Estimating of terrestrial carbon storage and its internal carbon exchange under equilibrium state

Abstract

Terrestrial carbon storage plays a crucial role in determining the global carbon cycle and regulating global climate. However, the carbon storage, as simulated by terrestrial biosphere models (TBMs), exhibits considerable inconsistency at the regional or global scale because the model structure, input dataset, and key parameter are quite different in TBMs. In this study, I proposed a detachable carbon cycle (DCC) model to simulate terrestrial carbon storage, internal carbon exchange, and the influx–efflux (IE) function of each carbon pool. The model was established based on a pool–and–flux scheme and contained 14 carbon pools, or carbon flow processes. Each process can be detached from the primary model and evaluated as an independent component. The average net primary productivity (NPP) from 1982 to 2008 was used as the influx carbon to drive the DCC model. The magnitude of the internal carbon exchanges of the DCC model was explicitly represented, and the carbon IE function of each carbon pool was fitted based on the characteristics of carbon flux. Results indicated that the terrestrial carbon storage was 2766.25 Pg, and carbon stored in vegetation and soil was 705.85 and 2022.00 Pg, respectively. Carbon stored in slow and passive pools accounted for 70.42% of the terrestrial carbon storage, and the slow pool contributes the highest amount of released CO2 among of all carbon pools during carbon decomposition. The IE functions exhibited a nonlinear curve feature and satisfactory adjust-R2. This study aimed to contribute to our understanding of the carbon cycle from non-equilibrium state to equilibrium state and can serve as a reference and framework for global carbon storage simulation research.