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Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions. NITROGEN 2022. [DOI: 10.3390/nitrogen3030031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Permafrost-affected tundra soils are large carbon (C) and nitrogen (N) reservoirs. However, N is largely bound in soil organic matter (SOM), and ecosystems generally have low N availability. Therefore, microbial induced N-cycling processes and N losses were considered negligible. Recent studies show that microbial N processing rates, inorganic N availability, and lateral N losses from thawing permafrost increase when vegetation cover is disturbed, resulting in reduced N uptake or increased N input from thawing permafrost. In this review, we describe currently known N hotspots, particularly bare patches in permafrost peatland or permafrost soils affected by thermokarst, and their microbiogeochemical characteristics, and present evidence for previously unrecorded N hotspots in the tundra. We summarize the current understanding of microbial N cycling processes that promote the release of the potent greenhouse gas (GHG) nitrous oxide (N2O) and the translocation of inorganic N from terrestrial into aquatic ecosystems. We suggest that certain soil characteristics and microbial traits can be used as indicators of N availability and N losses. Identifying N hotspots in permafrost soils is key to assessing the potential for N release from permafrost-affected soils under global warming, as well as the impact of increased N availability on emissions of carbon-containing GHGs.
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McLaren JR, Buckeridge KM. Enhanced plant leaf P and unchanged soil P stocks after a quarter century of warming in the arctic tundra. Ecosphere 2021. [DOI: 10.1002/ecs2.3838] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Jennie R. McLaren
- Department of Biological Sciences University of Texas at El Paso El Paso Texas 79968 USA
| | - Kate M. Buckeridge
- Department of Environmental Research and Innovation (ERIN) Luxembourg Institute of Science and Technology (LIST) 41 Rue du Brill 4422 Belvaux Luxembourg
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3
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Sitters J, Cherif M, Egelkraut D, Giesler R, Olofsson J. Long‐term heavy reindeer grazing promotes plant phosphorus limitation in arctic tundra. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13342] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Judith Sitters
- Department of Ecology and Environmental Science Umeå University Umeå Sweden
- Ecology and Biodiversity, Department Biology Vrije Universiteit Brussel Brussels Belgium
| | - Mehdi Cherif
- Department of Ecology and Environmental Science Umeå University Umeå Sweden
- Climate Impacts Research Centre, Department of Ecology and Environmental Science Umeå University Abisko Sweden
| | - Dagmar Egelkraut
- Department of Ecology and Environmental Science Umeå University Umeå Sweden
- Department of Biological Sciences University of Bergen Bergen Norway
| | - Reiner Giesler
- Department of Ecology and Environmental Science Umeå University Umeå Sweden
- Climate Impacts Research Centre, Department of Ecology and Environmental Science Umeå University Abisko Sweden
| | - Johan Olofsson
- Department of Ecology and Environmental Science Umeå University Umeå Sweden
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4
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Hopping KA, Knapp AK, Dorji T, Klein JA. Warming and land use change concurrently erode ecosystem services in Tibet. GLOBAL CHANGE BIOLOGY 2018; 24:5534-5548. [PMID: 30086187 DOI: 10.1111/gcb.14417] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/10/2018] [Accepted: 07/22/2018] [Indexed: 06/08/2023]
Abstract
Alpine meadows on the Tibetan Plateau comprise the largest alpine ecosystem in the world and provide critical ecosystem services, including forage production and carbon sequestration, on which people depend from local to global scales. However, the provision of these services may be threatened by climate warming combined with land use policies that are altering if and how pastoralists can continue to graze livestock, the dominant livelihood practice in this region for millennia. We synthesized findings from a climate warming and yak grazing experiment with landscape-level observations in central Tibet to gain insight into the trajectories of change that Tibet's alpine meadows will undergo in response to expected changes in climate and land use. We show that within 5 years, experimental warming drove an alpine community with intact, sedge-dominated turfs into a degraded state. With removal of livestock, consistent with policy intended to reverse degradation, a longer-term shift to a more shrub-dominated community will likely occur. Neither degraded nor shrub meadows produce forage or sequester carbon to the same degree as intact meadows, indicating that climate warming and drying will reduce the ability of Tibet's alpine meadows to provide key ecosystem services, and that livestock reduction policies intended to counteract trajectories of land degradation instead endanger contemporary livelihoods on the Tibetan Plateau.
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Affiliation(s)
- Kelly A Hopping
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado
| | - Alan K Knapp
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Tsechoe Dorji
- Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Lhasa, Tibet Autonomous Region, China
- CAS Center for Excellence in Tibetan Plateau Earth Science, Beijing, China
| | - Julia A Klein
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado
- Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, Colorado
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5
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Mauritz M, Bracho R, Celis G, Hutchings J, Natali SM, Pegoraro E, Salmon VG, Schädel C, Webb EE, Schuur EAG. Nonlinear CO 2 flux response to 7 years of experimentally induced permafrost thaw. GLOBAL CHANGE BIOLOGY 2017; 23:3646-3666. [PMID: 28208232 DOI: 10.1111/gcb.13661] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 01/19/2017] [Indexed: 06/06/2023]
Abstract
Rapid Arctic warming is expected to increase global greenhouse gas concentrations as permafrost thaw exposes immense stores of frozen carbon (C) to microbial decomposition. Permafrost thaw also stimulates plant growth, which could offset C loss. Using data from 7 years of experimental Air and Soil warming in moist acidic tundra, we show that Soil warming had a much stronger effect on CO2 flux than Air warming. Soil warming caused rapid permafrost thaw and increased ecosystem respiration (Reco ), gross primary productivity (GPP), and net summer CO2 storage (NEE). Over 7 years Reco , GPP, and NEE also increased in Control (i.e., ambient plots), but this change could be explained by slow thaw in Control areas. In the initial stages of thaw, Reco , GPP, and NEE increased linearly with thaw across all treatments, despite different rates of thaw. As thaw in Soil warming continued to increase linearly, ground surface subsidence created saturated microsites and suppressed Reco , GPP, and NEE. However Reco and GPP remained high in areas with large Eriophorum vaginatum biomass. In general NEE increased with thaw, but was more strongly correlated with plant biomass than thaw, indicating that higher Reco in deeply thawed areas during summer months was balanced by GPP. Summer CO2 flux across treatments fit a single quadratic relationship that captured the functional response of CO2 flux to thaw, water table depth, and plant biomass. These results demonstrate the importance of indirect thaw effects on CO2 flux: plant growth and water table dynamics. Nonsummer Reco models estimated that the area was an annual CO2 source during all years of observation. Nonsummer CO2 loss in warmer, more deeply thawed soils exceeded the increases in summer GPP, and thawed tundra was a net annual CO2 source.
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Affiliation(s)
- Marguerite Mauritz
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
| | - Rosvel Bracho
- School of Forest Resources and Conservation, University of Florida, Gainesville, FL, USA
| | - Gerardo Celis
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
| | - Jack Hutchings
- Department of Geological Sciences, University of Florida, Gainesville, FL, USA
| | | | - Elaine Pegoraro
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
| | - Verity G Salmon
- Environmental Sciences Division and Climate Change Sciences Institute, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Christina Schädel
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
| | - Elizabeth E Webb
- Department of Biology, University of Florida, Gainesville, FL, USA
| | - Edward A G Schuur
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
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6
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Prager CM, Naeem S, Boelman NT, Eitel JUH, Greaves HE, Heskel MA, Magney TS, Menge DNL, Vierling LA, Griffin KL. A gradient of nutrient enrichment reveals nonlinear impacts of fertilization on Arctic plant diversity and ecosystem function. Ecol Evol 2017; 7:2449-2460. [PMID: 28405308 PMCID: PMC5383475 DOI: 10.1002/ece3.2863] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/28/2017] [Accepted: 02/07/2017] [Indexed: 11/09/2022] Open
Abstract
Rapid environmental change at high latitudes is predicted to greatly alter the diversity, structure, and function of plant communities, resulting in changes in the pools and fluxes of nutrients. In Arctic tundra, increased nitrogen (N) and phosphorus (P) availability accompanying warming is known to impact plant diversity and ecosystem function; however, to date, most studies examining Arctic nutrient enrichment focus on the impact of relatively large (>25x estimated naturally occurring N enrichment) doses of nutrients on plant community composition and net primary productivity. To understand the impacts of Arctic nutrient enrichment, we examined plant community composition and the capacity for ecosystem function (net ecosystem exchange, ecosystem respiration, and gross primary production) across a gradient of experimental N and P addition expected to more closely approximate warming-induced fertilization. In addition, we compared our measured ecosystem CO 2 flux data to a widely used Arctic ecosystem exchange model to investigate the ability to predict the capacity for CO 2 exchange with nutrient addition. We observed declines in abundance-weighted plant diversity at low levels of nutrient enrichment, but species richness and the capacity for ecosystem carbon uptake did not change until the highest level of fertilization. When we compared our measured data to the model, we found that the model explained roughly 30%-50% of the variance in the observed data, depending on the flux variable, and the relationship weakened at high levels of enrichment. Our results suggest that while a relatively small amount of nutrient enrichment impacts plant diversity, only relatively large levels of fertilization-over an order of magnitude or more than warming-induced rates-significantly alter the capacity for tundra CO 2 exchange. Overall, our findings highlight the value of measuring and modeling the impacts of a nutrient enrichment gradient, as warming-related nutrient availability may impact ecosystems differently than single-level fertilization experiments.
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Affiliation(s)
- Case M Prager
- Department of Ecology, Evolution, and Environmental Biology Columbia University New York NY USA
| | - Shahid Naeem
- Department of Ecology, Evolution, and Environmental Biology Columbia University New York NY USA
| | - Natalie T Boelman
- Department of Earth and Environmental Sciences Columbia University New York NY USA; Lamont-Doherty Earth Observatory Columbia University Palisades NY USA
| | - Jan U H Eitel
- Geospatial Laboratory for Environmental Dynamics Department of Natural Resources and Society University of Idaho Moscow ID USA; McCall Outdoor Science School University of Idaho McCall ID USA
| | - Heather E Greaves
- Geospatial Laboratory for Environmental Dynamics Department of Natural Resources and Society University of Idaho Moscow ID USA
| | - Mary A Heskel
- Ecosystems Center Marine Biological Laboratory Woods Hole MA USA
| | - Troy S Magney
- Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA
| | - Duncan N L Menge
- Department of Ecology, Evolution, and Environmental Biology Columbia University New York NY USA
| | - Lee A Vierling
- Geospatial Laboratory for Environmental Dynamics Department of Natural Resources and Society University of Idaho Moscow ID USA; McCall Outdoor Science School University of Idaho McCall ID USA
| | - Kevin L Griffin
- Department of Ecology, Evolution, and Environmental Biology Columbia University New York NY USA; Department of Earth and Environmental Sciences Columbia University New York NY USA; Lamont-Doherty Earth Observatory Columbia University Palisades NY USA
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7
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Andresen CG, Lara MJ, Tweedie CE, Lougheed VL. Rising plant-mediated methane emissions from arctic wetlands. GLOBAL CHANGE BIOLOGY 2017; 23:1128-1139. [PMID: 27541438 DOI: 10.1111/gcb.13469] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 07/15/2016] [Indexed: 06/06/2023]
Abstract
Plant-mediated CH4 flux is an important pathway for land-atmosphere CH4 emissions, but the magnitude, timing, and environmental controls, spanning scales of space and time, remain poorly understood in arctic tundra wetlands, particularly under the long-term effects of climate change. CH4 fluxes were measured in situ during peak growing season for the dominant aquatic emergent plants in the Alaskan arctic coastal plain, Carex aquatilis and Arctophila fulva, to assess the magnitude and species-specific controls on CH4 flux. Plant biomass was a strong predictor of A. fulva CH4 flux while water depth and thaw depth were copredictors for C. aquatilis CH4 flux. We used plant and environmental data from 1971 to 1972 from the historic International Biological Program (IBP) research site near Barrow, Alaska, which we resampled in 2010-2013, to quantify changes in plant biomass and thaw depth, and used these to estimate species-specific decadal-scale changes in CH4 fluxes. A ~60% increase in CH4 flux was estimated from the observed plant biomass and thaw depth increases in tundra ponds over the past 40 years. Despite covering only ~5% of the landscape, we estimate that aquatic C. aquatilis and A. fulva account for two-thirds of the total regional CH4 flux of the Barrow Peninsula. The regionally observed increases in plant biomass and active layer thickening over the past 40 years not only have major implications for energy and water balance, but also have significantly altered land-atmosphere CH4 emissions for this region, potentially acting as a positive feedback to climate warming.
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Affiliation(s)
- Christian G Andresen
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
- Earth and Environmental Science Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Mark J Lara
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK, 99775, USA
| | - Craig E Tweedie
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Vanessa L Lougheed
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
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8
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Hicks Pries CE, van Logtestijn RSP, Schuur EAG, Natali SM, Cornelissen JHC, Aerts R, Dorrepaal E. Decadal warming causes a consistent and persistent shift from heterotrophic to autotrophic respiration in contrasting permafrost ecosystems. GLOBAL CHANGE BIOLOGY 2015; 21:4508-4519. [PMID: 26150277 DOI: 10.1111/gcb.13032] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 06/10/2015] [Indexed: 06/04/2023]
Abstract
Soil carbon in permafrost ecosystems has the potential to become a major positive feedback to climate change if permafrost thaw increases heterotrophic decomposition. However, warming can also stimulate autotrophic production leading to increased ecosystem carbon storage-a negative climate change feedback. Few studies partitioning ecosystem respiration examine decadal warming effects or compare responses among ecosystems. Here, we first examined how 11 years of warming during different seasons affected autotrophic and heterotrophic respiration in a bryophyte-dominated peatland in Abisko, Sweden. We used natural abundance radiocarbon to partition ecosystem respiration into autotrophic respiration, associated with production, and heterotrophic decomposition. Summertime warming decreased the age of carbon respired by the ecosystem due to increased proportional contributions from autotrophic and young soil respiration and decreased proportional contributions from old soil. Summertime warming's large effect was due to not only warmer air temperatures during the growing season, but also to warmer deep soils year-round. Second, we compared ecosystem respiration responses between two contrasting ecosystems, the Abisko peatland and a tussock-dominated tundra in Healy, Alaska. Each ecosystem had two different timescales of warming (<5 years and over a decade). Despite the Abisko peatland having greater ecosystem respiration and larger contributions from heterotrophic respiration than the Healy tundra, both systems responded consistently to short- and long-term warming with increased respiration, increased autotrophic contributions to ecosystem respiration, and increased ratios of autotrophic to heterotrophic respiration. We did not detect an increase in old soil carbon losses with warming at either site. If increased autotrophic respiration is balanced by increased primary production, as is the case in the Healy tundra, warming will not cause these ecosystems to become growing season carbon sources. Warming instead causes a persistent shift from heterotrophic to more autotrophic control of the growing season carbon cycle in these carbon-rich permafrost ecosystems.
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Affiliation(s)
- Caitlin E Hicks Pries
- Earth Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL, 32611, USA
| | - Richard S P van Logtestijn
- Department of Systems Ecology, Institute of Ecological Science, VU University Amsterdam, De Boelelaan 1085, NL-1081 HV, Amsterdam, the Netherlands
| | - Edward A G Schuur
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL, 32611, USA
| | - Susan M Natali
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL, 32611, USA
| | - Johannes H C Cornelissen
- Department of Systems Ecology, Institute of Ecological Science, VU University Amsterdam, De Boelelaan 1085, NL-1081 HV, Amsterdam, the Netherlands
| | - Rien Aerts
- Department of Systems Ecology, Institute of Ecological Science, VU University Amsterdam, De Boelelaan 1085, NL-1081 HV, Amsterdam, the Netherlands
| | - Ellen Dorrepaal
- Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, S-981 07, Abisko, Sweden
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Tian D, Niu S, Pan Q, Ren T, Chen S, Bai Y, Han X. Nonlinear responses of ecosystem carbon fluxes and water‐use efficiency to nitrogen addition in Inner Mongolia grassland. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12513] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dashuan Tian
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
- Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China
| | - Shuli Niu
- Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China
| | - Qingmin Pan
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
| | - Tingting Ren
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
| | - Shiping Chen
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
| | - Yongfei Bai
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
| | - Xingguo Han
- State Key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China
- State Key Laboratory of Forest and Soil Ecology Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China
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10
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Sundqvist MK, Liu Z, Giesler R, Wardle DA. Plant and microbial responses to nitrogen and phosphorus addition across an elevational gradient in subarctic tundra. Ecology 2014; 95:1819-35. [PMID: 25163116 DOI: 10.1890/13-0869.1] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Temperature and nutrients are major limiting factors in subarctic tundra. Experimental manipulation of nutrient availability along elevational gradients (and thus temperature) can improve our understanding of ecological responses to climate change. However, no study to date has explored impacts of nutrient addition along a tundra elevational gradient, or across contrasting vegetation types along any elevational gradient. We set up a full factorial nitrogen (N) and phosphorus (P) fertilization experiment in each of two vegetation types (heath and meadow) at 500 m, 800 m, and 1000 m elevation in northern Swedish tundra. We predicted that plant and microbial communities in heath or at lower elevations would be more responsive to N addition while communities in meadow or at higher elevations would be more responsive to P addition, and that fertilizer effects would vary more with elevation for the heath than for the meadow. Although our results provided little support for these predictions, the relationship between nutrient limitation and elevation differed between vegetation types. Most plant and microbial properties were responsive to N and/or P fertilization, but responses often varied with elevation and/or vegetation type. For instance, vegetation density significantly increased with N + P fertilization relative to the other fertilizer treatments, and this increase was greatest at the lowest elevation for the heath but at the highest elevation for the meadow. Arbuscular mycorrhizae decreased with P fertilization at 500 m for the meadow, but with all fertilizer treatments in both vegetation types at 800 m. Fungal to bacterial ratios were enhanced by N+ P fertilization for the two highest elevations in the meadow only. Additionally, microbial responses to fertilization were primarily direct rather than indirect via plant responses, pointing to a decoupled response of plant and microbial communities to nutrient addition and elevation. Because our study shows how two community types differ in their responses to fertilization and elevation, and because the temperature range across this gradient is approximately 3 degrees C, our study is informative about how nutrient limitation in tundra may be influenced by temperature shifts that are comparable to those expected under climate change during this century.
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11
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Heskel MA, Greaves HE, Turnbull MH, O'Sullivan OS, Shaver GR, Griffin KL, Atkin OK. Thermal acclimation of shoot respiration in an Arctic woody plant species subjected to 22 years of warming and altered nutrient supply. GLOBAL CHANGE BIOLOGY 2014; 20:2618-2630. [PMID: 24510889 DOI: 10.1111/gcb.12544] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 01/04/2014] [Indexed: 06/03/2023]
Abstract
Despite concern about the status of carbon (C) in the Arctic tundra, there is currently little information on how plant respiration varies in response to environmental change in this region. We quantified the impact of long-term nitrogen (N) and phosphorus (P) treatments and greenhouse warming on the short-term temperature (T) response and sensitivity of leaf respiration (R), the high-T threshold of R, and associated traits in shoots of the Arctic shrub Betula nana in experimental plots at Toolik Lake, Alaska. Respiration only acclimated to greenhouse warming in plots provided with both N and P (resulting in a ~30% reduction in carbon efflux in shoots measured at 10 and 20 °C), suggesting a nutrient dependence of metabolic adjustment. Neither greenhouse nor N+P treatments impacted on the respiratory sensitivity to T (Q10 ); overall, Q10 values decreased with increasing measuring T, from ~3.0 at 5 °C to ~1.5 at 35 °C. New high-resolution measurements of R across a range of measuring Ts (25-70 °C) yielded insights into the T at which maximal rates of R occurred (Tmax ). Although growth temperature did not affect Tmax , N+P fertilization increased Tmax values ~5 °C, from 53 to 58 °C. N+P fertilized shoots exhibited greater rates of R than nonfertilized shoots, with this effect diminishing under greenhouse warming. Collectively, our results highlight the nutrient dependence of thermal acclimation of leaf R in B. nana, suggesting that the metabolic efficiency allowed via thermal acclimation may be impaired at current levels of soil nutrient availability. This finding has important implications for predicting carbon fluxes in Arctic ecosystems, particularly if soil N and P become more abundant in the future as the tundra warms.
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Affiliation(s)
- Mary A Heskel
- Research School of Biology, Division of Plant Sciences, Building 46, Australian National University, Canberra, ACT 0200, Australia
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12
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DeMarco J, Mack MC, Bret-Harte MS, Burton M, Shaver GR. Long-term experimental warming and nutrient additions increase productivity in tall deciduous shrub tundra. Ecosphere 2014. [DOI: 10.1890/es13-00281.1] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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13
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Heskel MA, Anderson OR, Atkin OK, Turnbull MH, Griffin KL. Leaf- and cell-level carbon cycling responses to a nitrogen and phosphorus gradient in two Arctic tundra species. AMERICAN JOURNAL OF BOTANY 2012; 99:1702-1714. [PMID: 22984095 DOI: 10.3732/ajb.1200251] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
PREMISE OF THE STUDY Consequences of global climate change are detectable in the historically nitrogen- and phosphorus-limited Arctic tundra landscape and have implications for the terrestrial carbon cycle. Warmer temperatures and elevated soil nutrient availability associated with increased microbial activity may influence rates of photosynthesis and respiration. • METHODS This study examined leaf-level gas exchange, cellular ultrastructure, and related leaf traits in two dominant tundra species, Betula nana, a woody shrub, and Eriophorum vaginatum, a tussock sedge, under a 3-yr-old treatment gradient of nitrogen (N) and phosphorus (P) fertilization in the North Slope of Alaska. • KEY RESULTS Respiration increased with N and P addition-the highest rates corresponding to the highest concentrations of leaf N in both species. The inhibition of respiration by light ("Kok effect") significantly reduced respiration rates in both species (P < 0.001), ranged from 12-63% (mean 34%), and generally decreased with fertilization for both species. However, in both species, observed rates of photosynthesis did not increase, and photosynthetic nitrogen use efficiency generally decreased under increasing fertilization. Chloroplast and mitochondrial size and density were highly sensitive to N and P fertilization (P < 0.001), though species interactions indicated divergent cellular organizational strategies. • CONCLUSIONS Results from this study demonstrate a species-specific decoupling of respiration and photosynthesis under N and P fertilization, implying an alteration of the carbon balance of the tundra ecosystem under future conditions.
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Affiliation(s)
- Mary A Heskel
- Department of Ecology, Evolution, & Environmental Biology, 1200 Amsterdam Avenue, Columbia University, New York, New York 10027, USA.
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14
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Oberbauer SF, Tweedie CE, Welker JM, Fahnestock JT, Henry GHR, Webber PJ, Hollister RD, Walker MD, Kuchy A, Elmore E, Starr G. TUNDRA CO2FLUXES IN RESPONSE TO EXPERIMENTAL WARMING ACROSS LATITUDINAL AND MOISTURE GRADIENTS. ECOL MONOGR 2007. [DOI: 10.1890/06-0649] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
An ongoing debate in ecology revolves around how species composition and ecosystem function are related. To address the mechanistic controls of this relationship, we manipulated the composition of dissolved organic matter (DOM) fed to aquatic bacteria to determine effects on both bacterial activity and community composition. Sites along terrestrial to aquatic flow paths were chosen to simulate movement of DOM through catchments, and DOM was fed to downslope and control bacterial communities. Bacterial production was measured, and DOM chemistry and bacterial community composition (using denaturing gradient gel electrophoresis of 16S rRNA genes) were characterized following incubations. Bacterial production, dissolved organic carbon (DOC)-specific bacterial production, and DOC consumption were greatest in mesocosms fed soil water DOM; soil water DOM enhanced lake and stream bacterial production by 320-670% relative to lake and stream controls. Stream DOM added to lake bacteria depressed bacterial production relative to lake controls in the early season (-78%) but not the mid-season experiment. Addition of upslope DOM to stream and lake bacterial communities resulted in significant changes in bacterial community composition relative to controls. In four of five DOM treatments, the bacterial community composition converged to the DOM source community regardless of the initial inoculum. These results demonstrate that shifts in the supply of natural DOM were followed by changes in both bacterial production and community composition, suggesting that changes in function are likely predicated on at least an initial change in the community composition. The results indicate that variation in DOM composition of soil and surface waters influences bacterial community dynamics and controls rates of carbon processing in set patterns across the landscape.
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Affiliation(s)
- Kristin E Judd
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA.
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Willby NJ, Pulford ID, Flowers TH. Tissue nutrient signatures predict herbaceous-wetland community responses to nutrient availability. THE NEW PHYTOLOGIST 2001; 152:463-481. [PMID: 33862984 DOI: 10.1046/j.0028-646x.2001.00274.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
• An extensive survey of European wetlands was undertaken to compare the importance of growing conditions vs functional characteristics of vegetation in determining N, P and K contents. • Stress-tolerator dominated stands (S) had consistently lower nutrient contents and higher N : P ratios whereas ruderal-dominated (R) stands displayed the opposite pattern. Competitor (C) and competitor-stress tolerator (CS) stands were intermediate to R and S. • These patterns were mostly preserved after removing covariation between vegetation and environment, thus indicating constitutional differences in nutrient signatures between functionally differentiated vegetation. C and R stands were least likely to be nutrient limited. Half of the S stands were probably P-limited but C, CS and R stands rarely or never experienced P limitation. Inferred colimitation by K was twice as frequent in S stands compared with other vegetation. • This study extends the evidence for syndromes of traits closely linked to nutrient use efficiency that increase fitness under particular growing conditions. It also highlights patterns at a community level across a wide range of wetland types and suggests that tissue nutrient signatures will have diagnostic value in predicting community responses to perturbation in nutrient availability.
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Affiliation(s)
- N J Willby
- Department of Environmental & Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, Scotland
- Present address: Department of Environmental Science, University of Stirling, Stirling, FK9 4LA, UK
| | - I D Pulford
- Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland
| | - T H Flowers
- Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland
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Shaver GR, Bret-Harte MS, Jones MH, Johnstone J, Gough L, Laundre J, Chapin FS. SPECIES COMPOSITION INTERACTS WITH FERTILIZER TO CONTROL LONG-TERM CHANGE IN TUNDRA PRODUCTIVITY. Ecology 2001. [DOI: 10.1890/0012-9658(2001)082[3163:sciwft]2.0.co;2] [Citation(s) in RCA: 253] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Gordon C, Wynn JM, Woodin SJ. Impacts of increased nitrogen supply on high Arctic heath: the importance of bryophytes and phosphorus availability. THE NEW PHYTOLOGIST 2001; 149:461-471. [PMID: 33873333 DOI: 10.1046/j.1469-8137.2001.00053.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
• This study investigates effects of nitrogen and phosphorus on high Arctic heath vegetation, particularly bryophytes. • Heath communities received factorial combinations of nitrogen (0, 10 and 50 kg ha-1 yr-1 ) and phosphorus (0 and 5 kg ha-1 yr-1 ) in five applications per growing season, for 8 yr. • Nitrogen decreased lichen cover but did not affect cover of any other functional type. However, just 10 kg ha-1 yr-1 increased the proportion of physiologically active bryophte shoots, and decreased their nitrate assimilation capacity. Phosphorus had greater effects, and the combination of both nutrients altered species composition. Individual bryophyte species displayed contrasting responses to fertilization, suggesting that they should not be grouped as a single functional type. • The 'critical load' of nitrogen for Arctic heath lies below 10 kg ha-1 yr-1 . Nitrogen and phosphorus are colimiting in this sytem, so the critical load of nitrogen will be lower where phosphorus availability is greater. Responses of vegetation to any increase in net mineralisation due to soil warming will depend on the ratio in which nitrogen and phosphorus availabilities increase. The effects of nutrient enhancement are very persistent.
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Affiliation(s)
- C Gordon
- Department of Plant and Soil Science, Cruickshank Building, University of Aberdeen, St Machar Drive, Aberdeen, AB24 3UU, UK
| | - J M Wynn
- Department of Plant and Soil Science, Cruickshank Building, University of Aberdeen, St Machar Drive, Aberdeen, AB24 3UU, UK
| | - S J Woodin
- Department of Plant and Soil Science, Cruickshank Building, University of Aberdeen, St Machar Drive, Aberdeen, AB24 3UU, UK
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Bret-Harte MS, Shaver GR, Zoerner JP, Johnstone JF, Wagner JL, Chavez AS, Gunkelman RF, Lippert SC, Laundre JA. DEVELOPMENTAL PLASTICITY ALLOWSBETULA NANATO DOMINATE TUNDRA SUBJECTED TO AN ALTERED ENVIRONMENT. Ecology 2001. [DOI: 10.1890/0012-9658(2001)082[0018:dpabnt]2.0.co;2] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Weltzin JF, Pastor J, Harth C, Bridgham SD, Updegraff K, Chapin CT. RESPONSE OF BOG AND FEN PLANT COMMUNITIES TO WARMING AND WATER-TABLE MANIPULATIONS. Ecology 2000. [DOI: 10.1890/0012-9658(2000)081[3464:robafp]2.0.co;2] [Citation(s) in RCA: 221] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Johnson LC, Shaver GR, Cades DH, Rastetter E, Nadelhoffer K, Giblin A, Laundre J, Stanley A. PLANT CARBON–NUTRIENT INTERACTIONS CONTROL CO2EXCHANGE IN ALASKAN WET SEDGE TUNDRA ECOSYSTEMS. Ecology 2000. [DOI: 10.1890/0012-9658(2000)081[0453:pcnicc]2.0.co;2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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