Effects of Disturbance, Mangrove Community Type, and Management Blocks on Soil Organic Carbon (SOC) Stocks in Lamu, Kenya

Mangrove ecosystems are globally recognized for their exceptional capacity to sequester and store carbon, regulate coastal processes, and support biodiversity and local livelihoods. However, increasing anthropogenic disturbances continue to degrade mangrove ecosystems. Moreover, there remains inadequate understanding of how intact, disturbed, and restored mangrove systems differ in their capacity to store soil organic carbon (SOC) under varying geomorphological and hydrological conditions. This study examined the influence of disturbance, community types and blocking management approaches on SOC stocks in mangroves of the Lamu Archipelago, Kenya, with emphasis on intact, disturbed, and restored sites across different ecological settings. Soil cores were collected from Pate Island and Southern Swamp mangrove ecosystems at depths of 0–50 cm to determine soil bulk density and total organic carbon stocks. Data were analysed using non-parametric statistical tests and linear mixed-effects models to assess variations in SOC stocks across forest disturbance categories, mangrove community types, sediment depths, and mangrove blocks. The mixed-effects model revealed significant effects of forest disturbance status (LR χ2 = 120.843, p < 0.001), sediment depth (LR χ2 = 78.612, p < 0.001), mangrove community type (LR χ2 = 8.248, p = 0.004), and mangrove blocks (LR χ2 = 18.973, p < 0.001) on SOC stocks. Post-hoc comparisons indicated significantly higher SOC stocks in intact mangroves than in disturbed and restored mangroves (p < 0.001), with no significant difference between disturbed and restored ecosystems (p = 0.188). SOC stocks varied significantly across sediment depths, with the highest stocks recorded at 0–10 cm and the lowest at 30–40 cm. Fringing mangroves exhibited significantly higher SOC stocks than overwash communities (p = 0.004), while Pate Island recorded significantly higher stocks than Southern Swamp (p < 0.001). These findings demonstrate that forest disturbance, mangrove community type, sediment depth, and spatial variability significantly influence SOC storage, highlighting the importance of conserving intact mangroves, strengthening restoration efforts, and incorporating ecological variability into blue carbon accounting and climate change mitigation strategies in Kenya.