Seasonal variation in CH₄ emission and its 13C-isotopic signature from Spartina alterniflora and Scirpus mariqueter soils in an estuarine wetland

摘要

Although invasions by non-native species represent a major threat to biodiversity and ecosystem functioning, little attention has been paid to the potential impacts of these invasions on methane (CH₄) emission and its 13C-CH₄-isotope signature in salt marshes. An invasive perennial C₄ grass Spartina alterniflora has spread rapidly along the east coast of China since its introduction from North America in 1979. Since its intentional introduction to the Jiuduansha Island in the Yangtze River estuary in 1997, S. alterniflora monocultures have become the dominant component of the Jiuduansha’s vegetation, where monocultures of the native plant Scirpus mariqueter (a C₃ grass) used to dominate the vegetation for more than 30 years. We investigated seasonal variation in soil CH₄ emission and its 13C-CH₄-isotope signature from S. alterniflora and S. mariqueter marshes. The results obtained here show that S. alterniflora invasion increased soil CH₄ emissions compared to native S. mariqueter, possibly resulting from great belowground biomass of S. alterniflora, which might have affected soil microenvironments and /or CH₄ production pathways. CH₄ emissions from soils in both marshes followed similar seasonal patterns in CH₄ emissions that increased significantly from April to August and then decreased from August to October. CH₄ emissions were positively correlated with soil temperature, but negatively correlated with soil moisture for both S. alterniflora and S. mariqueter soils (p 0.05). Generally, the CH₄ emissions from both invasive S. alterniflora and native S. mariqueter soils in the salt marshes of Jiuduansha Island were very low (0.01–0.26 mg m-2 h-1), suggesting that S. alterniflora invasion along the east coast of China may not be a significant potential source of atmospheric CH₄. Keywords CH₄ emission - Stable carbon isotope - Soil properties - Plant invasion - Coastal sediments Responsible Editor: Klaus Butterbach-Bahl.