Abstract
Invasion of Spartina alterniflora in coastal areas of China increased methane (CH4) emissions. To elucidate the underlying mechanisms, we measured CH4 production potential, methanogen community structure and biogeochemical factors along a coastal wetland transect comprised of five habitat regions: open water, bare tidal flat, invasive S. alterniflora marsh and native Suaeda salsa and Phragmites australis marshes. CH4 production potential in S. alterniflora marsh was 10 times higher than that in other regions, and it was significantly correlated with soil organic carbon, dissolved organic carbon and trimethylamine concentrations, but was not correlated with acetate or formate concentrations. Although the diversity of methanogens was lowest in S. alterniflora marsh, invasion increased methanogen abundance by 3.48-fold, compared with native S. salsa and P. australis marshes due to increase of facultative Methanosarcinaceae rather than acetotrophic and hydrogenotrophic methanogens. Ordination analyses suggested that trimethylamine was the primary factor regulating shift in methanogen community structure. Addition of trimethylamine increased CH4 production rates by 1255-fold but only by 5.61- and 11.4-fold for acetate and H2/CO2, respectively. S. alterniflora invasion elevated concentration of non-competitive trimethylamine, and shifted methanogen community from acetotrophic to facultative methanogens, which together facilitated increased CH4 production potential.
Highlights
Site P. australis S. salsa S. alterniflora Bare tidal flat Open water F value P value
The invasion of exotic S. alterniflora to the coastal marsh significantly increased CH4 production potential by 192–967% above that recorded in the non-invaded regions
Ding et al.[30] found that plant species regulated the spatial variation of CH4 emissions in a freshwater marsh in the Sanjiang plain of China
Summary
Site P. australis S. salsa S. alterniflora Bare tidal flat Open water F value P value. Shifts of the dominant plant species in wetlands can directly or indirectly influence the abundance and community structure of methanogens by providing substrates through root exudates, root debris and litters[15] This process is more severe with invasive plants as they are often more efficient at acquiring and using resources and, exhibit a higher net primary productivity and biomass than do native plants[20]. Previous studies have shown that S. alterniflora invasions considerably increase SOC storage[6], levels of nitrogen[25] and sulfur[26], and the overall rates of nutrient cycling in soil[27] All such changes can potentially affect CH4 production either by increasing the substrates for methanogens or by increasing sulfates and other preferred electron acceptors in the invaded salt marshes[19,21].
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