Geographical-Scale Evidence Reveals Plant Nutrient as an Effective Indicator for Coastal Carbon Emissions

Plant traits could help in designing feasible strategies to mitigate global change in inland wetlands, but the correlations between plant traits and carbon emissions in coastal wetlands remain unclear. Here, we investigated the plant traits (including nutrient, structural, and biomass traits) and environmental conditions (including climate and soil properties) and determined the soil carbon emissions (methane (CH₄), carbon dioxide (CO₂), and their temperature sensitivities (<i>Q</i>₁₀ value)) from the soils of 90 coastal herbaceous wetlands differing in land use types along China's coastline. We further tested how environmental conditions affected plant traits and how these traits then altered carbon emissions. We found that plant traits had a greater effect on CH₄ and CO₂ emissions than on their <i>Q</i>₁₀ values, with nutrient traits being the key drivers in coastal herbaceous wetlands in China. In general, coastal herbaceous wetlands with larger leaf C and N contents combined with a lower leaf N:P ratio tended to have higher CH₄ emission; those with larger leaf C and P contents combined with a lower leaf N:P ratio tended to have higher CO₂ emission; and those with higher leaf N content and N:P ratio combined with a lower leaf C:P ratio tended to have higher <i>Q</i>₁₀ values of both CH₄ and CO₂. Notably, the predictive power of plant traits in coastal herbaceous wetlands varied significantly across heterogeneous environments influenced by climate and land use. Our results highlight the critical role of plant nutrient traits in driving soil carbon emissions and provide practical insights into understanding coastal carbon dynamics under pressures from climate and land use changes (e.g., coastal reclamation and plant invasion).