Differences in bacterial community structure and potential functions among Eucalyptus plantations with different ages and species of trees

Bacteria are the most abundant microbes in soil and play an important role in the carbon and nitrogen cycles. Currently, China has become the country with the second largest Eucalyptus planting area. However, the dynamic changes in the soil bacterial community in different Eucalyptus plantations has been poorly studied. In the present study, the bacterial community structure and potential function associated with Eucalyptus plantations of different ages (1- and 5(+)-year) and species (E. urophylla x E. grandis, E. camaldulens and E. pellita) in Zhanjiang, Guangdong Province, China were characterized using Illumina MiSeq. technology coupled with Functional Annotation of Prokaryotic Taxa (FAPROTAX) analysis. The results showed that the bacterial diversity increased with increasing plantation age, with different ages and species of trees forming distinct bacterial community and functional structures, respectively (P < 0.05 in all possible pairs). The most abundant phyla across all samples were Actinobacteria (35.9% of total sequences), Proteobacteria (20.5%), Chloroflexi (10.3%) and Acidobacteria (9.2%). With increasing plantation age, the bacterial community shifted from the phylum WPS-2 and order Sphingomonadales as dominant taxa to the order GP6. The community function also changed from carbon utilization to more nitrogen and sulfur cycling processes. The soil pH, organic carbon, water content and total nitrogen were identified as the key factors affecting both community structure and function. The results indicate that Eucalyptus plantation age has a greater effect on the bacterial community diversity and structure than Eucalyptus species. This study provides useful information on the importance of microbes for the sustainable management of Eucalyptus plantations in the future.