Nitrogen addition enhances stable soil carbon accumulation during ectomycorrhizal hyphae decomposition

Ectomycorrhizal fungi are pivotal drivers in storing carbon (C) in soil. Yet, whether and how ectomycorrhizal hyphae turnover controls soil organic carbon (SOC) accumulation under nitrogen (N) deposition remains unknown.

We quantified the responses of SOC and its physical fractions (particulate organic carbon, POC and mineral-associated organic carbon, MAOC) regulated by ectomycorrhizal hyphae decomposition to chronic N addition (25 kg N ha⁻¹ yr⁻¹, 50 kg N ha⁻¹ yr⁻¹). We also explored the microbial necromass C (i.e. amino sugar) contributions SOC accumulation mediated by ectomycorrhizal hyphae decomposition under N addition.

Our results showed that the ectomycorrhizal hyphae decomposition promoted the SOC sequestration dominated by MAOC accrual, and this positive effect was enhanced under N addition. Furthermore, the effects of N addition on stable SOC fraction accumulation during ectomycorrhizal hyphae decomposition was mainly attributed to the increase of microbial necromass C and the enhancement of mineral protection for SOC.

Our results highlight the importance of ectomycorrhizal hyphae decomposition in regulating stable SOC accumulation under N deposition. Collectively, our findings provide direct evidence for the significant role of ectomycorrhizal hyphae turnover on soil C dynamics, and contribute valuable insights into ectomycorrhizal hyphae turnover and associated soil C feedback under atmospheric N deposition.