九龙江河口潮滩湿地土壤有机碳储量、活性组分及稳定性沿淹水梯度的分布特征

Soil Organic Carbon Storage,Active Component Contents,and Stability Along a Flooding Gradient in the Tidal Wetland of the Jiulong River Estuary

淹水频率是影响河口潮滩湿地固碳潜力的关键环境因子之一.为了揭示淹水频率增加对河口潮滩湿地土壤碳动态的影响,对福建省九龙江河口潮滩剖面土壤有机碳(SOC)储量、活性有机碳组分和碳库稳定性指数CSI进行了测定与分析.结果表明,随着淹水频率的增加,SOC的储量减少54%,土壤活性有机碳组分MBC、DOC和LOC的含量亦随着淹水频率的增加而减少.随着淹水频率的增加,活性组分中DOC/SOC和LOC/SOC分别增加80%和26%,而MBC/SOC减少29%,说明随着淹水的增加土壤有机碳活性组分中MBC的相对累积速率变缓,LOC和DOC的相对累积速率增加.土壤POC和MAOC的含量随着淹水频率的增加分别减少81%和35%.土壤POC含量降低与土壤pH的增加有关,而土壤MAOC含量降低则与土壤黏粒的含量减少有关.土壤稳定性指数CSI随着淹水频率增加而增加246%.随着淹水频率的增加,河口潮滩湿地土壤有机碳储量降低,但是土壤有机碳的稳定性增加.矿物结合态有机碳是河口潮滩湿地土壤有机碳稳定性的主要保护机制,对河口潮滩湿地土壤碳汇具有重要意义.

Flooding is one of the key environmental factors affecting the carbon sequestration potential of estuarine tidal flat wetlands.In order to reveal the effect of flooding on soil carbon(C)sinks in estuarine tidal wetlands,we investigated and analyzed the soil organic carbon(SOC)storage,the contents of active SOC components,and SOC stability indicators across a tidal flat in the Jiulong River estuary in southeast China.The results showed that the SOC storage gradually decreased by 54%with the increase in flooding frequency.The change pattern of microbial biomass carbon(MBC),dissolved organic carbon(DOC),and liable organic carbon(LOC)followed the change pattern of the SOC storage.With the increase in flooding frequency,DOC/SOC and LOC/SOC increased by 80%and 26%,respectively,whereas MBC/SOC decreased by 29%.As flooding frequency increased,particulate organic carbon(POC)and mineral-associated organic carbon(MAOC)contents decreased by 81%and 35%,respectively.The decreases in POC contents were correlated with the increases in soil pH,whereas the decreases in MAOC contents were associated with the decline in clay contents.Soil carbon stability index(CSI)increased by 246%with increasing flooding frequency.These combined results indicated that SOC storage decreased,but SOC stability increased,with the increased flooding frequency.Mineral-bound organic carbon was the main protection mechanism for the SOC stability,which was of great significance to the soil C sink of the estuarine tidal wetlands.