[1]

Stevens CJ. 2019. Nitrogen in the environment. Science 363:578−580

doi: 10.1126/science.aav8215
[2]

Galloway JN, Dentener FJ, Capone DG, Boyer EW, Howarth RW, et al. 2004. Nitrogen cycles: past, present, and future. Biogeochemistry 70:153−226

doi: 10.1007/s10533-004-0370-0
[3]

Galloway JN, Townsend AR, Erisman JW, Bekunda M, Cai Z, et al. 2008. Transformation of the nitrogen cycle: recent trends, questions, and potential solutions. Science 320:889−892

doi: 10.1126/science.1136674
[4]

Liu X, Zhang Y, Han W, Tan A, Shen J, et al. 2013. Enhanced nitrogen deposition over China. Nature 494:459−462

doi: 10.1038/nature11917
[5]

Richardson K, Steffen W, Lucht W, Bendtsen J, Cornell SE, et al. 2023. Earth beyond six of nine planetary boundaries. Science Advances 9:eadh2458

doi: 10.1126/sciadv.adh2458
[6]

Chen ZL, Song W, Hu CC, Liu XJ, Chen GY, et al. 2022. Significant contributions of combustion-related sources to ammonia emissions. Nature Communications 13:7710

doi: 10.1038/s41467-022-35381-4
[7]

Song W, Liu XY, Hu CC, Chen GY, Liu XJ, et al. 2021. Important contributions of non-fossil fuel nitrogen oxides emissions. Nature Communications 12:243

doi: 10.1038/s41467-020-20356-0
[8]

Liu XY, Koba K, Koyama LA, Hobbie SE, Weiss MS, et al. 2018. Nitrate is an important nitrogen source for arctic tundra plants. Proceedings of the National Academy of Sciences of the United States of America 115:3398−3403

doi: 10.1073/pnas.1715382115
[9]

Hu CC, Liu XY, Driscoll AW, Kuang YW, Jack Brookshire EN, et al. 2024. Global distribution and drivers of relative contributions among soil nitrogen sources to terrestrial plants. Nature Communications 15:6407

doi: 10.1038/s41467-024-50674-6
[10]

Denk TRA, Mohn J, Decock C, Lewicka-Szczebak D, Harris E, et al. 2017. The nitrogen cycle: a review of isotope effects and isotope modeling approaches. Soil Biology and Biochemistry 105:121−137

doi: 10.1016/j.soilbio.2016.11.015
[11]

Wang YL, Song W, Yang W, Sun XC, Tong YD, et al. 2019. Influences of atmospheric pollution on the contributions of major oxidation pathways to PM2.5 nitrate formation in Beijing. Journal of Geophysical Research-Atmospheres 124:4174−4185

doi: 10.1029/2019JD030284
[12]

Shi G, Li C, Li Y, Chen Z, Ding M, et al. 2022. Isotopic constraints on sources, production, and phase partitioning for nitrate in the atmosphere and snowfall in coastal East Antarctica. Earth and Planetary Science Letters 578:117300

doi: 10.1016/j.jpgl.2021.117300
[13]

Zhang YL, Zhang W, Fan MY, Li J, Fang H, et al. 2022. A diurnal story of Δ17O(NO3−) in urban Nanjing and its implication for nitrate aerosol formation. NPJ Climate and Atmospheric Science 5:50

doi: 10.1038/s41612-022-00273-3
[14]

Zhang Z, Jiang Z, Zhou T, Geng L. 2024. Reconciling modeled and observed Δ17O (NO3−) in Beijing winter haze with heterogeneous chlorine chemistry. Journal of Geophysical Research: Atmospheres 129:e2023JD039740

doi: 10.1029/2023JD039740
[15]

Thiemens MH. 1999. Mass-independent isotope effects in planetary atmospheres and the early solar system. Science 283:341−345

doi: 10.1126/science.283.5400.341
[16]

Michalski G, Scott Z, Kabiling M, Thiemens MH. 2003. First measurements and modeling of Δ17O in atmospheric nitrate. Geophysical Research Letters 30:1870

doi: 10.1029/2003GL017015
[17]

Li T, Li J, Sun Z, Jiang H, Tian C, et al. 2023. High contribution of anthropogenic combustion sources to atmospheric inorganic reactive nitrogen in South China evidenced by isotopes. Atmospheric Chemistry and Physics 23:6395−6407

doi: 10.5194/acp-23-6395-2023
[18]

Fan MY, Zhang W, Zhang YL, Li J, Fang H, et al. 2023. Formation mechanisms and source apportionments of nitrate aerosols in a megacity of eastern China based on multiple isotope observations. Journal of Geophysical Research: Atmospheres 128:e2022JD038129

doi: 10.1029/2022JD038129
[19]

Altieri KE, Burger J, Language B, Piketh SJ. 2022. A case study in the wintertime Vaal Triangle Air-Shed Priority Area on the utility of the nitrogen stable isotopic composition of aerosol nitrate to identify NOx sources. Clean Air Journal 32:1−8

doi: 10.17159/caj/2022/32/1.12505
[20]

Passos RG, Matiatos I, Monteiro LR, Almeida RSSP, Lopes NP, et al. 2022. Imprints of anthropogenic air pollution sources on nitrate isotopes in precipitation in a tropical metropolitan area. Atmospheric Environment 288:119300

doi: 10.1016/j.atmosenv.2022.119300
[21]

Zong Z, Tian C, Li J, Syed JH, Zhang W, et al. 2020. Isotopic interpretation of particulate nitrate in the Metropolitan City of Karachi, Pakistan: insight into the oceanic contribution to NOx. Environmental Science & Technology 54:7787−7797

doi: 10.1021/acs.est.0c00490
[22]

Zong Z, Wang X, Tian C, Chen Y, Fang Y, et al. 2017. First assessment of NOx sources at a regional background site in North China using isotopic analysis linked with modeling. Environmental Science & Technology 51:5923−5931

doi: 10.1021/acs.est.6b06316
[23]

Luo L, Wu Y, Xiao H, Zhang R, Lin H, et al. 2019. Origins of aerosol nitrate in Beijing during late winter through spring. Science of the Total Environment 653:776−782

doi: 10.1016/j.scitotenv.2018.10.306
[24]

Zong Z, Tian C, Sun Z, Tan Y, Shi Y, et al. 2019. Long-term evolution of particulate nitrate pollution in North China: isotopic evidence from 10 offshore cruises in the Bohai Sea from 2014 to 2019. Journal of Geophysical Research: Atmospheres 127:e2022JD036567

doi: 10.1029/2022JD036567
[25]

Zhang ZE, Li J, Zhang R, Tian C, Sun Z, et al. 2024. Increase in agricultural-derived NHx and decrease in coal combustion-derived NOx result in atmospheric particulate N–NH4+ surpassing N–NO3− in the South China Sea. Environmental Science & Technology 58:6682−6692

doi: 10.1021/acs.est.3c09173
[26]

Song W, Liu XY, Houlton BZ, Liu CQ. 2022. Isotopic constraints confirm the significant role of microbial nitrogen oxides emissions from the land and ocean environment. National Science Review 9:nwac106

doi: 10.1093/nsr/nwac106
[27]

Xu W, Zhao Y, Wen Z, Chang Y, Pan Y, et al. 2022. Increasing importance of ammonia emission abatement in PM2.5 pollution control. Science Bulletin 67:1745−1749

doi: 10.1016/j.scib.2022.07.021
[28]

Fenn ME, Ross CS, Schilling SL, Baccus WD, Larrabee MA, et al. 2013. Atmospheric deposition of nitrogen and sulfur and preferential canopy consumption of nitrate in forests of the Pacific Northwest, USA. Forest Ecology and Management 302:240−253

doi: 10.1016/j.foreco.2013.03.042
[29]

Van Langenhove L, Verryckt LT, Bréchet L, Courtois EA, Stahl C, et al. 2020. Atmospheric deposition of elements and its relevance for nutrient budgets of tropical forests. Biogeochemistry 149:175−193

doi: 10.1007/s10533-020-00673-8
[30]

Fang Y, Yoh M, Koba K, Zhu W, Takebayashi YU, et al. 2011. Nitrogen deposition and forest nitrogen cycling along an urban−rural transect in southern China. Global Change Biology 17:872−885

doi: 10.1111/j.1365-2486.2010.02283.x
[31]

Guerrieri R, Templer P, Magnani F. 2021. Canopy exchange and modification of nitrogen fluxes in forest ecosystems. Current Forestry Reports 7:115−137

doi: 10.1007/s40725-021-00141-y
[32]

Liu XY, Liu MN, Qin WX, Song W. 2023. Isotope constraints on nitrate exchanges between precipitation and forest canopy. Global Biogeochemical Cycles 37:e2023GB007920

doi: 10.1029/2023GB007920
[33]

Zhang JB, Cai ZC, Zhu TB, Yang WY, Muüller C. 2013. Mechanisms for the retention of inorganic N in acidic forest soils of southern China. Scientific Reports 3:2342

doi: 10.1038/srep02342
[34]

Li Z, Tian D, Wang B, Wang J, Wang S, et al. 2019. Microbes drive global soil nitrogen mineralization and availability. Global Change Biology 25:1078−1088

doi: 10.1111/gcb.14557
[35]

Elrys AS, Ali A, Zhang H, Cheng Y, Zhang J, et al. 2021. Patterns and drivers of global gross nitrogen mineralization in soils. Global Change Biology 27:5950−5962

doi: 10.1111/gcb.15851
[36]

Isobe K, Ise Y, Kato H, Oda T, Vincenot CE, et al. 2020. Consequences of microbial diversity in forest nitrogen cycling: diverse ammonifiers and specialized ammonia oxidizers. The ISME Journal 14:12−25

doi: 10.1038/s41396-019-0500-2
[37]

Denk TRA, Kraus D, Kiese R, Butterbach-Bahl K, Wolf B. 2019. Constraining N cycling in the ecosystem model LandscapeDNDC with the stable isotope model SIMONE. Ecology 100:e02675

doi: 10.1002/ecy.2675
[38]

Houlton BZ, Sigman DM, Hedin LO. 2006. Isotopic evidence for large gaseous nitrogen losses from tropical rainforests. Proceedings of the National Academy of Sciences of the United States of America 103:8745−8750

doi: 10.1073/pnas.0510185103
[39]

Stark JM, Hart SC. 1997. High rates of nitrification and nitrate turnover in undisturbed coniferous forests. Nature 385:61−64

doi: 10.1038/385061a0
[40]

Zhang J, Zhu T, Cai Z, Müller C. 2011. Nitrogen cycling in forest soils across climate gradients in Eastern China. Plant and Soil 342:419−432

doi: 10.1007/s11104-010-0706-6
[41]

Zak J, Willig M, Moorhead D, Wildman H. 1994. Functional diversity of microbial communities: a quantitative approach. Soil Biology and Biochemistry 26:1101−1108

doi: 10.1016/0038-0717(94)90131-7
[42]

Kuypers MMM, Marchant HK, Kartal B. 2018. The microbial nitrogen-cycling network. Nature Reviews Microbiology 16:263−276

doi: 10.1038/nrmicro.2018.9
[43]

Xu SQ, Liu XY, Sun ZC, Hu CC, Wanek W, et al. 2021. Isotopic elucidation of microbial nitrogen transformations in forest soils. Global Biogeochemical Cycles 35:e2021GB007070

doi: 10.1029/2021GB007070
[44]

Philben M, Billings SA, Edwards KA, Podrebarac FA, van Biesen G, et al. 2018. Amino acid δ15N indicates lack of N isotope fractionation during soil organic nitrogen decomposition. Biogeochemistry 138:69−83

doi: 10.1007/s10533-018-0429-y
[45]

Enggrob KL, Larsen T, Peixoto L, Rasmussen J. 2020. Gram-positive bacteria control the rapid anabolism of protein-sized soil organic nitrogen compounds questioning the present paradigm. Scientific Reports 10:15840

doi: 10.1038/s41598-020-72696-y
[46]

Li X, Gao D, Li Y, Zheng Y, Dong H, et al. 2023. Increased nitrogen loading facilitates nitrous oxide production through fungal and chemodenitrification in estuarine and coastal sediments. Environmental Science & Technology 57:2660−2671

doi: 10.1021/acs.est.2c06602
[47]

Granger J, Sigman DM, Lehmann MF, Tortell PD. 2008. Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria. Limnology and Oceanography 53:2533−2545

doi: 10.4319/lo.2008.53.6.2533
[48]

Lewicka-Szczebak D, Well R, Giesemann A, Rohe L, Wolf U. 2013. An enhanced technique for automated determination of 15N signatures of N2, (N2+N2O) and N2O in gas samples. Rapid Communications in Mass Spectrometry 27:1548−1558

doi: 10.1002/rcm.6605
[49]

Wei H, Song X, Liu Y, Wang R, Zheng X, et al. 2023. In situ 15N-N2O site preference and O2 concentration dynamics disclose the complexity of N2O production processes in agricultural soil. Global Change Biology 29:4910−4923

doi: 10.1111/gcb.16753
[50]

Ti C, Ma S, Peng L, Tao L, Wang X, et al. 2021. Changes of δ15N values during the volatilization process after applying urea on soil. Environmental Pollution 270:116204

doi: 10.1016/j.envpol.2020.116204
[51]

Amundson R, Austin AT, Schuur EAG, Yoo K, Matzek V, et al. 2003. Global patterns of the isotopic composition of soil and plant nitrogen. Global Biogeochemical Cycles 17:1031

doi: 10.1029/2002GB001903
[52]

Liu XY, Koba K, Liu CQ, Li XD, Yoh M. 2012. Pitfalls and new mechanisms in moss isotope biomonitoring of atmospheric nitrogen deposition. Environmental Science & Technology 46:12557−12566

doi: 10.1021/es300779h
[53]

Liu XY, Wu D, Song X, Dong YP, Chen CJ, et al. 2020. A non-steady state model based on dual nitrogen and oxygen isotopes to constrain moss nitrate uptake and reduction. Journal of Geophysical Research: Biogeosciences 125:e2019JG005498

doi: 10.1029/2019JG005498
[54]

Dong YP, Huang H, Song W, Sun XC, Wang M, et al. 2019. Natural 13C and 15N abundance of moss-substrate systems on limestones and sandstones in a karst area of subtropical China. CATENA 180:8−15

doi: 10.1016/j.catena.2019.04.015
[55]

Liu XY, Koba K, Makabe A, Li XD, Yoh M, et al. 2013. Ammonium first: natural mosses prefer atmospheric ammonium but vary utilization of dissolved organic nitrogen depending on habitat and nitrogen deposition. New Phytologist 199:407−419

doi: 10.1111/nph.12284
[56]

Hu CC, Lei YB, Tan YH, Sun XC, Xu H, et al. 2019. Plant nitrogen and phosphorus utilization under invasive pressure in a montane ecosystem of tropical China. Journal of Ecology 107:372−386

doi: 10.1111/1365-2745.13008
[57]

Näsholm T, Ekblad A, Nordin A, Giesler R, Högberg M, et al. 1998. Boreal forest plants take up organic nitrogen. Nature 392:914−916

doi: 10.1038/31921
[58]

Chapin FS III, Moilanen L, Kielland K. 1993. Preferential use of organic nitrogen for growth by a non-mycorrhizal arctic sedge. Nature 361:150−153

doi: 10.1038/361150a0
[59]

Jones DL, Healey JR, Willett VB, Farrar JF, Hodge A. 2005. Dissolved organic nitrogen uptake by plants − an important N uptake pathway? Soil Biology and Biochemistry 37:413−423

doi: 10.1016/j.soilbio.2004.08.008
[60]

Zerihun A, McKenzie BA, Morton JD. 1998. Photosynthate costs associated with the utilization of different nitrogen-forms: influence on the carbon balance of plants and shoot-root biomass partitioning. New Phytologist 138:1−11

doi: 10.1046/j.1469-8137.1998.00893.x
[61]

Hu CC, Tian CG, Chen CJ, Song W, Yue X, et al. 2025. Increased carbon cost for nitrogen assimilation in plants under a warming climate. Nature Geoscience 18:1133−1137

doi: 10.1038/s41561-025-01816-y
[62]

Friedlingstein P, O'Sullivan M, Jones MW, Andrew RM, Bakker DCE, et al. 2023. Global carbon budget 2023. Earth System Science Data 15:5301−5369

doi: 10.5194/essd-15-5301-2023
[63]

Nadelhoffer KJ, Emmett BA, Gundersen P, Kjønaas OJ, Koopmans CJ, et al. 1999. Nitrogen deposition makes a minor contribution to carbon sequestration in temperate forests. Nature 398:145−148

doi: 10.1038/18205
[64]

Thomas RQ, Canham CD, Weathers KC, Goodale CL. 2010. Increased tree carbon storage in response to nitrogen deposition in the US. Nature Geoscience 3:13−17

doi: 10.1038/ngeo721
[65]

Tian C, Yue X, Zhou H, Lei Y, Ma Y, et al. 2021. Projections of changes in ecosystem productivity under 1.5°C and 2°C global warming. Global and Planetary Change 205:103588

doi: 10.1016/j.gloplacha.2021.103588
[66]

Oura N, Shindo J, Fumoto T, Toda H, Kawashima H. 2001. Effects of nitrogen deposition on nitrous oxide emissions from the forest floor. Water, Air, and Soil Pollution 130:673−678

doi: 10.1023/A:1013817031062
[67]

Yu H, Duan Y, Mulder J, Dörsch P, Zhu W, et al. 2023. Universal temperature sensitivity of denitrification nitrogen losses in forest soils. Nature Climate Change 13:726−734

doi: 10.1038/s41558-023-01708-2
[68]

Guo HR. 2022. Characteristic of carbon and nitrogen concentrations and isotopes in forest streams under high nitrogen deposition and their environmental significance. Doctoral thesis, Tianjin University, China (in Chinese)
[69]

Huang S, Wang F, Elliott EM, Zhu F, Zhu W, et al. 2020. Multiyear measurements on Δ17O of stream nitrate indicate high nitrate production in a temperate forest. Environmental Science & Technology 54:4231−4239

doi: 10.1021/acs.est.9b07839
[70]

Fang Y, Koba K, Makabe A, Takahashi C, Zhu W, et al. 2015. Microbial denitrification dominates nitrate losses from forest ecosystems. Proceedings of the National Academy of Sciences of the United States of America 112:1470−1474

doi: 10.1073/pnas.1416776112