Carbon accumulation in agroecosystems is regulated to a major extent by the variability of C:N:P stoichiometry. To understand the impact of C:N:P ratios and the cycling of limiting nutrients in the leaf–litter–aggregate continuum on soil C sequestration following afforesxtation, we assessed the contribution of aggregate-associated organic carbon (OC) to bulk soil OC accumulation, and examined the C, N, and P concentrations in leaves, litter, aggregates, and their stoichiometric couplings along an afforestation chronosequence. Averaged across the entire chronosequence, bulk soil OC stocks increased at the rate of 12.3 g m⁻² year⁻¹ at the 0–0.4-m depth, and significantly correlated with macroaggregates-associated OC stocks which increased on average by 114.5% with increasing stand age at soil depth of 0.4 m. Moreover, the C:P and N:P ratios of litter decreased by 19.7–33.0% and 7.6–26.8%, respectively, with increasing stand age, and were significantly associated with aggregate-associated C:P and N:P ratios. Both C:P and N:P ratios in microaggregates and clay-plus-silt fractions were, respectively, 18.0%, 13.3%, and 23.0%, 19.7% lower than those in macroaggregates, indicating a higher P availability in fine fractions. Macroaggregate-associated C:P and N:P ratios increased by 29.5 and 26.3%, respectively, at the 0–0.4-m depth with plantation age and were linked to the increased macroaggregate-associated OC stocks. Collectively, our results suggest that C:P and N:P ratios are good indicators of P cycling in ecosystem, and that P status under the control of aggregates may be an important factor for the sustainable accumulation of OC during afforestation.

中文翻译：

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C：N：P化学计量比解释造林过程中土壤有机碳的积累

农业生态系统中的碳积累在很大程度上受C：N：P化学计量比变化的调节。为了了解碳：氮：磷比率以及叶凋落物-骨料连续体中有限养分循环对土壤碳固存的影响，我们评估了骨料相关有机碳（OC）对土壤总OC积累的贡献。 ，并沿着造林的时间顺序检查了叶子，凋落物，聚集物中的碳，氮和磷浓度及其化学计量耦合。在整个时间序列上平均，散装土壤OC存量以12.3 g m - ² 年^-1的速率增加在0-0.4-m深度，与与大骨料相关的OC储量显着相关，随着土壤深度在0.4 m的增加，平均OC储量平均增加114.5％。此外，随着林分龄的增加，垫料的C：P和N：P比率分别降低了19.7–33.0％和7.6–26.8％，并且与骨料相关的C：P和N：P比率显着相关。微骨料中的C：P和N：P比率和粘土加粉砂级分的比率分别比大型骨料中的比率低18.0％，13.3％和23.0％，19.7％，表明细级分中的P利用率更高。随着种植年龄的增长，在0-0.4-m深度，大骨料相关的C：P和N：P比率分别增加了29.5％和26.3％，并且与大骨料相关的OC储量相关。总的来说，我们的结果表明C：P和N：