Recovery and variation of soil bacterial communities along a chronosequence of Eucalyptus plantation

Eucalyptus is harvested for wood and fiber production in many tropical and sub-tropical habitats globally. Plantation has been controversial because of its influence on the surrounding environment however the influence of massive Eucalyptus planting on soil microbial communities is unclear. Here we applied high-throughput sequencing of the 16S rRNA gene to assess the microbial community composition and diversity of planting chronosequences, involving two, five and ten years of Eucalyptus plantation, comparing with that of native secondary-forest in South China. We found that significant changes in the composition of soil bacteria occurred when the forests were converted from secondary-forest to Eucalyptus. The bacterial community structure was clearly distinct from control and five year samples after Eucalyptus was grown for two and ten years, highlighting the influence of this plantation on local soil microbial communities. These groupings indicated a cycle of impact (two- and ten- year plantations) and recovery (five-year plantations) in this chronosequence of Eucalyptus plantation. Community patterns were underpinned by shifts in soil properties such as pH and phosphorus concentration. Concurrenlty, key soil taxonomic groups such as Actinobacteria showed abundance shifts, increasing in impacted plantations and decreasing in recovered samples. Shifts in taxonomy were reflected in a shift in metabolic potential, including pathways for nutrient cycles such as carbon fixation, which changed in abundance over time following Eucalyptus plantation. Combined these results confirm that Eucalyptus plantation can change the community structure and diversity of soil microorganisms with strong implications for land-management and maintaining the health of these ecosystems.