Mangrove ecosystems have the potential to store large amounts of carbon but detailed studies on the fine scale spatial variability of biomass components and sediment organic carbon (SOC) and their relationships are lacking. Here we investigated the fine-scale spatial variation of SOC, aboveground and belowground biomass using systematic grid sampling in a temperate Avicennia marina ((Forssk.) Vierh) forest in Australia. We estimated aboveground biomass in a 9 × 9 sampling grid within a 0.16 ha plot and measured SOC, fine root biomass and necromass down to 1 m at 81 sampling points in an A. marina forest in Western Port Bay near Melbourne, Australia. We detected large differences in all measured carbon pools. SOC increased from low to high intertidal position but showed no consistent trend with depth. Aboveground biomass carbon was highly variable (mean 84 ± 56 Mg C ha⁻¹), and showed no consistent trends with intertidal position. The average total organic carbon stock at the study site was 207 ± 80 Mg C ha⁻¹. Aboveground biomass contributed 41% and coarse roots around 6% to the total carbon content of the forest. The bulk of organic carbon in the ecosystem was SOC (53%) and necromass was an important contributor to SOC. Aboveground biomass was a poor predictor of all belowground carbon pools. Our data indicate that 43 sediment cores would be required to determine mean SOC content at the level required by international carbon accounting standards. The high spatial variability of all carbon stocks in the system indicates that current sampling strategies for SOC need to be revised in order to improve predictions of the amount of carbon stored in blue carbon ecosystems.

红树林生态系统具有储存大量碳的潜力，但缺乏对生物量组分和沉积物有机碳 (SOC) 的精细尺度空间变异性及其关系的详细研究。在这里，我们使用系统网格采样在澳大利亚温带Avicennia marina ((Forssk.) Vierh)森林中研究了 SOC、地上和地下生物量的精细尺度空间变化。我们在 0.16 公顷地块内的 9 × 9 采样网格中估计了地上生物量，并在A. marina 的81 个采样点测量了 SOC、细根生物量和低至 1 m 的死生物量澳大利亚墨尔本附近西港湾的森林。我们在所有测量的碳库中发现了很大的差异。SOC 从低潮间带位置增加到高潮间带位置，但与深度没有一致的趋势。地上生物量碳变化很大（平均 84 ± 56 Mg C ha ^-1），并且与潮间带位置没有一致的趋势。研究地点的平均总有机碳储量为 207 ± 80 Mg C ha ^-1. 地上生物量占森林总碳含量的 41%，粗根约占 6%。生态系统中的大部分有机碳是 SOC (53%)，死尸是 SOC 的重要贡献者。地上生物量对所有地下碳库的预测都很差。我们的数据表明，需要 43 个沉积物核心才能确定国际碳核算标准要求的水平的平均 SOC 含量。系统中所有碳储量的高空间变异性表明，需要修改当前的 SOC 采样策略，以改进对蓝碳生态系统中储存的碳量的预测。