Biomass and carbon sequestration in four sub-montane forest types: Insights from multiple-year monitoring data in Indonesia

The Indonesian forests, encompassing approximately 95.5 million hectares, are vital for climate change mitigation through carbon storage and sequestration. This study assessed biomass dynamics, carbon stocks, and CO₂ sequestration across four sub-montane forest types: sub-montane natural secondary forest (SMSF), sub-montane pine forest (SMPF), sub-montane liquidambar forest (SMLF), and sub-montane agathis forest (SMAF), within Bodogol Resort, Gunung Gede Pangrango National Park (GGPNP). Four one-hectare permanent plots were monitored over three measurement periods to evaluate tree growth, regeneration, species composition, total biomass, and carbon sequestration. The results reveal that SMPF exhibited the highest biomass and carbon stock (528.91 Mg ha⁻¹, 264.46 MgC ha⁻¹), followed by SMAF (518.70 Mg ha⁻¹, 259.35 MgC ha⁻¹), SMLF (426.47 Mg ha⁻¹, 213.23 MgC ha⁻¹), and SMSF (327.36 Mg ha⁻¹, 163.68 MgC ha⁻¹). Biomass and carbon were strongly linked to forest characteristics, including basal area (BA) and tree height (stand structure) in SMAF and SMPF, species diversity and richness (species composition) in SMSF, while SMLF reflected the balanced influence of stand structure and species composition. Carbon sequestration rates declined as stands approached ecological climax, underscoring the role of stand development in regulating carbon dynamics. These findings highlight that forest type, stand structure, and species composition are key determinants of carbon storage capacity and that well-managed plantation forests offer significant contributions for sustainable forest management and climate change mitigation strategies in Indonesia.