Archaeal community succession with fine root growth in poplar plantation

The archaeal community structure in the rhizosphere soils might change with root growth, which is of great importance for understanding the interaction between roots and microbes. According to root colors, three groups of rhizosphere soils from first-order fine roots of poplar trees (Populus × euramericana) were sampled, including rhizosphere soils surrounding newly born roots (white color, WR), mature roots (yellow color, YR) and aged roots (brown color, BR). Total microbial DNA was extracted from the soils associated with poplar fine roots. The specific primers were used to amplify the 16S rDNA V4-V5 region of soil archaea, and the Illumina MiSeq platform was used for high-throughput sequencing analysis. The results showed that the observed OTU (operational taxonomic unit) abundance of archaeal community in WR and BR rhizosphere soils were similar, while the OTU abundance in YR rhizosphere soil were lower. The WR and BR shared 134 OTUs of archea, the YR and BR shared 87 OTUs, and the WR and BR shared 90 OTUs. The Chao1 index and the ACE index of archaeal community in YR rhizosphere soil were significantly lower than those of WR and BR, while the Simpson index and the Shannon index of BR were significantly lower than WR to YR. Results from the PERMANOVA analysis showed that archaeal community compositions in WR and BR rhizosphere soils were significantly different. Species annotation showed that there were 12 genera of archea in three rhizosphere soils, five genera in WR, 10 genera in YR, and six genera in BR, respectively. The similarity of the archaeal community composition in poplar rhizosphere soils gradually decreased from WR to BR, with large differences among different growth stages of fine roots. The dominant genus was Candidatus_Nitrososphaera, with a relative abundance of more than 70%, indicating this archaea group might be closely related to poplar fine roots development.