摘要:农业管理实践会干扰土壤生态系统，对土壤微生物特别是根系周围微生物产生不同影响，保护性耕作被认为是对土壤扰动较小的耕作方式，在全球范围内应用广泛，但其可持续性受到了秸秆覆盖可能会增加土壤病原微生物的挑战，对土壤微生物多样性的影响仍存在争议。因此，为全面了解黄土高原旱作麦田长期保护性耕作对土壤生态系统的影响，本研究依托山西省临汾市长达27年的保护性耕作试验平台，采用高通量测序技术，开展了土壤真菌群落结构和多样性对传统耕作（TT1）、免耕覆盖（NTS）、深松+免耕覆盖（SNTS）的响应分析。结果表明：与TT1相比，NTS和SNTS处理小麦根围土壤真菌组成及相对丰度发生了显著变化，NTS处理出现了未知真菌类群；各处理土壤真菌的主要优势菌门为子囊菌门、担子菌门和接合菌门；从属水平物种分布热图可以看出，与传统耕作相比，该地区多年的保护性耕作会加大小麦赤霉病发生的风险；UPGMA（非加权组平均法）分析表明，2种保护性耕作土壤真菌群落组成相似；TT1中具有显著差异的关键优势物种属担子菌门，NTS和SNTS处理的属子囊菌门；NTS处理土壤真菌丰富度和系统发育多样性最高，SNTS处理土壤真菌多样性最高；但土壤真菌多样性和丰富度指数在各处理间并无显著差异。综上，长期保护性耕作显著改变了土壤真菌群落结构及组成，提高了土壤真菌的丰富度和多样性，但不存在显著差异。同时该地区多年的保护性耕作可能会加大小麦赤霉病发生的风险。本研究对黄土高原旱作麦田区推广保护性耕作及土壤管理具有一定的指导意义。
关键词:保护性耕作/
小麦/
秸秆覆盖/
土壤真菌/
多样性/
高通量测序
Abstract:Different agricultural tillage practices create variable soil ecosystems that have different effects on soil microorganisms, especially those around the root system. Conservation tillage has numerous advantages and is used worldwide, but its sustainability has been challenged by the increase in soil pathogenic microorganisms caused by stubble mulching. To better understand the effects of long-term conservation tillage on the soil ecosystems in the dryland wheat regions of the Loess Plateau, this study used data from a 27-year conservation tillage experimental platform in Linfen, Shanxi Province, and high-throughput sequencing technology to investigate the response of the soil fungal community structure and diversity to different tillage treatments, including traditional tillage (TT1), no-tillage with stubble (NTS), and no-tillage with stubble after subsoiling (SNTS). The results showed that there were considerable differences in the composition and relative abundances of soil fungi among three treatments, and the NTS treatment included some unidentified or unknown fungi. Ascomycota, Basidiomycota, and Zygomycota were the dominant phyla of soil fungi in each treatment. Compared with TT1, the relative abundances of Ascomycota, Zygomycota, Chytridiomycota, and Glomeromycota increased under the two conservation tillage treatments, whereas the relative abundance of Basidiomycota significantly decreased. According to the heat map of species distribution at the genus level, the relative abundances of Gibberella and Fusarium increased compared to TT1 treatment, and Gibberella was the dominant genus under the two conservation tillage treatments. This indicated that long-term conservation tillage may increase the risk of wheat scab in this area. UPGMA (unweighted pair-group method with arithmetic means) showed that the soil fungal community composition was similar between the two conservation tillage treatments, which differed from the TT1 treatment. The key biomarker in the TT1 treatment belonged to Basidiomycota, whereas the key biomarkers belonged to Ascomycota for the NTS and SNTS treatments. The NTS treatment had the highest richness and PD_whole_tree of soil fungi, whereas the SNTS treatment had the highest diversity. However, there were no significant differences in the diversity and richness indices of soil fungi among three treatments. In conclusion, long-term conservation tillage significantly changed the structure and composition of soil fungal communities, and improved the richness and diversity of soil fungi with no significant differences among three treatments. Conservation tillage (for 27 years) may also increase the risk of wheat scab. Therefore, to minimize soil pathogens, appropriate stubble mulching frequency, no-tillage, conventional tillage or subsoiling rotation, and moderate shallow tillage should be examined in future soil management and conservation tillage studies. This study provides guidance for promoting conservation tillage and soil management in the dryland wheat regions of the Loess Plateau.
Key words:Conservation tillage/
Wheat/
Stubble mulching/
Soil fungi/
Diversity/
High-throughput sequencing
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