soil metagenome

As critical carbon sinks in terrestrial ecosystems, temperate forests exhibit complex responses to atmospheric nitrogen deposition. Through a 13 year controlled field experiment, we systematically investigated the effects of three N forms at two deposition levels on soil organic C dynamics. The experimental data revealed a three-phase SOC accumulation pattern, with aggregate-associated C showing enhancement. Particularly, silt-clay fractions demonstrated superior C sequestration capacity , suggesting strengthened physical protection through aggregate stabilization. Nuclear magnetic resonance spectroscopic analysis confirmed progressive increases in stable C pools, with aromatic and alkyl C . Microbial necromass accumulation contributed to SOC stock, enhancing biochemical resistance to decomposition. Metagenomic evidence revealed N-dependent microbial community restructuring, particularly diminished abundances of ligninolytic genes, which suppressed recalcitrant SOC mineralization. These dual regulation mechanisms - physical protection via aggregate formation and biochemical stabilization through microbial metabolic constraint - synergistically increased SOC stability. Our findings elucidate the C-N coupling mechanisms in forest soils under chronic N enrichment, providing critical insights for predicting terrestrial C sink potential under global change scenarios.