A spatially explicit dynamic biomass baseline for forest-management carbon projects in China

Abstract Forest carbon credits reward gains above a counterfactual baseline—the carbon stock expected without a project. Low baselines overstate additional mitigation, whereas high baselines can obscure real gains. Here we develop a spatially explicit, dynamic baseline framework for China using 24,237 forest-plot records and national forest datasets. We estimate pixel-level attainable potential maximum biomass from mature, low-disturbance forests and couple this ceiling to age-dependent growth curves. We project three no-project scenarios that progressively incorporate historical management rotations and observed biomass-loss regimes. A spatially varying biomass ceiling is sufficient for most forest strata; unconstrained growth produces consistently higher baselines than management-constrained scenarios, especially in intensively managed southern plantations. Incorporating observed biomass-loss events has little effect on national averages but alters local trajectories. Uncertainty is dominated by the attainable biomass ceiling rather than loss-event parameters. The framework provides an auditable and updateable basis for comparing counterfactual trajectories in forest carbon projects.