Nitrogen deposition reshapes plant nutrient acquisition strategies: a meta-analysis within the root economics space

Global nitrogen (N) deposition has fundamentally reshaped plant nutrient acquisition by altering mechanistic trade-offs between root exploration-exploitation strategies and mycorrhizal symbiosis. Through a meta-analysis of 135 studies spanning 153 sites, we demonstrate that N deposition stimulates root exploration (+84.6% root length density) and exploitation (+13.2% nitrogen content and +8.5% root biomass) while suppressing mycorrhizal dependence (-32.8% biomass, -18.73% colonized root length, -7.55% hyphal length), indicating a systemic shift toward root-autonomous nutrient acquisition. Divergent responses emerged between plant lifeforms: woody plants prioritize exploitation (+13.2% nitrogen content) over exploration capacity (-7.9% root length density), whereas herbaceous species exhibit synergistic enhancement of both strategies (+88% root length density, +13.2% nitrogen content and +71.3% root biomass). In contrast to N-only effects, Combined nitrogen and phosphorus additions reversed mycorrhizal suppression (+41.9% biomass), highlighting their persistent role in phosphorus acquisition under elevated nutrient conditions. The root economics space framework demonstrates predictive power, with plants possessing lower specific root length (SRL) and higher nitrogen content exhibiting stronger positive responses to N deposition, while those possessing higher SRL and lower nitrogen content showed reduced investment in root systems. These trait-mediated thresholds in carbon-nutrient tradeoffs refine our capacity to model belowground ecological responses to anthropogenic nitrogen perturbation, establishing a mechanistic basis for projecting ecosystem trajectories under global change.