设施土壤真菌的团聚体分异特征

Distribution characteristics of fungi in soil aggregates of greenhouse soil

【目的】探究真菌在设施土壤不同级别团聚体中的分布特征,明确真菌在微域环境下的生态适应机制。【方法】以华北平原长期设施条件下的潮土作为研究对象,比较不同级别团聚体的理化性质,利用荧光定量PCR和高通量测序技术,研究不同团聚体中真菌的丰度和群落组成。【结果】设施土壤的pH相较露天土壤降低了0.68个单位,而电导率、有机质含量和可溶性有机碳含量分别提高了30.6%、85.8%和94.1%,<0.5 mm的团聚体中有机质含量显著高于>0.5 mm的团聚体,而且微团聚体(<0.25 mm)的电导率值显著低于大团聚体(2~0.25 mm)和宏团聚体(>2 mm)。通过对真菌的ITS区扩增测序,设施土壤得到了871个OTUs,显著高于露天土壤(673个),设施土壤<0.25 mm团聚体的特有可操作分类单元(OTUs)最多,0.5~0.25 mm中特有OTUs最少;设施环境显著降低了真菌ITS基因的丰度,但是真菌α-多样性显著高于露天土壤,同时0.5~0.25 mm团聚体中真菌的α-多样性显著低于其他团聚体(P<0.05),而且主成分分析表明,设施环境和0.5~0.25 mm团聚体中真菌的群落结构有别于露天土壤和其他粒级的团聚体;潮土的优势菌门是被孢霉门和子囊菌门,而设施土壤中担子菌门和球囊菌门的占比显著高于露天土壤。【结论】相较露天土壤,设施土壤的真菌丰度显著降低,但真菌多样性显著升高,冗余分析表明,pH是影响设施土壤真菌群落结构变化的关键因素;设施土壤中的优势菌门为被孢霉门、子囊菌门、担子菌门和球囊菌门,且不同级别团聚体的真菌群落结构差异显著,其中,0.5~0.25 mm的大团聚体差异最为明显,冗余分析表明,可溶性有机碳含量是引起差异的关键因子。

[Objective]The aim of this study is to explore the distribution characteristics of fungi in different soil aggregates of greenhouse soil and ultimately clarify the ecological adaptation mechanism of fungi in soil micro-environment.[Methods]The changes in soil aggregate properties in greenhouse and open soil were compared,and the abundance and community structure of fungi in different soil aggregates were evaluated by quantitative PCR and high-throughput sequencing.[Results]The pH of greenhouse soil decreased by 0.68 units compared with open soil,while the conductivity,soil organic matter and dissolved organic carbon contents were increased by 30.6%,85.8%and 94.1%,respectively.The DOC content in aggregates with particle size below 0.5 mm was significantly higher than that in aggregates with particle size greater than 0.5 mm.The EC value of micro-aggregates(<0.25 mm)was significantly lower than that of macro-aggregates(2-0.25 mm)and mega-aggregates(>2 mm).Through amplification and sequencing of ITS gene,OTU numbers obtained from greenhouse soil were much more than that in open soil.There were highest and lowest specific OTU numbers in the aggregates with particle size below 0.25 mm and 0.5-0.25 mm size,respectively.The greenhouse environment significantly reduced the abundance of ITS gene,while increased theα-diversity of fungal community compared with open soil.Meanwhile,theα-diversity of aggregates with 0.5-0.25 mm particle size was the lowest among all aggregates(P<0.05).Moreover,principal coordinate analysis showed that the community structure of fungi in greenhouse environment and aggregates with 0.5-0.25 mm particle size were differed from that in open soil and other aggregates.The predominant fungi in soil were Mortierellomycota and Ascomycota at phylum level,while the relative abundances of Basidiomycota and Glomeromycota in soil were significantly higher than those in the open soil.[Conclusion]Compared with the open soil,the abundance of fungi was evidently decreased under greenhouse condition,while the diversity was increased.Redundancy analysis showed that pH was the key factor affecting the change of fungal community structure in greenhouse soil.The dominant fungi in the greenhouse soil were Mortierellomycota,Ascomycota,Basidiomycota and Glomeromycota at phylum level.Moreover,the community structures of fungi were significantly distinct among different levels of aggregates,especially in aggregates with 0.5-0.25 mm particle size.Redundancy analysis revealed that DOC was the key factor driving the difference among different levels of aggregates.