Response of the soil microbial community composition and biomass to a short-term Spartina alterniflora invasion in a coastal wetland of eastern China

Plant invasion has been reported to alter ecosystem carbon (C) and nitrogen (N) cycling processes and pools. The mechanisms involved in how plant invasion affects the soil microbial community-the primary mediator of soil C and N cycling-remain poorly understood. The objective of this study was therefore to evaluate the effect of plant invasion on the soil microbial community in a coastal wetland of eastern China. We investigated the impact of an exotic C-4 perennial grass, Spartina alterniflora, on the soil microbial community structure based on phospholipid fatty acids (PLFAs) analysis and chloroform fumigation-extraction by comparing it to that of bare flat and native C-3 plants Suaeda salsa and Phragmites australis communities. Spartina alterniflora invasion significantly increased soil microbial biomass C and the total and various types of PLFAs compared with bare flat, Suaeda salsa and Phragmites australis communities. Increased concentrations of soil moisture, electrical conductivity, water-soluble organic carbon (WSOC), and total, labile and recalcitrant soil organic C and N, and decreased soil pH in Spartina alterniflora community explained 65.9 % of the total variability in the PLFAs. WSOC and soil labile organic N were strongly correlated with PLFAs, whereas soil pH was negatively related to PLFAs. A 10-year Spartina alterniflora invasion significantly altered soil microbial biomass and community structure by increasing available substrate. The changes in soil microbial biomass and community structure may in turn enhance soil C and N sequestration in a coastal wetland of eastern China.