Abstract
Forest biomass and carbon storage models are crucial for inventorying, monitoring, and assessing forest resources. This study develops models specific to China's diverse forests, offering a methodological foundation for national carbon storage estimation and a reference for regional and global carbon sequestration projections. Utilizing data from 52,700 permanent plots obtained during China's 9th national forest inventory, we calculated biomass and carbon storage per hectare for 35 tree species groups using respective biomass models and carbon factors. We then constructed a hierarchical volume-based model system for forest biomass and carbon storage, applying weighted regression, dummy variable modeling, and simultaneous equations with error-in-variables. This system encompasses a single population, three forest categories (level I), 20 forest types (level II), and 74 forest sub-types (level III). Finally, assessment of these models was carried out with six evaluation indices, and comparative analyses with previously established biomass models were conducted. Determination coefficients (R²) for the population average, level I, II, and III dummy models exceed 0.78, 0.85, 0.92, and 0.95, respectively, with corresponding mean percent standard errors (MPSE) of approximately 22%, 21%, 15%, and 12%. Furthermore, mean prediction errors (MPE) have consistently lessened to below 0.5%, and total relative errors (TRE) approximate zero. Models for 20 forest types and 74 sub-types yield R² values above 0.87 and 0.85, with MPE values below 3% and 5%, respectively. Notably, the estimates of previous biomass models demonstrated considerable uncertainty, with TRE ranging from − 20–74%. However, accuracy has improved with larger sample sizes. In total biomass and carbon storage estimations, the R² values of dummy models for levels I, II, and III progressively increase and MPSE values decrease, whereas MPE and TRE remain relatively stable. The tiered model system of simultaneous equations developed herein offer a quantitative framework for precise evaluations of biomass and carbon storage across China's forests. For enhanced accuracy in such estimations, applying level III models is recommended whenever feasible.