Abstract: Litter plays an important role in ecosystems. To compare the diversity and community structure of microorganisms inside and outside litter, Casuarina equisetifolia were selected from three forests in Guilin coastal area of Haikou City, Hainan Province. Illumina Miseq high-throughput sequencing was used to analyze the diversity and composition of epiphytic and endophytic bacteria of litter. The results showed that the diversity of epiphytic bacteria was higher than that of endophytic bacteria. Moreover, the diversity and richness of bacteria inside and outside C. equisetifolia litter in the intermediate-aged forest were the highest, followed by young forest and mature forest. Proteobacteria and Actinobacteria were the most abundant at the phylum level, accounting for about 80% of the total. At the genus level, Curtobacterium, Jatrophihabitans, Mycobacterium, Actinomycetospora, Mucilaginibacter and Pseudomonas showed significant variation among different forest ages. PCoA results showed that the endophytic bacteria of litter were greatly affected by forest age, while the epiphytic bacteria were greatly affected by environmental factors. The fermentation broth of Bacillus amyloliquefaciens had the strongest allelopathic potential to C. equisetifolia seeds and 2,2′-methylenebis (6-tert-butyl-4-methyl-phenol) was found in it, indicating that B. amyloliquefaciens was involved in the synthesis of allelochemicals. The diversity of litter microbial community affected the allelopathy of C. equisetifolia, which laid a foundation for studying the role of microorganisms in the degradation process of C. equisetifolia litter.

Key words: Casuarina equisetifolia, endophytic and epiphytic bacteria, diversity, allelochemicals, litter decomposition