ORCID Profile
0000-0002-7413-3354
Current Organisations
University of Eastern Finland
,
University of Vienna
,
University of Innsbruck
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Publisher: American Geophysical Union (AGU)
Date: 11-2020
DOI: 10.1029/2020GB006678
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: Wiley
Date: 03-11-2022
DOI: 10.1111/GCB.15951
Abstract: Mountain birch forests (Betula pubescens Ehrh. ssp. czerepanovii) at the subarctic treeline not only benefit from global warming, but are also increasingly affected by caterpillar outbreaks from foliage-feeding geometrid moths. Both of these factors have unknown consequences on soil organic carbon (SOC) stocks and biogeochemical cycles. We measured SOC stocks down to the bedrock under living trees and under two stages of dead trees (12 and 55 years since moth outbreak) and treeless tundra in northern Finland. We also measured in-situ soil respiration, potential SOC decomposability, biological (enzyme activities and microbial biomass), and chemical (N, mineral N, and pH) soil properties. SOC stocks were significantly higher under living trees (4.1 ± 2.1 kg m²) than in the treeless tundra (2.4 ± 0.6 kg m²), and remained at an elevated level even 12 (3.7 ± 1.7 kg m²) and 55 years (4.9 ± 3.0 kg m²) after tree death. Effects of tree status on SOC stocks decreased with increasing distance from the tree and with increasing depth, that is, a significant effect of tree status was found in the organic layer, but not in mineral soil. Soil under living trees was characterized by higher mineral N contents, microbial biomass, microbial activity, and soil respiration compared with the treeless tundra soils under dead trees were intermediate between these two. The results suggest accelerated organic matter turnover under living trees but a positive net effect on SOC stocks. Slowed organic matter turnover and continuous supply of deadwood may explain why SOC stocks remained elevated under dead trees, despite the heavy decrease in aboveground C stocks. We conclude that the increased occurrence of moth damage with climate change would have minor effects on SOC stocks, but ultimately decrease ecosystem C stocks (49% within 55 years in this area), if the mountain birch forests will not be able to recover from the outbreaks.
Publisher: Springer Science and Business Media LLC
Date: 03-2021
DOI: 10.1038/S43247-021-00121-X
Abstract: Remediation of nitrate pollution of Earth’s rivers and aquifers is h ered by cumulative biogeochemical processes and nitrogen sources. Isotopes ( δ 15 N, δ 18 O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO 3 − ). We synthesized nitrate isotope data ( n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO 3 − (0.3 ± 0.2 mg L −1 , n = 2902) compared to aquifers (5.5 ± 5.1 mg L −1 , n = 2291) and slightly lower δ 15 N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ 18 O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO 3 − was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ 15 N and δ 18 O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies.
No related grants have been discovered for Christina Biasi.