潮沟曲流摆动对潮滩沉积物碳输出的影响——以江苏中部潮滩为例

Role of tidal meander migration on carbon release of tidal flat sediments:a case study of the central Jiangsu tidal flats

潮滩是全球固碳能力最高的生态系统之一,是缓解全球变暖的有效蓝色碳汇。针对潮滩碳汇功能,现有研究多关注生物作用下的碳输入过程,关于地貌演变,特别是潮沟曲流摆动引起的沉积物碳输出过程研究较少,因此无法准确评估潮滩碳汇功能的动态变化。研究结合野外观测、遥感反演与室内实验,探究了潮沟曲流摆动对潮滩沉积物碳输出过程的影响,从曲流摆动速率与有机碳空间分布特征两方面开展分析。研究结果表明:潮沟曲流摆动速率的空间差异可达数个量级,由粉砂滩的10^(-3) m/s锐减至互花米草盐沼滩的10^(-6) m/s;粉砂淤泥滩潮沟摆动速率存在显著的季节性差异,冬季摆动速率约为夏季的两倍;潮滩土壤有机碳含量呈海向递减趋势:互花米草盐沼滩(4.62 g/kg)>粉砂淤泥滩(2.61 g/kg)>粉砂滩(1.51 g/kg);综合考虑曲流摆动速率与土壤有机碳含量,发现粉砂滩沉积物碳输出速率显著高于互花米草盐沼滩,可达49.4 g C m^(-2) a^(-1),与该区域的碳埋藏速率相当。研究证实了潮沟曲流摆动对潮滩沉积物碳输出过程的重要性,为提升潮滩碳汇功能预测水平提供了重要的理论依据与数据支撑。

Tidal flats are among the ecosystems with the highest carbon sequestration capacity globally,serving as effective blue carbon sinks to mitigate global warming.Current research on this issue primarily focuses on carbon input processes driven by biological activities,while carbon output processes under geomorphic evolution,especially tidal meander migration,are limited.This knowledge gap makes it challenging to accurately predict and assess the carbon sequestration capability of tidal flats.Here we integrate field observations,remote sensing with laboratory experiments to investigate the impact of tidal meander migration on carbon release of tidal flat sediment.Results show that the range of variation characterizing the migration rates of tidal meanders can actually span many orders of magnitude,which sharply decreases from 10^(-3) m/s on silty flats to 10^(-6) m/s in salt marshes.The migration rates of tidal meanders in the muddy silt flats exhibit significantly seasonal variability,with the rates in winter being approximately twice of those observed in summer.The content of organic carbon in tidal flat soil demonstrates a seaward declining trend:salt marshes(4.62 g/kg)>muddy flats(2.61 g/kg)>silty flats(1.51 g/kg).By integrating the migration rate of tidal meanders and soil organic carbon content,we found that carbon release rate of sediment measured on silt flats(49.4 g C m^(-2) a^(-1))was much higher than in salt marshes and muddy flats,which is comparable to the carbon buried rate on unvegetated flats.Overall,our study confirms the importance of tidal meander migration on sediment carbon release,providing crucial theoretical foundations and data support for enhancing the prediction of carbon sink function of tidal flats.