Ecological niche differences regulate the assembly of bacterial community in endophytic and rhizosphere of Eucalyptus

The relationship between microorganisms and plants has been a hot topic of research because of its direct link to plant health and productivity, and these interactions are not limited to the soil. The structural and ecological variation of bacterial communities due to spatial isolation in different parts of plants is still unclear. Whether intensive management of Eucalyptus plantations affects this variation should also be concerned. To investigate the mechanisms underlying bacterial changes in different ecological niches of Eucalyptus and the stability of bacterial communities after continuous high-intensity planting of Eucalyptus, we studied the effects of long-term plantation of Eucalyptus on the structure, assembly patterns, and interactions of the bacterial community. Woodlands that planted with Eucalyptus urophylla S.T. Blake x Eucalyptus grandis Hill ex Maiden (Eucalyptus urograndis, hereafter E. urograndis) in three generations (10 years after planting) were selected for study, and the woodlands were cleared and replanted with E. urograndis. Rhizosphere soil, roots, stems, branches, and leaves of E. urograndis differing in age (2, 4, and 6 years) after planting were sampled, and the rhizosphere soil bacteria and endophytic bacterial communities of different parts were determined using the 16S rRNA technique. We detected structural variation in the soil and endophytic bacterial communities as well as variation in community assembly. Stochastic processes made large contributions to the assembly of highly abundant soil bacterial communities, as well as low-abundant endophytic bacterial communities of the branches and leaves (especially leaves), and this pattern may be strongly related to the ecological niches of the bacteria. The bacterial correlation network demonstrated that the properties of Eucalyptus soil and their endophytic bacterial communities can vary 6 years after successive plantings. Thus, measures should be taken to ecologically restore Eucalyptus woodlands after 15 years of high-intensity planting to ensure the stability of microbial community structure, the mainte-nance of adequate ecological properties during Eucalyptus planting, and the sustainable production and man-agement of Eucalyptus plantations.