Influence of Vegetation Dynamics on Soil Organic Carbon and Its Fractions in a Coastal Wetland

Coastal wetland ecosystems are highly efficient in sequestering carbon (C) to mitigate climate change. However, it is still unclear how vegetation dynamics affect soil organic carbon (SOC) and its fractions (labile and recalcitrant C (LC and RC)) in coastal wetlands. Here, we quantified the effects of saltmarsh vegetation dynamics on the SOC and its fractions using the invasive Spartina alterniflora and co-occurring native Phragmites australis communities as a model. SOC contents in these 2 communities showed similar spatial patterns with an inverted U-shaped curve from tidal mudflats to vegetated marshes. Our results suggested that plant ecophysiological traits play a primary role in regulating the spatial distribution of SOC. In addition, the lower ratio of leaf to shoot in P. australis community facilitates the accumulation of RC, while the lower soil pH in S. alterniflora may accelerate the decomposition of RC. The findings indicated that S. alterniflora could accumulate more C in the soil owing to its greater plant biomass and photosynthesis rate. However, the reduced soil pH by S. alterniflora invasion might restrain SOC accumulation. Our findings shed light on the impacts of long-term species invasion on SOC and its fractions in coastal wetlands under global changes.