Data from: Geochemical analyses reveal the importance of environmental history for blue carbon sequestration

Coastal habitats including saltmarshes and mangrove forests can accumulate and store significant blue carbon stocks, which may persist for millennia. Despite this implied stability, the distribution and structure of intertidal-supratidal wetlands is known to respond to changes imposed by geomorphic evolution, climatic, sea level and anthropogenic influences. In this study, we reconstruct environmental histories and biogeochemical conditions in four wetlands of similar contemporary vegetation in SE Australia. The objective is to assess the importance of historic factors to contemporary organic carbon (C) stocks and accumulation rates. Results from the four cores – two collected from marine influenced saltmarshes (WAP-M and POR-M) and two from fluvial influenced saltmarshes (WAP-F and POR-F) – highlight different environmental histories and preservation conditions. High C stocks are associated with the presence of a mangrove phase below the contemporary saltmarsh sediments in the POR-M and POR-F cores. 13C NMR analyses show this historic mangrove root C to be remarkably stable in its molecular composition despite its age, consistent with its position in deep sediments. WAP-M and WAP-F cores did not contain mangrove root C, however, significant preservation of char C (up to 46% of C in some depths) in WAP-F reveals the importance of historic catchment processes to this site. Together, these results highlight the importance of integrating historic ecosystem and catchment factors into attempts to upscale C accounting to broader spatial scales.

滨海生境（涵盖盐沼（saltmarsh）与红树林（mangrove forest））能够累积并储存可观的蓝碳（blue carbon）储量，此类碳库可留存达数千年之久。尽管这暗示了其内在稳定性，但现有研究表明，潮间带-潮上带湿地（intertidal-supratidal wetlands）的分布与结构会响应地貌演化、气候变化、海平面变动及人为活动带来的扰动。本研究针对澳大利亚东南部4处当代植被特征相似的湿地，重建其环境演化历史与生物地球化学条件。本研究的目标是评估历史因素对当代有机碳（organic carbon, C）储量及累积速率的影响程度。对4根沉积物岩芯（core）的分析结果呈现出迥异的环境演化历史与碳保存条件：其中2根采自海洋影响型盐沼（WAP-M与POR-M），另外2根采自河流影响型盐沼（WAP-F与POR-F）。POR-M与POR-F岩芯中，较高的有机碳储量与现代盐沼沉积物之下存在古红树林层位的现象显著相关。碳-13核磁共振（13C NMR）分析显示，尽管历经漫长地质年代，这些古红树林根系有机碳的分子组成仍保持极高稳定性，这与其赋存于深部沉积物中的位置一致。WAP-M与WAP-F岩芯则未检出红树林根系有机碳，但WAP-F岩芯中存在显著的炭质有机碳（char C）保存现象（部分深度下其占总有机碳比例可达46%），这揭示了流域历史过程对该湿地的重要影响。综合而言，上述结果凸显了在将碳核算（carbon accounting）拓展至更大空间尺度的研究中，整合历史生态系统与流域过程因素的必要性。