First Assessment of Carbon Stock in the Belowground Biomass of Brazilian Mangroves

ABSTRACT Studies on belowground roots biomass have increasingly reported the importance of the contribution of this compartment in carbon stock maintenance in mangrove forests. To date, there are no estimates of this contribution in Brazilian mangrove forests, although the country has the second largest area of mangroves worldwide. For this study, trenches dug in fringing forests in Guaratiba State Biological Reserve (Rio de Janeiro, Brazil) were used to evaluate the contribution of the different classes of roots and the vertical stratification of carbon stock. The total carbon stock average in belowground roots biomass in these forests was 104.41 ± 20.73 tC.ha−1. From that, an average of 84.13 ± 21.34 tC.ha−1 corresponded to the carbon stock only in fine roots, which have diameters smaller than 5 mm and are responsible for over 80% of the total belowground biomass. Most of the belowground carbon stock is concentrated in the first 40 cm below the surface (about 70%). The root:shoot ratio in this study is 1.14. These estimates demonstrate that the belowground roots biomass significantly contributes, more than 50%, to the carbon stock in mangrove forests. And the mangrove root biomass can be greater than that of other Brazilian ecosystems.

摘要：针对地下根系生物量（belowground roots biomass）的相关研究日益表明，该组分在红树林（mangrove forests）碳储量（carbon stock）维持过程中发挥着关键作用。尽管巴西拥有全球第二大的红树林面积，但截至目前，该国红树林中该组分的碳储量贡献尚无相关估算结果。本研究依托巴西里约热内卢州瓜拉蒂巴国家生物保护区岸带红树林中开挖的剖面沟，评估了不同径级根系的碳贡献及碳储量的垂直分层特征。该类森林地下根系生物量的总碳储量平均值为104.41±20.73 tC·ha⁻¹。其中，直径小于5毫米的细根（fine roots）碳储量平均值为84.13±21.34 tC·ha⁻¹，该类细根的地下生物量占总地下生物量的比例超过80%。约70%的地下碳储量集中在地表以下0~40厘米的深度范围内。本研究测得的根冠比（root:shoot ratio）为1.14。上述估算结果表明，地下根系生物量对红树林碳储量的贡献显著超过50%，且红树林根系生物量或高于巴西其他陆地生态系统。