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Tan Y, Chen Z, Liu W, Yang M, Du Z, Wang Y, Bol R, Wu D. Grazing exclusion alters denitrification N 2O/(N 2O + N 2) ratio in alpine meadow of Qinghai-Tibet Plateau. Sci Total Environ 2024; 912:169358. [PMID: 38135064 DOI: 10.1016/j.scitotenv.2023.169358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/06/2023] [Accepted: 12/11/2023] [Indexed: 12/24/2023]
Abstract
Grazing exclusion has been implemented worldwide as a nature-based solution for restoring degraded grassland ecosystems that arise from overgrazing. However, the effect of grazing exclusion on soil nitrogen cycle processes, subsequent greenhouse gas emissions and underlying mechanisms remain unclear. Here, we investigated the effect of four-year grazing exclusion on plant communities, soil properties, and soil nitrogen cycle-related functional gene abundance in an alpine meadow on the Qinghai-Tibet Plateau. Using an automated continuous-flow incubation system, we performed an incubation experiment and measured soil-borne N2O, N2, and CO2 fluxes to three successive "hot moment" events (precipitation, N deposition, and oxic-to-anoxic transition) between grazing-excluded and grazing soil. Higher soil N contents (total nitrogen, NH4+, NO3-) and extracellular enzyme activities (β-1,4-glucosidase, β-1,4-N-acetyl-glucosaminidase, cellobiohydrolase) are observed under grazing exclusion. The aboveground and litter biomass of plant community was significantly increased by grazing exclusion, but grazing exclusion decreased the average number of plant species and microbial diversity. The N2O + N2 fluxes observed under grazing exclusion were higher than those observed under free grazing. The N2 emissions and N2O/(N2O + N2) ratios observed under grazing exclusion were higher than those observed under free grazing in oxic conditions. Instead, higher N2O fluxes and lower denitrification functional gene abundances (nirS, nirK, nosZ, and nirK + nirS) under anoxia were found under grazing exclusion than under free grazing. The N2O site-preference value indicates that under grazing exclusion, bacterial denitrification contributes more to higher N2O production compared with under free grazing (81.6 % vs. 59.9 %). We conclude that grazing exclusion could improve soil fertility and plant biomass, nevertheless it may lower plant and microbial diversity and increase potential N2O emission risk via the alteration of the denitrification end-product ratio. This indicates that not all grassland management options result in a mutually beneficial situation among wider environmental goals such as greenhouse gas mitigation, biodiversity, and social welfare.
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Affiliation(s)
- Yuechen Tan
- Beijing Key Laboratory of Wetland Services and Restoration, Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China
| | - Zhu Chen
- College of Agriculture, Guizhou University, Guiyang 550025, China
| | - Weiwei Liu
- Beijing Key Laboratory of Wetland Services and Restoration, Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China
| | - Mengying Yang
- Guangzhou Research Institute of Environment Protection Co., Ltd., Guangzhou 510620, China
| | - Zhangliu Du
- Beijing Key Laboratory of Biodiversity and Organic Farming, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
| | - Yifei Wang
- Beijing Key Laboratory of Wetland Services and Restoration, Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China.
| | - Roland Bol
- Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; School of Natural Sciences, Environment Centre Wales, Bangor University, Bangor LL57 2UW, UK
| | - Di Wu
- Beijing Key Laboratory of Biodiversity and Organic Farming, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
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Kim T, Lee J, Hong SB, Park HJ, Lim JS. Dual isotope ratio normalization of nitrous oxide by bacterial denitrification of USGS reference materials. Talanta 2020; 219:121268. [PMID: 32887158 DOI: 10.1016/j.talanta.2020.121268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/08/2020] [Accepted: 06/09/2020] [Indexed: 10/24/2022]
Abstract
We measured the δ values of N2O using gas chromatography isotope ratio mass spectrometry with a preconcentrator (precon-GC-IRMS). The instrumental precision of the mass spectrometer was restricted to below the shot noise limit, which agreed with the theoretical and experimental results of 0.02‰ (δ15N) and 0.04‰ (δ18O), respectively. The precision of the measured δ values was significantly improved by the temperature regulation protocol of the LN2 preconcentrator, which was monitored by various temperature sensors placed along the U-trap. The reproducibility of the He-diluted N2O gas measurements resulted in 0.063‰ (δ15N) and 0.075‰ (δ18O) due to additional sources of uncertainty in the vials used for autosampling and in the general preconcentration process. Multipoint normalization of the dual δ values of the measured N2O samples was conducted using United States Geological Survey reference materials denitrified by Pseudomonas aureofaciens. Kaiser's ion correction method, based on International Atomic Energy Agency parameters, exhibited low bias for the atomic isotope ratio reduction of the nitrate reference material, for which the oxygen anomaly was considerably high. Dedicated corrections for net isotope fractionation and water exchange were important in improving uncertainties in the procedure for normalizing the oxygen isotope ratio. Blank measurements for correcting biases in isotope ratios caused by pre-dissolved nitrate and nitrite ions in the water solvent led to further improvements, i.e. beyond unevenly controlled net isotope fractionation, throughout the bacterial denitrification process. The uncertainty evaluation revealed that three-point normalization can significantly improve the normalization accuracy compared with two-point normalization. In addition, an alternative strategy was suggested for assigning δ18O using a CO2 lab tank, allowing its use as a reference material for N2O gas tanks.
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Affiliation(s)
- Taewan Kim
- Safety Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Gajeong-ro 267, Yuseong-gu, Daejeon, 34113, Republic of Korea; Science of Measurement, University of Science and Technology (UST), Gajeong-ro 217, Yuseong-gu, Daejeon, 34113, Republic of Korea
| | - Jeongsoon Lee
- Safety Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Gajeong-ro 267, Yuseong-gu, Daejeon, 34113, Republic of Korea; Science of Measurement, University of Science and Technology (UST), Gajeong-ro 217, Yuseong-gu, Daejeon, 34113, Republic of Korea
| | - Sang-Bum Hong
- Korea Polar Research Institute (KOPRI), 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - Ha Ju Park
- Korea Polar Research Institute (KOPRI), 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - Jeong Sik Lim
- Safety Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Gajeong-ro 267, Yuseong-gu, Daejeon, 34113, Republic of Korea; Science of Measurement, University of Science and Technology (UST), Gajeong-ro 217, Yuseong-gu, Daejeon, 34113, Republic of Korea.
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Zhang L, Trncik C, Andrade SLA, Einsle O. The flavinyl transferase ApbE of Pseudomonas stutzeri matures the NosR protein required for nitrous oxide reduction. Biochim Biophys Acta Bioenerg 2016; 1858:95-102. [PMID: 27864152 DOI: 10.1016/j.bbabio.2016.11.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 12/15/2022]
Abstract
The copper-containing enzyme nitrous oxide reductase (N2OR) catalyzes the transformation of nitrous oxide (N2O) to dinitrogen (N2) in microbial denitrification. Several accessory factors are essential for assembling the two copper sites CuA and CuZ, and for maintaining the activity. In particular, the deletion of either the transmembrane iron-sulfur flavoprotein NosR or the periplasmic protein NosX, a member of the ApbE family, abolishes N2O respiration. Here we demonstrate through biochemical and structural studies that the ApbE protein from Pseudomonas stutzeri, where the nosX gene is absent, is a monomeric FAD-binding protein that can serve as the flavin donor for NosR maturation via covalent flavinylation of a threonine residue. The flavin transfer reaction proceeds both in vivo and in vitro to generate post-translationally modified NosR with covalently bound FMN. Only FAD can act as substrate and the reaction requires a divalent cation, preferably Mg2+ that was also present in the crystal structure. In addition, the reaction is species-specific to a certain extent.
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Affiliation(s)
- Lin Zhang
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany
| | - Christian Trncik
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany
| | - Susana L A Andrade
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany
| | - Oliver Einsle
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany.
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