Sugarcane/soybean intercropping with reduced nitrogen addition is an important sustainable agricultural pattern that can alter soil ecological functions, thereby affecting straw decomposition in the soil. However, the mechanisms underlying changes in soil organic carbon (SOC) composition and microbial communities during straw decomposition under long-term intercropping with reduced nitrogen addition remain unclear. In this study, we conducted an in-situ microplot incubation experiment with C-labeled soybean straw residue addition in a two-factor (cropping pattern: sugarcane monoculture (MS) and sugarcane/soybean intercropping (SB); nitrogen addition levels: reduced nitrogen addition (N1) and conventional nitrogen addition (N2)) long-term experimental field plot. The results showed that the SBN1 treatment significantly increased the residual particulate organic carbon (POC) and residual microbial biomass carbon (MBC) contents during straw decomposition, and the straw carbon in soil was mainly conserved as POC. Straw addition changed the structure and reduced the diversity of the soil microbial community, but microbial diversity gradually recovered with decomposition time. During straw decomposition, the intercropping pattern significantly increased the relative abundances of Firmicutes and Ascomycota. In addition, straw addition reduced microbial network complexity in the sugarcane/soybean intercropping pattern but increased it in the sugarcane monoculture pattern. Nevertheless, microbial network complexity remained higher in the SBN1 treatment than in the MSN1 treatment. In general, the SBN1 treatment significantly increased the diversity of microbial communities and the relative abundance of microorganisms associated with organic matter decomposition, and the changes in microbial communities were mainly driven by the residual labile SOC fractions. These findings suggest that more straw carbon can be sequestered in the soil under sugarcane/soybean intercropping with reduced nitrogen addition to maintain microbial diversity and contribute to the development of sustainable agriculture.

中文翻译：

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减少氮添加的甘蔗/大豆间作提高了秸秆分解过程中残留物产生的不稳定土壤有机碳和土壤微生物网络的复杂性

减少氮添加的甘蔗/大豆间作是一种重要的可持续农业模式，可以改变土壤生态功能，从而影响土壤中秸秆的分解。然而，在长期间作减少氮添加的情况下，秸秆分解过程中土壤有机碳（SOC）组成和微生物群落变化的机制仍不清楚。在本研究中，我们进行了双因素添加C标记大豆秸秆的原位微区孵化实验（种植模式：甘蔗单作（MS）和甘蔗/大豆间作（SB）；氮添加水平：减氮添加（N1）和常规氮添加（N2））长期实验田地图。结果表明，SBN1处理显着提高了秸秆分解过程中残留颗粒有机碳（POC）和残留微生物量碳（MBC）含量，土壤中秸秆碳主要以POC形式保存。秸秆添加改变了土壤微生物群落的结构，降低了其多样性，但随着分解时间的延长，微生物多样性逐渐恢复。在秸秆分解过程中，间作模式显着增加了厚壁菌门和子囊菌门的相对丰度。此外，秸秆添加降低了甘蔗/大豆间作模式中的微生物网络复杂性，但增加了甘蔗单作模式中的微生物网络复杂性。然而，SBN1 处理中的微生物网络复杂性仍然高于 MSN1 处理。总的来说，SBN1处理显着增加了微生物群落的多样性和与有机物分解相关的微生物的相对丰度，并且微生物群落的变化主要由残留的不稳定SOC部分驱动。这些研究结果表明，甘蔗/大豆间作可以将更多的秸秆碳封存在土壤中，同时减少氮的添加，以维持微生物多样性，并有助于可持续农业的发展。