Objective To investigate the impact of continuous planting on the changes in the archaeal community in the rhizosphere soil of Casuarina equisetifolia Forst. plantations for understanding of the obstacle mechanism of continuous planting of C. equisetifolia and providing a solid theoretical basis for further exploration.

MethodsWe collected the rhizosphere soil from three C. equisetifolia plantations with varying generations of continuous planting (FCP, SCP, TCP). The rhizosphere soil from a natural arbor forest without C. equisetifolia was used as the control (CK). High-throughput sequencing of the archaeal community was performed using the Illumina NovaSeq sequencing platform.

ResultsA total of 1 146 390 effective sequences were obtained from the rhizosphere soil samples and bare land control soil, resulting in the identification of 998 515 ASVs with 100% sequence similarity. The analysis of Alpha diversity indicated that the observed number of species and Chao1 index decreased with successive generations. However, the Shannon index, Simpson index, and Pielou_e were highest in FCP, followed by TCP, and lowest in SCP. The results of the Beta diversity analysis, Principal Coordinate Analysis (PCoA), UPGMA cluster analysis, and Anosim analysis indicated variations in the species diversity of the archaeal community in the rhizosphere soil of C. equisetifolia across different continuous planting generations. However, the differences between different groups were not significant. A total of 5 phyla were detected, and the dominant bacterial phylum was Thaumarchaeota and the proportion of Thaumarchaeota showed a decreasing trend with the increase of planting generations. Compared with the control, FCP, SCP and TCP decreased by 17.42%, 50.97% and 51.51% respectively. The results of the correlation analysis between archaea community and soil physical and chemical properties revealed significant positive correlations between Thaumarchaeota and pH, TK, TN and TP. Additionally, Crenarchaeota showed significant correlations with AP and AN. There were significant differences in the correlations between different archaeal communities and soil physical and chemical factors.

Conclusion This study confirms that the archaeal community structure of the rhizosphere soil change significantly after multiple generations of continuous planting in C. equisetifolia plantations. It is speculated that the imbalance of the archaeal community structure is one of the key factors contributing to the imbalance of soil microecology. The study provides a theoretical foundation for understanding the causes of continuous planting obstacles in C. equisetifolia plantations.