Fine roots and mycorrhizal hyphae represent two critical pathways for plants to acquire nutrients, but their response mechanisms to variations in inorganic and organic nutrients remain inadequately understood. We conducted a meta-analysis on the effects of nitrogen (N), phosphorus (P), N-P combination and organic nutrient (ON) additions on root length (RL), root biomass (RB), root colonization (RC), hyphal length (HL), and hyphal biomass (HB) based on 738 root-hyphae observation pairs derived from 43 studies. We found that RB and RL increased by 27%–34% and 31%–36%, respectively, following N and/or P additions, whereas HL increased by 26% and RC decreased by 20%. ON addition exerted 2–3 times greater effects on hyphae than fine roots. N addition effects on HL, RB and RC significantly decreased with increasing experiment duration, amount of N addition and/or soil total P, conversely, its effect on HL and RL significantly intensified with soil total organic carbon. The effects of N and ON additions on RB exhibited significant positive and negative correlations, respectively, with their effects on HL in ectomycorrhizal hosts. No significant relationships were detected for arbuscular mycorrhizal hosts. Our results demonstrate that plants preferentially employ root-dependent acquisition strategies under high mineral N and P but rely more on hypha-dependent strategies under abundant organic N and P. This study underscores the necessity of integrating both roots and hyphae within current nutrient acquisition frameworks to evaluate the effects of global changes on carbon and N cycling.
Liu et al. (Fri,) studied this question.