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.

盐沼（saltmarsh）与红树林（mangrove forest）等海岸生境能够累积并储存大量蓝碳（blue carbon）储量，这些储量可留存数千年之久。尽管这类生境看似具有稳定性，但已知潮间带-潮上带湿地（intertidal-supratidal wetland）的分布与结构会响应地貌演化、气候变化、海平面变化及人为活动带来的干扰。
本研究针对澳大利亚东南部4处现代植被组成相似的湿地，重建其环境演化历史与生物地球化学特征，旨在评估历史因素对现代有机碳（C）储量及累积速率的影响程度。本次采集的4根沉积物岩芯（core）——其中2根采自受海洋影响的盐沼湿地（WAP-M与POR-M），另外2根采自受河流影响的盐沼湿地（WAP-F与POR-F）——结果显示不同湿地具有迥异的环境演化历史与碳保存条件。POR-M与POR-F岩芯中，现代盐沼沉积物下方存在红树林发育层位，对应着较高的碳储量。碳13核磁共振（13C NMR）分析结果显示，尽管埋藏年代久远，这些历史时期的红树林根系碳的分子组成仍保持极高稳定性，这与其赋存于深层沉积物中的位置相符。WAP-M与WAP-F岩芯未检出红树林根系碳，但WAP-F岩芯中存在大量炭化碳（char C）的保存（部分层位中其占总碳比例可达46%），这揭示了历史流域过程对该湿地的重要影响。综上，本研究结果凸显了在将碳核算拓展至更大空间尺度时，需整合历史生态系统与流域过程因素的重要性。