Background Benggang management is an important soil and water conservation measure in the southern red soil region, it plays a crucial role in maintaining ecosystem stability and improving the environment. However, research on the impact of Benggang management on carbon sink is still relatively limited. Thus, the objective of this study is to assess the carbon sink capability of Benggang management in terms of protecting soil and carbon, mitigating erosion and carbon emission, and promoting vegetation and carbon sequestration, as well as the differences in carbon sink capacity among different management models.

Methods We selected one un-managed Benggang (UB), one Benggang with a comprehensively managed (MB) and three Benggangs with a land cultivation and afforestation Bengang managed (AB) as the research objects in Anxi county, Fujian province. Soil samples were collected at intervals of 0-10, 10-20 and 20-40 cm from different depths in all selected Benggangs. SOC (soil organic carbon) was determined using a carbon-nitrogen analyzer. Soil bulk density was measured using the ring knife method. Data on tree species, diameter at breast height, and tree height were obtained through field surveys and sampling methods. The tree biomass was quantified using biomass equations and harvesting methods.

Results 1) Benggang management effectively protect soil and carbon, mitigate erosion and carbon emission, and promote vegetation and carbon sequestration. The carbon conservation, carbon emission reduction, and carbon sequestration capacity of MB are 32.00 t/hm², 23.47 t/hm² CO₂ and 35.86 t/hm² CO₂, respectively. Those of AB are 3.97-9.42 t/hm² C, 2.91-6.91 t/hm² CO₂ and 73.77-727.98 t/hm² CO₂, respectively. Based on this calculation, the managed Benggangs may increase carbon sequestration by 399.73×10⁴ t CO₂ in Anxi county. 2) The carbon sequestration effect of AB primarily relies on the enhancement of vegetation carbon stocks, accounting for 51.24%-97.35% of the total carbon sequestration, while for MB, it mainly relies on the enhancement of soil carbon stocks, accounting for 72.39% of the total carbon sequestration. 3) The carbon sequestration capacity of AB is higher than that of MB. The main reason for the difference between the two methods is the afforestation and management practices employed. 4) After approximately 10 years of Benggang management, the soil carbon density of the managed areas is currently lower than that of degraded following vegetation restoration in the southern red soil region. This suggests that there is considerable potential for improvement in the soil carbon density of Benggang management.

Conclusions Benggang management serves as a measure to prevent water and soil erosion and promote soil carbon conservation, and to reduce carbon emission, and carbon sequestration in the red soil hilly areas of southern China. The findings may provide scientific support for the selection of future Benggang management models and the assessment of their carbon sequestration capacity.