Abstract Atmospheric nitrogen (N) deposition affects soil nitrate (NO₃⁻) dynamics in forests, yet mechanisms driving NO₃⁻ accumulation in semi‐arid regions remain unclear. Here, we quantified atmospheric and microbial contributions to soil NO₃⁻ by analyzing 17O anomalies in 26 semi‐arid forests under high N deposition in northern China. Heavier N‐polluted temperate forests showed lower 17O anomalies in soil NO₃⁻ (1.0‰ ± 0.8‰), indicating lower atmospheric contributions (4.2% ± 3.2%), but higher atmospheric concentrations (0.3 ± 0.3 mg N kg−1) and microbial nitrification rates (459.7 ± 225.4 kg N ha−1 yr−1). Both contribution and concentration of atmospheric NO₃⁻ in soils increased with NO₃⁻ inputs, whereas nitrification rate positively correlated with N deposition independent of precipitation, suggesting deposited N pollutants rather than water as a main driver of soil NO₃⁻ production and accumulation. These findings are important for understanding sources and accumulation of NO₃⁻ in temperate forests under N deposition.
Observations from the Little Bunker
Last updated: August 18, 2025 04:13 PM
Atmospheric CO₂
425.4 ppm
+18.4
ppm/year
Atmospheric CH₄
1934.91 ppb
+9.11
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
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8.1 billion
+67
million/year