Abstract: Aims Revealing the response patterns of soil bacterial community to changes in vegetation type during secondary succession can improve our understanding of the mechanisms that structure the above- and below-ground interactions in ecosystems. Methods To investigate how soil bacterial diversity, taxa network structure and biomarkers shift with vegetation succession, this study measured soil carbon, nitrogen and phosphorus contents, as well as soil bacterial communities across shrubland, deciduous broad-leaved forest and evergreen broad-leaved forests, representing the early- middle- and late-successional stages, respectively, on Dajinshan Island, Shanghai. Important findings Soil nutrient contents were significantly higher in evergreen broad-leaved forest than in deciduous broad-leaved forest. However, soil bacterial diversity was significantly higher in deciduous broad-leaved forest than in evergreen broad-leaved forest, while soil nutrient content and bacterial diversity were medium in deciduous shrubland. The correlation network nodes, density and complexity of soil bacteria were highest in deciduous broad-leaved forest, medium in deciduous shrub, and lowest in evergreen broad-leaved forest. The dominant soil bacteria in deciduous shrubland and broad-leaved forest was Rhizobiales and Burkholderiales, respectively, which belong to functional group of nitrogen-fixing. The dominant soil bacterial in evergreen broad-leaved forest were characterized by functional groups of pathogenicity and resistance such as Xanthomonadales and Thermogemmatisporales, and functional group associated with cellulose degradation such as Acidobacteriales. These results suggest that changes in plant species composition and soil nutrient availability during island vegetation succession can greatly reshape species diversity, community composition, interactive network structure and biomarkers of soil bacteria. In evergreen broad-leaved forest, lowered soil bacterial diversity, simplified bacterial network structure, and emerged biomarkers of functional groups of pathogenicity and resistance suggest a response of belowground to the degraded trend of aboveground in the studied climax forest.

Key words: secondary succession, island, shrubland, forest, bacterial diversity, 16S rDNA