互花米草对苏北滨海湿地表土有机碳更新的影响

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

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(>250μm)和微团聚体组分(53～250μm)有机碳浓度均显著增加,而粉粒组分(2～53μm)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。

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（250 m and 53～250 m） of Spartina alterniflora-vegetated soil,while there was no obvious difference in fine fraction（2～53 m）.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（250 m）.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（250 m）.