Table_1_Effect of Tillage Treatment on the Diversity of Soil Arbuscular Mycorrhizal Fungal and Soil Aggregate-Associated Carbon Content.DOCX

No-tillage agriculture can sustain productivity and protect the environment. A comprehensive understanding of soil arbuscular mycorrhizal (AM) fungal diversity and soil carbon distribution within aggregate fractions is essential to the evaluation of no-tillage agriculture. The long-term field experiment included two tillage treatments (1) no tillage with straw returned to the soil (NTS), and (2) conventional mouldboard-plowing tillage without straw (CT), and was conducted on the Loess Plateau, north-western China, from October 2009. The soil samples were collected from the surface layer (0–20 cm depth) at the maturation stage of the summer maize (Zea mays L.) for analyzing aggregates separated by the dry-sieving method. The organic carbon content in the bulk soil and different particle size aggregates were measured using the dichromate oxidization method. The species compositions of soil AM fungi were compared by applying high-throughput sequencing of 18S rRNA. The results showed that the NTS had 9.1–12.2% higher percentage of soil macro-aggregates, resulting in 9.8% increase in mean weight diameter and 10.0% increase in bulk soil organic carbon content as compared with CT treatment. In addition, the NTS treatment had significantly higher percentages of Septoglomus and Glomus than the CT treatment. We also found some significant differences in the fungal communities of the soils of the two treatments. There was a strong positive relationship between bulk soil organic carbon and the percentages of Septoglomus and Glomus. Our results suggested that the NTS treatment had a protective effect on AM fungal community structures, which might play a key role in the development of agricultural sustainability in the Loess Plateau of China.

免耕农业可维持生产效能并保护生态环境。全面探明土壤丛枝菌根（arbuscular mycorrhizal, AM）真菌多样性及团聚体组分内的土壤碳分布特征，是科学评估免耕农业的核心前提。本长期田间试验设置两种耕作处理：（1）秸秆还田免耕（no tillage with straw returned to the soil, NTS）；（2）无秸秆还田常规翻耕（conventional mouldboard-plowing tillage without straw, CT），试验于2009年10月起在中国西北黄土高原正式开展。在夏玉米（Zea mays L.）成熟期，采集0~20 cm表层土壤样品，采用干筛法分离土壤团聚体；采用重铬酸钾氧化法测定原状土壤及不同粒径团聚体的有机碳含量；通过18S rRNA高通量测序技术，对比分析土壤AM真菌的物种组成。结果表明，相较于CT处理，NTS处理的土壤大团聚体占比提升9.1%~12.2%，进而使团聚体平均重量直径提升9.8%，原状土壤有机碳含量提升10.0%。此外，NTS处理下的隔孢球囊霉属（Septoglomus）与球囊霉属（Glomus）的相对占比显著高于CT处理。本研究还发现，两种处理的土壤真菌群落存在显著差异。原状土壤有机碳含量与隔孢球囊霉属、球囊霉属的相对占比呈显著正相关关系。本研究结果表明，NTS处理对AM真菌群落结构具有保护作用，这可能对中国黄土高原农业可持续发展起到关键支撑作用。