Surface Carbon Sequestration Rate of Coffee Agroforestry System in Bukit Riki Besar, South Bengkulu

The expansion of coffee plantations in hilly areas has the potential to affect carbon storage; however, research on the influence of slope gradient on the carbon sequestration rate of coffee agroforestry systems remains very limited. This study aimed to determine the surface carbon sequestration rate across different slope classes in the coffee agroforestry system of Bukit Riki Besar, South Bengkulu. Sampling was carried out across four slope classes (flat, 0–8%; gentle, 8–15%; moderately steep, 15–25%; steep, 25–45%) using purposive sampling with 20 × 20 m plots. The biomass of shade trees, coffee plants, and litter was calculated using allometric equations, while soil carbon was measured based on sampling depth and bulk density. The results showed that the highest tree biomass occurred on gentle slopes (12.04 ton ha⁻¹ year⁻¹), whereas the highest soil carbon stock and carbon sequestration rate were found on steep slopes, at 213.54 and 35.59 ton C ha⁻¹ year⁻¹, respectively. In conclusion, slope gradient is a determining factor in carbon distribution within coffee agroforestry systems; land management should therefore take topographic characteristics into account in order to optimize carbon storage.