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

Abstract

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 alternifloraand co-occurring nativePhragmites australiscommunities 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 inP. australiscommunity facilitates the accumulation of RC, while the lower soil pH inS. alternifloramay accelerate the decomposition of RC. The findings indicated thatS. alternifloracould accumulate more C in the soil owing to its greater plant biomass and photosynthesis rate. However, the reduced soil pH byS. alterniflorainvasion 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.