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Lyu M, Young CJ, Thompson DK, Styler SA. Influence of Fuel Properties on the Light Absorption of Fresh and Laboratory-Aged Atmospheric Brown Carbon Produced from Realistic Combustion of Boreal Peat and Spruce Foliage. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:5035-5046. [PMID: 38441875 DOI: 10.1021/acs.est.1c07091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Climate change has exacerbated fire activity in the boreal region. Consequently, smoldering boreal peatland fires are an increasingly important source of light-absorbing atmospheric organic carbon ("brown carbon"; BrC). To date, however, BrC from this source remains largely unstudied, which limits our ability to predict its climate impact. Here, we use size-exclusion chromatography coupled with diode array UV-vis detection to examine the molecular-size-dependent light absorption properties of fresh and photoaged aqueous BrC extracts collected during laboratory combustion of boreal peat and live spruce foliage. The atmospheric stability of BrC extracts varies with chromophore molecular size and fuel type: in particular, the high-molecular-weight fractions of both peat- and spruce-BrC are more resistant to photobleaching than their corresponding low-molecular-weight fractions, and total light absorption by peat-BrC persists over longer illumination timescales than that of spruce-BrC. Importantly, the BrC molecular size distribution itself varies with fuel properties (e.g., moisture content) and to an even greater extent with fuel type. Overall, our findings suggest that the accurate estimation of BrC radiative forcing, and the overall climate impact of wildfires, will require atmospheric models to consider the impact of regional diversity in vegetation/fuel types.
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Affiliation(s)
- Ming Lyu
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Cora J Young
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
| | - Dan K Thompson
- Natural Resources Canada─Northern Forestry Centre, Edmonton, Alberta T6H 3S5, Canada
| | - Sarah A Styler
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
- Department of Chemistry & Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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Sabrekov AF, Semenov MV, Terentieva IE, Krasnov GS, Kharitonov SL, Glagolev MV, Litti YV. Anaerobic methane oxidation is quantitatively important in deeper peat layers of boreal peatlands: Evidence from anaerobic incubations, in situ stable isotopes depth profiles, and microbial communities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 916:170213. [PMID: 38278226 DOI: 10.1016/j.scitotenv.2024.170213] [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: 09/28/2023] [Revised: 01/07/2024] [Accepted: 01/14/2024] [Indexed: 01/28/2024]
Abstract
Boreal peatlands store most of their carbon in layers deeper than 0.5 m under anaerobic conditions, where carbon dioxide and methane are produced as terminal products of organic matter degradation. Since the global warming potential of methane is much greater than that of carbon dioxide, the balance between the production rates of these gases is important for future climate predictions. Herein, we aimed to understand whether anaerobic methane oxidation (AMO) could explain the high CO2/CH4 anaerobic production ratios that are widely observed for the deeper peat layers of boreal peatlands. Furthermore, we quantified the metabolic pathways of methanogenesis to examine whether hydrogenotrophic methanogenesis is a dominant methane production pathway for the presumably recalcitrant deeper peat. To assess the CH4 cycling in deeper peat, we combined laboratory anaerobic incubations with a pathway-specific inhibitor, in situ depth patterns of stable isotopes in CH4, and 16S rRNA gene amplicon sequencing for three representative boreal peatlands in Western Siberia. We found up to a 69 % reduction in CH4 production due to AMO, which largely explained the high CO2/CH4 anaerobic production ratios and the in situ depth-related patterns of δ13C and δD in methane. The absence of acetate accumulation after inhibiting acetotrophic methanogenesis and the presence of sulfate- and nitrate-reducing anaerobic acetate oxidizers in the deeper peat indicated that these microorganisms use SO42- and NO3- as electron acceptors. Acetotrophic methanogenesis dominated net CH4 production in the deeper peat, accounting for 81 ± 13 %. Overall, anaerobic oxidation is quantitatively important for the methane cycle in the deeper layers of boreal peatlands, affecting both methane and its main precursor concentrations.
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Affiliation(s)
- Aleksandr F Sabrekov
- UNESCO Department "Environmental Dynamics and Global Climate Changes", Ugra State University, Khanty-Mansiysk, Russia.
| | - Mikhail V Semenov
- Laboratory of Soil Carbon and Microbial Ecology, Dokuchaev Soil Science Institute, Moscow, Russia
| | | | - George S Krasnov
- Laboratory of Postgenomic Research, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | | | - Mikhail V Glagolev
- UNESCO Department "Environmental Dynamics and Global Climate Changes", Ugra State University, Khanty-Mansiysk, Russia; Faculty of Soil Science, Lomonosov Moscow State University, Moscow, Russia
| | - Yuriy V Litti
- Winogradsky Institute of Microbiology, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia
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Identification of Dissolved Organic Matter Origin Using Molecular Level Analysis Methods. WATER 2022. [DOI: 10.3390/w14091317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Natural organic matter (NOM) is ubiquitous; however, its characteristics are not fully understood because NOM is a complex organic mixture that reflects the surrounding ecosystem. Identification of its molecular structure provides information for evaluating its environmental reactivity and behavior. This study characterized NOM regarding its molecular structure. The characteristics of different types of NOM, depending on their origin, were investigated using various analytical methods such as pyrolysis-gas chromatography-mass spectrometry, size exclusion chromatography, and fluorescence spectrometry. NOM was collected from three different sites: river water, wetland, and wastewater treatment plant effluent. The molecular size of NOM followed the order wetland > river water > wastewater treatment plant effluent. The fluorescence spectra distinguished the differences among the samples. The effluent contained the highest proportion of protein-like peaks, and the wetland sample showed the highest humic-like substance peak. The origin of NOM was investigated by classifying the pyrolyzed fragments from each sample. NOM from wetlands contains a large amount of lignin, which originates from terrestrial substances. Proteins were the major biocomponents of the effluent sample. The NOM in the river water contained proteins and lignin-derived compounds. The results show that NOM can be clearly identified through molecular-level analysis methods.
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Kim YS, Yun HS, Lee JH, Kim HS, Yoon HS. Environmental Factors Associated with the Eukaryotic Microbial Community and Microalgal Groups in the Mountain Marshes of South Korea. Pol J Microbiol 2021; 70:215-233. [PMID: 34349812 PMCID: PMC8326984 DOI: 10.33073/pjm-2021-019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 03/25/2021] [Accepted: 04/11/2021] [Indexed: 11/24/2022] Open
Abstract
The diversity indices of eukaryotic microalgal groups in the Jeonglyeongchi, Waegok, and Wangdeungjae marshes of Mount Jiri, Korea, were measured using Illumina MiSeq and culture-based analyses. Waegok marsh had the highest species richness, with a Chao1 value of 828.00, and the highest levels of species diversity, with Shannon and Simpson index values of 6.36 and 0.94, respectively, while Wangdeungjae marsh had the lowest values at 2.97 and 0.75, respectively. The predominant species in all communities were Phagocata sibirica (Jeonglyeongchi, 68.64%), Aedes albopictus (Waegok, 34.77%), Chaetonotus cf. (Waegok, 24.43%), Eimeria sp. (Wangdeungjae, 26.17%), and Eumonhystera cf. (Wangdeungjae, 22.27%). Relative abundances of the microalgal groups Bacillariophyta (diatoms) and Chlorophyta (green algae) in each marsh were respectively: Jeonglyeongchi 1.38% and 0.49%, Waegok 7.0% and 0.3%, and Wangdeungjae 10.41% and 4.72%. Illumina MiSeq analyses revealed 34 types of diatoms and 13 types of green algae. Only one diatom (Nitzschia dissipata) and five green algae (Neochloris sp., Chlamydomonas sp., Chlorococcum sp., Chlorella vulgaris, Scenedesmus sp.) were identified by a culture-based analysis. Thus, Illumina MiSeq analysis can be considered an efficient tool for analyzing microbial communities. Overall, our results described the environmental factors associated with geographically isolated mountain marshes and their respective microbial and microalgal communities.
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Affiliation(s)
- Young-Saeng Kim
- Research Institute of Ulleung-do and Dok-do, Kyungpook National University, Daegu, South Korea
| | - Hyun-Sik Yun
- Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, South Korea
| | - Jea Hack Lee
- Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, South Korea
| | - Han-Soon Kim
- Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, South Korea
| | - Ho-Sung Yoon
- Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, South Korea.,School of Life Sciences, BK21 FOUR KNU Creative BioResearch Group, Kyungpook National University, Daegu, South Korea
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Gharedaghloo B, Price JS. Assessing benzene and toluene adsorption with peat depth: Implications on their fate and transport. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 274:116477. [PMID: 33549841 DOI: 10.1016/j.envpol.2021.116477] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 12/05/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
After a hydrocarbon spill in a peatland, dissolution of water-soluble compounds including benzene and toluene introduces a dissolved-phase plume to the peatland groundwater system, while the adsorption of these solutes onto the peat matrix restrains their distribution velocity. The adsorption of benzene and toluene and its dependency on peat depth, thus degree of decomposition, are investigated. The batch adsorption experiments revealed that benzene and toluene adsorption isotherms in peat are linear, with adsorption coefficients ranging from 16.2 to 48.7 L/kg and 31.6-48.7 L/kg, respectively. In a vertical peat profile benzene adsorption decreased with depth, while toluene adsorption increased. Considering toluene adsorption onto cellulose is significantly less than toluene adsorption onto humic substance, the increase in toluene adsorption was attributed to decreasing cellulose and increasing humic substances with depth. Negligible competition for adsorption was observed between benzene and toluene at the measured concentrations. The retardation factors of benzene and toluene ranged respectively from 3.5 to 10.7 and from 5.4 to 17.7, both increasing with depth. Higher retardation in deeper peat coupled with lower hydraulic conductivity will lead to a weaker solute velocity in deeper peat, thus preferential migration of these dissolved-phase contaminants in shallow layers. The results can help predict the behavior of dissolved hydrocarbons in peatlands after a hydrocarbon spill.
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Affiliation(s)
- Behrad Gharedaghloo
- Department of Geography and Environmental Management, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada; Aquanty Inc., Waterloo, ON, N2L 5C6, Canada.
| | - Jonathan S Price
- Department of Geography and Environmental Management, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada
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St James AR, Yavitt JB, Zinder SH, Richardson RE. Linking microbial Sphagnum degradation and acetate mineralization in acidic peat bogs: from global insights to a genome-centric case study. ISME JOURNAL 2020; 15:293-303. [PMID: 32951020 DOI: 10.1038/s41396-020-00782-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 09/09/2020] [Accepted: 09/14/2020] [Indexed: 11/09/2022]
Abstract
Ombrotrophic bogs accumulate large stores of soil carbon that eventually decompose to carbon dioxide and methane. Carbon accumulates because Sphagnum mosses slow microbial carbon decomposition processes, leading to the production of labile intermediate compounds. Acetate is a major product of Sphagnum degradation, yet rates of hydrogenotrophic methanogenesis far exceed rates of aceticlastic methanogenesis, suggesting that alternative acetate mineralization processes exist. Two possible explanations are aerobic respiration and anaerobic respiration via humic acids as electron acceptors. While these processes have been widely observed, microbial community interactions linking Sphagnum degradation and acetate mineralization remain cryptic. In this work, we use ordination and network analysis of functional genes from 110 globally distributed peatland metagenomes to identify conserved metabolic pathways in Sphagnum bogs. We then use metagenome-assembled genomes (MAGs) from McLean Bog, a Sphagnum bog in New York State, as a local case study to reconstruct pathways of Sphagnum degradation and acetate mineralization. We describe metabolically flexible Acidobacteriota MAGs that contain all genes to completely degrade Sphagnum cell wall sugars under both aerobic and anaerobic conditions. Finally, we propose a hypothetical model of acetate oxidation driven by changes in peat redox potential that explain how bogs may circumvent aceticlastic methanogenesis through aerobic and humics-driven respiration.
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Affiliation(s)
- Andrew R St James
- School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, USA.
| | - Joseph B Yavitt
- Department of Natural Resources, Cornell University, Ithaca, NY, USA
| | | | - Ruth E Richardson
- School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, USA
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Zhang G, Yu X, Xu J, Duan H, Rafay L, Zhang Q, Li Y, Liu Y, Xia S. Effects of environmental variation on stable isotope abundances during typical seasonal floodplain dry season litter decomposition. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 630:1205-1215. [PMID: 29554742 DOI: 10.1016/j.scitotenv.2018.02.298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/23/2018] [Accepted: 02/25/2018] [Indexed: 06/08/2023]
Abstract
Unique hydrological characteristics and complex topography can create wide-ranging dry season environmental heterogeneity in response to groundwater level across China's Jiangxi Province Poyang Lake wetland. Soil traits are one of several fluctuating environmental variables. To determine the effects of soil variables on stable isotope (δ13C and δ15N) abundances during decomposition, we performed a field experiment using Carex cinerascens along a groundwater level gradient (GT-L: -25 to -50cm, GT-LM: -15 to -25cm, GT-MH: -5 to -15cm, GT-H: 5 to -5cm) in a shallow lake. Twelve soil properties-including total organic carbon (TOC), nitrogen (N), pH, moisture, bulk density, clay, silt, sand, peroxidase, cellulase, microbial biomass carbon (MBC), and microbial biomass nitrogen-were measured in surface soil samples to assess soil environmental conditions. Analyses were performed to determine the effects of soil traits and lignin degradation on changes in stable isotope abundances. This study revealed that stable isotope abundances were significantly lower at high groundwater levels than at low groundwater levels. Lignin degradation was associated with a decrease in both δ13C and δ15N abundances. These two stable isotopes were positively related with soil N and bulk density, but negatively with pH and microbial quotient (MBC/TOC). Variation partitioning analysis (VPA) showed that soil variables and lignin decay rates explained 80.1% of the δ13C variation and 42.8% of the δ15N variation. Soil chemical and biological variables exhibited significant interactions with lignin decay rates, indicating they may affect stable isotope abundances via complex mechanisms. Our results indicate that the change in stable isotope abundances during decomposition may be affected directly by soil variables or indirectly through lignin degradation. Our results provide useful insight for understanding the roles of litter decomposition and soil traits in changing environmental conditions of seasonal floodplain wetlands.
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Affiliation(s)
- Guangshuai Zhang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiubo Yu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Jun Xu
- Donghu Experimental Station of Lake Ecosystem, State Key Lab of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China
| | - Houlang Duan
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Loretta Rafay
- School of Environmental and Forest Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Quanjun Zhang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ya Li
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Liu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Shaoxia Xia
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
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8
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The Composition and Stability of Clay-Associated Organic Matter along a Soil Profile. SOIL SYSTEMS 2018. [DOI: 10.3390/soilsystems2010016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Morris JT, Barber DC, Callaway JC, Chambers R, Hagen SC, Hopkinson CS, Johnson BJ, Megonigal P, Neubauer SC, Troxler T, Wigand C. Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state. EARTH'S FUTURE 2016; 4:110-121. [PMID: 27819012 PMCID: PMC5074445 DOI: 10.1002/2015ef000334] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/10/2016] [Accepted: 03/14/2016] [Indexed: 05/29/2023]
Abstract
A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes that the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD = 1/[LOI/k1 + (1-LOI)/k2], where k1 and k2 are the self-packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k1 and k2 were estimated to be 0.085 ± 0.0007 g cm-3 and 1.99 ± 0.028 g cm-3, respectively. Based on the fitted organic density (k1) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr-1. Thus, tidal peatlands are unlikely to indefinitely survive a higher rate of sea-level rise in the absence of a significant source of mineral sediment. Application of k2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr-1. Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr-1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sediment concentration, sediment-capture efficiency, and episodic events.
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Affiliation(s)
- James T Morris
- Department of Biological Sciences, Belle W. Baruch Institute for Marine & Coastal Sciences University of South Carolina Columbia South Carolina USA
| | - Donald C Barber
- Department of Geology Bryn Mawr College Bryn Mawr Pennsylvania USA
| | - John C Callaway
- Department of Environmental Science University of San Francisco San Francisco California USA
| | - Randy Chambers
- Keck Environmental Field Laboratory College of William and Mary Williamsburg Virginia USA
| | - Scott C Hagen
- Department of Civil & Environmental Engineering and Center for Computation & Technology Louisiana State University Baton Rouge Louisiana USA
| | | | | | | | - Scott C Neubauer
- Department of Biology Virginia Commonwealth University Richmond Virginia USA
| | - Tiffany Troxler
- Department of Biological Sciences, Southeast Environmental Research Center Florida International University Miami Florida USA
| | - Cathleen Wigand
- Atlantic Ecology Division U.S. EPA, Office of Research and Development, National Health and Environmental Effects Research Laboratory Narragansett Rhode Island USA
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Rice AV, Tsuneda A, Currah RS. In vitro decomposition of Sphagnum by some microfungi resembles white rot of wood. FEMS Microbiol Ecol 2006; 56:372-82. [PMID: 16689870 DOI: 10.1111/j.1574-6941.2006.00071.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The abilities of some ascomycetes (Myxotrichaceae) from a Sphagnum bog in Alberta to degrade cellulose, phenolics, and Sphagnum tissue were compared with those of two basidiomycetes. Most Myxotrichaceae degraded cellulose and tannic acid, and removed cell-wall components simultaneously from Sphagnum tissues, whereas the basidiomycetes degraded cellulose and insoluble phenolics, and preferentially removed the polyphenolic matrix from Sphagnum cell walls. Mass losses from Sphagnum varied from up to 50% for some ascomycetes to a maximum of 35% for the basidiomycetes. The decomposition of Sphagnum by the Myxotrichaceae was analogous to the white rot of wood and indicates that these fungi have the potential to cause significant mineralization of carbon in bogs.
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Affiliation(s)
- Adrianne V Rice
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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Robson TM, Pancotto VA, Ballaré CL, Sala OE, Scopel AL, Caldwell MM. Reduction of solar UV-B mediates changes in the Sphagnum capitulum microenvironment and the peatland microfungal community. Oecologia 2004; 140:480-90. [PMID: 15179579 DOI: 10.1007/s00442-004-1600-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Accepted: 04/20/2004] [Indexed: 10/26/2022]
Abstract
The influence of near-ambient and reduced solar UV-B radiation on a peatland microfungal community was assessed by exposing experimental plots to UV-selective filtration. Replicate plots were covered with special plastic films to effect treatments of near-ambient and attenuated solar UV-B. The microfungal community from the top 1 cm of Sphagnum capitulum in a Tierra del Fuego peatland was censused throughout three growing seasons, between 1999 and 2002. Sphagnum capitula under near-ambient UV-B were more compressed and held more water than capitula under reduced UV-B. This water had a greater conductivity and was more acidic under near-ambient UV-B, as would be expected with increased leaching from the Sphagnum leaves. Nine regularly occurring hyphal fungi from the peatland were identified, at least to genus. Over three field seasons, no treatment effect on total fungal colony abundance was recorded, but individual species abundance was increased (Mortierella alpina), decreased (Penicillium frequentans), or was unaffected (P. thomii, Aureobasidium) by near-ambient UV-B. Species richness was also slightly lower under near-ambient UV-B. These treatment differences were smaller than seasonal or inter-annual fluctuations in abundance and species richness. In a growth chamber experiment, lamp UV-B treatments indicated that realistic fluxes of UV-B can inhibit fungal growth in some species. In addition to this direct UV-B effect, we suggest that changes in the peatland fungal community under near-ambient solar UV-B may also result from increased nutrient and moisture availability in the Sphagnum capitulum. The subtle nature of the responses of peatland fungi to solar UV-B suggests that most fungal species we encountered are well adapted to current solar UV-B fluxes in Tierra del Fuego.
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Affiliation(s)
- T Matthew Robson
- The Ecology Center, Utah State University, Logan, UT 84322-5205, USA.
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