Based on nutrient cycling of the second generation of Chinese fir plantation at fast-growing stage,the model of biogeochemical cycles was established by using compartment.Simulation results showed that the storage of N,P,K,Ca and Mg in each compartment increase significantly except the soil compartment by using two methods.The nutrient elements accumulation above ground compartment needs 6 years and 9 years to restore to the state before thinni...