Spartina alterniflora invasion altered soil greenhouse gas emissions via affecting labile organic carbon in a coastal wetland

Abstract

Coastal wetlands are vital carbon repositories with a substantial soil carbon storage potential; as such, they play a crucial role in global carbon sequestration and climate regulation. The most invasive species in the global coastal zone, Spartina alterniflora, has significantly affected the ecosystem functions and nutrient cycling of coastal wetlands. However, it is uncertain how S. alterniflora invasion affects the driving mechanism of greenhouse gas (GHG) emissions by causing changes in the soil labile organic carbon (LOC) pool. Therefore, we investigated the mediating role of soil LOC in influencing the impact of Spartina alterniflora invasion on soil GHG emissions. Our study was conducted in the coastal wetlands of the Dongtai Tiaozini Wetland Reserve in Yancheng, China. The relationship between variations in soil LOC components and GHG emissions in coastal wetlands was analyzed by measuring these variables across areas with high, moderate, and no invasion of S. alterniflora. The results showed that as the degree of invasion intensified, emissions of carbon dioxide (CO₂), nitrous oxide (N₂O), and the global warming potential (GWP) showed significant increasing trends, while methane (CH₄) emissions tended to increase first and then decrease. Compared with CO₂ emissions in the non-invasive plots of S. alterniflora, CO₂ emissions in moderately and highly invasive plots increased by 166.68 % and 403.35 %, respectively (P < 0.05). Similarly, N₂O emissions increased by 34.67 % and 303.03 %, respectively (P < 0.01), and the GWP increased by 683.87 % and 947.32 %, respectively (P < 0.01). For CH₄ emissions, moderate invasion represented a carbon source, and high invasion represented a carbon sink. The findings indicated that S. alterniflora invasion alters GHG emissions by modifying the soil LOC components and the ratio of LOC to soil organic carbon. These results provide a robust data foundation for understanding changes in carbon cycling and predicting feedback mechanisms on climate change in the context of S. alterniflora invasions in coastal wetlands.