Comparison of Soil Microbial Composition and Diversity Between Mixed and Monoculture Rubber Plantations in Hainan Province, China

This study aimed to compare monoculture and mixed rubber plantations in terms of their soil bacterial and fungal composition. An Illumina MiSeq sequencing analysis was performed to investigate the composition and diversity of the soil bacterial and fungal communities among three different rubber (Hevea brasiliensis) plantations: monoculture, Mixed 1 (Hevea brasiliensis and Mytilaria laosensis), and Mixed 2 (Hevea brasiliensis and Michelia macclurei) in Hainan. The results showed that the bacterial composition of the three rubber plantations was basically similar. However, there was a significant difference in fungal communities among the three rubber plantations at both the phylum and operational taxonomic unit level. The species richness, Chao, and Shannon diversity of bacterial communities of monoculture rubber plantations were higher than the Mixed 1 and Mixed 2 rubber plantations, whereas all diversity indexes of fungal communities were relatively equal for the monoculture and mixed rubber plantations. Soil nutrition (such as total nitrogen and total potassium) and soil pH are the main drivers of the bacterial composition (p<.001). However, soil pH and water content are the main drivers of the fungal composition (p<.001), and to some extent, soil pH can increase soil bacteria diversity. We suggest that alkaline fertilizers should be applied in mixed rubber plantations to improve the soil pH and, consequently, to increase the total diversity of the rubber plantation.