Against the backdrop of global change, coastal salt marshes are regarded as vital “blue carbon” ecosystems due to their substantial carbon‑sequestration potential. However, over the past three decades, the invasive plant Spartina alterniflora—native to the Atlantic coast of North America—has spread rapidly across China’s coastal salt marshes, continuously disrupting wetland ecological structures and biogeochemical processes, thereby introducing new uncertainties into the blue carbon functions of these ecosystems. Does the expansion of Spartina alterniflora enhance the carbon‑sequestration capacity of salt marshes, or does it quietly undermine the regulatory functions of this critical ecosystem? A study published in Estuarine, Coastal and Shelf Science provides an answer.
Why is this study worth paying attention to?
Coastal ecosystems such as salt marshes, mangrove forests, and seagrass beds constitute vital nature‑based solutions to climate change, playing a pivotal role through key services including carbon sequestration, shoreline protection, and biodiversity conservation. Spartina alterniflora, a globally invasive coastal plant, has spread extensively along China’s coastlines, profoundly altering wetland structure and biogeochemical cycles. Existing research indicates that while the invasion of S. alterniflora promotes soil carbon accumulation, it may also substantially increase greenhouse gas emissions, thereby offsetting some of the blue carbon benefits. Nevertheless, the dynamic patterns of methane (CH₄) and carbon dioxide (CO₂) fluxes across different stages of invasion, as well as their underlying driving mechanisms, remain poorly understood due to the lack of systematic quantitative studies.
Recently, the research team led by Professor Xu Ligang at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, focused on the coastal salt marshes of Dongtai, Yancheng, Jiangsu Province. Based on year-round in situ continuous observations, they systematically quantified the impacts of Spartina alterniflora invasion on CH₄ and CO₂ fluxes and elucidated the underlying driving mechanisms. Their findings indicate that the ongoing expansion of Spartina alterniflora markedly increases greenhouse gas emissions, posing a significant threat to the blue carbon functions and climate‑regulating capacity of coastal wetlands.
Figure 1. Location of the salt marsh sampling sites in Dongtai City, Yancheng (a and b), field photographs (c), and the current distribution pattern of the dominant plant communities (d).
Research Methodology
Plot establishment: The study site is located in the salt marshes of Dongtai City, Yancheng Municipality, Jiangsu Province. To assess the impact of Spartina alterniflora invasion on carbon fluxes in salt marshes, the research team established five representative plots within this coastal salt marsh.
Mudflat (MF)
Invasion of Spartina alterniflora, 10 years (SA10)
Invasive Spartina alterniflora, 20 years (SA20)
Native plant Suaeda salsa (SS)
Native plant: Common reed (PA)
Monitoring indicators: CO₂ and CH₄ fluxes, aboveground biomass (AGB) and belowground biomass (BGB), soil moisture, salinity, particle-size distribution, soil organic carbon (SOC), total nitrogen (TN), and other parameters.
Data analysis: Employing redundancy analysis (RDA), variance partitioning analysis (VPA), and piecewise structural equation modeling (piecewiseSEM) to elucidate driving mechanisms.
The study employed the PS-3010 Automatic Soil CO₂/CH₄ Flux System (Beijing Lijia United Technology Limited) in conjunction with a miniature portable greenhouse gas analyzer to measure CH₄ and CO₂ fluxes at the sampling plots. Prior to measurements, instrument connections were established, the system was preheated, the chamber seal was verified, and water vapor equilibrium was confirmed. Once gas concentrations stabilized—after 40 seconds of chamber equilibration—measurements commenced, with a flux collection period of 200 seconds, followed by a 90‑second chamber purge. Valid observation data were then selected based on the linear slope of the time‑series changes in greenhouse gas concentrations.
Figure 2. AGB (a), litterfall (b), and BGB (e) for different salt marsh plants
Figure 3. Net CH₄ exchange fluxes (a and b) and cumulative CH₄ fluxes (c and d) across different salt marshes.
Figure 4. Net ecosystem exchange (NEE) (a and b), ecosystem respiration (ER) (c and d), gross primary productivity (GPP) (e and f), and cumulative NEE (g and h) across different salt marshes.
Figure 5. CO₂ equivalent carbon flux (i.e., radiative balance) for invasive and native salt marshes in Yancheng, China.
Figure 6. Analysis of environmental factor pathways influencing (a) CH₄ flux, (b) NEE, (c) GPP, and (d) ER in salt marshes using segmented SEM.
Key Findings
(1) The invasion of Spartina alterniflora significantly increases vegetation biomass and alters soil physicochemical properties as well as carbon and nitrogen characteristics.
(2) CH₄ emissions increased markedly, with emissions during the growing season significantly higher than those in the non-growing season; SA10 exhibited the highest emissions.
(3) In the early stages of invasion, photosynthetic carbon fixation predominates, resulting in a carbon sink; as invasion duration increases, respiration and decomposition intensify, and the system shifts to a carbon source.
(4) Both SA10 and SA20 exhibit positive radiative balance, manifesting as a warming effect;
(5) At the same time, the temperature sensitivity (Q₁₀) of ecosystem respiration increases, reducing resilience to climate warming;
(6) Soil texture (clay and sand content) and vegetation biomass are the primary controlling factors of CH₄ emissions;
(7) Environmental factors directly influence GPP and ER, exerting a positive indirect effect on NEE.
Conclusion
This study systematically characterized the dynamics of greenhouse gas fluxes along an invasion chronosequence of Spartina alterniflora and quantitatively assessed its climatic effects. The results indicate that the invasion of Spartina alterniflora significantly alters the patterns of greenhouse gas fluxes in coastal salt marshes, generally amplifying the warming effect of the ecosystem and posing a threat to blue carbon functions and climate regulation capacity. These findings can provide data support for China’s targeted management of Spartina alterniflora invasions and the conservation of blue carbon ecosystems. Future research should continue long-term monitoring over broader spatial scales and timeframes, incorporating processes such as lateral carbon fluxes, to more comprehensively evaluate the impacts of invasive plant expansion on the ecological functions of coastal wetlands and regional carbon budgets.
Journal published in: Estuarine, Coastal and Shelf Science [Impact Factor: 2.6]
Research institutions: Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences; Longdong University; Nanjing University of Finance & Economics, among others.
Study site: Salt marshes in Dongtai City, Yancheng, Jiangsu Province
Equipment used: PS-3010 Automatic Soil CO₂/CH₄ Flux System
DOI: https://doi.org/10.1016/j.ecss.2025.109591