Abstract
The carbon cycle is significantly affected by Spartina alterniflora invasion through its impact on blue carbon in many salt marshes. To determine the impacts on soil organic carbon (SOC), we studied the vertical and horizontal distribution of SOC. And stable carbon isotopes were used to explore the impact of the age of S. alterniflora invasion on SOC in Chongming Dongtan wetland located in the Yangtze River estuary, China. The results showed that the SOC concentration was higher in the S. alterniflora community than that in the native Phragmites australis community. The age of invasion and the SOC concentration increased with increasing elevation, while the SOC concentration decreased with increasing soil depth. The δ13C value became less negative at greater depth, which was related to the contribution from 13C- enriched carbon sources after 3 years of invasion. After 7 and 10 years, the δ13C value became more negative at greater depth in both communities. S. alterniflora had a positive effect on the soil carbon pool, and its contribution was related to soil depth. In the low tidal marshes, the contribution of S. alterniflora was negatively correlated with soil depth, while it was positively correlated with soil depth in the high tidal marshes. The results from this study will contribute to improved understanding of future ecological consequences.
Highlights
‘Blue carbon’, which refers to carbon sequestered in salt marsh, seagrass, and mangrove ecosystems, is important for understanding the link between terrestrial and oceanic carbon cycles[1,2,3]
The corresponding aboveground biomass of the S. alterniflora community was 3525, 2800 and 3104 g m−2 for the low, middle, and high tidal marshes, respectively; and these values were more than three times higher than those recorded for the P. australis community (Table 1)
The average soil organic carbon (SOC) concentrations in all soil layers rapidly increased from approximately 2% to 8% across an area about 200 m from the mudflat to the vegetated tidal marsh which the distance reached 1000 m
Summary
‘Blue carbon’, which refers to carbon sequestered in salt marsh, seagrass, and mangrove ecosystems, is important for understanding the link between terrestrial and oceanic carbon cycles[1,2,3]. Population changes in native species within the plant community alter the ecosystem structure and the soil carbon pool[6]. Changes in the dominant species within a plant community may alter ecosystem structures and material cycling processes, which in turn alter above- and belowground carbon pools, net primary productivity, plant growth rates, litter quality and quantity, and nutrient and carbon mineralization rates[11]. The effect of invasive plants on soil carbon pools is critically important for understanding changes in carbon cycles. C3 plants have been reported to exhibit δ13C values between −35 and −20‰, while those of C4 plants range between −19 and −9‰25–27 These values are widely used to study the source of soil organic matter. If the climate and environmental conditions are the same for all sampled plots in a given study, the variation in the soil isotope composition can be employed to measure the newly generated SOC after S. alterniflora invasion
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