Intercropping is an effective cultivation practice to develop sustainable agroecosystems and increase soil organic carbon (SOC) and nitrogen (N) with rich crop diversity. With increased duration, the changes in soil N availability might affect microbial and plant growth and consequently regulate the intercropping effects on SOC sequestration. However, the response of intercropping effects on SOC components to soil N availability has been poorly explored. In this study, we constructed a global database with 939 paired data (intercropping vs. monoculture) from 60 publications. We found that intercropping increased SOC (by 7.94%), microbial biomass carbon (MBC, by 23.73%), particulate organic carbon (POC, by 23.27%), and dissolved organic carbon (DOC, by 16.46%) compared to monoculture. The intercropping effects (percentage change, %) on SOC content strongly depends on soil N availability (soil C: N) and the interactions with duration and crop types. In N-limited soils (soil C: N > 15), intercropping increased SOC and POC contents by 14% and 31%, respectively, which were 2–3 times higher than those in N-rich soils (soil C: N < 15). It implies higher intercropping effects in more N-limited soils. In addition, intercropping increased MBC:SOC by 63% in N-limited but not in N-rich soils, indicating greater contributions of microbial-derived C to SOC storage in N-limited but not in N-rich soils. This might be attributed to that the stimulated microbial decomposition of soil organic matter counterbalanced the microbial-derived C accumulation in N-rich soils. Taken together, these results indicate that soil N availability regulates the intercropping effects on SOC content and the contributions of microbial-derived C to SOC storage. Overall, these findings highlight the importance of soil N availability on SOC content with intercropping, implying that intercropping is a suitable agricultural approach especially in N-limited soils and nutrient management should be carefully considered in long-term intercropping experiments.

中文翻译：

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土壤氮素有效性介导间作对全球范围内土壤有机碳的积极影响

间作是发展可持续农业生态系统、增加土壤有机碳（SOC）和氮（N）以及丰富作物多样性的有效耕作方法。随着持续时间的增加，土壤氮素有效性的变化可能会影响微生物和植物的生长，从而调节间作对 SOC 固存的影响。然而，间作对 SOC 成分的影响对土壤氮素有效性的响应却鲜有探讨。在这项研究中，我们构建了一个全球数据库，其中包含来自 60 份出版物的 939 条配对数据（间作与单作）。我们发现，与单一种植相比，间作增加了 SOC（增加 7.94%）、微生物生物量碳（MBC，增加 23.73%）、颗粒有机碳（POC，增加 23.27%）和溶解有机碳（DOC，增加 16.46%）。间作对 SOC 含量的影响（百分比变化，%）很大程度上取决于土壤氮的有效性（土壤 C:N）以及与持续时间和作物类型的相互作用。在限氮土壤（土壤C：N>15）中，间作使SOC和POC含量分别增加14％和31％，比富氮土壤（土壤C：N<15）高2-3倍）。这意味着在氮限制较多的土壤中间作效果更高。此外，在限氮土壤中，间作使 MBC:SOC 增加了 63%，但在富氮土壤中却没有增加，这表明在限氮土壤中，微生物来源的 C 对 SOC 储存的贡献更大，但在富氮土壤中则不然。这可能是由于微生物对土壤有机质的分解作用抵消了富氮土壤中微生物产生的碳积累。综上所述，这些结果表明土壤氮素有效性调节间作对 SOC 含量的影响以及微生物来源的 C 对 SOC 储存的贡献。总体而言，这些发现强调了土壤氮素有效性对间作 SOC 含量的重要性，这意味着间作是一种合适的农业方法，特别是在氮有限的土壤中，并且在长期间作实验中应仔细考虑养分管理。