水稻秸秆还田时间对土壤真菌群落结构的影响

为揭示水稻秸秆还田对土壤真菌群落结构的长期影响,采用荧光定量PCR和PCR-DGGE技术分析了秸秆还田90,180,270 d和360 d的土壤真菌基因丰度和群落结构组成演变趋势,并利用冗余分析(RDA)研究土壤真菌群落结构变化与环境因子的关系。结果表明:随着秸秆还田时间的增加,土壤真菌群体数量和多样性指数(H、R和E)显著增加,在360 d时达到最高。对DGGE图谱的特征条带进行胶回收、测序,系统进化分析表明,土壤真菌主要种群包括:接合菌(Zygomycete sp.)、盐腐霉菌(Pythium salinum)、肉盘菌(Uncultured Sarcosomataceae)、牛粪盘菌(Ascobolus stercorarius)、大链壶菌(Lagenidium giganteum)、青霉菌(Penicillium sp.)、曲霉属真菌(Aspergillus sp.)和疏绵状丝孢菌(Thermomyces lanuginosus)、灰绿曲霉菌(Aspergillus glaucus)、禾谷多粘菌(Polymyxa graminis)和枝顶孢霉菌(Acremonium sp.),其中青霉菌(Penicillium sp.)、曲霉属真菌(Aspergillus sp.)和枝顶孢霉菌(Acremonium sp.)具有纤维素降解能力,而枝顶孢霉菌(Acremonium sp.)在90 d时成为新的优势菌群。RDA分析表明,90 d和180 d秸秆还田与对照土壤的真菌群落结构较为类似,270 d和360 d的秸秆还田与对照土壤的真菌群落结构发生了明显变化。土壤有机碳、pH和速效磷是引起土壤真菌群落结构及多样性变异的主要因素。

Rice straw return of different decomposition days altered soil fungal community structure

The decomposition of plant residue is largely mediated by microorganisms, such as soil fungi and bacteria, which are very sensitive to changes in their soil environments. Numerous studies at the microbial community level have emphasized the influence of residue return on functional capacity and the characterization of phenotypic traits. Furthermore, previous studies have also shown that fungi dominate the early stages of decomposition in semi-natural unfertilized soils. The long-term impact of straw return on soil ecosystems, especially fungal gene abundance and community composition, is unclear. In the present study, based on the analysis of soil properties, we investigated the effect of rice straw return on the population size and community structure of soil fungi under different straw return days, using real-time PCR and PCR-DGGE. Subsequently, the correlation between fungal community and soil environmental factors was analyzed using redundancy analysis (RDA). Treatments in the present study were based on different return days (90, 180, 270, and 360 d), and a soil with no straw return and similar topography was used as the control. Each treatment had three replicates. The copy numbers of soil fungal ITS ranged from 2.61×10⁷ to 6.46×10⁷ per g of dry soil and was greatly influenced by straw return days. The 360-d treatment yielded the highest copy numbers, whereas the 90-d treatment yielded the lowest copy numbers. The diversity indices (H, R, and E) increased significantly with increasing straw decomposition time and reached maximum values under the 360-d treatment. The DGGE patterns suggested that straw return altered the fungal community, and significant differences were observed among the treatments with different return days. Eleven DGGE bands were re-amplified, sequenced, and aligned using BLAST; and phylogenetic analysis revealed that the soil fungal community of the straw return included Zygomycete sp., Pythium salinum, uncultured Sarcosomataceae, Ascobolus stercorarius, Lagenidium giganteum, Penicillium sp., Aspergillus sp., Thermomyces lanuginosus, Aspergillus glaucus, Polymyxa graminis, and Acremonium sp., among which Penicillium sp., Aspergillus sp., and Acremonium sp. are able to degrade cellulose. RDA analysis suggested the 90-d and 180-d treatments were similar and clearly distinct from the 270-d and 360-d treatments along both the first and second ordination axes, which indicated a pronounced difference in the community composition of soil fungi at the late straw return stage and a slight difference in the early stage, respectively. The eigenvalues of the first two axes of the fungal RDA results were 0.309 and 0.144 and accounted for 80.7% of the total eigenvalue, which suggested qualified ordination results. The first two axes of the species-environment relationship from the RDA results explained 74.8% of the total variance. Among the six soil parameters measured, the influence of available K, alkaline-hydrolyzed N, total N were not significant (P<0.05), but soil organic carbon, pH, and available P were the main factors that influenced the variation of fungal community structure and diversity. The results suggested that long-term straw return had a significant impact on soil fungal composition and that soil organic carbon, pH, and available P are important factors in the dynamics of soil fungal communities.