稻田土壤古菌群落组成对秸秆还田的响应

Responses of archaeal community composition in paddy soils to straw return

为探讨秸秆还田下稻田土壤古菌群落的演替规律及其驱动因子,本研究开展室内稻田土壤淹水培养试验,利用高通量测序技术,研究了淹水培养第0、15、30 d和60 d时不同量小麦秸秆(0、1%、2%和5%)施用下两种类型的稻田土壤(高砂土和黄泥土)古菌群落组成的动态变化及其影响因子。结果表明:秸秆还田导致土壤pH显著降低,而土壤电导率(EC)、总碳(TC)、总氮(TN)、碳氮比(C/N)以及土壤孔隙水中溶解性有机碳(DOC)、还原性亚铁[Fe(Ⅱ)]和总铁(Fe)含量显著增加,并且当秸秆还田量为5%时,上述土壤指标改变量最大。基于高通量测序技术发现,两种类型稻田土壤的优势古菌均为奇古菌门(Thanumarchaeota)。在淹水培养的0～30 d,秸秆还田对奇古菌门的相对丰度没有显著影响,维持在97%～98%;然而,在培养的第60 d,与未施用秸秆相比,秸秆施用下两种类型稻田土壤中奇古菌门的相对丰度显著降低(P<0.05),并且随着秸秆施用量的增加,奇古菌门丰度的降低程度越大。主成分分析(PCA)结果显示两种不同类型土壤的古菌群落存在着显著差异(P<0.05),表明土壤类型是土壤古菌群落结构的重要影响因子。与未施用秸秆的土壤相比,5%秸秆施用显著改变了高砂土古菌群落结构,而1%秸秆施用显著改变了黄泥土壤古菌群落结构。进一步对不同量秸秆施用下土壤古菌群落结构的分析发现,秸秆施用量为5%时高砂土壤古菌群落显著不同于秸秆施用量为1%和2%的土壤,而1%和2%秸秆施用量之间并无显著差异;而对黄泥土,仅秸秆施用量为1%和2%时古菌群落存在着显著差异。为了进一步探究土壤古菌群落迁移的驱动因子,冗余分析(RDA)发现,pH和C/N比是秸秆还田下两种类型土壤古菌群落迁移的重要影响因子。综合分析认为,秸秆还田主要通过改变土壤性质来调控古菌群落结构,而不同类型土壤的古菌群落结构对秸秆还田的响应亦不同。

To explore the impacts of straw return on the composition of archaeal communities in paddy soils,different amounts of wheat straw(0,1%,2%,and 5%)were incorporated into two types of paddy soils(silty and clayed soil),which were incubated with flooding in the labover a 60 d period.At time intervals of 0,15,30,and 60 d,soil samples were collected and analyzed for soil physico-chemical propertiesand archaeal communities based on high-throughput sequencing.Results showed that straw addition significantly decreased soil pH whileincreasing soil electricity conductivity(EC),total carbon and nitrogen(TC and TN)contents,and C/N ratio and concentrations of dissolve organic carbon(DOC),ferrous[Fe(Ⅱ)],and total ferric(Fe)in soil porewater(P<0.05).Higher application rates of straw lead to greaterchanges in the soil properties.Based on illumina sequencing technology,the major component of the archaeal community was Thaumarchaeota at the phylum level for both soils with and without wheat straw.During the incubation period of 0~30 d,straw return had insignificant influences on the relative abundance of Thaumarchaeota for both soils,which was maintained at 97%~98%.However,at the time interval of 60 d,straw addition at rates of 1%,2%,and 5%significantly reduced the relative abundances of Thaumarchaeota in both soils.Principle component analysis(PCA)based on archaeal abundance at the species level showed that there were significant(P<0.05)differences in archaealcommunity composition between the two soil types,indicating soil-dependent archaeal community composition.Compared to that in unamended soils,significant shifts in archaeal community composition were observed in the silty soil when amended with 5%straw,and in theclayed soil when amended with 1%straw.Further analyses showed significant(P<0.05)differences in archaeal community compositions ofthe silty soil between low(1%and 2%)and high(5%)rates of straw incorporation,whereas there were insignificant differences between 1%and 2%straw treatments.Unlike the silty soil,significant differences in archaeal community compositions were observed for the clayed soilswhen amended with 1%and 2%of straw.Using an envfit function(999 permutations),soil pH,EC,C/N ratio,DOC,Fe(Ⅱ),and Fe that significantly correlated with the archaeal community composition at the species level were selected in an RDA analysis,revealing that pH andC/N ratio were the dominant variables that significantly contributed to the variance of archaeal communities in both soils.In conclusion,straw addition significantly changed archaeal community composition by altering soil chemical characteristics,and the response of soil archaeal community composition to straw return depended on soil type.