Abstract
Microbial nitrogen use efficiency (NUE) reflects the allocation of microbially-acquired N between growth (anabolism) and the release of inorganic N to the environment (catabolism), and is central to understanding soil N cycling. However, the effects of N addition on microbial NUE are unclear. We determined microbial NUE in surface (0–10 cm) and subsurface (10–20 cm) soils in a temperate forest by the combined substrate-independent 18O-H2O tracer technique and 15N isotope pool dilution in a multi-level N addition experiment. We found that high N treatment (75 kg N ha−1 yr−1 as urea fertilizer) significantly decreased NUE in surface soil, but not in the subsurface soil. The decrease in NUE in surface soil was related to soil acidification, likely induced by N addition, and to reduced phosphorus availability, suggesting increased phosphorus limitation to microbial metabolism with N addition. Microbial NUE was inversely related to inorganic N flux (as NH4+) in both surface and subsurface soils and positively related to microbial biomass in surface soil. Our empirical evidence confirms that microbial NUE is a sensitive proxy and controlling branchpoint between soil microbial N immobilization and inorganic N cycling, which should be explicitly included in biogeochemical models to better predict soil N dynamics.
Original language | English |
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Article number | 117159 |
Number of pages | 10 |
Journal | Geoderma |
Volume | 453 |
Early online date | 25 Dec 2024 |
DOIs | |
Publication status | Published - Jan 2025 |
Austrian Fields of Science 2012
- 106026 Ecosystem research
- 106022 Microbiology
Keywords
- Global change
- Microbial growth
- Nutrient limitation
- soil C storage
- Soil depth
- soil N transformation