Impact of Spartina alterniflora invasion on soil bacterial community and associated greenhouse gas emission in the Jiuduansha wetland of China

Abstract

Coastal wetlands are essential sources of greenhouse gases (GHGs) emission, and lots of them are invaded by Spartina alterniflora across different climate zones. We chose Jiuduansha wetland as a typical wetland ecosystem with minimal human activities to study the impacts and interactions between S. alterniflora invasion, soil functional microorganisms, and GHGs emission. Our findings indicated that in comparison to the mudflat and S. mariqueter habitat, the S. alterniflora invasion increased soil carbon dioxide (CO2) emission, which was highly positively related to aboveground biomass, soil organic carbon (SOC), and the ammonium‑nitrogen (NH4+-N) concentration, but negatively related to the nitrate‑nitrogen (NO3–-N) concentration. The relative abundances of soil C-decomposing bacteria increased in S. alterniflora habitat compared with S. mariqueter habitat. Compared with the P. australis habitat, S. alterniflora invasion reduced soil CO2 emission, which was negatively related to salinity. The relative abundances of soil C-fixing bacteria (phylum Chloroflexi) and functional genes (acsA-F and rbcL) decreased in S. alterniflora habitat. Moreover, the S. alterniflora invasion increased soil methane (CH4) emission compared with the S. mariqueter and P. australis habitats, which was positively related to aboveground biomass, SOC and NH4+-N concentration, and negatively related to the NO3–-N concentration. Besides, the relative abundances of CH4 oxidation functional genes were decreased in S. alterniflora habitat compared with the S. mariqueter and P. australis habitats. Meanwhile, the oxidation of CH4 to methanol was mainly regulated by mmoX gene at our study site. Thus, the soil CO2 and CH4 emissions after S. alterniflora invasion were regulated by soil environmental factors and soil C-fixing, C-decomposing, and CH4 oxidation functional microorganisms. Our results are helpful to better understand the mechanisms involved in the impacts of S. alterniflora invasions on GHG emissions in coastal wetlands.