互花米草入侵对长江口湿地土壤碳动态的影响

为了评价互花米草入侵对长江河口湿地土壤碳动态的影响，利用配对的试验设计在长江口崇明东滩湿地的高潮滩和低潮滩各设置1条入侵种互花米草与土著种的配对样线.结果表明，与土著植物相比，互花米草入侵显著增加了长江口湿地的植物碳库、土壤微生物碳、土壤总碳库和有机碳库，而对占土壤总碳库60%以上的无机碳库无显著影响，意味着互花米草入侵导致的土壤总碳库改变主要是通过增加土壤有机碳库来实现的.高潮滩互花米草和芦苇群落的年均土壤呼吸强度分别为（210.02±4.90），（157.79±6.39）mg/（m²·h）；低潮滩互花米草和海三棱藨草群落年均土壤CO₂排放速率分别为（157.41±5.27），（110.90±5.16）mg/（m²·h），表明互花米草入侵显著增加长江口湿地的土壤呼吸.上述结果意味着互花米草入侵同时增加土壤碳输入和碳输出，但入侵也显著增加了土壤碳库表明入侵增加的土壤碳输入显著高于增加的土壤碳输出.本研究表明互花米草入侵可能会增强了长江河口湿地的土壤碳汇强度和固碳能力.但仍然需要长期系统的监测研究，以便全面定量评估互花米草入侵我国滨海湿地的综合生态影响.

Effects of Spartina alterniflora invasion on soil carbon dynamics in wetlands of the Yangtze River estuary

This study investigated the effects of Spartina alterniflora invasion on soil carbon dynamics and tried to reveal the potential underlying mechanisms of these effects in wetlands of the Yangtze River estuary. Herein, each sampling transect was set up separately in the high and low tide zones of the Dongtan wetland in the Yangtze River estuary. Three sites were distributed evenly on each transect. A pair-wise experiment was designed between S. alterniflora (invasive plant) and Phragmites australis (native plant) stands in the high tide zone, and S. alterniflora and Scirpus mariqueter (native plant) stands in the low tide zone, which was used to minimize the potential effects of background heterogeneities. Compared with the native plant stands, the S. alterniflora invasion significantly increased the plant carbon, soil total carbon (TC), and soil organic carbon pools. There was no significant difference in the soil inorganic carbon (SIC) pool between plant stands or tide zones. The estimated SIC pool in the Dongtan wetland accounted for more than 60% of the soil TC pool in the soil profile to a depth of 100cm. The lack of difference in the SIC pool between the S. alterniflora and native plant stands demonstrated that the soil TC pool in coastal wetland soils did not reflect the effects of invasion. The mean soil respiration rates were (210.02±4.90) and (157.79±6.39)mg/(m²·h) in the S. alterniflora and P. australis stands in the high tide zone, and (157.41±5.27) and (110.90±5.16)mg/(m²·h) in the S. alterniflora and S. mariqueter stands in the low tide zone, respectively. This indicated that the S. alterniflora invasion significantly enhanced soil respiration in the Yangtze River estuary. These results showed that the S. alterniflora invasion simultaneously increased soil carbon input and carbon output, but the invasion also significantly increased the soil carbon pool, suggesting that the invasion-related increase in the soil carbon input was significantly higher than the invasion-related increase in the soil carbon output. As shown above, S. alterniflora invasion into the Yangtze River estuary could strengthen the soil carbon sequestration capacity and net carbon sink of wetlands in the background of global climate change. However, long-term systematic monitoring and study are still needed in order to comprehensively evaluate the ecological impacts of S. alterniflora invasion into China's coastal wetlands.