Changes in soil microbial community structure and activity in a cedar plantation invaded by moso bamboo

• Moso bamboo is fast-growing and can invade neighboring forest with its rhizome system.
• Bamboo invasion reduced cellulase and xylanase activities.
• Bamboo invasion reduced SOM but increased Cmic/Corg and Nmic/Ntot.
• Low G+/G− ratio and values of stress indicators referred to increase of easily decomposable SOM in bamboo soil.
• Bacterial and fungal community structure findings on DGGE were both associated with bamboo invasion.

Moso bamboo is fast-growing and can invade a neighboring forest with its rhizome system. We investigated the effect of bamboo invasion on an adjacent Japanese cedar plantation in terms of soil microbial biomass, activities and community structure by analysis of phospholipid-derived fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) profiles. In the cedar-plantation soil invaded by bamboo, soil microbial biomass C (Cmic) decreased and biomass N (Nmic) increased, which reduced Cmic/Nmic. Similarly, soil cellulase and xylanase activities decreased with invasion, indicating that bamboo invasion into the cedar plantation facilitated changes in microbial biomass and activities by changing soil biochemical properties. The proportion of total PLFAs that was attributed to all bacteria, Gram-positive (G+) bacteria and Gram-negative (G−) bacteria, was reduced with invasion. The ratio of G+/G− bacteria, 16:ω7t to 16:1ω7c, and cyclopropyl fatty acids to their precursors (i.e., cy17:0/16:1ω7 and cy19:0/18:1ω7c) was highest in cedar-plantation soil, suggesting that environmental stress for soil bacterial communities is alleviated in bamboo invaded soils. Low ratio of G+/G− in the bamboo-plantation and transition-zone soil was associated with increased level of easily decomposable organic matter (Cmic/Corg and Nmic/Ntot) in bamboo-invaded soil. Principle component analysis of PLFA content separated the cedar-plantation soil from bamboo and transition-zone soil. DGGE analysis revealed that change in both bacterial and fungal community structure was associated with bamboo invasion. Bamboo invasion caused significant changes in soil microbial activities and community structure in the Japanese cedar plantation.

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