Warming and wetting could turn alpine grasslands into emerging nitrous oxide hotspots in arid northwest China
Maximum Academic Press
image:
Different lowercase letters indicate significant differences among land-use types (p < 0.05).
view moreCredit: The authors
By measuring N₂O fluxes along an elevation gradient from 313 to 2,901 meters above sea level, the team discovered that alpine grasslands may become increasingly important sources of this potent greenhouse gas under future climate scenarios.
Nitrous oxide is nearly 300 times more powerful than carbon dioxide over a 100-year period and is also a major ozone-depleting substance. Globally, soils account for more than 60% of atmospheric N₂O emissions, largely through microbial processes known as nitrification and denitrification. Arid and semi-arid ecosystems cover roughly 40% of the Earth’s land surface but have historically been considered minor contributors to global N₂O budgets due to limited water availability. However, northern China’s arid regions are experiencing warmer and wetter conditions under climate change, potentially stimulating microbial nitrogen cycling and greenhouse gas release. At the same time, agricultural intensification—including irrigation and fertilizer use—has dramatically altered soil nutrient dynamics. Yet little is known about how elevation and land use interact to control N₂O emissions in arid mountain landscapes.
A study (DOI: 10.48130/nc-0025-0022) published in Nitrogen Cycling on 23 January 2026 by Longfei Yu’s team, Tsinghua University, provides new insight into how both natural and managed soils in northwestern China could amplify climate feedbacks in a rapidly changing environment.
Using in situ chamber-based N₂O flux measurements combined with analyses of soil physicochemical properties, inorganic nitrogen substrates, nitrogen-cycling functional genes (amoA, nirK, nirS, nosZ), and multivariate statistics including regression, principal component analysis (PCA), and random forest modeling, the researchers investigated how vegetation type and elevation jointly regulate N₂O emissions. At low elevation, cropland soils exhibited N₂O fluxes two orders of magnitude higher than natural ecosystems (mean 181.32 µg N m⁻² h⁻¹), coinciding with greater soil moisture, relatively high inorganic N availability, and elevated functional gene abundance, indicating strong denitrification potential under irrigation and fertilization. In contrast, barelands showed negligible or even negative fluxes under extremely dry conditions despite inorganic N accumulation. Grassland soils emitted modest N₂O at low elevation but showed a clear increase with elevation, reaching 11.09 µg N m⁻² h⁻¹ at 2,901 m. This trend paralleled rising water-filled pore space (R² = 0.58, p < 0.001), declining pH, and increased abundances of AOA and nirK, while nosZ abundance declined, suggesting enhanced incomplete denitrification under wetter conditions. Forest soils displayed the opposite elevational pattern: higher emissions at low elevation (up to 10.21 µg N m⁻² h⁻¹) and sharp declines at higher elevations. Here, N₂O fluxes were strongly linked to soil temperature (R² = 0.46, p < 0.001) rather than moisture, and denitrification gene abundances decreased with elevation despite increasing soil carbon and nitrogen pools. PCA and random forest analyses consistently identified moisture and denitrification genes as dominant predictors in grasslands, whereas temperature and organic nutrient variables were the primary controls in forests, demonstrating contrasting regulatory mechanisms along the elevation gradient.
Overall, the study indicates that warming and increased precipitation in arid northern China may turn alpine grasslands into emerging N₂O hotspots by stimulating moisture-driven denitrification. It also underscores the dominant contribution of irrigated croplands, where fertilization and dry–wet cycles trigger strong emission pulses, highlighting the need for improved nitrogen management. Furthermore, expanding planted forests in desert oases may carry unintended greenhouse gas costs under shifting climatic conditions.
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References
DOI
Original Souce URL
https://doi.org/10.48130/nc-0025-0022
Funding information
This work was financially supported by the National Natural Science Foundation of China (NSFC Grant No. 42577331), and the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2025B1515020013). Longfei Yu acknowledges support from the Scientific Research Start-up Funds (Grant No. QD2022010C) from Tsinghua Shenzhen International Graduate School, and the Tianchi Talent Programme of Xinjiang Uygur Autonomous Region.
About Nitrogen Cycling
Nitrogen Cycling is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Soil N2O emission along an elevation gradient in the arid zone of Xinjiang, Northwestern China
Erhai Lake basin identified as a major atmospheric nitrogen exporter in southwest China
Maximum Academic Press
image:
(a), (c) Dry deposition: concentration and flux. (b), (d) Wet deposition: volume-weighted mean (VWM) concentration and flux. Data are presented as mean ± standard deviation across nine monitoring sites for dry deposition and seven sites for wet deposition.
view moreCredit: The authors
By combining high-resolution emission inventories with systematic measurements of wet and dry deposition, the team determined that annual emissions surpass local deposition by more than 8,200 tons of nitrogen. The analysis shows that ammonia emissions are overwhelmingly driven by agricultural activities, whereas nitrogen oxide emissions originate primarily from the transportation sector.
Reactive nitrogen—including ammonia (NH₃), nitrogen oxides (NOₓ), ammonium, and nitrate—plays a key role in air pollution, climate change, and ecosystem degradation. NH₃ promotes fine particulate matter (PM₂.₅) formation, while NOₓ drives ozone and secondary aerosol production. Excess nitrogen deposition can acidify soils, trigger lake eutrophication, and reduce biodiversity. Although China has significantly reduced NOₓ emissions through industrial and transportation controls, agricultural NH₃ emissions have remained largely unchanged. Previous studies often assessed emissions or deposition separately, leaving uncertainties in overall nitrogen budgets. The Erhai Lake Basin, a sensitive subtropical plateau ecosystem undergoing agricultural reform, provides an ideal case for an integrated source–sink evaluation.
A study (DOI: 10.48130/nc-0025-0018) published in Nitrogen Cycling on 19 January 2026 by Wen Xu’s team, China Agricultural University, provides the first integrated source–sink assessment demonstrating that the Erhai Lake Basin is a substantial net exporter of atmospheric reactive nitrogen, offering critical scientific evidence for coordinated agricultural and transportation emission control in fragile plateau lake ecosystems.
Using a bottom-up emission inventory combined with spatial analysis and a nine-site atmospheric monitoring network, the researchers first quantified NH₃ and NOₓ emissions for 2022 and then measured wet and dry nitrogen deposition across the basin in 2023 to construct a complete atmospheric Nr budget. The emission inventory integrated detailed activity data and sector-specific emission factors, while deposition fluxes were derived from measured gaseous concentrations, precipitation chemistry, and inferential dry deposition calculations. Results showed that total Nr emissions reached 10,720.4 t N yr⁻¹, with NOₓ-N (55.6%) slightly exceeding NH₃-N (44.4%). Agriculture overwhelmingly dominated NH₃ emissions (91.7%), split between livestock (48.9%)—mainly dairy cattle, laying hens, and hogs—and fertilizer application (42.8%), primarily from maize, vegetables, fruit trees, soybeans, and rice. In contrast, transportation accounted for 98.2% of NOₓ emissions, driven largely by heavy-duty trucks and passenger vehicles. Spatial mapping revealed concentrated agricultural NH₃ hotspots in northern townships such as Sanying and Zibihu, whereas vehicle-related NOₓ emissions were more evenly distributed around urban and transport hubs. Deposition monitoring showed an annual average total Nr flux of 10.4 ± 1.0 kg N ha⁻¹ yr⁻¹, dominated by reduced nitrogen (68.9%), with dry deposition contributing 58.2% of the total. NH₃ was the principal component of dry flux, while NH₄⁺ dominated precipitation chemistry. Seasonally, deposition peaked in summer and shifted between dry-dominated pathways in winter and spring and wet-dominated pathways in summer and autumn. When emissions were compared with deposition, a pronounced surplus emerged: the basin exported 8,201.2 t N yr⁻¹ overall, including large surpluses of both reduced (3,001.7 t) and oxidized nitrogen (5,420.8 t). These consistent imbalances across sub-regions confirm that the ELB functions as a substantial net atmospheric source of reactive nitrogen.
In conclusion, the Erhai Lake Basin functions as a significant hotspot of reactive nitrogen export, with atmospheric inputs contributing markedly to the lake’s total nitrogen burden despite moderate per-area deposition. The large emission surplus highlights the necessity of coordinated mitigation strategies. Effective management must simultaneously reduce agricultural ammonia through improved manure and fertilizer practices while curbing transportation-related NOₓ via cleaner vehicles and stricter standards to prevent offsetting gains and ensure sustainable ecosystem protection.
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References
DOI
Original Souce URL
https://doi.org/10.48130/nc-0025-0018
Funding information
This work was supported by the Major Science and Technology Project of Yunnan Province (Grant No. 202202AE090034), the National Natural Science Foundation of China (Grant No. 42175137), and the National Key Research and Development Program of China (Grant No. 2021YFD1700902).
About Nitrogen Cycling
Nitrogen Cycling is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
A large net source revealed by the atmospheric reactive nitrogen budget in a subtropical plateau lake basin, southwest China
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