Abstract: Due to large-scale commercial logging and prolonged anthropogenic disturbances over the past decades, large tropical secondary forests (SFs) have been converted into rubber plantations (RPs), which have substantial impacts on soil bacterial community via altering soil properties. However, how forest conversion affects soil bacterial community composition and diversity is still poorly understood. To address this, we compared the soil bacterial communities and physicochemical properties between typical SFs and RPs in Hainan Island. The results showed that SF exhibited higher soil organic matter, total nitrogen, total carbon and pH compared with RP, particularly in the 0–10-cm layer. Besides, the soil bulk density in SF was lower than that in RP. The bacterial community composition and microbial networks were significantly varied between SF and RP. The dominant soil bacterial phyla in SF were Proteobacteria (27.4%–28.7%), followed by Acidobacteria (19.0%–19.8%), while Chloroflexi prevailed in RP (27.9%–28.5%), followed by Acidobacteria (20.9%–24.4%). Furthermore, SF exhibited more complex microbial networks owing to its higher edges, degree and links compared with RP. Meanwhile, bacterial community assembly in SF was primarily governed by deterministic processes, while stochastic processes dominated RP. The soil bacterial α-diversity in SF was higher than that in RP, which was primarily dominated by pH. Our findings demonstrate that converting SFs to RPs does not favor soil microbial diversity and stability, as it decreases soil pH, suggesting that sustainable management strategies should prevent soil acidification in RPs.

Key words: secondary forest, rubber plantation, soil physicochemical properties, soil bacterial community diversity, soil bacterial community composition