Nitrogen input decreases microbial nitrogen use efficiency in surface soils of a temperate forest in northeast China

Lifei Sun, Yanci Qiao, Wolfgang Wanek, Daryl L. Moorhead, Yongxing Cui, Yujiao Peng, Liquan Song, Baoqing Hu, Tuo Zhang, Shuailin Li (Corresponding author)

Publications: Contribution to journalArticlePeer Reviewed

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 languageEnglish
Article number117159
Number of pages10
JournalGeoderma
Volume453
Early online date25 Dec 2024
DOIs
Publication statusPublished - 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

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