互花米草对苏北滨海湿地表土有机碳更新的影响

自互花米草引入苏北滨海湿地后,逐渐替代本土植物盐蒿并形成单一植被的互花米草湿地.选择苏北地区盐蒿湿地及不同生长年限的互花米草湿地,采集其表层土壤样品,分别测定全土和分离的土壤粒径组分中总有机碳及δ13C值,分析湿地土壤有机碳浓度及其同位素组成的变化.结果表明,互花米草引入盐蒿湿地后,表层土壤有机碳浓度显著增加(增量达70%),且随着互花米草生长时间延长而明显增加.与盐蒿湿地相比,互花米草湿地土壤中大团聚体(>250mm)和微团聚体组分(53~250mm)有机碳浓度均显著增加,而粉粒组分(2~53mm)则无明显变化.互花米草湿地土壤原状土及各粒径组分的δ13C值均明显高于盐蒿土壤,源于互花米草的新碳在各粒径组分中均有分布,但主要富集在大团聚体组分中,占该组分总碳的31%~43%,说明互花米草生长对土壤有机碳浓度增加主要反映在粗粒径组分中,而对粉、黏粒组分则影响较小.

Effects of plant invasion along a Spartina alterniflora chronosequence on organic carbon dynamics in coastal wetland in north Jiangsu

Spartina alterniflora, an invasive grass, had rapidly replaced native plant Suaeda salsa since its intentional introduction to the coastal wetlands in Eastern China. Impacts of plant invasion along a Spartina alterniflora chronosequence on soil organic carbon (SOC) dynamics were investigated. The concentrations of SOC in bulk soil increased 70% from 2.89g/kg soil in remnant Suaeda salsa-vegetated soil to 4.90g/kg in 14-year Spartina alterniflora soil, and these values enhanced significantly along its chronosequence. The increase mainly resulted from a high quantity of organic residues incorporated in the soil. Compared with Suaeda salsa-vegetated soil, The SOC concentration increased significantly in coarse fraction (>250mm and 53~250mm) of Spartina alterniflora-vegetated soil, while there was no obvious difference in fine fraction (2~53mm). The δ13C values of SOC for either bulk soil or particle-size fractions were evidently higher in Spartina alterniflora-vegetated soil than in Suaeda salsa-vegetated soil. There was Spartina alterniflora-derived C in all particle-size fraction, however 31%~43% of the Spartina alterniflora-derived C distributed in the coarse fraction (>250mm). It was concluded in this study that Spartina alterniflora invasion significantly promoted SOC accumulation of surface soil in coastal wetland, and new C accumulation profoundly resulted in increasing SOC concentration of the coarse fraction (>250mm).