CNP_data.xlsx

Deciphering the linkage between ecological stoichiometry and ecosystem functioning under anthropogenic nitrogen (N) deposition is critical for understanding the impact of afforestation on terrestrial carbon (C) sequestration. Nevertheless, how stoichiometric asymmetry of above- vs. belowground under long-term N addition change with stand age remains unclear. In this study, we investigated the changes of stoichiometry after a decadal N addition with three levels (control: no N addition; low: 20 kg N ha⁻¹ year⁻¹; and high: 50 kg N ha⁻¹ year⁻¹) in three temperate larch plantations (<i>Larix principis-rupprechtii</i>) over age sequences (young, intermediate, and mature stands) in North China. We found that low N addition had no impact on both above- (leaf and litter) and belowground (soil and microbes) stoichiometry. In contrast, high N addition caused a significant asymmetry of above- vs. belowground stoichiometry and the asymmetry diminished during stand development. After 10-year N inputs, the young and intermediate plantations shifted from N limitation to N and P co-limitation but the mature plantation remained in N limitation. Conversely, soil microorganisms were in P limitation across the three plantations. The wider niche differentiation (N limitation for trees but P limitation for microorganisms) under long-term N inputs may be responsible for the faster speed in approaching stoichiometric homeostasis in the mature plantation than in the young plantation. Our findings provide a stoichiometric-based insight into mechanisms of the large C sink in young forests especially the C stock is asymmetry between above- and belowground, and highlight the need for considering the role of flexible stoichiometry when forecasting the future forest C sink.