Species-specific relationships between net primary productivity and forest age for subtropical China

The relationship between net primary productivity (NPP) and forest age varies among forest species, yet there were no available NPP–age relationships established for various forest species in subtropical China for use in forest carbon modeling. This study explored the NPP–age relationships for seven forest species in subtropical China using data from the Strategic Priority Project of Carbon Budget (SPPCB), National Forest Inventory (NFI) Type I (NFI-I), and Type II (NFI-II) data using the Semi-Empirical Model (SEM). Forest species included Pinus massoniana (P. massoniana), Cunninghamia lanceolata (C. lanceolata), Eucalyptus robusta (Eucalyptus), Other Coniferous Forests (OCF), Softwood Broadleaf (SWB), Hardwood Broadleaf excluding Eucalyptus (HWB), and Mixed Forests (MF). Based on these three datasets, we were able to derive subtropical forest species-specific NPP–age relationships. Compared with China-wide NPP–age relationships previously derived from the SPPCB dataset, these species-specific relationships derived in this study resulted in improved simulations of aboveground biomass for subtropical forests using a process-based InTEC model, suggesting that these species-specific NPP–age relationships are valuable for forest carbon modeling and management in subtropical China.