ORCID Profile
0000-0001-8589-1428
Current Organisation
Universität Hamburg
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Publisher: Authorea, Inc.
Date: 13-09-2023
Publisher: Wiley
Date: 13-09-2022
DOI: 10.1002/RCM.9370
Abstract: Stable isotope approaches are increasingly applied to better understand the cycling of inorganic nitrogen (N i ) forms, key limiting nutrients in terrestrial and aquatic ecosystems. A systematic comparison of the accuracy and precision of the most commonly used methods to analyze δ 15 N in NO 3 − and NH 4 + and interlaboratory comparison tests to evaluate the comparability of isotope results between laboratories are, however, still lacking. Here, we conducted an interlaboratory comparison involving 10 European laboratories to compare different methods and laboratory performance to measure δ 15 N in NO 3 − and NH 4 + . The approaches tested were (a) microdiffusion (MD), (b) chemical conversion (CM), which transforms N i to either N 2 O (CM‐N 2 O) or N 2 (CM‐N 2 ), and (c) the denitrifier (DN) methods. The study showed that standards in their single forms were reasonably replicated by the different methods and laboratories, with laboratories applying CM‐N 2 O performing superior for both NO 3 − and NH 4 + , followed by DN. Laboratories using MD significantly underestimated the “true” values due to incomplete recovery and also those using CM‐N 2 showed issues with isotope fractionation. Most methods and laboratories underestimated the at% 15 N of N i of labeled standards in their single forms, but relative errors were within maximal 6% deviation from the real value and therefore acceptable. The results showed further that MD is strongly biased by nonspecificity. The results of the environmental s les were generally highly variable, with standard deviations (SD) of up to ± 8.4‰ for NO 3 − and ± 32.9‰ for NH 4 + SDs within laboratories were found to be considerably lower (on average 3.1‰). The variability could not be connected to any single factor but next to errors due to blank contamination, isotope normalization, and fractionation, and also matrix effects and analytical errors have to be considered. The inconsistency among all methods and laboratories raises concern about reported δ 15 N values particularly from environmental s les.
Publisher: Springer Science and Business Media LLC
Date: 07-12-2021
DOI: 10.1038/S41467-021-27386-2
Abstract: In contrast to the well-recognized permafrost carbon (C) feedback to climate change, the fate of permafrost nitrogen (N) after thaw is poorly understood. According to mounting evidence, part of the N liberated from permafrost may be released to the atmosphere as the strong greenhouse gas (GHG) nitrous oxide (N 2 O). Here, we report post-thaw N 2 O release from late Pleistocene permafrost deposits called Yedoma, which store a substantial part of permafrost C and N and are highly vulnerable to thaw. While freshly thawed, unvegetated Yedoma in disturbed areas emit little N 2 O, emissions increase within few years after stabilization, drying and revegetation with grasses to high rates (548 (133–6286) μg N m −2 day −1 median with (range)), exceeding by 1–2 orders of magnitude the typical rates from permafrost-affected soils. Using targeted metagenomics of key N cycling genes, we link the increase in in situ N 2 O emissions with structural changes of the microbial community responsible for N cycling. Our results highlight the importance of extra N availability from thawing Yedoma permafrost, causing a positive climate feedback from the Arctic in the form of N 2 O emissions.
Publisher: Authorea, Inc.
Date: 11-09-2023
Publisher: American Geophysical Union (AGU)
Date: 04-2023
DOI: 10.1029/2022JG007322
Abstract: The greenhouse gas (GHG) balance of boreal peatlands in permafrost regions will be affected by climate change through disturbances such as permafrost thaw and wildfire. Although the future GHG balance of boreal peatlands including ponds is dominated by the exchange of both carbon dioxide (CO 2 ) and methane (CH 4 ), disturbance impacts on fluxes of the potent GHG nitrous oxide (N 2 O) could contribute to shifts in the net radiative balance. Here, we measured monthly (April to October) fluxes of N 2 O, CH 4 , and CO 2 from three sites located across the sporadic and discontinuous permafrost zones of western Canada. Undisturbed permafrost peat plateaus acted as N 2 O sinks (−0.025 mg N 2 O m −2 d −1 ), but N 2 O uptake was lower from burned plateaus (−0.003 mg N 2 O m −2 d −1 ) and higher following permafrost thaw in the thermokarst bogs (−0.054 mg N 2 O m −2 d −1 ). The thermokarst bogs had below‐ambient N 2 O soil gas concentrations, suggesting that denitrification consumed atmospheric N 2 O during reduction to dinitrogen. Atmospheric uptake of N 2 O in peat plateaus and thermokarst bogs increased with soil temperature and soil moisture, suggesting sensitivity of N 2 O consumption to further climate change. Four of five peatland ponds acted as N 2 O sinks (−0.018 mg N 2 O m −2 d −1 ), with no influence of thermokarst expansion. One pond with high nitrate concentrations had high N 2 O emissions (0.30 mg N 2 O m −2 d −1 ). Overall, our study suggests that the future net radiative balance of boreal peatlands will be dominated by impacts of wildfire and permafrost thaw on CH 4 and CO 2 fluxes, while the influence from N 2 O is minor.
Publisher: Springer Science and Business Media LLC
Date: 23-07-2020
DOI: 10.1007/S11104-020-04638-6
Abstract: Environmental factors controlling nitrous oxide (N 2 O) uptake in forest soils are poorly known, and the atmospheric impact of the forest N 2 O sink is not well constrained compared to that of methane (CH 4 ). We compared nitrous oxide (N 2 O) and CH 4 fluxes over two growing seasons in boreal forest soils located in Eastern Finland. Within a spruce forest, we compared plots with long-term nitrogen (N) fertilization history and non-fertilized plots, and additionally pine forest plots without a fertilization history. The flux data was complemented with measurements of climatic conditions and soil physical and chemical characteristics, in order to identify factors affecting N 2 O and CH 4 fluxes. Non-fertilized spruce forest soils showed the highest cumulative N 2 O uptake among the sites, whereas the pine forest site displayed low cumulative N 2 O emission. Nitrous oxide uptake was favored by high soil silt and water content. The low temperature seasons, spring and autumn, had the highest N 2 O uptake, likely associated with high soil water content typical for these seasons. In the spruce forest the N 2 O uptake was seasonally decoupled from the CH 4 uptake. Applying the Global Warming Potential (GWP) approach, the cooling effect of N 2 O uptake in the spruce forest was on average 35% of that of CH 4 uptake showing that N 2 O uptake should be considered when evaluating the atmospheric impact of boreal forests.
No related grants have been discovered for Carolina Voigt.