Changes in bacterial communities and functions associated with litter degradation during forest succession caused by forest disease

Forest succession affects aboveground vegetation and belowground microbial community composition, in which litter degradation plays an important role in nutrient cycling. However, limited information is available on how microbial communities change during litter degradation in forests undergoing succession due to disease. In this study, the bacterial communities and functions in litter degradation along the forest succession from pure Pinus forest (PPF), mixed Pinus and Liquidambar forest (MPF and MLF) and pure Liquidambar forest (PLF) were investigated. The results showed the bacterial community richness and diversity in both needles/leaves and branch litters increased progressively with forest succession. Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria were the most abundant bacterial phyla in the litter degradation along forest succession. The abundance of Bacteroidetes in branch increased significantly, while the abundance of genus Paraburkholderia decreased along forest succession. The different forests formed distinct bacterial community structures during litter decomposition. Functionally, chemoheterotrophy was the most abundant functional guild, followed by nitrogen fixation, intracellular parasitism and urealysis. The abundance of nitrogen fixation increased significantly along forest succession. Similarly, the different forests formed distinct bacterial functional structures in the needle/leaf along the succession. However, only two functional structures were formed in the branch. These results suggest that the bacterial community and its functions undergo significant changes during forest succession, particularly from the pure pine to mixed pine forest. These results provide a clear understanding of the changes in bacterial communities and functions during litter degradation in forests undergoing disease-induced succession.