互花米草入侵对长江河口湿地CH4排放的影响

为了探讨互花米草入侵对长江河口湿地CH₄排放的影响以及入侵至不同潮位对CH₄排放影响程度的差异及其可能机制，采用邻近互花米草与土著植物群落相配对的试验设计，在长江口东滩湿地的高潮滩和低潮滩各设置1条样线.结果表明，与土著植物相比，互花米草入侵显著增加了长江河口湿地的植物生物量，显著增加了土壤含水量、土壤有机碳含量、总氮含量、微生物碳和氮含量.高潮滩互花米草群落年均CH₄排放强度为（0.68±0.08）mg/（m²·h），显著高于芦苇群落（0.21±0.01）mg/（m²·h），低潮滩互花米草和海三棱藨草群落年均CH₄排放速率分别为（8.31±0.50）和（3.93±0.18）mg/（m²·h），前者显著高于后者.此外，高潮滩互花米草与芦苇群落之间年均CH₄排放强度的差异为（0.47±0.08）mg/（m²·h），显著低于低潮滩互花米草与海三棱藨草群落之间年均CH₄排放强度的差异（4.37±0.48）mg/（m²·h）.上述结果表明，互花米草入侵通过改善CH₄产生所需底物的质和量，增加土壤含水量和微生物的量，从而显著增加了长江河口湿地CH₄排放量.互花米草入侵至低潮滩增加的CH₄排放量是互花米草入侵至高潮滩的10倍左右，表明互花米草入侵至长江河口湿地对CH₄排放的影响程度可能会有很强的空间异质性，互花米草入侵至更厌氧的土壤环境可能会对CH₄排放的影响程度更大.本研究可为准确估算互花米草入侵对中国海岸带湿地CH₄排放的影响程度，科学管理和合理利用海岸带湿地资源以及应对全球气候变化提供理论依据和科技支撑.

Effects of Spartina alterniflora invasion on CH4 emissions from wetlands of the Yangtze River estuary,China

Spartina alterniflora, an invasive alien species, spreads rapidly in the coastal zones of China. It has become the most important invasive plant in coastal wetlands of China and has significant impacts on ecological structure and function of the key zone to the earth. CH₄ is an important greenhouse gas and second only to CO₂. In order to investigate effects of Spartina alterniflora invasion on CH₄ emission and reveal the potential underlying mechanisms of these effects in coastal wetlands of China, each transect was set up in the high and low marshes of wetlands in the Yangtze River estuary, respectively. A pair-wise experimental design between S. alterniflora (invasive plant) and Phragmites australis (native plant) stands in the high marsh, and S. alterniflora and Scirpus mariqueter (native plant) stands in the low marsh, was used at each site of the two transects to minimize the potential effects of background heterogeneities. Compared with native plant stands, S. alterniflora invasion significantly increased plant biomass. Invasion-increase in plant biomass was significantly higher in the high marsh than that in the low marsh, which is beneficial to carbon accumulation in the early succession of coastal ecosystem. S. alterniflora invasion also significantly increased soil moisture, soil organic carbon content, soil nitrogen content, soil microbial biomass carbon and nitrogen contents of coastal wetlands of China. CH₄ emission rates were significantly higher under S. alterniflora than P. australis stands in the high marsh, with mean values of (0.68 ±0.08) mg/(m²·h) and (0.21 ±0.01) mg/(m²·h), respectively. In the low marsh, mean CH₄ emission rate under S. alterniflora stands was (8.31 ±0.50) mg/(m²·h) during the study period, which was significantly higher than that under S. mariqueter stands ((8.31 ±0.50) mg/(m²·h)). The difference in mean CH₄ emission between S. alterniflora and P. australis stands in the high marsh ((0.47 ±0.08) mg/(m²·h)) was significantly lower than that between S. alterniflora and S. mariqueter stands in the low marsh ((4.37 ±0.48) mg/(m²·h)). Our results indicated that the S. alterniflora invasion significantly enhanced CH₄emissions from coastal wetlands of China, probably mainly through improving the quality and quantity of substrates required for CH₄ production, increasing soil microbial biomass and moisture. The invasion-related CH₄ emissions were highly spatially variable; this variability may have been driven by the soil's anaerobic environments, induced by hydrological dynamics. These results can be applied to more reliably estimate and predict invasion-induced changes in CH₄ emissions from wetlands in the context of global climate change. These results also can provide theoretical basis and scientific support for scientific management and rational utilization of coastal zone resources as well as coping with global climate change.