Nitrous oxide dynamics across nitrogen and pH gradients in headwater streams
- 1Aarhus University (Aarhus, Denmark)
Abstract
Headwater streams in agricultural landscapes can contribute substantially to nitrous oxide (N ₂ O) emissions, yet the environmental controls on stream N ₂ O dynamics remain poorly resolved, particularly in systems with low pH. We investigated 72 Danish headwater streams spanning broad gradients in pH (5.0–8.8), land use, and soil type to identify the main drivers of N ₂ O variability. Nitrate (NO3-) was the strongest predictor of N ₂ O saturation, and its positive association with N ₂ O intensified under acidic conditions according to linear mixed models. In the same model, ammonium, dissolved organic carbon, and stream depth also showed significant but weaker positive relationships with N ₂ O. Spatial differences among streams explained considerably more variation than seasonal or regional patterns, underscoring the dominance of local factors. Streams with pH < 6 consistently exhibited higher N ₂ O saturation, and generalized additive modelling indicated a marked decline in N ₂ O levels beginning near pH 6. Despite generally high N ₂ O saturation, approximately 9 % of observations displayed undersaturation, which occurred mainly in streams with low NO3- concentrations and across all seasons. Our results indicate that acidic, weakly buffered catchments may enhance in-stream N ₂ O accumulation even at moderate nitrogen levels. These findings highlight the need to consider pH-related controls when assessing N ₂ O dynamics in freshwater networks and when designing mitigation strategies for agricultural landscapes.
Versions
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BibTeX
@article{carstensen2026nitrous,
title = {{Nitrous oxide dynamics across nitrogen and pH gradients in headwater streams}},
author = {Mette V. Carstensen and Annelies J. Veraart and Ida F. Peterse and Nicole Wrage-Mönnig and Joachim Audet},
journal = {Biogeosciences},
year = {2026},
month = oct,
doi = {10.5194/bg-23-7661-2026},
url = {https://bg.copernicus.org/articles/23/7661/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Nitrous oxide dynamics across nitrogen and pH gradients in headwater streams
AU - Mette V. Carstensen
AU - Annelies J. Veraart
AU - Ida F. Peterse
AU - Nicole Wrage-Mönnig
AU - Joachim Audet
PY - 2026
DA - 2026/10/30
JO - Biogeosciences
DO - 10.5194/bg-23-7661-2026
UR - https://bg.copernicus.org/articles/23/7661/2026/
AB - Headwater streams in agricultural landscapes can contribute substantially to nitrous oxide (N ₂ O) emissions, yet the environmental controls on stream N ₂ O dynamics remain poorly resolved, particularly in systems with low pH. We investigated 72 Danish headwater streams spanning broad gradients in pH (5.0–8.8), land use, and soil type to identify the main drivers of N ₂ O variability. Nitrate (NO3-) was the strongest predictor of N ₂ O saturation, and its positive association with N ₂ O intensified under acidic conditions according to linear mixed models. In the same model, ammonium, dissolved organic carbon, and stream depth also showed significant but weaker positive relationships with N ₂ O. Spatial differences among streams explained considerably more variation than seasonal or regional patterns, underscoring the dominance of local factors. Streams with pH < 6 consistently exhibited higher N ₂ O saturation, and generalized additive modelling indicated a marked decline in N ₂ O levels beginning near pH 6. Despite generally high N ₂ O saturation, approximately 9 % of observations displayed undersaturation, which occurred mainly in streams with low NO3- concentrations and across all seasons. Our results indicate that acidic, weakly buffered catchments may enhance in-stream N ₂ O accumulation even at moderate nitrogen levels. These findings highlight the need to consider pH-related controls when assessing N ₂ O dynamics in freshwater networks and when designing mitigation strategies for agricultural landscapes.
SN - 1726-4189
ER -