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openOpenDec 2015View details →

13C and 15N Content in Arctic Tussock Tundra and Wet Sedge Vegetation

This file contains 13C and 15N content from tussock tundra and wet sedge vegetation collected from experiemental plots during the years 2001-2006.

openOpenFeb 2021View details →

Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating Research (CiPEHR): leaf C, N, delta-13C, delta-15N at peak biomass; 2009-2019

The Carbon in Permafrost Experimental Heating Research (CiPEHR) project addresses the following questions: 1) Does ecosystem warming cause a net release of C from the ecosystem to the atmosphere?, 2) Does the decomposition of old C, that comprises the bulk of the soil C pool, influence ecosystem C loss?, and 3) How do winter and summer warming alone, and in combination, affect ecosystem C exchange? We are answering these questions using a combination of field and laboratory experiments to measure ecosystem carbon balance and radiocarbon isotope ratios at a warming experiment located in an upland tundra field site near Healy, Alaska in the foothills of the Alaska Range. This data set includes carbon (C) and nitrogen (N) elemental and isotope content in leaves collected from winter warming, summer warming, and control treatment plots at CiPEHR.

openOpenMay 2017View details →

Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating Research (CiPEHR): C, N, delta-13C, delta-15N from senescent leaves, 2009-2015.

openOpenAug 2018View details →

Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating Research (CiPEHR): leaf SLA, C, N, P, Ca, delta-13C, delta-15N at peak biomass, 2017

openOpenAug 2018View details →

Eight Mile Lake Research Watershed, Thaw Gradient: leaf SLA, C, N, P, Ca, Mg, delta-13C, delta-15N at peak biomass, 2017

In this larger study, we are asking the question: Is old carbon that comprises the bulk of the soil organic matter pool released in response to thawing of permafrost? We are answering this question by using a combination of field and laboratory experiments to measure radiocarbon isotope ratios in soil organic matter, soil respiration, and dissolved organic carbon, in tundra ecosystems. The objective of these proposed measurements is to develop a mechanistic understanding of the SOM sources contributing to C losses following permafrost thawing. We are making these measurements at an established tundra field site near Healy, Alaska in the foothills of the Alaska Range. Field measurements center on a natural experiment where permafrost has been observed to warm and thaw over the past several decades. This area represents a gradient of sites each with a different degree of change due to permafrost thawing. As such, this area is unique for addressing questions at the time and spatial scales relevant for change in arctic ecosystems.

opencc-zeroOct 2023View details →

Contrasting effects of indigenous arbuscular mycorrhizal fungi on nitrogen absorption of C3 and C4 grasses: Evidence from microcosm and 15N labeling experiments

Background and aims Nitrogen (N) captured by arbuscular mycorrhizal (AM) symbiosis is a major pathway in the N uptake of host plants. However, the relative contribution of arbuscular mycorrhizal fungi (AMF) to N uptake in different plant functional types has not been well assessed. Methods Two dominant plant species in semiarid steppe ecosystems on the Mongolian plateau, i.e. Leymus chinensis (C3 grass) and Cleistogenes squarrosa (C4 grass), were selected in this study. We conducted a greenhouse manipulation experiment using novel microcosms combined with 15N labeling techniques and investigated the effect of indigenous AMF on plant growth and quantified their relative contribution to N uptake under high and low levels of available soil N. Results Indigenous AMF contribute more to N uptake in C3 grass than that in C4 grass, and mycorrhizal partners act as parasites for C4 plant growth. For L. chinensis, indigenous AM symbiosis suppressed plant growth under low soil N but improved plant growth under high soil N conditions. AMF contributed to c. 23% and 20% of the total plant N uptake under low and high soil N conditions, respectively. For C. squarrosa, indigenous AM symbiosis consistently inhibited plant growth under both low and high soil N conditions, and the percent contributions of AMF to N uptake were only c. 9% and 7%, respectively. Conclusions Our results demonstrate that indigenous AM symbiosis plays a vital role in N uptake by host plants, even in the absence of a positive growth response. AMF can modify the fitness of C3 and C4 grasses and thereby alter plant community composition and ecosystem N cycling, particularly under high N conditions. Our study has important implications for improving global N cycling models in the face of increasing global N deposition.

opencc-zeroJun 2022View details →

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N,13C) study

Salt marshes exist along the gradient of the marine mudflat to the terrestrial dunes, with a gradient of shore height and associated plant zonation. The lower salt marsh (LSM) extends from the mean high tidal level to 35 cm above that level and is followed by the upper salt marsh (USM). Despite changes in the amount of allochthonous marine input and in abiotic conditions, little is known about changes in the trophic structure and used of basal resources by the soil macrofauna along marine – terrestrial boundaries. Natural variations in carbon stable isotope ratios (δ¹³C signatures) allow insight into basal resources of consumers such as marine algae, terrestrial C3 and C4 photosynthesising plants. Furthermore, variations in nitrogen stable isotope ratios (δ¹5N signatures) allow insight into the trophic position of consumers. We investigated spatial and temporal changes in stable isotope signatures in salt marsh soil macrofauna of the island of Spiekeroog, German Wadden Sea. The range of δ¹⁵N signatures indicated no changes in food chain length across salt marsh zones with consumers in both zones comprising primary decomposer, secondary decomposer and first order predators. However, the trophic position of individual species changed between zones, but in particular with season. Contrasting δ¹⁵N signatures, the range in δ¹³C signatures in the LSM was twice that in the USM indicating a wider range of resources consumed. Bayesian mixing models indicated predominant autochthonous resource use in both the LSM and USM, with the use of marine allochthonous resources never exceeding 29.6%. However, the models also indicate an increase in the use of marine resources in certain species in the LSM with no use in the USM. Overall, the results indicate that the resource use of salt marsh macrofauna varies more in space than in time, with the food web being generally based on autochthonous rather than allochthonous resources. However, there also is trophic plasticity in certain species across both temporal and spatial scales including variations in the use of allochthonous resources. Generally, however, marine input contributes little to the nutrition of salt marsh soil macroinvertebrates.

opencc-by-4.0Dec 2020View details →

Delta-15N values for leaf and soil samples from a mesocosm experiment looking at dung beetle presence and the movement of dung-derived nitrogen (DDN)

Description: We deployed 18 mesocosms into each of the ecosystem types (logged forest and oil palm) in mid-May 2016, to give the soil one month to recover from the disturbance. We constructed mesocosms from black plastic containers, 40 cm diameter and 25 cm high after removing the base. We dug mesocosms 20 cm into the ground leaving 5cm above the surface. We arranged them in a 6 x 3 grid with a minimum of 3 m between each mesocosm to minimise interaction between the soil nutrient cycling in each mesocosm. As proximity of the seedlings to mature trees may increase competition for nitrogen and other nutrients we recorded the distance of each mesocosm to the nearest mature tree (any species with diameter at breast height > 30 cm) for inclusion in our analyses. We randomly selected 12 of the mesocosms, to receive 15N-labelled dung patties weighing 300 ± SD 2.27 g in logged forest and 410 ± SD 2.04 g in oil palm. We populated six randomly selected mesocoms from within those 12 treated with dung with a standardised dung beetle communities (Fig. 1, Table S2). The remaining six mesocosms were left as soil only controls. We covered each mesocosm with a fine nylon mesh secured with a rubber belt to prevent beetles leaving or colonising the mesocosms, and to standardise any microclimatic effects between treatments. However, after 48 hours we opened the dung beetle treatments for a 24 hours period to allow the beetles to emigrate rather than forcing them to artificially stay in the same pat (cf. Roslin 2000; Slade et al. 2017), and then re-covered the mesocosms with netting. We sampled soil seven times from logged forest over the course of the experiment. Any remaining surface dung was removed prior to soil sampling, and replaced thereafter, in order to reduce the possibility of contamination. If a soil core was unsuccessful (most likely due to beetle channels) a second core was taken directly beside. On each sample day, a core of 10cm depth was taken and split into vertical horizons 0- 2cm, 2-5 cm and 5-10cm. We sampled leaves eight times over the eight-month duration of the experiment, with high frequency during the first month, aimed to capture the initial assimilation of DDN into the plants. We collected one leaf from the Dipterocarpaceae or palm seedlings for each sample event. For dipterocarp seedlings we alternated collection of the terminal leaf from top and bottom (leaving the topmost, newest leaf) between consecutive sample days, and for palm seedlings we sampled the two penultimate leaflets from alternating sides of the mid-stem, from the youngest fully formed frond. As assimilated 15N did not plateau in logged forest during the 8-month timeframe of the experiment, we took a sample after 21 months in order to determine whether all DDN had been turned over in the plant biomass after this time. The leaf and soil samples were dried at 60°C for a minimum of 48 hours. We then ground samples to a fine powder using a ball mill (Retsch UK Ltd., Hope, UK). We weighed ground samples into 6 x 4 mm ultraclean tin capsules (Elemental Microanalysis Ltd., Okehampton, UK) using an ultra-microbalance with readability 1 μg (Mettler-Toledo, Greifensee, Switzerland) to provide sufficient elemental carbon and nitrogen for analysis by continuous flow isotope ratio mass spectrometry (SERCON, Crewe, UK). Isotope ratios are expressed in per mil (‰) relative to international reference standards (Rstandard), which are Atmospheric Nitrogen and Vienna PeeDee Belemnite (VPDB) for nitrogen and carbon, respectively. The delta value describes the isotopic composition of each sample, which signifies a measurement of difference relative to laboratory standards. The calculation of δ values is given by: δHX = [(RSAMPLE /RSTANDARD −1)]*1000Project: This dataset was collected as part of the following SAFE research project: <a href="https://www.safeproject.net/projects/project_view/11">Using stable isotopes to link biogeochemical processes to biodiversity of conservation concern</a>Funding: These data were collected as part of research funded by: <ul><li>NERC (Research grant, NE/K016148/1)</li></ul>This dataset is released under the CC-BY 4.0 licence, requiring that you cite the dataset in any outputs, but has the additional condition that you acknowledge the contribution of these funders in any outputs.Permits: These data were collected under permit from the following authorities:<ul><li>Sabah Biodiversity Centre (SABC) (Research licence JKM/MBS.1000-2/2 (374) )</li><li>Sabah Biodiversity Centre (SABC) (Research licence JKM/MBS.1000-2/2 JLD.4 (41))</li><li>Sabah Biodiversity Centre (SABC) (Research licence JKM.1000-2/2 JLD.5 (153))</li></ul>XML metadata: GEMINI compliant metadata for this dataset is available <a href="https://www.safeproject.net/datasets/xml_metadata?id=5113431">here</a>Files: This consists of 1 file: 3_Kemp_15N_mesocosms_data.xlsx3_Kemp_15N_mesocosms_data.xlsxThis file contains dataset metadata and 3 data tables:<ol><li>OP leaf (described in worksheet OP_leaf)Description: Details the δ15N of leaves sampled in oil palm from palm seedlings across eight sample days up to day 233. Number of fields: 13Number of data rows: 144Fields: <ul><li>Name: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)</li><li>Day: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)</li><li>Day2: Experimental day as a factor (Field type: id)</li><li>Mesocosm: Unique identifier for each of the 18 mesocosms (Field type: id)</li><li>Treatment: Treatment assignment (Field type: categorical)</li><li>DistMature: Distance from the nearest mature tree (any species with diameter at breast height > 30 cm). (Field type: numeric)</li><li>Weight: Sample weight (Field type: numeric)</li><li>Beam.Area.N: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)</li><li>ugN: Measure of the elemental nitrogen content of the sample (Field type: numeric)</li><li>d15N: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)</li><li>Beam.Area.C: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)</li><li>ugC: Measure of the elemental carbon content of the sample (Field type: numeric)</li><li>d13C: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)</li></ul></li><li>LFE leaf (described in worksheet LFE_leaf)Description: Details the δ15N of leaves sampled in logged forest, taken from dipterocarp seedlings across nine sample days, up to day 625.Number of fields: 13Number of data rows: 147Fields: <ul><li>Name: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)</li><li>Day: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)</li><li>Day2: Experimental day as a factor (Field type: id)</li><li>Mesocosm: Unique identifier for each of the 18 mesocosms (Field type: id)</li><li>Treatment: Treatment assignment (Field type: categorical)</li><li>DistMature: Distance from the nearest mature tree (any species with diameter at breast height > 30 cm). (Field type: numeric)</li><li>Weight: Sample weight (Field type: numeric)</li><li>Beam.Area.N: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)</li><li>ugN: Measure of the elemental nitrogen content of the sample (Field type: numeric)</li><li>d15N: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)</li><li>Beam.Area.C: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)</li><li>ugC: Measure of the elemental carbon content of the sample (Field type: numeric)</li><li>d13C: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)</li></ul></li><li>LFE soil (described in worksheet LFE_soil)Description: Details the δ15N of soil sampled in logged forest across seven sample days up to day 64Number of fields: 14Number of data rows: 375Fields: <ul><li>Name: Code for date (ddmm), mesocosms ID and depth (00 = surface; 02 = 2 cm belowground; 05 = 5 cm belowground, and 10 = 10 cm belowground) (Field type: id)</li><li>Day: Experimental day as the number of days since day zero (defined by the planting of the seedlings, either dipterocarps or palms) (Field type: id)</li><li>day2: Experimental day as a factor (Field type: id)</li><li>Mesocosm: Unique identifier for each of the 18 mesocosms (Field type: id)</li><li>Treatment: Treatment assignment (Field type: categorical)</li><li>DistMature: Distance from the nearest mature tree (any species with diameter at breast height > 30 cm). (Field type: numeric)</li><li>Depth: The depth which the soil sample was taken from, i.e. 0002 is the horizon between the ground surface and 2 cm belowground (Field type: numeric)</li><li>Weight: Sample weight (Field type: numeric)</li><li>Beam.Area.N: Measure of the nitrogen peak i.e. calculated as the area under the nitrogen curve by Calisto software. This value is directly related to N_weight. (Field type: numeric)</li><li>ugN: Measure of the elemental nitrogen content of the sample (Field type: numeric)</li><li>d15N: the delta value of the sample, which describes the ration of 15N: 14N isotopes (Field type: numeric)</li><li>Beam.Area.C: Measure of the carbon peak i.e. calculated as the area under the carbon curve by Calisto software. This value is directly related to C_weight (Field type: numeric)</li><li>ugC: Measure of the elemental carbon content of the sample (Field type: numeric)</li><li>d13C: the delta value of the sample, which describes the ration of 13C: 12C isotopes (Field type: numeric)</li></ul></li></ol>Date range: 2016-05-01 to 2017-02-01Latitudinal extent: 4.5000 to 5.0700Longitudinal extent: 116.7500 to 117.8200

opencc-by-4.0Jan 2020View details →

Hyperpolarized [15N]nitrate as a potential long lived hyperpolarized contrast agent for MRI

Primary data for DOI: <a href="https://doi.org/10.1016/j.jmr.2019.01.001">10.1016/j.jmr.2019.01.001</a> Title: Hyperpolarized [15N]nitrate as a potential long lived hyperpolarized contrast agent for MRI Authors: Ayelet Gamliel, Sivaranjan Uppala, Gal Sapir, Talia Harris, Atara Nardi-Schreiber, David Shaul, Jacob Sosna, J. Moshe Gomori, Rachel Katz-Brull Description: The primary datasets in this archive contain data presented in the above publication and consist of 15N-NMR spectra in solutions. Please consult the Archive Guide.

opencc-by-4.0May 2023View details →

Gradients 4 - TN397 - 15N and 13C

Standard protocols were used to measure in vitro primary productivity via the 13C radiotracer method [Lengendre et al., 1996] and N2-fixation rate measurements via 15N2 isotopic gas method described by Montoya et al., 1996. Briefly, water samples were collected before dawn in ~4.3L polycarbonate bottles, a total of 4ml of enriched 15N2 gas was added via syringe. Bottles were then injected with 1 ml of 47mM 13C bicarbonate stock and gently mixed by inversion.  Bottles were incubated either on deck in incubators screened to 48% of surface irradiance and plumbed with flow through surface seawater for temperature regulation or on drifting arrays that allowed for incubations to happen at original light levels. All bottles were incubated for ~ 24hr. Time zero bottles were also collected and sacrificed for each station/depth. Following dawn to dawn incubations, each sample was filtered onto a combusted 25mm glass fiber filter, filters were folded in half and placed in combusted aluminum foil and stored at -20°C for later analysis. Post-cruise, all filters were thawed and dried overnight at 60°C. Samples were then balled into Sn boats and plated for analysis. The carbon and nitrogen isotopic composition (13C and 15N, respectively) were analyzed by continuous-flow isotope ratio mass spectrometry by the Biogeochemical Stable Isotope Facility at University of Hawaii (https://www.soest.hawaii.edu/GG/isotope_biogeochem/index_files/Page532.htm). Time stamp is in UTC.

opencc-zeroSep 2023View details →

Data for: Tree-ring 15N isotope of red alder

Nitrogen (N) accretion rates under N2-fixing tree species can vary with site condition and possibly decline over time with down-regulation of N fixation. Tree-ring δ15N may depict these site-specific, long-term patterns in N dynamics, but field trials with N2-fixing tree species are lacking. We examined whether tree-ring δ15N of N2-fixing red alder (Alnus rubra) would mirror N accretion rates and δ15N of soils. We sampled a 27-year-old replacement series trial on southeastern Vancouver Island with red alder and coastal Douglas-fir (Pseudotsuga menziesii) in five proportions (0/100, 11/89, 25/75, 50/50, and 100/0, respectively). An escalation in forest floor N content was evident with an increasing proportion of red alder, equivalent to a difference of approximately 750 kg N ha-1 between 100% Douglas-fir vs. 100% alder. The forest floor horizon was also enriched in δ15N under denser red alder treatments. Red alder had a consistent quadratic fit in tree-ring δ15N over time, with a net increase of 1.5‰, on average, before declining slightly. Douglas-fir tree-ring δ15N, in contrast, was largely unchanged over time (in 3 of 4 plots) but significantly enriched in the 50/50 mix. The minor differences in current litter N content and leaf δ15N between alder and Douglas-fir suggests the declining trend in alder tree-ring δ15N could coincide with lower N-fixation rates, either by down-regulation via nitrate availability or loss in alder vigour with shading and drought. We suggest tree-ring δ15N can provide insights into the abiotic constraints and facultative/obligate nature of N fixation for N2-fixing trees.

opencc-by-4.0Sep 2023View details →

Magic Angle Spinning Effects on Longitudinal NMR Relaxation: 15N in L-Histidine

Experimental datasets for the publication entitled: Magic Angle Spinning Effects on Longitudinal NMR Relaxation: 15N in L-Histidine