifunctional adaptation for postfire microorganisms. THE ISME JOURNAL 2024; 18:wrae022. [PMID: 38366029 PMCID: PMC11069360 DOI: 10.1093/ismejo/wrae022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/01/2024] [Accepted: 02/02/2024] [Indexed: 02/18/2024]
Abstract
Wildfires affect soils in multiple ways, leading to numerous challenges for colonizing microorganisms. Although it is thought that fire-adapted microorganisms lie at the forefront of postfire ecosystem recovery, the specific strategies that these organisms use to thrive in burned soils remain largely unknown. Through bioactivity screening of bacterial isolates from burned soils, we discovered that several Paraburkholderia spp. isolates produced a set of unusual rhamnolipid surfactants with a natural methyl ester modification. These rhamnolipid methyl esters (RLMEs) exhibited enhanced antimicrobial activity against other postfire microbial isolates, including pyrophilous Pyronema fungi and Amycolatopsis bacteria, compared to the typical rhamnolipids made by organisms such as Pseudomonas spp. RLMEs also showed enhanced surfactant properties and facilitated bacterial motility on agar surfaces. In vitro assays further demonstrated that RLMEs improved aqueous solubilization of polycyclic aromatic hydrocarbons, which are potential carbon sources found in char. Identification of the rhamnolipid biosynthesis genes in the postfire isolate, Paraburkholderia kirstenboschensis str. F3, led to the discovery of rhlM, whose gene product is responsible for the unique methylation of rhamnolipid substrates. RhlM is the first characterized bacterial representative of a large class of integral membrane methyltransferases that are widespread in bacteria. These results indicate multiple roles for RLMEs in the postfire lifestyle of Paraburkholderia isolates, including enhanced dispersal, solubilization of potential nutrients, and inhibition of competitors. Our findings shed new light on the chemical adaptations that bacteria employ to navigate, grow, and outcompete other soil community members in postfire environments.
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Affiliation(s)
- Mira D Liu
- Department of Chemistry, University of California, Berkeley, CA 94720, United States
| | - Yongle Du
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, United States
| | - Sara K Koupaei
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, United States
| | - Nicole R Kim
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, United States
| | - Monika S Fischer
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, United States
| | - Wenjun Zhang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, United States
| | - Matthew F Traxler
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, United States
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Nelson AR, Fegel TS, Danczak RE, Caiafa MV, Roth HK, Dunn OI, Turvold CA, Borch T, Glassman SI, Barnes RT, Rhoades CC, Wilkins MJ. Soil microbiome feedbacks during disturbance-driven forest ecosystem conversion. THE ISME JOURNAL 2024; 18:wrae047. [PMID: 38502869 DOI: 10.1093/ismejo/wrae047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/12/2024] [Accepted: 03/17/2024] [Indexed: 03/21/2024]
Abstract
Disturbances cause rapid changes to forests, with different disturbance types and severities creating unique ecosystem trajectories that can impact the underlying soil microbiome. Pile burning-the combustion of logging residue on the forest floor-is a common fuel reduction practice that can have impacts on forest soils analogous to those following high-severity wildfire. Further, pile burning following clear-cut harvesting can create persistent openings dominated by nonwoody plants surrounded by dense regenerating conifer forest. A paired 60-year chronosequence of burn scar openings and surrounding regenerating forest after clear-cut harvesting provides a unique opportunity to assess whether belowground microbial processes mirror aboveground vegetation during disturbance-induced ecosystem shifts. Soil ectomycorrhizal fungal diversity was reduced the first decade after pile burning, which could explain poor tree seedling establishment and subsequent persistence of herbaceous species within the openings. Fine-scale changes in the soil microbiome mirrored aboveground shifts in vegetation, with short-term changes to microbial carbon cycling functions resembling a postfire microbiome (e.g. enrichment of aromatic degradation genes) and respiration in burn scars decoupled from substrate quantity and quality. Broadly, however, soil microbiome composition and function within burn scar soils converged with that of the surrounding regenerating forest six decades after the disturbances, indicating potential microbial resilience that was disconnected from aboveground vegetation shifts. This work begins to unravel the belowground microbial processes that underlie disturbance-induced ecosystem changes, which are increasing in frequency tied to climate change.
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Affiliation(s)
- Amelia R Nelson
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, United States
| | - Timothy S Fegel
- Rocky Mountain Research Station, US Forest Service, Fort Collins, CO 80526, United States
| | - Robert E Danczak
- Division of Biological Sciences, Pacific Northwest National Laboratory, Richland, WA 99354, United States
| | - Marcos V Caiafa
- Department of Microbiology and Plant Pathology, University of California Riverside, Riverside, CA 92521, United States
| | - Holly K Roth
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, United States
| | - Oliver I Dunn
- The Environmental Studies Program, Colorado College, Colorado Springs, CO 80946, United States
| | - Cosette A Turvold
- The Environmental Studies Program, Colorado College, Colorado Springs, CO 80946, United States
| | - Thomas Borch
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, United States
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, United States
- Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, United States
| | - Sydney I Glassman
- Department of Microbiology and Plant Pathology, University of California Riverside, Riverside, CA 92521, United States
| | - Rebecca T Barnes
- The Environmental Studies Program, Colorado College, Colorado Springs, CO 80946, United States
| | - Charles C Rhoades
- Rocky Mountain Research Station, US Forest Service, Fort Collins, CO 80526, United States
| | - Michael J Wilkins
- Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, United States
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Venice F, Vizzini A, Danti R, Della Rocca G, Mello A. Responses of a soil fungal community to severe windstorm damages in an old silver fir stand. Front Microbiol 2023; 14:1246874. [PMID: 38029204 PMCID: PMC10668432 DOI: 10.3389/fmicb.2023.1246874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 09/25/2023] [Indexed: 12/01/2023] Open
Abstract
Forests are increasingly threatened by climate change and the Anthropocene seems to have favored the emergence and adaptation of pathogens. Robust monitoring methods are required to prevent biodiversity and ecosystems losses, and this imposes the choice of bioindicators of habitat health. Fungal communities are increasingly recognized as fundamental components in nearly all natural and artificial environments, and their ecosystem services have a huge impact in maintaining and restoring the functionality of ecosystems. We coupled metabarcoding and soil analyses to infer the dynamics of a fungal community inhabiting the old silver fir stand in Vallombrosa (Italy), which is known to be afflicted by both Armillaria and Annosum root rot. The forest was affected in 2015, by a windstorm which caused a partial falling and uprooting of trees. The remaining stand, not affected by the windstorm, was used as a comparison to infer the consequences of the ecosystem disturbance. We demonstrated that the abundance of pathogens alone is not able to explain the soil fungal differences shown by the two areas. The fungal community as a whole was equally rich in the two areas, even if a reduction of the core ectomycorrhizal mycobiome was observed in the wind-damaged area, accompanied by the increase of wood saprotrophs and arbuscular mycorrhizas. We hypothesize a reshaping of the fungal community and a potentially ongoing re-generation of its functionalities. Our hypothesis is driven by the evidence that key symbiotic, endophytic, and saprotrophic guilds are still present and diversified in the wind-damaged area, and that dominance of single taxa or biodiversity loss was not observed from a mycological point of view. With the present study, we aim at providing evidence that fungal communities are fundamental for the monitoring and the conservation of threatened forest ecosystems.
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Affiliation(s)
- Francesco Venice
- Institute for Sustainable Plant Protection (IPSP) - SS Turin - National Research Council (CNR), Turin, Italy
- Department of Life Sciences and System Biology, University of Turin, Turin, Italy
| | - Alfredo Vizzini
- Institute for Sustainable Plant Protection (IPSP) - SS Turin - National Research Council (CNR), Turin, Italy
- Department of Life Sciences and System Biology, University of Turin, Turin, Italy
| | - Roberto Danti
- Institute for Sustainable Plant Protection (IPSP) - National Research Council (CNR), Sesto Fiorentino (FI), Italy
| | - Gianni Della Rocca
- Institute for Sustainable Plant Protection (IPSP) - National Research Council (CNR), Sesto Fiorentino (FI), Italy
| | - Antonietta Mello
- Institute for Sustainable Plant Protection (IPSP) - SS Turin - National Research Council (CNR), Turin, Italy
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7
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Fischer MS, Patel NJ, de Lorimier PJ, Traxler MF. Prescribed fire selects for a pyrophilous soil sub-community in a northern California mixed conifer forest. Environ Microbiol 2023; 25:2498-2515. [PMID: 37553729 DOI: 10.1111/1462-2920.16475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 07/20/2023] [Indexed: 08/10/2023]
Abstract
Prescribed fire is a critical strategy for mitigating the effects of catastrophic wildfires. While the above-ground response to fire has been well-documented, fewer studies have addressed the effect of prescribed fire on soil microorganisms. To understand how soil microbial communities respond to prescribed fire, we sampled four plots at a high temporal resolution (two burned, two controls), for 17 months, in a mixed conifer forest in northern California, USA. Using amplicon sequencing, we found that prescribed fire significantly altered both fungal and bacterial community structure. We found that most differentially abundant fungal taxa had a positive fold-change, while differentially abundant bacterial taxa generally had a negative fold-change. We tested the null hypothesis that these communities assembled due to neutral processes (i.e., drift and/or dispersal), finding that >90% of taxa fit this neutral prediction. However, a dynamic sub-community composed of burn-associated indicator taxa that were positively differentially abundant was enriched for non-neutral amplicon sequence variants, suggesting assembly via deterministic processes. In synthesizing these results, we identified 15 pyrophilous taxa with a significant and positive response to prescribed burns. Together, these results lay the foundation for building a process-driven understanding of microbial community assembly in the context of the classical disturbance regime of fire.
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Affiliation(s)
- Monika S Fischer
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Neem J Patel
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Phillip J de Lorimier
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Matthew F Traxler
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
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8
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Mulla L, Hernández-Gómez O. Wildfires disturb the natural skin microbiota of terrestrial salamanders. Environ Microbiol 2023; 25:2203-2215. [PMID: 37340556 DOI: 10.1111/1462-2920.16452] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 06/04/2023] [Indexed: 06/22/2023]
Abstract
Environmental change can disturb natural associations between wildlife and microbial symbionts, in many cases to the detriment of host health. We used a North American terrestrial salamander system to assess how the skin microbiota of amphibians responds to wildfires. In northern California's redwood/oak forests, we assessed how recent wildfires affected the skin microbiota of three different salamander species (Taricha sp., Batrachoseps attenuatus, and Ensatina eschscholtzii) over two different sampling seasons in 2018 and 2021. We found species-specific responses to wildfire disturbance on the alpha diversity of the skin microbiota of terrestrial salamanders, although burning in general altered the composition of the skin microbiota. The effect of burning on alpha diversities and body condition indices varied by sampling season, suggesting an additional effect of annual climatic conditions on body condition and skin microbiota response. We tested all salamanders for Batrachochytrium dendrobatidis and found four infected individuals in 2018 and none in 2021. Our study documents correlations in the skin microbiota response to an increasing source of disturbance in western North American ecosystems. In addition, our results highlight the need to consider the effects of increased wildfire regimes/intensities and longitudinal effects on wildlife-associated microbiota and animal health.
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Affiliation(s)
- Lubna Mulla
- Department of Natural Sciences and Mathematics, School of Health and Natural Sciences, Dominican University of California, San Rafael, California, USA
| | - Obed Hernández-Gómez
- Department of Natural Sciences and Mathematics, School of Health and Natural Sciences, Dominican University of California, San Rafael, California, USA
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9
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Barbour KM, Weihe C, Walters KE, Martiny JBH. Testing the contribution of dispersal to microbial succession following a wildfire. mSystems 2023; 8:e0057923. [PMID: 37747204 PMCID: PMC10654055 DOI: 10.1128/msystems.00579-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 07/28/2023] [Indexed: 09/26/2023] Open
Abstract
IMPORTANCE Identifying the mechanisms underlying microbial community succession is necessary for predicting how microbial communities, and their functioning, will respond to future environmental change. Dispersal is one mechanism expected to affect microbial succession, yet the difficult nature of manipulating microorganisms in the environment has limited our understanding of its contribution. Using a dispersal exclusion experiment, this study isolates the specific effect of environmental dispersal on bacterial and fungal community assembly over time following a wildfire. The work demonstrates the potential to quantify dispersal impacts on soil microbial communities over time and test how dispersal might further interact with other assembly processes in response to environmental change.
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Affiliation(s)
- Kristin M. Barbour
- Department of Ecology and Evolutionary Biology, University of California-Irvine, Irvine, California, USA
| | - Claudia Weihe
- Department of Ecology and Evolutionary Biology, University of California-Irvine, Irvine, California, USA
| | | | - Jennifer B. H. Martiny
- Department of Ecology and Evolutionary Biology, University of California-Irvine, Irvine, California, USA
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10
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Greenwood L, Nimmo DG, Egidi E, Price JN, McIntosh R, Frew A. Fire shapes fungal guild diversity and composition through direct and indirect pathways. Mol Ecol 2023; 32:4921-4939. [PMID: 37452603 DOI: 10.1111/mec.17068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 06/20/2023] [Accepted: 07/03/2023] [Indexed: 07/18/2023]
Abstract
Fire has shaped global ecosystems for millennia by directly killing organisms and indirectly altering habitats and resources. All terrestrial ecosystems, including fire-prone ecosystems, rely on soil-inhabiting fungi, where they play vital roles in ecological processes. Yet our understanding of how fire regimes influence soil fungi remains limited and our knowledge of these interactions in semiarid landscapes is virtually absent. We collected soil samples and vegetation measurements from sites across a gradient in time-since-fire ages (0-75 years-since-fire) and fire frequency (burnt 0-5 times during the recent 29-year period) in a semiarid heathland of south-eastern Australia. We characterized fungal communities using ITS amplicon-sequencing and assigned fungi taxonomically to trophic guilds. We used structural equation models to examine direct, indirect and total effects of time-since-fire and fire frequency on total fungal, ectomycorrhizal, saprotrophic and pathogenic richness. We used multivariate analyses to investigate how total fungal, ectomycorrhizal, saprotrophic and pathogenic species composition differed between post-fire successional stages and fire frequency classes. Time-since-fire was an important driver of saprotrophic richness; directly, saprotrophic richness increased with time-since-fire, and indirectly, saprotrophic richness declined with time-since-fire (resulting in a positive total effect), mediated through the impact of fire on substrates. Frequently burnt sites had lower numbers of saprotrophic and pathogenic species. Post-fire successional stages and fire frequency classes were characterized by distinct fungal communities, with large differences in ectomycorrhizal species composition. Understanding the complex responses of fungal communities to fire can be improved by exploring how the effects of fire flow through ecosystems. Diverse fire histories may be important for maintaining the functional diversity of fungi in semiarid regions.
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Affiliation(s)
- Leanne Greenwood
- Gulbali Institute, Charles Sturt University, Thurgoona, New South Wales, Australia
| | - Dale G Nimmo
- Gulbali Institute, Charles Sturt University, Thurgoona, New South Wales, Australia
| | - Eleonora Egidi
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, New South Wales, Australia
| | - Jodi N Price
- Gulbali Institute, Charles Sturt University, Thurgoona, New South Wales, Australia
| | | | - Adam Frew
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, New South Wales, Australia
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