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 invasiveSpartina 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.

Automated summary

Coastal wetland ecosystems, such as saltmarshes, are effective in sequestering carbon to mitigate climate change. The effects of vegetation dynamics, specifically the invasive Spartina alterniflora and native Phragmites australis communities, on soil organic carbon (SOC) and its fractions were examined. The study found that plant ecophysiological traits influence the spatial distribution of SOC, and the different vegetation communities have different impacts on its accumulation and decomposition. These findings provide insights into the impacts of long-term species invasion on SOC in coastal wetlands under global changes.