Coastal wetlands, such as mangrove and saltmarsh environments, can store significant amounts of soil organic carbon (SOC); however, most studies focus on tropical and subtropical environments. We assessed SOC stocks and fractions in temperate mangrove (two sites) and saltmarsh (sites SM1, SM2 and SM3) environments in southern Australia. The SOC fractions were separated according to particulate organic carbon (POC), humic carbon (HC) and recalcitrant carbon (RC) by size fractionation. Saltmarsh sites generally had the highest SOC content (up to 12.4% SOC). The POC fraction was the highest at the surface in the saltmarsh site and decreased relative to the HC and RC fractions with depth. Conversely, the proportion of POC at the mangrove sites did not decrease with depth, forming up to 76% of the SOC. The vertical displacement of soil of up to 5.8 mm year–1 at the saltmarsh sites, measured using root ingrowth bags, suggest significant contributions of POC via root materials. Retention of these POC inputs are likely to be related to waterlogging, which decreases decomposition rates – with much lower soil moisture content at SM1, where the lowest POC content occurred below the surface, compared with SM2 and SM3.

中文翻译：

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温带红树林和盐沼土壤中的有机碳含量

沿海湿地，如红树林和盐沼环境，可以储存大量的土壤有机碳 (SOC)；然而，大多数研究集中在热带和亚热带环境。我们评估了澳大利亚南部温带红树林（两个地点）和盐沼（地点 SM1、SM2 和 SM3）环境中的 SOC 储量和组分。根据颗粒有机碳 (POC)、腐植碳 (HC) 和顽固碳 (RC) 通过尺寸分级分离 SOC 部分。盐沼场地通常具有最高的 SOC 含量（高达 12.4% 的 SOC）。POC 分数在盐沼场地的表面最高，并且相对于 HC 和 RC 分数随着深度的增加而减少。相反，红树林地点的 POC 比例没有随着深度的增加而减少，形成高达 76% 的 SOC。土壤垂直位移可达5。8 毫米年-1 在盐沼地点，使用根向内生长袋测量，表明 POC 对根材料的显着贡献。这些 POC 输入的保留可能与内涝有关，这会降低分解率——与 SM2 和 SM3 相比，SM1 的土壤水分含量低得多，其中最低的 POC 含量出现在地表以下。