珠江口红树林湿地土壤碳的分布特征和影响因素研究

Distribution patterns and influencing factors of soil carbon storage in mangrove wetland at the Pear River Estuary

红树林土壤是重要的“蓝碳”库,在缓解气候变化中发挥着重要作用.由于人类活动的影响,珠江口红树林湿地经历了复杂的土地覆盖变化过程,其土壤碳分布特征和影响因素需要深入探究.本研究以珠江口淇澳岛红树林湿地为研究对象,通过实地调查、采样和测定,分析了该区域5种主要土地覆盖类型(原始秋茄林、无瓣海桑林、无瓣海桑伐迹地、废弃鱼塘和光滩)的土壤有机碳(SOC)储量、SOC稳定性,以及植被碳储量、土壤理化性质对土壤碳分布的影响.结果表明,淇澳岛红树林湿地的SOC储量在不同覆盖类型间存在显著性差异.其中原始秋茄林的SOC储量最高,达185 t·hm^(-2),是新生光滩的1.8倍.秋茄林的SOC更多地储存在浅层土壤(0~50 cm)中.通过同位素分析发现,秋茄林SOC的稳定性高于其他土地覆盖类型,有利于SOC的长期固存.植被碳储量与SOC储量呈显著正相关关系,且在浅层土壤中相关性更显著,植被碳输入对浅层SOC累积的促进作用更大.土壤C∶N、水分和pH值等理化性质也影响了红树林湿地土壤碳库的大小.滨海地区在恢复红树林湿地时,有必要考虑不同土地覆盖类型和土壤特性对提升土壤碳汇的影响.

Mangrove soils are important“blue carbon”pools and play a critical role in mitigating climate change.Due to increasing human activities,mangrove wetlands have experienced disturbance due to land cover change.The distribution and influencing factors of soil carbon under different land covers need to be further explored.Here,by examining five land cover types(native Kandelia obovata,Sonneratia apetala Buch.-Ham.,Sonneratia apetala removal,abandoned fishponds and mudflats)of the mangrove wetland located at Qi’ao Island in the estuary of the Pearl River,China,we quantified soil organic carbon(SOC)stocks,SOC stability,and effects of vegetation carbon stock and soil properties on SOC.Our results showed that SOC stocks among different land covers were significantly different.Native Kandelia obovata stored the highest SOC,reaching 185 t·hm^(-2),which was 1.8 times of that in the new mudflat.The SOC of Kandelia obovata distributed more in the top soils(0~50 cm).The isotope analysis revealed that the SOC stability of native Kandelia obovata was higher than that of other land cover types,which enhanced long-term SOC sequestration.There was a positive correlation between vegetation carbon stock and SOC stock,especially in the shallow soils.Soil C∶N,water and pH also affected the size of soil carbon pools.Our study highlights that different land cover types and soil properties should be considered when restoring mangrove wetlands and increasing SOC stock along the coast.