Influence of tide levels and community composition on soil carbon sequestration in mangrove largest wetland Leizhou Peninsula, China

Mangroves play a vital role in mitigating atmospheric carbon dioxide by storing substantial quantity of carbon in their soils. Unlike terrestrial forests where most carbon is stored in living trees, mangroves store approximately 70–90% of their carbon in the soil. Mangrove soil carbon dynamics and their driving factors have been extensively studied globally, there remains a significant lack of region-specific data, particularly in southern China. To address this gap, we conducted a field investigation across six mangrove wetland sites in China’s largest reserve, located on the Leizhou Peninsula. We collected 144 soil core samples from 48 sampling points. Our objectives were to assess mangrove biomass and soil carbon stocks across different tidal levels and to identify the primary direct and indirect environmental drivers influencing carbon storage. Soil carbon stocks in this area ranged from 23.29 to 287.69 Mg C/ha, with significant variation observed based on mangrove community composition. Notably, mixed-species mangrove stands exhibited higher soil carbon storage compared to a single species. The non-native species Sonneratia apetala contributed less to carbon sequestration than native species. Across most sites, Avicennia marina demonstrated higher carbon storage than other species, highlighting its significant role in carbon sequestration. Structural Equation Modeling (SEM) revealed that elevation and tidal level were the most influential factors affecting soil carbon stocks. Principal component analysis further confirmed that high tidal levels and 10–30 cm soil layers were crucial for carbon accumulation. These findings underscore importance of tidal dynamics in mangrove carbon sequestration and highlight potential of high tidal zones for enhancing carbon storage in coastal ecosystems. We advocate for the prioritization of native, mixed communities, high-carbon-storing species in restoration efforts to maximize carbon burial. This study advances mangrove research by moving from global estimates to local drivers, specifically quantifying how tide levels, species composition, and environmental factors control carbon storage in the Leizhou Peninsula. Besides that, this study will provide a theoretical basis for future research and supports strategies to enhance the blue carbon potential of China’s largest mangrove wetland system.