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Hupperts SF, Islam KS, Gundale MJ, Kardol P, Sundqvist MK. Warming influences carbon and nitrogen assimilation between a widespread Ericaceous shrub and root-associated fungi. THE NEW PHYTOLOGIST 2024; 241:1062-1073. [PMID: 37950517 DOI: 10.1111/nph.19384] [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: 09/07/2023] [Accepted: 10/19/2023] [Indexed: 11/12/2023]
Abstract
High-latitude ecosystems are warming faster than other biomes and are often dominated by a ground layer of Ericaceous shrubs, which can respond positively to warming. The carbon-for-nitrogen (C-for-N) exchange between Ericaceous shrubs and root-associated fungi may underlie shrub responses to warming, but has been understudied. In a glasshouse setting, we examined the effects of warming on the C-for-N exchange between the Ericaceous shrub Empetrum nigrum ssp. hermaphroditum and its root-associated fungi. We applied different 13 C and 15 N isotope labels, including a simple organic N form (glycine) and a complex organic N form (moss litter) and quantified their assimilation into soil, plant biomass, and root fungal biomass pools. We found that warming lowered the amount of 13 C partitioned to root-associated fungi per unit of glycine 15 N assimilated by E. nigrum, but only in the short term. By contrast, warming increased the amount of 13 C partitioned to root-associated fungi per unit of moss 15 N assimilated by E. nigrum. Our study suggests that climate warming affects the short-term exchange of C and N between a widespread Ericaceous shrub and root-associated fungi. Furthermore, while most isotope tracing studies use labile N sources, we demonstrate that a ubiquitous recalcitrant N source may produce contrasting results.
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Affiliation(s)
- Stefan F Hupperts
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 901 83, Sweden
| | - Kazi Samiul Islam
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 901 83, Sweden
| | - Michael J Gundale
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 901 83, Sweden
| | - Paul Kardol
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 901 83, Sweden
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences (SLU), Uppsala, 750 07, Sweden
| | - Maja K Sundqvist
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 901 83, Sweden
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2
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Andresen LC, Bodé S, Björk RG, Michelsen A, Aerts R, Boeckx P, Cornelissen JHC, Klanderud K, van Logtestijn RSP, Rütting T. Patterns of free amino acids in tundra soils reflect mycorrhizal type, shrubification, and warming. MYCORRHIZA 2022; 32:305-313. [PMID: 35307782 PMCID: PMC9184409 DOI: 10.1007/s00572-022-01075-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
The soil nitrogen (N) cycle in cold terrestrial ecosystems is slow and organically bound N is an important source of N for plants in these ecosystems. Many plant species can take up free amino acids from these infertile soils, either directly or indirectly via their mycorrhizal fungi. We hypothesized that plant community changes and local plant community differences will alter the soil free amino acid pool and composition; and that long-term warming could enhance this effect. To test this, we studied the composition of extractable free amino acids at five separate heath, meadow, and bog locations in subarctic and alpine Scandinavia, with long-term (13 to 24 years) warming manipulations. The plant communities all included a mixture of ecto-, ericoid-, and arbuscular mycorrhizal plant species. Vegetation dominated by grasses and forbs with arbuscular and non-mycorrhizal associations showed highest soil free amino acid content, distinguishing them from the sites dominated by shrubs with ecto- and ericoid-mycorrhizal associations. Warming increased shrub and decreased moss cover at two sites, and by using redundancy analysis, we found that altered soil free amino acid composition was related to this plant cover change. From this, we conclude that the mycorrhizal type is important in controlling soil N cycling and that expansion of shrubs with ectomycorrhiza (and to some extent ericoid mycorrhiza) can help retain N within the ecosystems by tightening the N cycle.
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Affiliation(s)
- Louise C Andresen
- Department of Earth Science, University of Gothenburg, Gothenburg, Sweden.
| | - Samuel Bodé
- Isotope Bioscience Laboratory (ISOFYS), Department of Green Chemistry and Technology, Ghent University, Ghent, Belgium
| | - Robert G Björk
- Department of Earth Science, University of Gothenburg, Gothenburg, Sweden
- Gothenburg Global Biodiversity Centre, Gothenburg, Sweden
| | | | - Rien Aerts
- Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Pascal Boeckx
- Isotope Bioscience Laboratory (ISOFYS), Department of Green Chemistry and Technology, Ghent University, Ghent, Belgium
| | - J Hans C Cornelissen
- Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Kari Klanderud
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Aas, Norway
| | | | - Tobias Rütting
- Department of Earth Science, University of Gothenburg, Gothenburg, Sweden
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3
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Baggesen N, Li T, Seco R, Holst T, Michelsen A, Rinnan R. Phenological stage of tundra vegetation controls bidirectional exchange of BVOCs in a climate change experiment on a subarctic heath. GLOBAL CHANGE BIOLOGY 2021; 27:2928-2944. [PMID: 33709612 PMCID: PMC8251604 DOI: 10.1111/gcb.15596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/08/2021] [Indexed: 06/08/2023]
Abstract
Traditionally, biogenic volatile organic compound (BVOC) emissions are often considered a unidirectional flux, from the ecosystem to the atmosphere, but recent studies clearly show the potential for bidirectional exchange. Here we aimed to investigate how warming and leaf litter addition affect the bidirectional exchange (flux) of BVOCs in a long-term field experiment in the Subarctic. We also assessed changes in net BVOC fluxes in relation to the time of day and the influence of different plant phenological stages. The study was conducted in a full factorial experiment with open top chamber warming and annual litter addition treatments in a tundra heath in Abisko, Northern Sweden. After 18 years of treatments, ecosystem-level net BVOC fluxes were measured in the experimental plots using proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). The warming treatment increased monoterpene and isoprene emissions by ≈50%. Increasing temperature, due to diurnal variations, can both increase BVOC emission and simultaneously, increase ecosystem uptake. For any given treatment, monoterpene, isoprene, and acetone emissions also increased with increasing ambient air temperatures caused by diurnal variability. Acetaldehyde, methanol, and sesquiterpenes decreased likely due to a deposition flux. For litter addition, only a significant indirect effect on isoprene and monoterpene fluxes (decrease by ~50%-75%) was observed. Litter addition may change soil moisture conditions, leading to changes in plant species composition and biomass, which could subsequently result in changes to BVOC emission compositions. Phenological stages significantly affected fluxes of methanol, isoprene and monoterpenes. We suggest that plant phenological stages differ in impacts on BVOC net emissions, but ambient air temperature and photosynthetically active radiation (PAR) also interact and influence BVOC net emissions differently. Our results may also suggest that BVOC fluxes are not only a response to changes in temperature and light intensity, as the circadian clock also affects emission rates.
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Affiliation(s)
- Nanna Baggesen
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Center for Permafrost (CENPERM)University of CopenhagenCopenhagen KDenmark
| | - Tao Li
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Center for Permafrost (CENPERM)University of CopenhagenCopenhagen KDenmark
| | - Roger Seco
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Center for Permafrost (CENPERM)University of CopenhagenCopenhagen KDenmark
| | - Thomas Holst
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Department of Physical Geography and Ecosystem ScienceCentre for GeoBiosphere ScienceLund UniversityLundSweden
| | - Anders Michelsen
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Center for Permafrost (CENPERM)University of CopenhagenCopenhagen KDenmark
| | - Riikka Rinnan
- Terrestrial Ecology SectionDepartment of BiologyUniversity of CopenhagenCopenhagen ØDenmark
- Center for Permafrost (CENPERM)University of CopenhagenCopenhagen KDenmark
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4
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Angot H, McErlean K, Hu L, Millet DB, Hueber J, Cui K, Moss J, Wielgasz C, Milligan T, Ketcherside D, Bret-Harte MS, Helmig D. Biogenic volatile organic compound ambient mixing ratios and emission rates in the Alaskan Arctic tundra. BIOGEOSCIENCES (ONLINE) 2020; 17:6219-6236. [PMID: 35222652 PMCID: PMC8872036 DOI: 10.5194/bg-17-6219-2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Rapid Arctic warming, a lengthening growing season, and the increasing abundance of biogenic volatile-organic-compound-emitting shrubs are all anticipated to increase atmospheric biogenic volatile organic compounds (BVOCs) in the Arctic atmosphere, with implications for atmospheric oxidation processes and climate feedbacks. Quantifying these changes requires an accurate understanding of the underlying processes driving BVOC emissions in the Arctic. While boreal ecosystems have been widely studied, little attention has been paid to Arctic tundra environments. Here, we report terpenoid (isoprene, monoterpenes, and sesquiterpenes) ambient mixing ratios and emission rates from key dominant vegetation species at Toolik Field Station (TFS; 68°38' N, 149°36' W) in northern Alaska during two back-to-back field campaigns (summers of 2018 and 2019) covering the entire growing season. Isoprene ambient mixing ratios observed at TFS fell within the range of values reported in the Eurasian taiga (0-500 parts per trillion by volume - pptv), while monoterpene and sesquiterpene ambient mixing ratios were respectively close to and below the instrumental quantification limit (~ 2 pptv). Isoprene surface emission rates ranged from 0.2 to 2250 μgC m-2 h-1 (mean of 85 μgC m-2 h-1) and monoterpene emission rates remained, on average, below 1 μgC m-2 h-1 over the course of the study. We further quantified the temperature dependence of isoprene emissions from local vegetation, including Salix spp. (a known isoprene emitter), and compared the results to predictions from the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1). Our observations suggest a 180 %-215 % emission increase in response to a 3-4°C warming, and the MEGAN2.1 temperature algorithm exhibits a close fit with observations for enclosure temperatures in the 0-30°C range. The data presented here provide a baseline for investigating future changes in the BVOC emission potential of the under-studied Arctic tundra environment.
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Affiliation(s)
- Hélène Angot
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Katelyn McErlean
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Lu Hu
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA
| | - Dylan B. Millet
- Department of Soil, Water, and Climate, University of Minnesota, Minneapolis–Saint Paul, MN, USA
| | - Jacques Hueber
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Kaixin Cui
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Jacob Moss
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Catherine Wielgasz
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA
| | - Tyler Milligan
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
| | - Damien Ketcherside
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA
| | | | - Detlev Helmig
- Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
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5
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Akther H, Rousk K. High heavy metal load does not inhibit nitrogen fixation in moss-cyanobacteria associations. ECOTOXICOLOGY (LONDON, ENGLAND) 2019; 28:1169-1176. [PMID: 31696444 DOI: 10.1007/s10646-019-02127-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/12/2019] [Indexed: 06/10/2023]
Abstract
Nitrogen (N2) fixation by moss-associated cyanobacteria is one of the main sources of new N input in pristine ecosystems such as boreal forests and arctic tundra. Given the non-vascular physiology of mosses, they are especially sensitive to e.g. increased N input and heavy metal deposition. While the effects of increased N input on moss-associated N2 fixation has been comprehensively assessed, hardly any reports exist on the effects of increased heavy metal load on this key ecosystem function. To address this knowledge gap, we made use of an extreme metal pollution gradient in boreal forests of Northern Sweden originating from a metal mine and its associated smelters. We collected the common moss Pleurozium schreberi, known to host cyanobacteria, along a distance gradient away from the metal source of pollution and measured moss-metal content (Fe, Cu, Zn, Pb) as well as N2 fixation. We found a strong distance gradient in moss-metal content for all investigated metals: a sharp decline in metal content with distance away from the metal pollution source. However, we found a similarly steep gradient in moss-associated N2 fixation, with highest activity closest to the metal source of pollution. Hence, while mosses may be sensitive to increased heavy metal inputs, the activity of colonising cyanobacteria seem to be unaffected by heavy metals, and consequently, ecosystem function may not be compromised by elevated metal input.
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Affiliation(s)
- Hasna Akther
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, DK-2100, 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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6
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Plant–plant interactions could limit recruitment and range expansion of tall shrubs into alpine and Arctic tundra. Polar Biol 2018. [DOI: 10.1007/s00300-018-2355-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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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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8
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Yuan ZY, Jiao F, Shi XR, Sardans J, Maestre FT, Delgado-Baquerizo M, Reich PB, Peñuelas J. Experimental and observational studies find contrasting responses of soil nutrients to climate change. eLife 2017; 6. [PMID: 28570219 PMCID: PMC5453695 DOI: 10.7554/elife.23255] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 04/29/2017] [Indexed: 11/16/2022] Open
Abstract
Manipulative experiments and observations along environmental gradients, the two most common approaches to evaluate the impacts of climate change on nutrient cycling, are generally assumed to produce similar results, but this assumption has rarely been tested. We did so by conducting a meta-analysis and found that soil nutrients responded differentially to drivers of climate change depending on the approach considered. Soil carbon, nitrogen, and phosphorus concentrations generally decreased with water addition in manipulative experiments but increased with annual precipitation along environmental gradients. Different patterns were also observed between warming experiments and temperature gradients. Our findings provide evidence of inconsistent results and suggest that manipulative experiments may be better predictors of the causal impacts of short-term (months to years) climate change on soil nutrients but environmental gradients may provide better information for long-term correlations (centuries to millennia) between these nutrients and climatic features. Ecosystem models should consequently incorporate both experimental and observational data to properly assess the impacts of climate change on nutrient cycling. DOI:http://dx.doi.org/10.7554/eLife.23255.001
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Affiliation(s)
- Z Y Yuan
- State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China.,Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resource, Yangling, China
| | - F Jiao
- State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China.,Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resource, Yangling, China
| | - X R Shi
- State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China.,Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resource, Yangling, China
| | - Jordi Sardans
- Global Ecology Unit CREAF-CSIC-UAB, Consejo Superior de Investigaciones Científicas (CSIC), Bellaterra, Spain.,CREAF, Cerdanyola del Vallès, Spain
| | - Fernando T Maestre
- Departamento de Biología y Geología, Física y Química Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain
| | - Manuel Delgado-Baquerizo
- Departamento de Biología y Geología, Física y Química Inorgánica, Universidad Rey Juan Carlos, Móstoles, Spain.,Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
| | - Peter B Reich
- Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, Australia.,Department of Forest Resources, University of Minnesota, Minnesota, United States
| | - Josep Peñuelas
- Global Ecology Unit CREAF-CSIC-UAB, Consejo Superior de Investigaciones Científicas (CSIC), Bellaterra, Spain.,CREAF, Cerdanyola del Vallès, Spain
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9
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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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10
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Rousk K, Michelsen A. Ecosystem nitrogen fixation throughout the snow-free period in subarctic tundra: effects of willow and birch litter addition and warming. GLOBAL CHANGE BIOLOGY 2017; 23:1552-1563. [PMID: 27391280 DOI: 10.1111/gcb.13418] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 06/20/2016] [Indexed: 06/06/2023]
Abstract
Nitrogen (N) fixation in moss-associated cyanobacteria is one of the main sources of available N for N-limited ecosystems such as subarctic tundra. Yet, N2 fixation in mosses is strongly influenced by soil moisture and temperature. Thus, temporal scaling up of low-frequency in situ measurements to several weeks, months or even the entire growing season without taking into account changes in abiotic conditions cannot capture the variation in moss-associated N2 fixation. We therefore aimed to estimate moss-associated N2 fixation throughout the snow-free period in subarctic tundra in field experiments simulating climate change: willow (Salix myrsinifolia) and birch (Betula pubescens spp. tortuosa) litter addition, and warming. To achieve this, we established relationships between measured in situ N2 fixation rates and soil moisture and soil temperature and used high-resolution measurements of soil moisture and soil temperature (hourly from May to October) to model N2 fixation. The modelled N2 fixation rates were highest in the warmed (2.8 ± 0.3 kg N ha-1 ) and birch litter addition plots (2.8 ± 0.2 kg N ha-1 ), and lowest in the plots receiving willow litter (1.6 ± 0.2 kg N ha-1 ). The control plots had intermediate rates (2.2 ± 0.2 kg N ha-1 ). Further, N2 fixation was highest during the summer in the warmed plots, but was lowest in the litter addition plots during the same period. The temperature and moisture dependence of N2 fixation was different between the climate change treatments, indicating a shift in the N2 fixer community. Our findings, using a combined empirical and modelling approach, suggest that a longer snow-free period and increased temperatures in a future climate will likely lead to higher N2 fixation rates in mosses. Yet, the consequences of increased litter fall on moss-associated N2 fixation due to shrub expansion in the Arctic will depend on the shrub species' litter traits.
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Affiliation(s)
- Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, Copenhagen, 2100, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, Copenhagen, 1350, Denmark
| | - Anders Michelsen
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, Copenhagen, 2100, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, Copenhagen, 1350, Denmark
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11
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Westergaard-Nielsen A, Lund M, Pedersen SH, Schmidt NM, Klosterman S, Abermann J, Hansen BU. Transitions in high-Arctic vegetation growth patterns and ecosystem productivity tracked with automated cameras from 2000 to 2013. AMBIO 2017; 46:39-52. [PMID: 28116683 PMCID: PMC5258658 DOI: 10.1007/s13280-016-0864-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Climate-induced changes in vegetation phenology at northern latitudes are still poorly understood. Continued monitoring and research are therefore needed to improve the understanding of abiotic drivers. Here we used 14 years of time lapse imagery and climate data from high-Arctic Northeast Greenland to assess the seasonal response of a dwarf shrub heath, grassland, and fen, to inter-annual variation in snow-cover, soil moisture, and air and soil temperatures. A late snow melt and start of growing season is counterbalanced by a fast greenup and a tendency to higher peak greenness values. Snow water equivalents and soil moisture explained up to 77 % of growing season duration and senescence phase, highlighting that water availability is a prominent driver in the heath site, rather than temperatures. We found a significant advance in the start of spring by 10 days and in the end of fall by 11 days, resulting in an unchanged growing season length. Vegetation greenness, derived from the imagery, was correlated to primary productivity, showing that the imagery holds valuable information on vegetation productivity.
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Affiliation(s)
- Andreas Westergaard-Nielsen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Oestervoldgade 10, 1350, Copenhagen, Denmark.
- Center for Permafrost (CENPERM), University of Copenhagen, Oestervoldgade 10, 1350, Copenhagen, Denmark.
| | - Magnus Lund
- Department for Bioscience, Arctic Research Centre, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Stine Højlund Pedersen
- Department for Bioscience, Arctic Research Centre, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Niels Martin Schmidt
- Department for Bioscience, Arctic Research Centre, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Stephen Klosterman
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Jakob Abermann
- Greenland Survey, Asiaq, Svend Jungep Aqqutaa 8, 3900, Nuuk, Greenland
| | - Birger Ulf Hansen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Oestervoldgade 10, 1350, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Oestervoldgade 10, 1350, Copenhagen, Denmark
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12
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13
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The Sensitivity of Moss-Associated Nitrogen Fixation towards Repeated Nitrogen Input. PLoS One 2016; 11:e0146655. [PMID: 26731691 PMCID: PMC4712137 DOI: 10.1371/journal.pone.0146655] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/21/2015] [Indexed: 11/23/2022] Open
Abstract
Nitrogen (N2) fixation is a major source of available N in ecosystems that receive low amounts of atmospheric N deposition. In boreal forest and subarctic tundra, the feather moss Hylocomium splendens is colonized by N2 fixing cyanobacteria that could contribute fundamentally to increase the N pool in these ecosystems. However, N2 fixation in mosses is inhibited by N input. Although this has been shown previously, the ability of N2 fixation to grow less sensitive towards repeated, increased N inputs remains unknown. Here, we tested if N2 fixation in H. splendens can recover from increased N input depending on the N load (0, 5, 20, 80, 320 kg N ha-1 yr-1) after a period of N deprivation, and if sensitivity towards increased N input can decrease after repeated N additions. Nitrogen fixation in the moss was inhibited by the highest N addition, but was promoted by adding 5 kg N ha-1 yr-1, and increased in all treatments during a short period of N deprivation. The sensitivity of N2 fixation towards repeated N additions seem to decrease in the 20 and 80 kg N additions, but increased in the highest N addition (320 kg N ha-1 yr-1). Recovery of N in leachate samples increased with increasing N loads, suggesting low retention capabilities of mosses if N input is above 5 kg N ha-1 yr-1. Our results demonstrate that the sensitivity towards repeated N additions is likely to decrease if N input does not exceed a certain threshold.
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Schollert M, Kivimäenpää M, Valolahti HM, Rinnan R. Climate change alters leaf anatomy, but has no effects on volatile emissions from Arctic plants. PLANT, CELL & ENVIRONMENT 2015; 38:2048-60. [PMID: 25737381 DOI: 10.1111/pce.12530] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 02/20/2015] [Accepted: 02/23/2015] [Indexed: 05/22/2023]
Abstract
Biogenic volatile organic compound (BVOC) emissions are expected to change substantially because of the rapid advancement of climate change in the Arctic. BVOC emission changes can feed back both positively and negatively on climate warming. We investigated the effects of elevated temperature and shading on BVOC emissions from arctic plant species Empetrum hermaphroditum, Cassiope tetragona, Betula nana and Salix arctica. Measurements were performed in situ in long-term field experiments in subarctic and high Arctic using a dynamic enclosure system and collection of BVOCs into adsorbent cartridges analysed by gas chromatography-mass spectrometry. In order to assess whether the treatments had resulted in anatomical adaptations, we additionally examined leaf anatomy using light microscopy and scanning electron microscopy. Against expectations based on the known temperature and light-dependency of BVOC emissions, the emissions were barely affected by the treatments. In contrast, leaf anatomy of the studied plants was significantly altered in response to the treatments, and these responses appear to differ from species found at lower latitudes. We suggest that leaf anatomical acclimation may partially explain the lacking treatment effects on BVOC emissions at plant shoot-level. However, more studies are needed to unravel why BVOC emission responses in arctic plants differ from temperate species.
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Affiliation(s)
- Michelle Schollert
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen Ø, 2100, Denmark
- Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen K, 1350, Denmark
| | - Minna Kivimäenpää
- Department of Environmental Science, University of Eastern Finland, Kuopio, 70211, Finland
| | - Hanna M Valolahti
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen Ø, 2100, Denmark
- Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen K, 1350, Denmark
| | - Riikka Rinnan
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen Ø, 2100, Denmark
- Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen K, 1350, Denmark
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15
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Dawes MA, Philipson CD, Fonti P, Bebi P, Hättenschwiler S, Hagedorn F, Rixen C. Soil warming and CO2 enrichment induce biomass shifts in alpine tree line vegetation. GLOBAL CHANGE BIOLOGY 2015; 21:2005-21. [PMID: 25471674 DOI: 10.1111/gcb.12819] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/18/2014] [Indexed: 05/26/2023]
Abstract
Responses of alpine tree line ecosystems to increasing atmospheric CO2 concentrations and global warming are poorly understood. We used an experiment at the Swiss tree line to investigate changes in vegetation biomass after 9 years of free air CO2 enrichment (+200 ppm; 2001-2009) and 6 years of soil warming (+4 °C; 2007-2012). The study contained two key tree line species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above-ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO2 enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m(-2) ) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO2 led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above-ground mass was not altered by soil warming or elevated CO2 . However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (-40% for all roots <2 mm in diameter at 0-20 cm soil depth) but no change with CO2 enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the tree line, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning.
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Affiliation(s)
- Melissa A Dawes
- WSL Institute for Snow and Avalanche Research - SLF, Flüelastrasse 11, CH-7260, Davos Dorf, Switzerland; Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland
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16
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Rousk K, Sorensen PL, Lett S, Michelsen A. Across-habitat comparison of diazotroph activity in the subarctic. MICROBIAL ECOLOGY 2015; 69:778-87. [PMID: 25403111 DOI: 10.1007/s00248-014-0534-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 11/03/2014] [Indexed: 05/03/2023]
Abstract
Nitrogen (N) fixation by N2-fixing bacteria (diazotrophs) is the primary N input to pristine ecosystems like boreal forests and subarctic and arctic tundra. However, the contribution by the various diazotrophs to habitat N2 fixation remains unclear. We present results from in situ assessments of N2 fixation of five diazotroph associations (with a legume, lichen, feather moss, Sphagnum moss and free-living) incorporating the ground cover of the associations in five typical habitats in the subarctic (wet and dry heath, polygon-heath, birch forest, mire). Further, we assessed the importance of soil and air temperature, as well as moisture conditions for N2 fixation. Across the growing season, the legume had the highest total as well as the highest fraction of N2 fixation rates at habitat level in the heaths (>85 % of habitat N2 fixation), whereas the free-living diazotrophs had the highest N2 fixation rates in the polygon heath (56 %), the lichen in the birch forest (87 %) and Sphagnum in the mire (100 %). The feather moss did not contribute more than 15 % to habitat N2 fixation in any of the habitats despite its high ground cover. Moisture content seemed to be a major driver of N2 fixation in the lichen, feather moss and free-living diazotrophs. Our results show that the range of N2 fixers found in pristine habitats contribute differently to habitat N2 fixation and that ground cover of the associates does not necessarily mirror contribution.
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Affiliation(s)
- Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark,
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17
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Hollister RD, May JL, Kremers KS, Tweedie CE, Oberbauer SF, Liebig JA, Botting TF, Barrett RT, Gregory JL. Warming experiments elucidate the drivers of observed directional changes in tundra vegetation. Ecol Evol 2015; 5:1881-95. [PMID: 26140204 PMCID: PMC4485969 DOI: 10.1002/ece3.1499] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 02/23/2015] [Accepted: 03/10/2015] [Indexed: 11/11/2022] Open
Abstract
Few studies have clearly linked long-term monitoring with in situ experiments to clarify potential drivers of observed change at a given site. This is especially necessary when findings from a site are applied to a much broader geographic area. Here, we document vegetation change at Barrow and Atqasuk, Alaska, occurring naturally and due to experimental warming over nearly two decades. An examination of plant cover, canopy height, and community indices showed more significant differences between years than due to experimental warming. However, changes with warming were more consistent than changes between years and were cumulative in many cases. Most cases of directional change observed in the control plots over time corresponded with a directional change in response to experimental warming. These included increases in canopy height and decreases in lichen cover. Experimental warming resulted in additional increases in evergreen shrub cover and decreases in diversity and bryophyte cover. This study suggests that the directional changes occurring at the sites are primarily due to warming and indicates that further changes are likely in the next two decades if the regional warming trend continues. These findings provide an example of the utility of coupling in situ experiments with long-term monitoring to accurately document vegetation change in response to global change and to identify the underlying mechanisms driving observed changes.
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Affiliation(s)
- Robert D Hollister
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401
| | - Jeremy L May
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401 ; Department of Biological Sciences, Florida International University 11200 SW 8th Street, Miami, Florida, 33199
| | - Kelseyann S Kremers
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401 ; Department of Biological Sciences, University of Notre Dame Notre Dame, Indiana, 46556
| | - Craig E Tweedie
- Department of Biology, University of Texas at El Paso El Paso, Texas, 79968
| | - Steven F Oberbauer
- Department of Biological Sciences, Florida International University 11200 SW 8th Street, Miami, Florida, 33199
| | - Jennifer A Liebig
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401
| | - Timothy F Botting
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401
| | - Robert T Barrett
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401
| | - Jessica L Gregory
- Biology Department, Grand Valley State University 1 Campus Drive, Allendale, Michigan, 49401
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Hedwall PO, Skoglund J, Linder S. Interactions with successional stage and nutrient status determines the life-form-specific effects of increased soil temperature on boreal forest floor vegetation. Ecol Evol 2015; 5:948-60. [PMID: 25750720 PMCID: PMC4338976 DOI: 10.1002/ece3.1412] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 01/06/2015] [Indexed: 11/10/2022] Open
Abstract
The boreal forest is one of the largest terrestrial biomes and plays a key role for the global carbon balance and climate. The forest floor vegetation has a strong influence on the carbon and nitrogen cycles of the forests and is sensitive to changes in temperature conditions and nutrient availability. Additionally, the effects of climate warming on forest floor vegetation have been suggested to be moderated by the tree layer. Data on the effects of soil warming on forest floor vegetation from the boreal forest are, however, very scarce. We studied the effects on the forest floor vegetation in a long-term (18 years) soil warming and fertilization experiment in a Norway spruce stand in northern Sweden. During the first 9 years, warming favored early successional species such as grasses and forbs at the expense of dwarf shrubs and bryophytes in unfertilized stands, while the effects were smaller after fertilization. Hence, warming led to significant changes in species composition and an increase in species richness in the open canopy nutrient limited forest. After another 9 years of warming and increasing tree canopy closure, most of the initial effects had ceased, indicating an interaction between forest succession and warming. The only remaining effect of warming was on the abundance of bryophytes, which contrary to the initial phase was strongly favored by warming. We propose that the suggested moderating effects of the tree layer are specific to plant life-form and conclude that the successional phase of the forest may have a considerable impact on the effects of climate change on forest floor vegetation and its feedback effects on the carbon and nitrogen cycles, and thus on the climate.
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Affiliation(s)
- Per-Ola Hedwall
- Swedish University of Agricultural Sciences, SLU, Southern Swedish Forest Research Centre PO Box 49, SE-230 53, Alnarp, Sweden
| | | | - Sune Linder
- Swedish University of Agricultural Sciences, SLU, Southern Swedish Forest Research Centre PO Box 49, SE-230 53, Alnarp, Sweden
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19
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Rinnan R, Steinke M, McGenity T, Loreto F. Plant volatiles in extreme terrestrial and marine environments. PLANT, CELL & ENVIRONMENT 2014; 37:1776-89. [PMID: 24601952 DOI: 10.1111/pce.12320] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 02/26/2014] [Indexed: 05/15/2023]
Abstract
This review summarizes the current understanding on plant and algal volatile organic compound (VOC) production and emission in extreme environments, where temperature, water availability, salinity or other environmental factors pose stress on vegetation. Here, the extreme environments include terrestrial systems, such as arctic tundra, deserts, CO₂ springs and wetlands, and marine systems such as sea ice, tidal rock pools and hypersaline environments, with mangroves and salt marshes at the land-sea interface. The emission potentials at fixed temperature and light level or actual emission rates for phototrophs in extreme environments are frequently higher than for organisms from less stressful environments. For example, plants from the arctic tundra appear to have higher emission potentials for isoprenoids than temperate species, and hypersaline marine habitats contribute to global dimethyl sulphide (DMS) emissions in significant amounts. DMS emissions are more widespread than previously considered, for example, in salt marshes and some desert plants. The reason for widespread VOC, especially isoprenoid, emissions from different extreme environments deserves further attention, as these compounds may have important roles in stress resistance and adaptation to extremes. Climate warming is likely to significantly increase VOC emissions from extreme environments both by direct effects on VOC production and volatility, and indirectly by altering the composition of the vegetation.
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Affiliation(s)
- Riikka Rinnan
- Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen Ø, DK-2100, Denmark; Centre for Permafrost (CENPERM), University of Copenhagen, Copenhagen K, DK-1350, Denmark
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20
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Andresen LC, Dungait JAJ, Bol R, Selsted MB, Ambus P, Michelsen A. Bacteria and fungi respond differently to multifactorial climate change in a temperate heathland, traced with 13C-glycine and FACE CO2. PLoS One 2014; 9:e85070. [PMID: 24454793 PMCID: PMC3893180 DOI: 10.1371/journal.pone.0085070] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 11/22/2013] [Indexed: 11/19/2022] Open
Abstract
It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g(-1) soil) of (13)C-labeled glycine ((13)C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The (13)C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. (13)C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS). Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated (13)C in all treatments, whereas fungi had minor or no glycine derived (13)C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G(+) bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was (13)C-depleted (δ(13)C = 12.2‰) compared to ambient (δ(13)C = ∼-8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern to future changes in substrate availability and climatic factors.
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Affiliation(s)
| | - Jennifer A. J. Dungait
- Sustainable Soils and Grassland Systems Department, Rothamsted Research-North Wyke, Okehampton, United Kingdom
| | - Roland Bol
- Sustainable Soils and Grassland Systems Department, Rothamsted Research-North Wyke, Okehampton, United Kingdom
- Institute of Bio- and Geosciences, Forschungszentrum Jülich, Jülich, Germany
| | - Merete B. Selsted
- Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Per Ambus
- Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Anders Michelsen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
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21
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Johnstone JF, Henkelman J, Allen K, Helgason W, Bedard-Haughn A. Controlled soil warming powered by alternative energy for remote field sites. PLoS One 2014; 8:e82903. [PMID: 24386125 PMCID: PMC3873302 DOI: 10.1371/journal.pone.0082903] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 11/07/2013] [Indexed: 11/19/2022] Open
Abstract
Experiments using controlled manipulation of climate variables in the field are critical for developing and testing mechanistic models of ecosystem responses to climate change. Despite rapid changes in climate observed in many high latitude and high altitude environments, controlled manipulations in these remote regions have largely been limited to passive experimental methods with variable effects on environmental factors. In this study, we tested a method of controlled soil warming suitable for remote field locations that can be powered using alternative energy sources. The design was tested in high latitude, alpine tundra of southern Yukon Territory, Canada, in 2010 and 2011. Electrical warming probes were inserted vertically in the near-surface soil and powered with photovoltaics attached to a monitoring and control system. The warming manipulation achieved a stable target warming of 1.3 to 2 °C in 1 m(2) plots while minimizing disturbance to soil and vegetation. Active control of power output in the warming plots allowed the treatment to closely match spatial and temporal variations in soil temperature while optimizing system performance during periods of low power supply. Active soil heating with vertical electric probes powered by alternative energy is a viable option for remote sites and presents a low-disturbance option for soil warming experiments. This active heating design provides a valuable tool for examining the impacts of soil warming on ecosystem processes.
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Affiliation(s)
- Jill F. Johnstone
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail:
| | - Jonathan Henkelman
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Kirsten Allen
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Warren Helgason
- Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Angela Bedard-Haughn
- Department of Soil Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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22
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García-Descalzo L, García-López E, Postigo M, Baquero F, Alcazar A, Cid C. Eukaryotic microorganisms in cold environments: examples from Pyrenean glaciers. Front Microbiol 2013; 4:55. [PMID: 23515855 PMCID: PMC3601304 DOI: 10.3389/fmicb.2013.00055] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 02/26/2013] [Indexed: 11/13/2022] Open
Abstract
Little is known about the viability of eukaryotic microorganisms preserved in icy regions. Here we report on the diversity of microbial eukaryotes in ice samples derived from four Pyrenean glaciers. The species composition of eukaryotic communities in these glaciers is unknown mostly because of the presence of a multi-year ice cap, and it is not clear whether they harbor the same populations. The recent deglaciation of these areas is allowing an easy access to glacial layers that correspond to the “Little Ice Age” although some isolated deposits are attributed to previous glacial cycles. In this study, we use molecular 18S rRNA-based approaches to characterize some of the microbial eukaryotic populations associated with Pyrenean glaciers. Firstly, we performed a chemical and microscopical characterization of ice samples. Secondly, molecular analyses revealed interesting protist genetic diversity in glaciers. In order to understand the microbial composition of the ice samples the eukaryotic communities resident in the glacial samples were examined by amplifying community DNA and constructing clone libraries with 18S rRNA primers. After removal of potential chimeric sequences and dereplication of identical sequences, phylogenetic analysis demonstrated that several different protists could be identified. Protist diversity was more phylum rich in Aneto and Monte Perdido glaciers. The dominant taxonomic groups across all samples (>1% of all sequences) were Viridiplantae and Rhizaria. Significant variations in relative abundances of protist phyla between higher and lower glaciers were observed. At the genus level, significant differences were also recorded for the dominant genera Chloromonas, Raphidonema, Heteromita, Koliella, and Bodomorpha. In addition, protist community structure showed significant differences between glaciers. The relative abundances of protist groups at different taxonomic levels correlated with the altitude and area of glaciers and with pH of ice, but little or no relationships to other chemical characteristics were found.
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Affiliation(s)
- Laura García-Descalzo
- Microbial Evolution Laboratory, Centro de Astrobiología (Consejo Superior de Investigaciones Cientificas - Instituto Nacional de Técnica Aeroespacial) Torrejón de Ardoz, Madrid, Spain
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23
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Rinnan R, Michelsen A, Bååth E. Fungi benefit from two decades of increased nutrient availability in tundra heath soil. PLoS One 2013; 8:e56532. [PMID: 23437159 PMCID: PMC3577890 DOI: 10.1371/journal.pone.0056532] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 01/10/2013] [Indexed: 11/18/2022] Open
Abstract
If microbial degradation of carbon substrates in arctic soil is stimulated by climatic warming, this would be a significant positive feedback on global change. With data from a climate change experiment in Northern Sweden we show that warming and enhanced soil nutrient availability, which is a predicted long-term consequence of climatic warming and mimicked by fertilization, both increase soil microbial biomass. However, while fertilization increased the relative abundance of fungi, warming caused only a minimal shift in the microbial community composition based on the phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) profiles. The function of the microbial community was also differently affected, as indicated by stable isotope probing of PLFA and NLFA. We demonstrate that two decades of fertilization have favored fungi relative to bacteria, and increased the turnover of complex organic compounds such as vanillin, while warming has had no such effects. Furthermore, the NLFA-to-PLFA ratio for (13)C-incorporation from acetate increased in warmed plots but not in fertilized ones. Thus, fertilization cannot be used as a proxy for effects on warming in arctic tundra soils. Furthermore, the different functional responses suggest that the biomass increase found in both fertilized and warmed plots was mediated via different mechanisms.
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Affiliation(s)
- Riikka Rinnan
- Department of Biology, Lund University, Lund, Sweden
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
| | - Anders Michelsen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Copenhagen, Denmark
| | - Erland Bååth
- Department of Biology, Lund University, Lund, Sweden
- * E-mail:
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24
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Johansson M, Jonasson C, Sonesson M, Christensen TR. The man, the myth, the legend: Professor Terry V. Callaghan and his 3M concept. AMBIO 2012; 41 Suppl 3:175-7. [PMID: 22864691 PMCID: PMC3535064 DOI: 10.1007/s13280-012-0300-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Margareta Johansson
- Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
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