Abstract: We examined the species and content of phenolic acids in rhizosphere soil of replanted Casuarina equisetifolia plantations (including first rotation plantation (FCP), second rotation plantation (SCP) and third rotation plantation (TCP)) in Fujian Huian Chihu State-owned Shelter Forest Farm by high performance liquid chromatography (HPLC). The ratio of phenolic acids in rhizosphere soil was simulated to explore its effect on the growth of key soil microbes. The results showed that five kinds of phenolic acids were detected in the root exudates of C. equisetifolia, including vanillic acid, ferulic acid, gallic acid, cumaric acid, and salicylic acid, with an average ratio of 32∶6∶19∶5∶8. The total content of phenolic acids increased with increasing rotation generations. Among the five phenolic compounds, vanillic acid, gallic acid, cumaric acid, and salicylic acid accumulated in SCP and TCP, while the content of ferulic acid showed a decreasing trend with increasing rotation generations (P>0.05). The phenolic acids mixture at their ratios explored in the C. equisetifolia soil significantly accelerated mycelial growth of Fusarium oxysporum, but inhibited Bacillus amyloliquefacien. Salicylic acid had the strongest positive or negative effects on the growth of pathogenic or beneficial microorganisms. Therefore, the mixture of phenolic compounds played a role in affecting the growth of soil microorganisms, resulting in the structure imbalance of rhizosphere microbial community, and consequently leading to consecutive planting obstacles. Our results provide a theoretical reference for alleviating consecutive planting obstacles in the production and management of C. equisetifoliaplantations.

Key words: consecutive planting obstacle, Casuarina equisetifolia, phenolic compounds, high performance liquid chromatography (HPLC).