Impact of Spartina alterniflora invasion on soil CH4 emissions and their temperature sensitivity in coastal wetlands.

Abstract

The invasive Spartina alterniflora is rapidly expanding along China's southeast coast, profoundly altering wetland soil properties, and methane (CH4) fluxes. However, the mechanism underlying the relationship between these environmental changes triggered by the invasion and the variations in CH4 emissions remain to be further deeply explored. We compared S. alterniflora-invaded wetlands with native Cyperus malaccensis wetlands through a one-year field monitoring and complementary laboratory experiments. The findings indicate that S. alterniflora invasion markedly decreased soil bulk density (4.3%) and increased water content (7.5%), while altering bacterial communities, notably increasing Microbulbifer (165.3%) and decreasing Anaeromyxobacter (61.7%) relative abundances. Consequently, cumulative soil CH4 emissions significantly increased by 354.9%, whereas CH4 emission temperature sensitivity (Q10) decreased by 79.8% (p < 0.05). CH4 emissions were positively correlated with the content of mineral-associated organic carbon (MAOC), dissolved organic carbon (DOC), total nitrogen (TN), soil temperature, and Microbulbifer abundance. Conversely, CH4 emissions were negatively related to clay content, particulate organic carbon (POC), and the abundances of Anaeromyxobacter. Q10 values were primarily influenced by soil texture, nutrient levels (TN, TP), MBC, and Microbulbifer abundance. Our findings indicate that the encroachment of S. alterniflora increases CH4 emissions while decreasing their Q10 by modifying soil physicochemical conditions, influenced by its plant traits. These findings highlight the critical need to manage S. alterniflora expansion to mitigate coastal wetland greenhouse gas emissions.