Atmospheric nitrogen deposition affects forest plant and soil system carbon: nitrogen: phosphorus stoichiometric flexibility: A meta-analysis

Abstract Aims To investgate how increased nitrogen (N) deposition influences the balance and distribution of carbon (C), N, and phosphorus (P) in forest plant–soil–microbe systems, and whether these effects relate with different N forms and environment factors. Methods We conducted a global meta-analysis from 101 articles to get 751 observations (including plant, soil and microbial biomass C, N and P nutrients and stoichiometry) under different N addition levels (0–50, 50–100, >100 kg ha-1 year-1 of N), duration (0–5, >5 year), forms (understory, canopy), and status (ammonium N, nitrate N, organic N, mixed N). Results and conclusions N addition had an substantial effects on the plant-soil-microbial C:N:P stoichiometry. Specifically, N addition considerably increased plant N:P (leaf: 14.98%, root: 13.29%), plant C:P (leaf: 6.8%, root: 25.44%), soil N:P (13.94%), soil C:P (10.86%), microbial biomass N:P (23.58%), and microbial biomass C:P ratios (12.62%), while simultaneously decreased plant C:N ratio (leaf: 6.49%, root: 9.02%). Notably, soil C:N ratio exhibited opposite changes under low N and high N addition. Plant C:N:P ratios were most affected by short-term N addition, while soil C:N:P ratios responded primarily to long-term N treatment. Additionally, organic N had a stronger impact on soil C:N and C:P ratios, whereas ammonia N significantly affected the soil N:P ratio. Positive correlations were identified among N:P and C:P ratios across plants, soil, and microbes, highlighting their interdependence within the ecosystem. Moreover, N deposition not only influenced the flexibility of C:N:P stoichiometry but also intensified P limitation among microorganisms in forest plant-soil-microbial systems.