Dominant role of arbor forests in carbon stock enhancement: dynamics and associated factors of vegetation carbon storage in Pingxiang, China

Abstract

Understanding the dynamics and associated factors of forest vegetation carbon storage is critical for assessing terrestrial carbon stocks and guiding regional carbon neutrality strategies. This study investigated how vegetation type, stand age, and forest origin jointly shape carbon storage in the subtropical forests of a prefecture-level city. Using forest resource inventory data from Pingxiang City, Jiangxi Province (2003, 2013, and 2019), we quantified carbon storage across diverse vegetation types using volume-biomass conversion and average biomass methods. Results reveal a substantial increase in total forest carbon storage from 28.19 × 105 tC to 58.63 × 105 tC over 16 years (average annual carbon-stock increment: 1.90 × 105 tC, growth rate: 6.71%). Arbor forests were the primary contributor, with their proportion rising from 42.40% to 57.64% and carbon density increasing from 8.88 to 21.04 tC/hm2. Mixed forests showed the largest increase within arbor forests, associated with both expansion in area and an increase in carbon density. A midpoint decomposition indicated that changes in carbon density explained approximately 93.5% of the 2003–2019 increase in total forest-vegetation carbon storage, whereas area expansion explained approximately 6.5%; for mixed forests, the corresponding contributions were approximately 29.2% (density) and 70.8% (area). These findings highlight that afforestation and targeted plantation management, particularly age-class optimization and species diversification, are key strategies for enhancing regional forest carbon stocks.