Soil microbial community composition along chronosequence of the introduction of Phragmites australis at Suncheon Bay

Vegetations of coastal wetlands play a vital role in providing numerous ecological services to the coastal ecosystem and are also key factors affecting the biogeochemical processes in the soil. The acreage of Phragmites australis is expanding and gradually replacing the Suaeda japonica at Suncheon Bay, Republic of Korea. However, the changes in soil microbial community composition caused by Phragmites introduction is poorly characterized. In the present study, soil cores were collected to a depth of 1m (divided into 10 segments of 10 cm) from Suaedavegetated, the boundary of Suaeda- and Phragmites-vegetated, Phragmites-vegetated marshes (after 5 and 10 years of the introduction). These samples were analyzed for physico-chemical characteristics, enzyme activities, soil microbial community (phospholipid fatty acids profiling) and abundance of functional genes related to the methane cycle (mcrA, pmoA and dsrA). Results showed that introduction the of Phragmites increased the water content, pH and dissolved organic carbon content in the soil. The contents of total PLFA and microbial group biomarkers of PLFA were observed to be higher in the surface soil and decreased with soil depth. Early introduction of Phragmites (10 yr) sediments had the significantly highest concentrations of total as well as other microbial biomarkers PLFAs compared with other salt marshes. The relative abundance of biomarker PLFAs of Gram-negative bacteria was significantly higher in Phragmites compared to other salt marshes. The abundance of mcrA was significantly highest in Phragmites salt marshes (10 yr) and mixed salt marshes while the abundance of mcrA, pmoA and dsrA were lowest in Suaeda marshes. Our results reflect the chronological effects of the introduction of Phragmites on the physicochemical and microbial community composition which contribute to establishing the relationship between the plant introduction and soil biogeochemical processes in coastal salt marshes.

Automated summary

The introduction of Phragmites has led to changes in soil microbial community composition in Suncheon Bay, Republic of Korea. The water content, pH, and dissolved organic carbon content in the soil increased. The abundance of certain microbial biomarkers was higher in Phragmites-vegetated marshes compared to other salt marshes.