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22 results for “N2 fixation”
Data from: Heterogeneity in habitat and nutrient availability facilitate the co-occurrence of N2 fixation and denitrification across wetland - stream - lake ecotones of Lakes Superior and Huron
Great Lakes coastlines are mosaics of wetland, stream, and lake habitats, characterized by a high degree of spatial heterogeneity that may facilitate the co-occurrence of seemingly incompatible biogeochemical processes due to variation in environmental factors that favor each process. We measured nutrient limitation and rates of N2 fixation and denitrification along transects in 5 wetland - stream - lake ecotones with different nutrient loading in Lakes Superior and Huron and hypothesized that rates of both processes would be related to nutrient limitation status, habitat type, and environmental characteristics including temperature, nutrient concentrations, and organic matter quality. This data package includes information on sampling sites, dates and locations; rates of N fixation and denitrification measured at each site, date and transect location; and biomass information from nutrient diffusing substrates deployed on the study transects.
Temporal transect of moss-associated N2 fixation rates in Anchorage, Fairbanks, and Toolik
This is a dataset coving multiple moss species (Hylocomium splendens, Ptilium crista-castrensis, Pleurozium schreberi, Sphagnum sp., others) and their associated d15N following incubation with 15N2 in June, July, and August over the course of one growing season in 2017. Three sites at each location (Anchorage, Fairbanks, and Toolik Field Station) were sampled. We measured rates of nitrogen fixation using 15N2 incubations in a common garden close to the sites of collection.
Reciprocal transplant of mosses from Arctic tundra to alpine tundra and associated N2 fixation rates
In the summer of 2018, 12 cores were taken at Toolik Field Station. Six of those cores were retransplanted into their home environment, while six we transplanted to Eight Mile Lake. At Eight Mile Lake, the same procedure was followed. One year later, these transplants were revisited and associated N2 fixation rates were measured for Hylocomium splendens, Pleurozium scheberi and Aulacomnium turgidum using 15N2 gas incubations.
Patterns of and controls over nitrogen inputs by green alder (Alnus viridis spp. fruticosa) to a secondary successional chronosequence in interior Alaska I - N2 Fixation and Soil Temperature
We measured rates of nitrogen fixation by Alnus viridis spp. fruticosa and concurrent subcanopy soil temperature at BNZ LTER. To do so we utilized replicate (n=3/stage) stands of a seral sequence of successional stages maintained by the Bonanza Creek Long-Term Ecological Research program (BNZ LTER). At each of the 9 replicate stands we selected a total of 70 individual shrubs. During each of 7 sampling periods, 3 across the growing season of 1997 and 4 during 1998, we randomly selected 10 of 70 A. viridis spp. fruticosa at each replicate stand. We used acetylene reduction assays (ARA) to estimate rates of N2 fixation at each of the selected shrubs and concurrently measured soil temperature at each shrub. The attached database may be utilized to (1) elucidate seasonal trends in rates of N2 fixation by A. viridis spp. fruticosa across a boreal forest chronosequence and (2) investigate soil temperature controls over rates of N2 fixation. It may also be used to statistically analyze differences between years, successional stages and replicates within successional stage in both rates of ARA and temperature. We developed this database to describe seasonal trends of rates of nitrogen fixation by A. viridis spp. fruticosa across a boreal forest chronosequence and to elucidate soil temperature controls over rates.
Moss species and precipitation mediate experimental warming stimulation of growing season N2 fixation in subarctic tundra
<p>Climate change in high latitude regions leads to both higher temperatures and more precipitation but their combined effects on terrestrial ecosystem processes are poorly understood. In nitrogen (N) limited and often moss-dominated tundra and boreal ecosystems, moss-associated N<sub>2</sub> fixation is an important process that provides new N. We tested if high mean annual precipitation enhanced experimental warming effects on growing season N<sub>2</sub> fixation in three common arctic-boreal moss species adapted to different moisture conditions and evaluated their N contribution to the landscape level. We measured <em>in situ</em> N<sub>2</sub> fixation rates in <em>Hylocomium splendens</em>, <em>Pleurozium schreberi</em> and <em>Sphagnum</em> spp. from June to September in subarctic tundra in Sweden. We exposed mosses occurring along a natural precipitation gradient (mean annual precipitation: 571-1155 mm) to eight years of experimental summer warming using open-top chambers before our measurements. We modelled species-specific seasonal N input to the ecosystem at the colony and landscape level. Higher mean annual precipitation increased N<sub>2</sub> fixation, especially during peak growing seasons and in feather mosses. For <em>Sphagnum-</em>associated N<sub>2</sub> fixation,<em> </em>high mean annual<em> </em>precipitation reversed a small negative warming response. By contrast, in the dry-adapted feather moss species higher mean annual precipitation led to negative warming effects<em>.</em> Modelled total growing season N inputs for <em>Sphagnum </em>spp. colonies were 2-3 times that of feather mosses on an area basis. However, at the landscape level where feather mosses were more abundant, they contributed 50% more N than <em>Sphagnum</em>. The discrepancy between modelled estimates of species-specific N input via N<sub>2</sub> fixation at the moss core versus ecosystem scale exemplifies how moss cover is essential for evaluating the impact of altered N<sub>2</sub> fixation. Importantly, combined effects of warming and higher mean annual precipitation may not lead to similar responses across moss species, which could affect moss fitness and their abilities to buffer environmental changes. </p>
Moss species and precipitation mediate experimental warming stimulation of growing season N2 fixation in subarctic tundra
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Data from: Rising CO2 accelerates phosphorus and molybdenum limitation of N2-fixation in young tropical trees
Background and Aims: Nitrogen fixation may be critical for supplying the nitrogen (N) needed to maintain the tropical carbon sink in a world of rising atmospheric CO2. However, we do not know whether increased CO2 acts to exacerbate nutrient limitation on the fixation process itself. We experimentally test this idea by growing N2-fixing plants in pre-Industrial (280 ppm), present-day (400 ppm), and doubled (800 ppm) atmospheric CO2. Methods: In a greenhouse experiment, we grew tree seedlings from N2-fixing species and a non-fixing species at three CO2 concentrations with control, +P (phosphorus), +Mo (molybdenum), and +P+Mo nutrient treatments. Results: We found nutrient limitation to be minimal at pre-Industrial CO2, but with increasing CO2 fixer growth and fixation became increasingly limited by P and by a P-by-Mo interaction. At 400 ppm, plants with +P grew ~50% faster and fixed 10-15x more N2 based on nodule mass and nitrogenase activity. At 800 ppm, plants with +P+Mo grew 200% more, and fixed 25x more N2, suggesting Mo-P co-limitation at elevated CO2. Conclusion: Our findings imply that complex patterns of nutrient limitation can develop as CO2 rises, potentially suppressing tropical N2-fixation and new inputs of N needed to sustain the tropical carbon sink.
N2 fixation rates at Mer Bleue bog, Ontario, Canada
<p>This dataset contains bi-weekly measurements of N2 fixation rates and ancillary measurements at the Mer Bleue bog in Ontario, Canada. A detailed description of the dataset can be found in the accompanying publication Zivkovic et al. (Journal of Geophysical Research - Biogeosciences, in review).</p>
Data from: Rising CO2 accelerates phosphorus and molybdenum limitation of N2-fixation in young tropical trees
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N2 fixation and DDN transfer in coral reefs
<p>Dataset for the manuscript "An efficient transfer loop of diazotroph derived nitrogen in coral reefs"</p>
Divergent responses of symbiotic and asymbiotic N2 fixation to seawater additions
<p>Sea level rise-associated seawater intrusion exerts substantial impacts on the structure and function of coastal ecosystems. As nitrogen (N) availability is closely related to the structure and function of ecosystems, it is crucial to understand how seawater intrusion impacts biological N<sub>2</sub> fixation, a major pathway of new N input to natural ecosystems.</p> <p>Here, a seawater addition experiment with two N<sub>2</sub>-fixing plant species (<i>Acacia auriculiformis</i> and <i>Casuarina equisetifolia</i>) and ten non-N<sub>2</sub>-fixing plant species was conducted to simulate sea level rise-associated seawater intrusion. The experiment included control (0 mm seawater yr<sup>-1</sup>), low seawater addition (LSW, 200 mm seawater yr<sup>-1</sup>), and high seawater addition (HSW, 400 mm seawater yr<sup>-1</sup>). </p> <p>Symbiotic N<sub>2</sub> fixation (SNF) rate of <i>A. auriculiformis</i> was significantly higher under LSW (but not for HSW) than the control. For <i>C. equisetifolia</i>, SNF rates under LSW and HSW significantly increased by 8.0 and 19.5 times, respectively, compared with the control. In contrast, asymbiotic N<sub>2</sub> fixation rates under LSW and HSW significantly decreased by 18.5% and 30.4%, respectively, across all the plant species.</p> <p>Our findings suggest that the responses of biological N<sub>2</sub> fixation to seawater intrusion are divergent either among different N<sub>2</sub>-fixing plant species or between symbiotic and asymbiotic forms, which should be considered in terrestrial ecosystem models in order to improve the prediction of N dynamics under climate changes.</p>
Data from: Trophic cascades in the bryosphere: The impact of global change factors on top-down control of cyanobacterial N2-fixation
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Divergent responses of symbiotic and asymbiotic N2 fixation to seawater additions
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Heterotrophic N2-fixation contributes to nitrogen economy of a common wetland sedge, Schoenoplectus californicus
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Data from: A single evolutionary innovation drives the deep evolution of symbiotic N2-fixation in angiosperms
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RNA-Seq provides new insights into the nitrogen response of Azoarcus olearius BH72 during N2-fixation beyond the nitrogen fixation process
GEO Series GSE176473. Azoarcus olearius. 6 samples. Type: Expression profiling by high throughput sequencing.
Transcriptional cycle suited to daytime N2 fixation in the unicellular cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A)
GEO Series GSE100124. Candidatus Atelocyanobacterium thalassae. 12 samples. Type: Expression profiling by array.
Symbiotic moss-cyanobacteria associations as a novel source of biological N2-fixation in temperate grasslands
<p><span><span><span><span><span><span><span><span><span><span><span><b>Aims. </b>Terrestrial mosses contribute significantly to nitrogen budgets in boreal forests through symbiotic associations with N<sub>2</sub>-fixing cyanobacteria, but few studies have considered these interactions in temperate systems. We investigated how N<sub>2</sub>-fixation by moss-cyanobacterial associations contribute spatio-temporally to site-level N dynamics in a western North American prairie ecosystem.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Methods. </b>We first tested for the presence of N<sub>2</sub>-fixing cyanobacteria on six moss species using epi-fluorescence light microscopy. We then used an acetylene reduction assay to estimate monthly N<sub>2</sub>-fixation rates in moss-cyanobacteria associations across three prairies located in the Puget Sound, Washington State, USA. We evaluated temperature and precipitation effects on N<sub>2</sub>-fixation activity. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Results. </b>We confirmed the presence of N<sub>2</sub>-fixing cyanobacteria on three moss species (<i>Pleurozium schreberi </i>(Brid.) Mitt.<i>, Racomitrium elongatum </i>Frisvoll<i>, Rhytidiadelphus triquetrus </i>(Hedw) Warnst.) and found species, site and seasonal variation in N<sub>2</sub>-fixation rates. <i>Racomitrium elongatum</i> exhibited the highest N<sub>2</sub>-fixation rates, with peaks in April and August. We found that temperature and precipitation were strongly correlated with N<sub>2</sub>-fixation rates and likelihood of activity. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Conclusions. </b>Our results highlight a previously undescribed source of biological N<sub>2</sub>-fixation in temperate grasslands. Changes in the distribution and activity of these species due to climate change and management practices could impact stand-level nitrogen dynamics. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span> </span></span></span></span></span></span></span></span></span></span></span></p>
Symbiotic moss-cyanobacteria associations as a novel source of biological N2-fixation in temperate grasslands
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Data from: Effects of ultraviolet radiation on photosynthetic performance and N2 fixation in Trichodesmium erythraeum IMS 101
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Allen Brain Atlas
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