A generalized, lumped-parameter ecological model PnET-CN was calibrated and validated for a subtropical coniferous plantation in southern China. PnET-CN model describes the biogeochemical cycles of carbon (C) and nitrogen (N) and can assist in estimating carbon sequestration potential. For validation of PnET-CN, data from coniferous forest plantations in southern China was used. Simulated daily gross primary productivity (GPP) from 2005 to 2007 agreed well with observations (R²=0.56, S.D.=0.009). Simulations of monthly soil respiration (R_s) from 2005–2007 agreed well with R_s observations (R²=0.67, S.D. =0.03). Simulated annual net primary productivity (NPP) from 1998–2006 was 803±33 gCm^-2a^-1, about 4% higher than NPP observation (752±51 gCm^-2a^-1). Simulations of annual NEP from 2005^-2007 only overestimate 9 gCm^-2a^-1 (4%), 4 gCm^-2a^-1 (1%) and 34 gCm^-2a^-1 (8%) compared to NEP observations, respectively. Simulated annual foliar N concentration (FolNCon) (1.09%) is 10% lower than observed monthly FolNCon (0.87%–1.58%). Simulated annual N leaching (0.26 gNm^-2) is about 10% lower than leaching observation (0.29 gNm^-2). PnET-CN model validation indicates that PnET-CN is capable to simulate daily GPP, annual NPP, annual NEP, monthly R_s, annual FolNCon and annual nitrate N leaching for subtropical coniferous plantations in southern China. The results obtained from the validation test revealed that PnET-CN model can be used to simulate carbon sequestration of planted coniferous forests in southern China to a high level of precision. Sensitivity analysis suggests that great care should be taken in developing generalizations as to how forests will respond to a changing climate. PnET-CN performed satisfactorily in comparison to other models that have already been calibrated and validated in coniferous planted subtropical forests in China. Based on PnET-CN validation and its comparison to other models, future improvement of PnET-CN should focus on seasonal foliar N dynamics and the effects of water stress on autotrophic respirations in subtropical coniferous plantations in southern China.