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Ishak S, Rondeau-Leclaire J, Faticov M, Roy S, Laforest-Lapointe I. Boreal moss-microbe interactions are revealed through metagenome assembly of novel bacterial species. Sci Rep 2024; 14:22168. [PMID: 39333734 PMCID: PMC11437008 DOI: 10.1038/s41598-024-73045-z] [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: 06/17/2024] [Accepted: 09/12/2024] [Indexed: 09/30/2024] Open
Abstract
Moss-microbe interactions contribute to ecosystem processes in boreal forests. Yet, how host-specific characteristics and the environment drive the composition and metabolic potential of moss microbiomes is still poorly understood. In this study, we use shotgun metagenomics to identify the taxonomy and metabolic potential of the bacteria of four moss species of the boreal forests of Northern Québec, Canada. To characterize moss bacterial community composition and diversity, we assembled the genomes of 110 potentially novel bacterial species. Our results highlight that moss genus, species, gametophyte section, and to a lesser extent soil pH and soil temperature, drive moss-associated bacterial community composition and diversity. In the brown gametophyte section, two Stigonema spp. showed partial pathway completeness for photosynthesis and nitrogen fixation, while all brown-associated Hyphomicrobiales had complete assimilatory nitrate reduction pathways and many nearly complete carbon fixation pathways. Several brown-associated species showed partial to complete pathways for coenzyme M and F420 biosynthesis, important for methane metabolism. In addition, green-associated Hyphomicrobiales (Methylobacteria spp.) displayed potential for the anoxygenic photosystem II pathway. Overall, our findings demonstrate how host-specific characteristics and environmental factors shape the composition and metabolic potential of moss bacteria, highlighting their roles in carbon fixation, nitrogen cycling, and methane metabolism in boreal forests.
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Affiliation(s)
- Sarah Ishak
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada.
| | | | - Maria Faticov
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada
| | - Sébastien Roy
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Isabelle Laforest-Lapointe
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre SÈVE, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada.
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2
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Alvarenga DO, Clasen LA, Thomsen AMR, Andersen RF, Rousk K. Light drives nitrogen fixation in tropical montane cloud forests in Costa Rica. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 940:173631. [PMID: 38823705 DOI: 10.1016/j.scitotenv.2024.173631] [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: 04/06/2024] [Revised: 05/24/2024] [Accepted: 05/28/2024] [Indexed: 06/03/2024]
Abstract
Tropical montane cloud forests are high altitude ecosystems characterized by very high ambient humidity, which favors organisms that depend on the environment for their water status, such as bryophytes and their nitrogen-fixing symbionts. Bryophyte-associated N2 fixation is a major source of new N in several northern environments, but their contributions to the N cycle in other ecosystems is still poorly understood. In this work, we evaluated N2 fixation rates associated with epiphytic bryophytes growing along the stems of pumpwood trees (Cecropia sp.) as well as in surrounding litter and soil from a primary and a secondary cloud forests in the Talamanca Mountain Range, Costa Rica. Nitrogen fixation was significantly higher in substrates from the secondary forest compared to those from the primary forest. Overall, N2 fixation rates associated with epiphytic bryophytes were 57 times those of litter and 270 times what was measured in soil. Further, light intensity was the major factor influencing N2 fixation rates in all substrates. Increased access to light in disturbed cloud forests may therefore favor bryophyte-associated N2 fixation, potentially contributing to the recovery of these ecosystems.
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Affiliation(s)
- Danillo Oliveira Alvarenga
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark.
| | - Lina Avila Clasen
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Amanda Maria Rydgren Thomsen
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Rune Fromm Andersen
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Kathrin Rousk
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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3
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Lett S, Christiansen CT, Dorrepaal E, Michelsen A. Moss species and precipitation mediate experimental warming stimulation of growing season N 2 fixation in subarctic tundra. GLOBAL CHANGE BIOLOGY 2024; 30:e17401. [PMID: 39041207 DOI: 10.1111/gcb.17401] [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: 09/01/2023] [Revised: 05/27/2024] [Accepted: 06/09/2024] [Indexed: 07/24/2024]
Abstract
Climate change in high latitude regions leads to both higher temperatures and more precipitation but their combined effects on terrestrial ecosystem processes are poorly understood. In nitrogen (N) limited and often moss-dominated tundra and boreal ecosystems, moss-associated N2 fixation is an important process that provides new N. We tested whether high mean annual precipitation enhanced experimental warming effects on growing season N2 fixation in three common arctic-boreal moss species adapted to different moisture conditions and evaluated their N contribution to the landscape level. We measured in situ N2 fixation rates in Hylocomium splendens, Pleurozium schreberi and Sphagnum spp. from June to September in subarctic tundra in Sweden. We exposed mosses occurring along a natural precipitation gradient (mean annual precipitation: 571-1155 mm) to 8 years of experimental summer warming using open-top chambers before our measurements. We modelled species-specific seasonal N input to the ecosystem at the colony and landscape level. Higher mean annual precipitation clearly increased N2 fixation, especially during peak growing season and in feather mosses. For Sphagnum-associated N2 fixation, high mean annual precipitation reversed a small negative warming response. By contrast, in the dry-adapted feather moss species higher mean annual precipitation led to negative warming effects. Modelled total growing season N inputs for Sphagnum spp. colonies were two to three times that of feather mosses at an area basis. However, at the landscape level where feather mosses were more abundant, they contributed 50% more N than Sphagnum. The discrepancy between modelled estimates of species-specific N input via N2 fixation at the moss core versus ecosystem scale, exemplify how moss cover is essential for evaluating impact of altered N2 fixation. Importantly, combined effects of warming and higher mean annual precipitation may not lead to similar responses across moss species, which could affect moss fitness and their abilities to buffer environmental changes.
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Affiliation(s)
- Signe Lett
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
| | - Casper T Christiansen
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
| | - Ellen Dorrepaal
- Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
| | - Anders Michelsen
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
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4
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Baev V, Gecheva G, Apostolova E, Gozmanova M, Yahubyan G. Exploring the Metatranscriptome of Bacterial Communities of Two Moss Species Thriving in Different Environments-Terrestrial and Aquatic. PLANTS (BASEL, SWITZERLAND) 2024; 13:1210. [PMID: 38732425 PMCID: PMC11085137 DOI: 10.3390/plants13091210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 04/22/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024]
Abstract
Mosses host diverse bacterial communities essential for their fitness, nutrient acquisition, stress tolerance, and pathogen defense. Understanding the microbiome's taxonomic composition is the first step, but unraveling their functional capabilities is crucial for grasping their ecological significance. Metagenomics characterizes microbial communities by composition, while metatranscriptomics explores gene expression, providing insights into microbiome functionality beyond the structure. Here, we present for the first time a metatranscriptomic study of two moss species, Hypnum cupressiforme (Hedw.) and Platyhypnidium riparioides (Hedw.) Dixon., renowned as key biomonitors of atmospheric and water pollution. Our investigation extends beyond taxonomic profiling and offers a profound exploration of moss bacterial communities. Pseudomonadota and Actinobacteria are the dominant bacterial phyla in both moss species, but their proportions differ. In H. cupressiforme, Actinobacteria make up 62.45% and Pseudomonadota 32.48%, while in P. riparioides, Actinobacteria account for only 25.67% and Pseudomonadota 69.08%. This phylum-level contrast is reflected in genus-level differences. Our study also shows the expression of most genes related to nitrogen cycling across both microbiomes. Additionally, functional annotation highlights disparities in pathway prevalence, including carbon dioxide fixation, photosynthesis, and fatty acid biosynthesis, among others. These findings hint at potential metabolic distinctions between microbial communities associated with different moss species, influenced by their specific genotypes and habitats. The integration of metatranscriptomic data holds promise for enhancing our understanding of bryophyte-microbe partnerships, opening avenues for novel applications in conservation, bioremediation, and sustainable agriculture.
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Affiliation(s)
- Vesselin Baev
- Department of Molecular Biology, Faculty of Biology, University of Plovdiv, Tzar Assen 24, 4000 Plovdiv, Bulgaria; (E.A.); (M.G.)
| | - Gana Gecheva
- Department of Ecology and Environmental Conservation, Faculty of Biology, University of Plovdiv, Tzar Assen 24, 4000 Plovdiv, Bulgaria;
| | - Elena Apostolova
- Department of Molecular Biology, Faculty of Biology, University of Plovdiv, Tzar Assen 24, 4000 Plovdiv, Bulgaria; (E.A.); (M.G.)
| | - Mariyana Gozmanova
- Department of Molecular Biology, Faculty of Biology, University of Plovdiv, Tzar Assen 24, 4000 Plovdiv, Bulgaria; (E.A.); (M.G.)
| | - Galina Yahubyan
- Department of Molecular Biology, Faculty of Biology, University of Plovdiv, Tzar Assen 24, 4000 Plovdiv, Bulgaria; (E.A.); (M.G.)
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5
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Yuan M, Na M, Hicks LC, Rousk J. Limiting resources for soil microbial growth in climate change simulation treatments in the subarctic. Ecology 2024; 105:e4210. [PMID: 37989722 DOI: 10.1002/ecy.4210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 09/06/2023] [Accepted: 10/04/2023] [Indexed: 11/23/2023]
Abstract
The microbial use of resources to sustain life and reproduce influences for example, decomposition and plant nutrient provisioning. The study of "limiting factors" has shed light on the interaction between plants and their environment. Here, we investigated whether carbon (C), nitrogen (N), or phosphorus (P) was limiting for soil microorganisms in a subarctic tundra heath, and how changes in resource availability associated with climate change affected this. We studied samples in which changes in resource availability due to climate warming were simulated by the addition of birch litter and/or inorganic N. To these soils, we supplied factorial C (as glucose), N (as NH4 NO3 ), and P (as KH2 PO4 /K2 HPO4 ) additions ("limiting factor assays," LFA), to determine the limiting factors. The combination of C and P induced large growth responses in all soils and, combined with a systematic tendency for growth increases by C, this suggested that total microbial growth was primarily limited by C and secondarily by P. The C limitation was alleviated by the field litter treatment and strengthened by N fertilization. The microbial growth response to the LFA-C and LFA-P addition was strongest in the field-treatment that combined litter and N addition. We also found that bacteria were closer to P limitation than fungi. Our results suggest that, under a climate change scenario, increased C availability resulting from Arctic greening, treeline advance, and shrubification will reduce the microbial C limitation, while increased N availability resulting from warming will intensify the microbial C limitation. Our results also suggest that the synchronous increase of both C and N availability might lead to a progressive P limitation of microbial growth, primarily driven by bacteria being closer to P limitation. These shifts in microbial resource limitation might lead to a microbial targeting of the limiting element from organic matter, and also trigger competition for nutrients between plants and microorganisms, thus modulating the productivity of the ecosystem.
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Affiliation(s)
- Mingyue Yuan
- Section of Microbial Ecology, Department of Biology, Lund University, Lund, Sweden
| | - Meng Na
- Section of Microbial Ecology, Department of Biology, Lund University, Lund, Sweden
- School of Forestry, Northeast Forestry University, Harbin, China
| | - Lettice C Hicks
- Section of Microbial Ecology, Department of Biology, Lund University, Lund, Sweden
| | - Johannes Rousk
- Section of Microbial Ecology, Department of Biology, Lund University, Lund, Sweden
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6
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Chen Q, Long C, Bao Y, Men X, Zhang Y, Cheng X. The dominant genera of nitrogenase (nifH) affects soil biological nitrogen fixation along an elevational gradient in the Hengduan mountains. CHEMOSPHERE 2024; 347:140722. [PMID: 37972867 DOI: 10.1016/j.chemosphere.2023.140722] [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: 09/04/2023] [Revised: 11/01/2023] [Accepted: 11/12/2023] [Indexed: 11/19/2023]
Abstract
Biological nitrogen (N) fixation by diazotrophic microbes is an essential process for the N input. However, the patterns of biological N fixation and its biological or environmental mechanism along an elevational gradient in mountain ecosystems are not fully understood. In this study, a field experiment was conducted in the Hengduan Mountains to investigate the biological N fixation associated with the diversity and abundance of the nifH gene. Our results showed that both the abundance of the nifH gene and the biological N fixation displayed hump-shaped trends along an elevation gradient in the wet and dry seasons. However, the diversity of the nifH gene showed an inverse unimodal trend along an elevation gradient. We observed that biological N fixation was jointly associated with the abundance of the nifH gene, especially dominant genera, as well as soil chartacteristics. Among them, clay content played a preeminent role in the regulation of N fixation potentially through the formation of microaggregates and microenvironments. In general, our results revealed that biological N fixation was correlated with the abundance of microorganisms, especially dominant genera, and soil texture. These results highlighted the importance of dominant genera, which should be considered in the modeling and forecasting of N cycling under future environmental change.
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Affiliation(s)
- Qiong Chen
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Chunyan Long
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Yong Bao
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Xiuxian Men
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Yong Zhang
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China
| | - Xiaoli Cheng
- Key Laboratory of Soil Ecology and Health in Universities of Yunnan Province, School of Ecology and Environmental Sciences, Yunnan University, Kunming 650500, PR China.
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7
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Porada P, Bader MY, Berdugo MB, Colesie C, Ellis CJ, Giordani P, Herzschuh U, Ma Y, Launiainen S, Nascimbene J, Petersen I, Raggio Quílez J, Rodríguez-Caballero E, Rousk K, Sancho LG, Scheidegger C, Seitz S, Van Stan JT, Veste M, Weber B, Weston DJ. A research agenda for nonvascular photoautotrophs under climate change. THE NEW PHYTOLOGIST 2023; 237:1495-1504. [PMID: 36511294 DOI: 10.1111/nph.18631] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Nonvascular photoautotrophs (NVP), including bryophytes, lichens, terrestrial algae, and cyanobacteria, are increasingly recognized as being essential to ecosystem functioning in many regions of the world. Current research suggests that climate change may pose a substantial threat to NVP, but the extent to which this will affect the associated ecosystem functions and services is highly uncertain. Here, we propose a research agenda to address this urgent question, focusing on physiological and ecological processes that link NVP to ecosystem functions while also taking into account the substantial taxonomic diversity across multiple ecosystem types. Accordingly, we developed a new categorization scheme, based on microclimatic gradients, which simplifies the high physiological and morphological diversity of NVP and world-wide distribution with respect to several broad habitat types. We found that habitat-specific ecosystem functions of NVP will likely be substantially affected by climate change, and more quantitative process understanding is required on: (1) potential for acclimation; (2) response to elevated CO2 ; (3) role of the microbiome; and (4) feedback to (micro)climate. We suggest an integrative approach of innovative, multimethod laboratory and field experiments and ecophysiological modelling, for which sustained scientific collaboration on NVP research will be essential.
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Affiliation(s)
- Philipp Porada
- Ecological Modelling, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany
| | - Maaike Y Bader
- Ecological Plant Geography, University of Marburg, Deutschhausstr. 10, 35032, Marburg, Germany
| | - Monica B Berdugo
- Ecological Plant Geography, University of Marburg, Deutschhausstr. 10, 35032, Marburg, Germany
| | - Claudia Colesie
- School of Geosciences, University of Edinburgh, Edinburgh, EH9 3JW, UK
| | | | | | - Ulrike Herzschuh
- Polar Terrestrial Environmental Systems, Alfred Wegener Institute, Telegrafenberg A45, 14473, Potsdam, Germany
| | - Yunyao Ma
- Ecological Modelling, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany
| | - Samuli Launiainen
- Ecosystems and Modeling, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790, Helsinki, Finland
| | - Juri Nascimbene
- BIOME Lab, Department of Biological, Geological and Environmental Sciences, Alma Mater Studiorum University of Bologna, 40126, Bologna, Italy
| | - Imke Petersen
- Ecological Modelling, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany
| | - José Raggio Quílez
- Department of Pharmacology, Pharmacognosy and Botany, Universidad Complutense de Madrid, E-28040, Madrid, Spain
| | | | - Kathrin Rousk
- Department of Biology, University of Copenhagen, Universitetsparken 15, 2100, København, Denmark
| | - Leopoldo G Sancho
- Department of Pharmacology, Pharmacognosy and Botany, Universidad Complutense de Madrid, E-28040, Madrid, Spain
| | - Christoph Scheidegger
- Biodiversity and Conservation Biology, Eidg. Forschungsanstalt WSL, Zürcherstr. 111, 8903, Birmensdorf, Switzerland
| | - Steffen Seitz
- Soil Science and Geomorphology, University of Tübingen, Rümelinstr. 19-23, 72070, Tübingen, Germany
| | - John T Van Stan
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, 2121 Euclid Ave., Cleveland, OH, 44115, USA
| | - Maik Veste
- Institute of Environmental Sciences, Brandenburgische Technische Universität Cottbus-Senftenberg, Konrad-Wachsmann-Allee 6, 03046, Cottbus, Germany
| | - Bettina Weber
- Division of Plant Sciences, Institute for Biology, University of Graz, Holteigasse 6, A-8010, Graz, Austria
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128, Mainz, Germany
| | - David J Weston
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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8
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Dynamic carbon-nitrogen coupling under global change. SCIENCE CHINA. LIFE SCIENCES 2023; 66:771-782. [PMID: 36680674 DOI: 10.1007/s11427-022-2245-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 11/21/2022] [Indexed: 01/22/2023]
Abstract
Carbon-nitrogen coupling is a fundamental principle in ecosystem ecology. However, how the coupling responds to global change has not yet been examined. Through a comprehensive and systematic literature review, we assessed how the dynamics of carbon processes change with increasing nitrogen input and how nitrogen processes change with increasing carbon input under global change. Our review shows that nitrogen input to the ecosystem mostly stimulates plant primary productivity but inconsistently decreases microbial activities or increases soil carbon sequestration, with nitrogen leaching and nitrogenous gas emission rapidly increasing. Nitrogen fixation increases and nitrogen leaching decreases to improve soil nitrogen availability and support plant growth and ecosystem carbon sequestration under elevated CO2 and temperature or along ecosystem succession. We conclude that soil nitrogen cycle processes continually adjust to change in response to either overload under nitrogen addition or deficiency under CO2 enrichment and ecosystem succession to couple with carbon cycling. Indeed, processes of both carbon and nitrogen cycles continually adjust under global change, leading to dynamic coupling in carbon and nitrogen cycles. The dynamic coupling framework reconciles previous debates on the "uncoupling" or "decoupling" of ecosystem carbon and nitrogen cycles under global change. Ecosystem models failing to simulate these dynamic adjustments cannot simulate carbon-nitrogen coupling nor predict ecosystem carbon sequestration well.
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Chen KH, Nelson J. A scoping review of bryophyte microbiota: diverse microbial communities in small plant packages. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:4496-4513. [PMID: 35536989 DOI: 10.1093/jxb/erac191] [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: 12/31/2021] [Accepted: 05/05/2022] [Indexed: 06/14/2023]
Abstract
Plant health depends not only on the condition of the plant itself but also on its diverse community of microbes, or microbiota. Just like the better-studied angiosperms, bryophytes (mosses, liverworts, and hornworts) harbor diverse communities of bacteria, archaea, fungi, and other microbial eukaryotes. Bryophytes are increasingly recognized as important model systems for understanding plant evolution, development, physiology, and symbiotic interactions. Much of the work on bryophyte microbiota in the past focused on specific symbiont types for each bryophyte group, but more recent studies are taking a broader view acknowledging the coexistence of diverse microbial communities in bryophytes. Therefore, this review integrates studies of bryophyte microbes from both perspectives to provide a holistic view of the existing research for each bryophyte group and on key themes. The systematic search also reveals the taxonomic and geographic biases in this field, including a severe under-representation of the tropics, very few studies on viruses or eukaryotic microbes beyond fungi, and a focus on mycorrhizal fungi studies in liverworts. Such gaps may have led to errors in conclusions about evolutionary patterns in symbiosis. This analysis points to a wealth of future research directions that promise to reveal how the distinct life cycles and physiology of bryophytes interact with their microbiota.
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Affiliation(s)
- Ko-Hsuan Chen
- Biodiversity Research Center, Academia Sinica, Taipei, Taiwan
| | - Jessica Nelson
- Maastricht Science Programme, Maastricht University, Maastricht, The Netherlands
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10
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Alvarenga DO, Rousk K. Unraveling host-microbe interactions and ecosystem functions in moss-bacteria symbioses. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:4473-4486. [PMID: 35728619 DOI: 10.1093/jxb/erac091] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Mosses are non-vascular plants usually found in moist and shaded areas, with great ecological importance in several ecosystems. This is especially true in northern latitudes, where mosses are responsible for up to 100% of primary production in some ecosystems. Mosses establish symbiotic associations with unique bacteria that play key roles in the carbon and nitrogen cycles. For instance, in boreal environments, more than 35% of the nitrogen fixed by diazotrophic symbionts in peatlands is transferred to mosses, directly affecting carbon fixation by the hosts, while moss-associated methanotrophic bacteria contribute 10-30% of moss carbon. Further, half of ecosystem N input may derive from moss-cyanobacteria associations in pristine ecosystems. Moss-bacteria interactions have consequences on a global scale since northern environments sequester 20% of all the carbon generated by forests in the world and stock at least 32% of global terrestrial carbon. Different moss hosts influence bacteria in distinct ways, which suggests that threats to mosses also threaten unique microbial communities with important ecological and biogeochemical consequences. Since their origin ~500 Ma, mosses have interacted with bacteria, making these associations ideal models for understanding the evolution of plant-microbe associations and their contribution to biogeochemical cycles.
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Affiliation(s)
- Danillo O Alvarenga
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark
- Centre for Permafrost, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
| | - Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark
- Centre for Permafrost, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
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11
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Scharn R, Negri IS, Sundqvist MK, Løkken JO, Bacon CD, Antonelli A, Hofgaard A, Nilsson RH, Björk RG. Limited decadal growth of mountain birch saplings has minor impact on surrounding tundra vegetation. Ecol Evol 2022; 12:e9028. [PMID: 35784030 PMCID: PMC9219107 DOI: 10.1002/ece3.9028] [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: 02/01/2022] [Revised: 05/24/2022] [Accepted: 05/27/2022] [Indexed: 11/11/2022] Open
Abstract
Temperatures over the Arctic region are increasing at three times the rate of the global average. Consequently, Arctic vegetation is changing and trees are encroaching into the tundra. In this study, we examine the establishment and growth of mountain birch (Betula pubescens ssp. tortuosa), which forms the treeline in subarctic Europe, and its impact on community composition across the treeline ecotone nearby Abisko, Sweden. Birch advancement along elevational gradients was studied by comparing data collected in 2016 with data collected 10 and 15 years previously. Species identity, cover, and phylogenetic relatedness were used to assess the impact of birch encroachment on community composition. Our results show that birch occurrence above the treeline did not affect plant community composition, probably owing to the observed lack of significant growth due to herbivore browsing, nitrogen limitation, or a reduction in snow cover. Independent of birch performance, the tundra community structure shifted toward a novel community dissimilar from the forest plant community found below the treeline. Taken together, our findings are explained by species-specific responses to climate change, rather than by a linear forest advance. Future treeline advancements are likely more restricted than previously expected.
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Affiliation(s)
- Ruud Scharn
- Department of Earth SciencesUniversity of GothenburgGothenburgSweden
- Gothenburg Global Biodiversity CentreGothenburgSweden
| | - Isabel S. Negri
- Department of Earth SciencesUniversity of GothenburgGothenburgSweden
- School of BiosciencesCardiff UniversityCardiffUK
| | - Maja K. Sundqvist
- Department of Earth SciencesUniversity of GothenburgGothenburgSweden
- Department of Forest Ecology and ManagementSwedish University of Agricultural SciencesUmeåSweden
| | - Jørn O. Løkken
- Norwegian Institute for Nature ResearchTrondheimNorway
- Department of BiologyNorwegian University of Science and TechnologyTrondheimNorway
| | - Christine D. Bacon
- Gothenburg Global Biodiversity CentreGothenburgSweden
- Department of Biological and Environmental SciencesUniversity of GothenburgGothenburgSweden
| | - Alexandre Antonelli
- Gothenburg Global Biodiversity CentreGothenburgSweden
- Department of Biological and Environmental SciencesUniversity of GothenburgGothenburgSweden
- Royal Botanical Gardens KewRichmondUK
- Department of Plant SciencesUniversity of OxfordOxfordUK
| | | | - R. Henrik Nilsson
- Gothenburg Global Biodiversity CentreGothenburgSweden
- Department of Biological and Environmental SciencesUniversity of GothenburgGothenburgSweden
| | - Robert G. Björk
- Department of Earth SciencesUniversity of GothenburgGothenburgSweden
- Gothenburg Global Biodiversity CentreGothenburgSweden
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12
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Klarenberg IJ, Keuschnig C, Russi Colmenares AJ, Warshan D, Jungblut AD, Jónsdóttir IS, Vilhelmsson O. Long-term warming effects on the microbiome and nifH gene abundance of a common moss species in sub-Arctic tundra. THE NEW PHYTOLOGIST 2022; 234:2044-2056. [PMID: 34719786 DOI: 10.1111/nph.17837] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 10/17/2021] [Indexed: 06/13/2023]
Abstract
Bacterial communities form the basis of biogeochemical processes and determine plant growth and health. Mosses harbour diverse bacterial communities that are involved in nitrogen fixation and carbon cycling. Global climate change is causing changes in aboveground plant biomass and shifting species composition in the Arctic, but little is known about the response of moss microbiomes in these environments. Here, we studied the total and potentially active bacterial communities associated with Racomitrium lanuginosum in response to a 20-yr in situ warming in an Icelandic heathland. We evaluated the effect of warming and warming-induced shrub expansion on the moss bacterial community composition and diversity, and nifH gene abundance. Warming changed both the total and the potentially active bacterial community structure, while litter abundance only affected the total bacterial community structure. The abundance of nifH genes was negatively affected by litter abundance. We also found shifts in the potentially nitrogen-fixing community, with Nostoc decreasing and noncyanobacterial diazotrophs increasing in relative abundance. Our data suggest that the moss microbial community and potentially nitrogen fixing taxa will be sensitive to future warming, partly via changes in litter and shrub abundance.
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Affiliation(s)
- Ingeborg J Klarenberg
- Natural Resource Sciences, University of Akureyri, Borgir i Nordurslod, Akureyri, 600, Iceland
- Faculty of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 102, Reykjavík, Iceland
| | - Christoph Keuschnig
- Environmental Microbial Genomics, Laboratoire Ampère, École Centrale de Lyon, Université de Lyon, Avenue Guy de Collongue 36, Écully, 69134, France
| | - Ana J Russi Colmenares
- Faculty of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 102, Reykjavík, Iceland
| | - Denis Warshan
- Faculty of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 102, Reykjavík, Iceland
| | - Anne D Jungblut
- Life Sciences Department, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
| | - Ingibjörg S Jónsdóttir
- Faculty of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 102, Reykjavík, Iceland
| | - Oddur Vilhelmsson
- Natural Resource Sciences, University of Akureyri, Borgir i Nordurslod, Akureyri, 600, Iceland
- BioMedical Center, University of Iceland, Vatnsmýrarvegur 16, 101, Reykjavík, Iceland
- School of Biological Sciences, University of Reading, Whiteknights, Reading, RG6 6AJ, UK
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13
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Permin A, Horwath AB, Metcalfe DB, Priemé A, Rousk K. ‘High nitrogen‐fixing rates associated with ground‐covering mosses in a tropical mountain cloud forest will decrease drastically in a future climate’. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Aya Permin
- Terrestrial Ecology Section, Department of Biology University of Copenhagen Copenhagen Denmark
- Center for Permafrost (CENPERM) University of Copenhagen Copenhagen Denmark
| | - Aline B. Horwath
- Biological and Environmental Sciences, Faculty of Natural Sciences University of Stirling Stirling UK
| | - Daniel B. Metcalfe
- Department of Physical Geography and Ecosystem Science Lund University SE Lund Sweden
- Department of Ecology and Environmental Science SE Umeå Sweden
| | - Anders Priemé
- Center for Permafrost (CENPERM) University of Copenhagen Copenhagen Denmark
- Section of Microbiology, Department of Biology University of Copenhagen Copenhagen Denmark
| | - Kathrin Rousk
- Terrestrial Ecology Section, Department of Biology University of Copenhagen Copenhagen Denmark
- Center for Permafrost (CENPERM) University of Copenhagen Copenhagen Denmark
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14
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Burnett MS, Schütte UM, Harms TK. WIDESPREAD CAPACITY FOR DENITRIFICATION ACROSS A BOREAL FOREST LANDSCAPE. BIOGEOCHEMISTRY 2022; 158:215-232. [PMID: 36186670 PMCID: PMC9518932 DOI: 10.1007/s10533-022-00895-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 01/18/2022] [Indexed: 06/16/2023]
Abstract
A warming climate combined with frequent and severe fires cause permafrost to thaw, especially in the region of discontinuous permafrost, where soil temperatures may only be a few degrees below 0 °C. Soil thaw releases carbon (C) and nitrogen (N) into the actively cycling pools, and whereas C emissions following permafrost thaw are well documented, the fates of N remain unclear. Denitrification could release N from ecosystems as nitrous oxide (N2O) or nitrogen gas (N2), but the contributions of these processes to the high-latitude N cycle remain uncertain. We quantified microbial capacity for denitrification and N2O production in boreal soils, lakes, and streams using anoxic C- and N-amended assays, and assessed correlates of denitrifying enzyme activity (DEA) in Interior Alaska. Riparian soils and stream sediments supported the highest potential rates of denitrification, upland soils were intermediate, and lakes supported lower rates, whereas deep permafrost soils supported little denitrification. Time since fire had no effect on denitrification potential in upland soils. Across all landscape positions, DEA was negatively correlated with ammonium pools. Within each landscape position, potential rate of denitrification increased with soil or sediment organic matter content. Widespread N loss to denitrification in boreal forests could constrain the capacity for N-limited primary producers to maintain C stocks in soils following permafrost thaw.
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Affiliation(s)
- Melanie S. Burnett
- Institute of Arctic Biology and Department of Biology & Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska 99775, United States of America
- Department of Earth and Planetary Science, McGill University, Montréal, Quebec H3A 2A7, Canada
| | - Ursel M.E. Schütte
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, United States of America
| | - Tamara K. Harms
- Institute of Arctic Biology and Department of Biology & Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska 99775, United States of America
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15
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Liu X, Rousk K. The moss traits that rule cyanobacterial colonization. ANNALS OF BOTANY 2022; 129:147-160. [PMID: 34628495 PMCID: PMC8796673 DOI: 10.1093/aob/mcab127] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 10/08/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND AND AIMS Cyanobacteria associated with mosses represent a main nitrogen (N) source in pristine, high-latitude and -altitude ecosystems due to their ability to fix N2. However, despite progress made regarding moss-cyanobacteria associations, the factors driving the large interspecific variation in N2 fixation activity between moss species remain elusive. The aim of the study was to identify the traits of mosses that determine cyanobacterial colonization and thus N2 fixation activity. METHODS Four moss species varying in N2 fixation activity were used to assess cyanobacterial abundance and activity to correlate it with moss traits (morphological, chemical, water-balance traits) for each species. KEY RESULTS Moss hydration rate was one of the pivotal traits, explaining 56 and 38 % of the variation in N2 fixation and cyanobacterial colonization, respectively, and was linked to morphological traits of the moss species. Higher abundance of cyanobacteria was found on shoots with smaller leaves, and with a high frequency of leaves. High phenol concentration inhibited N2 fixation but not colonization. These traits driving interspecific variation in cyanobacterial colonization, however, are also affected by the environment, and lead to intraspecific variation. Approximately 24 % of paraphyllia, filamentous appendages on Hylocomium splendens stems, were colonized by cyanobacteria. CONCLUSIONS Our findings show that interspecific variations in moss traits drive differences in cyanobacterial colonization and thus, N2 fixation activity among moss species. The key traits identified here that control moss-associated N2 fixation and cyanobacterial colonization could lead to improved predictions of N2 fixation in different moss species as a function of their morphology.
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Affiliation(s)
- Xin Liu
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen, Denmark
| | - Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen, Denmark
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16
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Meyer N, Xu Y, Karjalainen K, Adamczyk S, Biasi C, van Delden L, Martin A, Mganga K, Myller K, Sietiö OM, Suominen O, Karhu K. Living, dead, and absent trees-How do moth outbreaks shape small-scale patterns of soil organic matter stocks and dynamics at the Subarctic mountain birch treeline? GLOBAL CHANGE BIOLOGY 2022; 28:441-462. [PMID: 34672044 DOI: 10.1111/gcb.15951] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 06/13/2023]
Abstract
Mountain birch forests (Betula pubescens Ehrh. ssp. czerepanovii) at the subarctic treeline not only benefit from global warming, but are also increasingly affected by caterpillar outbreaks from foliage-feeding geometrid moths. Both of these factors have unknown consequences on soil organic carbon (SOC) stocks and biogeochemical cycles. We measured SOC stocks down to the bedrock under living trees and under two stages of dead trees (12 and 55 years since moth outbreak) and treeless tundra in northern Finland. We also measured in-situ soil respiration, potential SOC decomposability, biological (enzyme activities and microbial biomass), and chemical (N, mineral N, and pH) soil properties. SOC stocks were significantly higher under living trees (4.1 ± 2.1 kg m²) than in the treeless tundra (2.4 ± 0.6 kg m²), and remained at an elevated level even 12 (3.7 ± 1.7 kg m²) and 55 years (4.9 ± 3.0 kg m²) after tree death. Effects of tree status on SOC stocks decreased with increasing distance from the tree and with increasing depth, that is, a significant effect of tree status was found in the organic layer, but not in mineral soil. Soil under living trees was characterized by higher mineral N contents, microbial biomass, microbial activity, and soil respiration compared with the treeless tundra; soils under dead trees were intermediate between these two. The results suggest accelerated organic matter turnover under living trees but a positive net effect on SOC stocks. Slowed organic matter turnover and continuous supply of deadwood may explain why SOC stocks remained elevated under dead trees, despite the heavy decrease in aboveground C stocks. We conclude that the increased occurrence of moth damage with climate change would have minor effects on SOC stocks, but ultimately decrease ecosystem C stocks (49% within 55 years in this area), if the mountain birch forests will not be able to recover from the outbreaks.
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Affiliation(s)
- Nele Meyer
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
- Department of Soil Ecology, University of Bayreuth, Bayreuth, Germany
| | - Yi Xu
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Katri Karjalainen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
| | - Sylwia Adamczyk
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
- Natural Resources Institute Finland (Luke), Helsinki, Finland
| | - Christina Biasi
- Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
| | - Lona van Delden
- Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - Angela Martin
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Kevin Mganga
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
- Department of Agricultural Sciences, South Eastern Kenya University, Kitui, Kenya
| | - Kristiina Myller
- Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
| | - Outi-Maaria Sietiö
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Otso Suominen
- Biodiversity Unit, Kevo Subarctic Research Institute, University of Turku, Turku, Finland
| | - Kristiina Karhu
- Department of Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
- Helsinki Institute of Life Science (Hilife), University of Helsinki, Helsinki, Finland
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17
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Alvarenga DO, Rousk K. Indirect effects of climate change inhibit N 2 fixation associated with the feathermoss Hylocomium splendens in subarctic tundra. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 795:148676. [PMID: 34247067 DOI: 10.1016/j.scitotenv.2021.148676] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 06/15/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Mosses can be responsible for up to 100% of net primary production in arctic and subarctic tundra, and their associations with diazotrophic cyanobacteria have an important role in increasing nitrogen (N) availability in these pristine ecosystems. Predictions about the consequences of climate change in subarctic environments point to increased N mineralization in soil and higher litter deposition due to warming. It is not clear yet how these indirect climate change effects impact moss-cyanobacteria associations and N2 fixation. This work aimed to evaluate the effects of increased N and litter input on biological N2 fixation rates associated with the feathermoss Hylocomium splendens from a tundra heath. H. splendens samples were collected near Abisko, northern Sweden, from a field experiment with annual additions of ammonium chloride and dried birch litter and the combination of both for three years. Samples were analyzed for N2 fixation, cyanobacterial colonization, C and N content and pH. Despite the high N additions, no significant differences in moss N content were found. However, differences between treatments were observed in N2 fixation rates, cyanobacterial colonization and pH, with the combined ammonium+litter treatment causing a significant reduction in the number of branch-colonizing cyanobacteria and N2 fixation, and ammonium additions significantly lowering moss pH. A significant, positive relationship was found between N2 fixation rates, moss colonization by cyanobacteria and pH levels, showing a clear drop in N2 fixation rates at lower pH levels even if larger cyanobacterial populations were present. These results suggest that increased N availability and litter deposition resulting from climate change not only interferes with N2 fixation directly, but also acidifies moss microhabitats and reduces the abundance of associated cyanobacteria, which could eventually impact the N cycle in the Subarctic.
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Affiliation(s)
- Danillo O Alvarenga
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark; Centre for Permafrost, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark.
| | - Kathrin Rousk
- Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark; Centre for Permafrost, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark
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18
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Extreme freeze-thaw cycles do not affect moss-associated nitrogen fixation across a temperature gradient, but affect nutrient loss from mosses. ACTA OECOLOGICA 2021. [DOI: 10.1016/j.actao.2021.103796] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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19
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Swanson L, Li T, Rinnan R. Contrasting responses of major and minor volatile compounds to warming and gall-infestation in the Arctic willow Salix myrsinites. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 793:148516. [PMID: 34174616 DOI: 10.1016/j.scitotenv.2021.148516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 06/11/2021] [Accepted: 06/14/2021] [Indexed: 06/13/2023]
Abstract
Climate change is altering high-latitude ecosystems in multiple facets, including increased insect herbivory pressure and enhanced emissions of volatile organic compounds (VOC) from vegetation. Yet, joint impacts of climatic drivers and insect herbivory on VOC emissions from the Arctic remain largely unknown. We examined how one-month warming by open-top plastic tents, yielding a 3-4 °C air temperature increase, and the natural presence of gall-forming eriophyoid mites, Aculus tetanothrix, individually and in combination, affect VOC emissions from whortle leaved willow, Salix myrsinites, at two elevations in an Arctic heath tundra of Abisko, Northern Sweden. We measured VOC emissions three times in the peak growing season (July) from intact and gall-infested branches using an enclosure technique and gas chromatography-mass spectrometry, and leaf chemical composition using near-infrared reflectance spectroscopy (NIRS). Isoprene accounted for 91% of the VOCs emitted by S. myrsinites. Isoprene emission rates tended to be higher at the high than low elevation during the measurement periods (42 μg g-1 DW h-1 vs. 23 μg g-1 DW h-1) even when temperature differences were accounted for. Experimental warming increased isoprene emissions by approximately 54%, but decreased emissions of some minor compound groups, such as green leaf volatiles (GLV) and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). In contrast, gall-infestation did not affect isoprene emissions but stimulated emissions of DMNT, sesquiterpenes and GLVs, particularly under ambient conditions at the low elevation. The NIRS-based chemical composition of the leaves varied between the two elevations and was affected by warming and gall-infestation. Our study suggests that under elevated temperatures, S. myrsinites increases emissions of isoprene, a highly effective compound for protection against oxidative stress, while an infestation by A. tetanothrix mites induces emissions of herbivore enemy attractants like DMNT, sesquiterpenes and GLVs. Under both conditions, warming effects on isoprene remain but mite effects on DMNT, sesquiterpenes and GLVs diminish.
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Affiliation(s)
- Laura Swanson
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Tao Li
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark; Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
| | - Riikka Rinnan
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark; Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
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20
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The relationship of C and N stable isotopes to high-latitude moss-associated N 2 fixation. Oecologia 2021; 197:283-295. [PMID: 34319437 DOI: 10.1007/s00442-021-05005-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 07/23/2021] [Indexed: 10/20/2022]
Abstract
Moss-associated N2 fixation by epiphytic microbes is a key biogeochemical process in nutrient-limited high-latitude ecosystems. Abiotic drivers, such as temperature and moisture, and the identity of host mosses are critical sources of variation in N2 fixation rates. An understanding of the potential interaction between these factors is essential for predicting N inputs as moss communities change with the climate. To further understand the drivers and results of N2 fixation rate variation, we obtained natural abundance values of C and N isotopes and an associated rate of N2 fixation with 15N2 gas incubations in 34 moss species collected in three regions across Alaska, USA. We hypothesized that δ15N values would increase toward 0‰ with higher N2 fixation to reflect the increasing contribution of fixed N2 in moss biomass. Second, we hypothesized that δ13C and N2 fixation would be positively related, as enriched δ13C signatures reflect abiotic conditions favorable to N2 fixation. We expected that the magnitude of these relationships would vary among types of host mosses, reflecting differences in anatomy and habitat. We found little support for our first hypothesis, with only a modest positive relationship between N2 fixation rates and δ15N in a structural equation model. We found a significant positive relationship between δ13C and N2 fixation only in Hypnales, where the probability of N2 fixation activity reached 95% when δ13C values exceeded - 30.4‰. We conclude that moisture and temperature interact strongly with host moss identity in determining the extent to which abiotic conditions impact associated N2 fixation rates.
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21
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Yun R, Jin Y, Li J, Chen Z, Lyu Z, Zhao Y, Cui D. The annual rhythmic differentiation of Populus davidiana growth–climate response under a warming climate in The Greater Hinggan Mountains. Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01549] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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22
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Increased Above- and Belowground Plant Input Can Both Trigger Microbial Nitrogen Mining in Subarctic Tundra Soils. Ecosystems 2021. [DOI: 10.1007/s10021-021-00642-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
AbstractLow nitrogen (N) availability in the Arctic and Subarctic constrains plant productivity, resulting in low litter inputs to soil. Increased N availability and litter inputs as a result of climate change, therefore, have the potential to impact the functioning of these ecosystems. We examined plant and microbial responses to chronic inorganic N (5 g m−2 year−1) and/or litter (90 g m−2 year−1), supplied during three growing seasons. We also compared the response to more extreme additions, where the total cumulative additions of N (that is, 15 g m−2) and litter (that is, 270 g m−2) were concentrated into a single growth season. Plant productivity was stimulated by N additions and was higher in the extreme addition plots than those with chronic annual additions. Microbial community structure also differed between the chronic and extreme plots, and there was a significant relationship between plant and microbial community structures. Despite differences in microbial structure, the field treatments had no effect on microbial growth or soil C mineralization. However, gross N mineralization was higher in the N addition plots. This led to a lower ratio of soil C mineralization to gross N mineralization, indicating microbial targeting of N-rich organic matter (“microbial N-mining”), likely driven by the increased belowground C-inputs due to stimulated plant productivity. Surprisingly, aboveground litter addition also decreased ratio of soil C mineralization to gross N mineralization. Together, these results suggest that elevated N availability will induce strong responses in tundra ecosystems by promoting plant productivity, driving changes in above- and belowground community structures, and accelerating gross N mineralization. In contrast, increased litter inputs will have subtle effects, primarily altering the ratio between C and N derived from soil organic matter.
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23
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Lasso E, Matheus-Arbeláez P, Gallery RE, Garzón-López C, Cruz M, Leon-Garcia IV, Aragón L, Ayarza-Páez A, Curiel Yuste J. Homeostatic Response to Three Years of Experimental Warming Suggests High Intrinsic Natural Resistance in the Páramos to Warming in the Short Term. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.615006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Páramos, tropical alpine ecosystems, host one of the world’s most diverse alpine floras, account for the largest water reservoirs in the Andes, and some of the largest soil carbon pools worldwide. It is of global importance to understand the future of this extremely carbon-rich ecosystem in a warmer world and its role on global climate feedbacks. This study presents the result of the first in situ warming experiment in two Colombian páramos using Open-Top Chambers. We evaluated the response to warming of several ecosystem carbon balance-related processes, including decomposition, soil respiration, photosynthesis, plant productivity, and vegetation structure after 3 years of warming. We found that OTCs are an efficient warming method in the páramo, increasing mean air temperature by 1.7°C and mean daytime temperature by 3.4°C. The maximum air temperature differences between OTC and control was 23.1°C. Soil temperature increased only by 0.1°C. After 3 years of warming using 20 OTC (10 per páramo) in a randomized block design, we found no evidence that warming increased CO2 emissions from soil respiration, nor did it increase decomposition rate, photosynthesis or productivity in the two páramos studied. However, total C and N in the soil and vegetation structure are slowly changing as result of warming and changes are site dependent. In Sumapaz, shrubs, and graminoids cover increased in response to warming while in Matarredonda we observed an increase in lichen cover. Whether this change in vegetation might influence the carbon sequestration potential of the páramo needs to be further evaluated. Our results suggest that páramos ecosystems can resist an increase in temperature with no significant alteration of ecosystem carbon balance related processes in the short term. However, the long-term effect of warming could depend on the vegetation changes and how these changes alter the microbial soil composition and soil processes. The differential response among páramos suggest that the response to warming could be highly dependent on the initial conditions and therefore we urgently need more warming experiments in páramos to understand how specific site characteristics will affect their response to warming and their role in global climate feedbacks.
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24
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Wu C, Wei X, Hu Z, Liu Y, Hu Y, Qin H, Chen X, Wu J, Ge T, Zhran M, Su Y. Diazotrophic Community Variation Underlies Differences in Nitrogen Fixation Potential in Paddy Soils Across a Climatic Gradient in China. MICROBIAL ECOLOGY 2021; 81:425-436. [PMID: 32901387 DOI: 10.1007/s00248-020-01591-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 08/28/2020] [Indexed: 06/11/2023]
Abstract
Biological nitrogen (N2) fixation as a source of new N input into the soil by free-living diazotrophs is important for achieving sustainable rice agriculture. However, the dominant environmental drivers or factors influencing N2 fixation and the functional significance of the diazotroph community structure in paddy soil across a climatic gradient are not yet well understood. Thus, we characterized the diazotroph community and identified the ecological predictors of N2 fixation potential in four different climate zones (mid-temperate, warm-temperate, subtropical, and tropical paddy soils) in eastern China. Comprehensive nifH gene sequencing, functional activity detection, and correlation analysis with environmental factors were estimated. The potential nitrogenase activity (PNA) was highest in warm-temperate regions, where it was 6.2-, 2.9-, and 2.2-fold greater than in the tropical, subtropical, and mid-temperate regions, respectively; nifH gene abundance was significantly higher in warm-temperate and subtropical zones than in the tropical or mid-temperate zones. Diazotroph diversity was significantly higher in the tropical climate zone and significantly lower in the mid-temperate zone. Non-metric multidimensional scaling and canonical correlation analysis indicated that paddy soil diazotroph populations differed significantly among the four climate zones, mainly owing to differences in climate and soil pH. Structural equation models and automatic linear models revealed that climate and nutrients indirectly affected PNA by affecting soil pH and diazotroph community, respectively, while diazotroph community, C/P, and nifH gene abundance directly affected PNA. And C/P ratio, pH, and the diazotroph community structure were the main predictors of PNA in paddy soils. Collectively, the differences in diazotroph community structure have ecological significance, with important implications for the prediction of soil N2-fixing functions under climate change scenarios.
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Affiliation(s)
- Chuanfa Wu
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
| | - Xiaomeng Wei
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ziye Hu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, 315211, China
| | - Yi Liu
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China.
- Key Laboratory of Agro-ecological Processes in Subtropical Regions, Taoyuan Agro-ecosystem Research Station, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China.
| | - Yajun Hu
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
| | - Hongling Qin
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
- Key Laboratory of Agro-ecological Processes in Subtropical Regions, Taoyuan Agro-ecosystem Research Station, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
| | - Xiangbi Chen
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
| | - Jinshui Wu
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tida Ge
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
| | - Mostafa Zhran
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China
- Soil and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Abou-Zaabl, 13759, Egypt
| | - Yirong Su
- Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China.
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25
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Renaudin M, Darnajoux R, Bellenger JP. Quantification of Moss-Associated Cyanobacteria Using Phycocyanin Pigment Extraction. Front Microbiol 2021; 11:611792. [PMID: 33469453 PMCID: PMC7813775 DOI: 10.3389/fmicb.2020.611792] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/30/2020] [Indexed: 12/04/2022] Open
Abstract
In the boreal forest, cyanobacteria can establish associations with feather moss and realize the biological nitrogen fixation (BNF) reaction, consisting in the reduction of atmospheric dinitrogen into bioavailable ammonium. In this ecosystem, moss-associated cyanobacteria are the main contributors to BNF by contributing up to 50% of new N input. Current environmental changes driven by anthropogenic activities will likely affect cyanobacteria activity (i.e., BNF) and populations inhabiting mosses, leading to potential important consequences for the boreal forest. Several methods are available to efficiently measure BNF activity, but quantifying cyanobacteria biomass associated with moss is challenging because of the difficulty to separate bacteria colonies from the host plant. Attempts to separate cyanobacteria by shaking or sonicating in water were shown to be poorly efficient and repeatable. The techniques commonly used, microscopic counting and quantitative PCR (qPCR) are laborious and time-consuming. In aquatic and marine ecosystems, phycocyanin (PC), a photosynthesis pigment produced by cyanobacteria, is commonly used to monitor cyanobacteria biomass. In this study, we tested if PC extraction and quantification can be used to estimate cyanobacteria quantity inhabiting moss. We report that phycocyanin can be easily extracted from moss by freeze/thaw disturbance of cyanobacteria cells and can be quickly and efficiently measured by spectrofluorometry. We also report that phycocyanin extraction is efficient (high recovery), repeatable (relative SD < 13%) and that no significant matrix effects were observed. As for aquatic systems, the main limitation of cyanobacteria quantification using phycocyanin is the difference of cellular phycocyanin content between cyanobacteria strains, suggesting that quantification can be impacted by cyanobacteria community composition. Nonetheless, we conclude that phycocyanin extraction and quantification is an easy, rapid, and efficient tool to estimate moss-associated cyanobacteria number.
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Affiliation(s)
- Marie Renaudin
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Romain Darnajoux
- Department of Geosciences, Princeton University, Princeton, NJ, United States
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26
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Kristensen JA, Michelsen A, Metcalfe DB. Background insect herbivory increases with local elevation but makes minor contribution to element cycling along natural gradients in the Subarctic. Ecol Evol 2020; 10:11684-11698. [PMID: 33144993 PMCID: PMC7593201 DOI: 10.1002/ece3.6803] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 08/24/2020] [Accepted: 08/27/2020] [Indexed: 11/19/2022] Open
Abstract
Herbivores can exert major controls over biogeochemical cycling. As invertebrates are highly sensitive to temperature shifts (ectothermal), the abundances of insects in high-latitude systems, where climate warming is rapid, is expected to increase. In subarctic mountain birch forests, research has focussed on geometrid moth outbreaks, while the contribution of background insect herbivory (BIH) to elemental cycling is poorly constrained. In northern Sweden, we estimated BIH along 9 elevational gradients distributed across a gradient in regional elevation, temperature, and precipitation to allow evaluation of consistency in local versus regional variation. We converted foliar loss via BIH to fluxes of C, nitrogen (N), and phosphorus (P) from the birch canopy to the soil to compare with other relevant soil inputs of the same elements and assessed different abiotic and biotic drivers of the observed variability. We found that leaf area loss due to BIH was ~1.6% on average. This is comparable to estimates from tundra, but considerably lower than ecosystems at lower latitudes. The C, N, and P fluxes from canopy to soil associated with BIH were 1-2 orders of magnitude lower than the soil input from senesced litter and external nutrient sources such as biological N fixation, atmospheric deposition of N, and P weathering estimated from the literature. Despite the minor contribution to overall elemental cycling in subarctic birch forests, the higher quality and earlier timing of the input of herbivore deposits to soils compared to senesced litter may make this contribution disproportionally important for various ecosystem functions. BIH increased significantly with leaf N content as well as local elevation along each transect, yet showed no significant relationship with temperature or humidity, nor the commonly used temperature proxy, absolute elevation. The lack of consistency between the local and regional elevational trends calls for caution when using elevation gradients as climate proxies.
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Affiliation(s)
- Jeppe A. Kristensen
- Department of Physical Geography and Ecosystem ScienceLund UniversityLundSweden
- Geological Survey of Denmark and GreenlandCopenhagenDenmark
| | - Anders Michelsen
- Department of BiologyTerrestrial Ecology SectionUniversity of CopenhagenCopenhagenDenmark
- Center for PermafrostUniversity of CopenhagenCopenhagenDenmark
| | - Daniel B. Metcalfe
- Department of Physical Geography and Ecosystem ScienceLund UniversityLundSweden
- Department of Ecology and Environmental SciencesUmeå Umeå UniversitetUmeåSweden
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27
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Jean M, Holland-Moritz H, Melvin AM, Johnstone JF, Mack MC. Experimental assessment of tree canopy and leaf litter controls on the microbiome and nitrogen fixation rates of two boreal mosses. THE NEW PHYTOLOGIST 2020; 227:1335-1349. [PMID: 32299141 DOI: 10.1111/nph.16611] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 03/16/2020] [Indexed: 06/11/2023]
Abstract
Nitrogen (N2 )-fixing moss microbial communities play key roles in nitrogen cycling of boreal forests. Forest type and leaf litter inputs regulate moss abundance, but how they control moss microbiomes and N2 -fixation remains understudied. We examined the impacts of forest type and broadleaf litter on microbial community composition and N2 -fixation rates of Hylocomium splendens and Pleurozium schreberi. We conducted a moss transplant and leaf litter manipulation experiment at three sites with paired paper birch (Betula neoalaskana) and black spruce (Picea mariana) stands in Alaska. We characterized bacterial communities using marker gene sequencing, determined N2 -fixation rates using stable isotopes (15 N2 ) and measured environmental covariates. Mosses native to and transplanted into spruce stands supported generally higher N2 -fixation and distinct microbial communities compared to similar treatments in birch stands. High leaf litter inputs shifted microbial community composition for both moss species and reduced N2 -fixation rates for H. splendens, which had the highest rates. N2 -fixation was positively associated with several bacterial taxa, including cyanobacteria. The moss microbiome and environmental conditions controlled N2 -fixation at the stand and transplant scales. Predicted shifts from spruce- to deciduous-dominated stands will interact with the relative abundances of mosses supporting different microbiomes and N2 -fixation rates, which could affect stand-level N inputs.
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Affiliation(s)
- Mélanie Jean
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, 86011, USA
- Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada
| | - Hannah Holland-Moritz
- Cooperative Institute for Research in Environmental Sciences and Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - April M Melvin
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
- Independent researcher, Washington, DC, 20001, USA
| | - Jill F Johnstone
- Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Michelle C Mack
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, 86011, USA
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28
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Stuart JEM, Holland-Moritz H, Lewis LR, Jean M, Miller SN, McDaniel SF, Fierer N, Ponciano JM, Mack MC. Host Identity as a Driver of Moss-Associated N2 Fixation Rates in Alaska. Ecosystems 2020. [DOI: 10.1007/s10021-020-00534-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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29
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Hicks LC, Leizeaga A, Rousk K, Michelsen A, Rousk J. Simulated rhizosphere deposits induce microbial N-mining that may accelerate shrubification in the subarctic. Ecology 2020; 101:e03094. [PMID: 32379897 DOI: 10.1002/ecy.3094] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/06/2020] [Accepted: 04/03/2020] [Indexed: 01/12/2023]
Abstract
Climate change is exposing high-latitude systems to warming and a shift towards more shrub-dominated plant communities, resulting in increased leaf-litter inputs at the soil surface, and more labile root-derived organic matter (OM) input in the soil profile. Labile OM can stimulate the mineralization of soil organic matter (SOM); a phenomenon termed "priming." In N-poor subarctic soils, it is hypothesized that microorganisms may "prime" SOM in order to acquire N (microbial N-mining). Increased leaf-litter inputs with a high C/N ratio might further exacerbate microbial N demand, and increase the susceptibility of N-poor soils to N-mining. We investigated the N-control of SOM mineralization by amending soils from climate change-simulation treatments in the subarctic (+1.1°C warming, birch litter addition, willow litter addition, and fungal sporocarp addition) with labile OM either in the form of glucose (labile C; equivalent to 400 µg C/g fresh [fwt] soil) or alanine (labile C + N; equivalent to 400 µg C and 157 µg N/g fwt soil), to simulate rhizosphere inputs. Surprisingly, we found that despite 5 yr of simulated climate change treatments, there were no significant effects of the field-treatments on microbial process rates, community structure or responses to labile OM. Glucose primed the mineralization of both C and N from SOM, but gross mineralization of N was stimulated more than that of C, suggesting that microbial SOM use increased in magnitude and shifted to components richer in N (i.e., selective microbial N-mining). The addition of alanine also resulted in priming of both C and N mineralization, but the N mineralization stimulated by alanine was greater than that stimulated by glucose, indicating strong N-mining even when a source of labile OM including N was supplied. Microbial carbon use efficiency was reduced in response to both labile OM inputs. Overall, these findings suggest that shrub expansion could fundamentally alter biogeochemical cycling in the subarctic, yielding more N available for plant uptake in these N-limited soils, thus driving positive plant-soil feedbacks.
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Affiliation(s)
- Lettice C Hicks
- Section of Microbial Ecology, Department of Biology, Lund University, Ecology Building, Lund, 223 62, Sweden
| | - Ainara Leizeaga
- Section of Microbial Ecology, Department of Biology, Lund University, Ecology Building, Lund, 223 62, Sweden
| | - Kathrin Rousk
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, Copenhagen, DK-2100, Denmark.,Centre for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, Copenhagen, DK-1350, Denmark
| | - Anders Michelsen
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, Copenhagen, DK-2100, Denmark.,Centre for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, Copenhagen, DK-1350, Denmark
| | - Johannes Rousk
- Section of Microbial Ecology, Department of Biology, Lund University, Ecology Building, Lund, 223 62, Sweden
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30
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Liu X, Wang Z, Li X, Rousk K, Bao W. High nitrogen resorption efficiency of forest mosses. ANNALS OF BOTANY 2020; 125:557-563. [PMID: 31840155 PMCID: PMC7102953 DOI: 10.1093/aob/mcz199] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Accepted: 12/10/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND AIMS Nutrient resorption from senescing tissue is a key mechanism for plants to conserve nutrients, and can affect the nutrient dynamics of ecosystems. Yet, our limited knowledge of nitrogen (N) resorption and release from mosses hampers our understanding of the role of mosses as N sources and, thereby, N cycling in moss-dominated ecosystems. The aims of this study were to estimate N resorption efficiency (NRE) of two moss species, identify the pathways of N release from the mosses and to provide a better understanding of N cycling and budgeting strategies of mosses. METHODS The dynamics of N allocation along annual moss segments of two dominant moss species (Actinothuidium hookeri and Hylocomium splendens) were assessed in old-growth fir forests using an in situ15N tracer experiment. KEY RESULTS The NRE of A. hookeri and H. splendens was 61 and 52 %, respectively. While the mosses lost 23 and 33 % N from live tissues via leaching, 15 and 14 % of N remained in senesced tissues (>3 years old) in A. hookeri and H. splendens, respectively. CONCLUSIONS Both mosses resorbed the majority of their tissue N, but a considerable amount of N was lost from live segments. Our results highlight the crucial role mosses play as N sinks in ecosystems, since N retention (resorbed and sequestered in senescent tissue) outweighed N loss via leaching. However, the sink strength depends on temperature and precipitation, which will change in a future climate. The values for NRE, leaching, etc. estimated here can help improve biogeochemical models aiming to complete N budgets for moss-abundant ecosystems.
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Affiliation(s)
- Xin Liu
- Chinese Academy of Sciences (CAS) Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Zhe Wang
- Chinese Academy of Sciences (CAS) Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
- College of Life Sciences, Shanghai Normal University, Shanghai, China
| | - Xiaoming Li
- Chinese Academy of Sciences (CAS) Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
| | - Weikai Bao
- Chinese Academy of Sciences (CAS) Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
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31
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Salazar A, Rousk K, Jónsdóttir IS, Bellenger J, Andrésson ÓS. Faster nitrogen cycling and more fungal and root biomass in cold ecosystems under experimental warming: a meta-analysis. Ecology 2020; 101:e02938. [PMID: 31750541 PMCID: PMC7027553 DOI: 10.1002/ecy.2938] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 10/01/2019] [Accepted: 10/18/2019] [Indexed: 11/13/2022]
Abstract
Warming can alter the biogeochemistry and ecology of soils. These alterations can be particularly large in high northern latitude ecosystems, which are experiencing the most intense warming globally. In this meta-analysis, we investigated global trends in how experimental warming is altering the biogeochemistry of the most common limiting nutrient for biological processes in cold ecosystems of high northern latitudes (>50°): nitrogen (N). For comparison, we also analyzed cold ecosystems at intermediate and high southern latitudes. In addition, we examined N-relevant genes and enzymes, and the abundance of belowground organisms. Together, our findings suggest that warming in cold ecosystems increases N mineralization rates and N2 O emissions and does not affect N fixation, at least not in a consistent way across biomes and conditions. Changes in belowground N fluxes caused by warming lead to an accumulation of N in the forms of dissolved organic and root N. These changes seem to be more closely linked to increases in enzyme activity that target relatively labile N sources, than to changes in the abundance of N-relevant genes (e.g., amoA and nosZ). Finally, our analysis suggests that warming in cold ecosystems leads to an increase in plant roots, fungi, and (likely in an indirect way) fungivores, and does not affect the abundance of archaea, bacteria, or bacterivores. In summary, our findings highlight global trends in the ways warming is altering the biogeochemistry and ecology of soils in cold ecosystems, and provide information that can be valuable for prediction of changes and for management of such ecosystems.
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Affiliation(s)
- Alejandro Salazar
- Faculty of Life and Environmental SciencesUniversity of IcelandSturlugata 7101ReykjavíkIceland
| | - Kathrin Rousk
- Department of BiologyTerrestrial Ecology SectionUniversity of CopenhagenUniversitetsparken 152100CopenhagenDenmark
- Center for Permafrost (CENPERM)University of CopenhagenØster Voldgade 101350CopenhagenDenmark
| | - Ingibjörg S. Jónsdóttir
- Faculty of Life and Environmental SciencesUniversity of IcelandSturlugata 7101ReykjavíkIceland
| | - Jean‐Philippe Bellenger
- Centre SeveDepartment of ChemistryFaculty of SciencesUniversite de SherbrookeJ1K2R1SherbrookeQuebecCanada
| | - Ólafur S. Andrésson
- Faculty of Life and Environmental SciencesUniversity of IcelandSturlugata 7101ReykjavíkIceland
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32
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Zheng M, Chen H, Li D, Luo Y, Mo J. Substrate stoichiometry determines nitrogen fixation throughout succession in southern Chinese forests. Ecol Lett 2019; 23:336-347. [PMID: 31802606 DOI: 10.1111/ele.13437] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/29/2019] [Accepted: 11/08/2019] [Indexed: 01/23/2023]
Abstract
The traditional view holds that biological nitrogen (N) fixation often peaks in early- or mid-successional ecosystems and declines throughout succession based on the hypothesis that soil N richness and/or phosphorus (P) depletion become disadvantageous to N fixers. This view, however, fails to support the observation that N fixers can remain active in many old-growth forests despite the presence of N-rich and/or P-limiting soils. Here, we found unexpected increases in N fixation rates in the soil, forest floor, and moss throughout three successional forests and along six age-gradient forests in southern China. We further found that the variation in N fixation was controlled by substrate carbon(C) : N and C : (N : P) stoichiometry rather than by substrate N or P. Our findings highlight the utility of ecological stoichiometry in illuminating the mechanisms that couple forest succession and N cycling.
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Affiliation(s)
- Mianhai Zheng
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.,Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, 510650, China.,Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.,University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Hao Chen
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
| | - Dejun Li
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
| | - Yiqi Luo
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Jiangming Mo
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.,Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, 510650, China.,Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China
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Zheng M, Zhou Z, Luo Y, Zhao P, Mo J. Global pattern and controls of biological nitrogen fixation under nutrient enrichment: A meta-analysis. GLOBAL CHANGE BIOLOGY 2019; 25:3018-3030. [PMID: 31120621 DOI: 10.1111/gcb.14705] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 05/05/2019] [Accepted: 05/15/2019] [Indexed: 06/09/2023]
Abstract
Biological nitrogen (N) fixation (BNF), an important source of N in terrestrial ecosystems, plays a critical role in terrestrial nutrient cycling and net primary productivity. Currently, large uncertainty exists regarding how nutrient availability regulates terrestrial BNF and the drivers responsible for this process. We conducted a global meta-analysis of terrestrial BNF in response to N, phosphorus (P), and micronutrient (Micro) addition across different biomes (i.e, tropical/subtropical forest, savanna, temperate forest, grassland, boreal forest, and tundra) and explored whether the BNF responses were affected by fertilization regimes (nutrient-addition rates, duration, and total load) and environmental factors (mean annual temperature [MAT], mean annual precipitation [MAP], and N deposition). The results showed that N addition inhibited terrestrial BNF (by 19.0% (95% confidence interval [CI]: 17.7%-20.3%); hereafter), Micro addition stimulated terrestrial BNF (30.4% [25.7%-35.3%]), and P addition had an inconsistent effect on terrestrial BNF, i.e., inhibiting free-living N fixation (7.5% [4.4%-10.6%]) and stimulating symbiotic N fixation (85.5% [25.8%-158.7%]). Furthermore, the response ratios (i.e., effect sizes) of BNF to nutrient addition were smaller in low-latitude (<30°) biomes (8.5%-36.9%) than in mid-/high-latitude (≥30°) biomes (32.9%-61.3%), and the sensitivity (defined as the absolute value of response ratios) of BNF to nutrients in mid-/high-latitude biomes decreased with decreasing latitude (p ≤ 0.009; linear/logarithmic regression models). Fertilization regimes did not affect this phenomenon (p > 0.05), but environmental factors did affect it (p < 0.001) because MAT, MAP, and N deposition accounted for 5%-14%, 10%-32%, and 7%-18% of the variance in the BNF response ratios in cold (MAT < 15°C), low-rainfall (MAP < 2,500 mm), and low-N-deposition (<7 kg ha-1 year-1 ) biomes, respectively. Overall, our meta-analysis depicts a global pattern of nutrient impacts on terrestrial BNF and indicates that certain types of global change (i.e., warming, elevated precipitation and N deposition) may reduce the sensitivity of BNF in response to nutrient enrichment in mid-/high-latitude biomes.
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Affiliation(s)
- Mianhai Zheng
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenghu Zhou
- Center for Ecological Research, Northeast Forestry University, Harbin, China
| | - Yiqi Luo
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ
| | - Ping Zhao
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Jiangming Mo
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
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Goth A, Michelsen A, Rousk K. Railroad derived nitrogen and heavy metal pollution does not affect nitrogen fixation associated with mosses and lichens at a tundra site in Northern Sweden. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 247:857-865. [PMID: 30731311 DOI: 10.1016/j.envpol.2019.01.101] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/07/2019] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
Traffic derived nitrogen (N) and heavy metal pollution is a well-known phenomenon, but little explored in otherwise pristine ecosystems such as subarctic tundra. Here, the main source of N input to the ecosystem is via N2 fixation by moss- and lichen-associated bacteria. While inhibitory effects of N deposition on moss-associated N2 fixation have been reported, we still lack understanding of the effects of traffic derived N and heavy metal deposition on this ecosystem function in an otherwise pristine setting. To test this, we established a distance gradient (0-1280 m) away from a metal pollution source -a railway transporting iron ore that passes through a subarctic birch forest. We assessed the effects of railway-derived pollution on N2 fixation associated with two moss species Pleurozium schreberi, Hylocomium splendens and with the lichen Peltigera aphthosa. Deposition and availability of N and heavy metals (Fe, Cu, Zn, Pb) as well as the respective contents in moss, lichen and soil was assessed. While we found a steep gradient in metal concentration in moss, lichen and soil with distance away from the pollution source, N deposition did not change, and with that, we could not detect a distance gradient in moss- or lichen-associated N2 fixation. Hence, our results indicate that N2 fixing bacteria are either not inhibited by heavy metal deposition, or that they are protected within the moss carpet and lichen tissue.
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Affiliation(s)
- Astrid Goth
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark
| | - Anders Michelsen
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
| | - Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark; Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark.
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Rousk K, Sorensen PL, Michelsen A. What drives biological nitrogen fixation in high arctic tundra: Moisture or temperature? Ecosphere 2018. [DOI: 10.1002/ecs2.2117] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Kathrin Rousk
- Department of Biology; Terrestrial Ecology Section; University of Copenhagen; Universitetsparken 15 2100 Copenhagen Denmark
- Center for Permafrost (CENPERM); University of Copenhagen; Øster Voldgade 10 1350 Copenhagen Denmark
| | - Pernille Laerkedal Sorensen
- Department of Biology; Terrestrial Ecology Section; University of Copenhagen; Universitetsparken 15 2100 Copenhagen Denmark
| | - Anders Michelsen
- Department of Biology; Terrestrial Ecology Section; University of Copenhagen; Universitetsparken 15 2100 Copenhagen Denmark
- Center for Permafrost (CENPERM); University of Copenhagen; Øster Voldgade 10 1350 Copenhagen Denmark
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Dynarski KA, Houlton BZ. Nutrient limitation of terrestrial free-living nitrogen fixation. THE NEW PHYTOLOGIST 2018; 217:1050-1061. [PMID: 29165820 DOI: 10.1111/nph.14905] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/18/2017] [Indexed: 05/27/2023]
Abstract
Nitrogen (N) fixation by free-living bacteria is a primary N input pathway in many ecosystems and sustains global plant productivity. Uncertainty exists over the importance of N, phosphorus (P) and molybdenum (Mo) availability in controlling free-living N fixation rates. Here, we investigate the geographic occurrence and variability of nutrient constraints to free-living N fixation in the terrestrial biosphere. We compiled data from studies measuring free-living N fixation in response to N, P and Mo fertilizers. We used meta-analysis to quantitatively determine the extent to which N, P and Mo stimulate or suppress N fixation, and if environmental variables influence the degree of nutrient limitation of N fixation. Across our compiled dataset, free-living N fixation is suppressed by N fertilization and stimulated by Mo fertilization. Additionally, free-living N fixation is stimulated by P additions in tropical forests. These findings suggest that nutrient limitation is an intrinsic property of the biochemical demands of N fixation, constraining free-living N fixation in the terrestrial biosphere. These findings have implications for understanding the causes and consequences of N limitation in coupled nutrient cycles, as well as modeling and forecasting nutrient controls over carbon-climate feedbacks.
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Affiliation(s)
- Katherine A Dynarski
- Department of Land, Air, and Water Resources, University of California, Davis, 1 Shields Ave., Davis, CA, 95616, USA
| | - Benjamin Z Houlton
- Department of Land, Air, and Water Resources, University of California, Davis, 1 Shields Ave., Davis, CA, 95616, USA
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Rousk K, Degboe J, Michelsen A, Bradley R, Bellenger JP. Molybdenum and phosphorus limitation of moss-associated nitrogen fixation in boreal ecosystems. THE NEW PHYTOLOGIST 2017; 214:97-107. [PMID: 27883187 DOI: 10.1111/nph.14331] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/15/2016] [Indexed: 05/27/2023]
Abstract
Biological nitrogen fixation (BNF) performed by moss-associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high-latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both. BNF in dominant mosses was measured with the acetylene reduction assay (ARA) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a 15 N2 tracer technique to assess the ARA to N2 fixation conversion ratios at our subarctic site. BNF was up to four-fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : 15 N2 ratios increased with increasing Mo additions. These findings show that N2 fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability.
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Affiliation(s)
- Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - Jefferson Degboe
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
| | - Anders Michelsen
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - Robert Bradley
- Département de Biologie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
| | - Jean-Philippe Bellenger
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
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