A STUDY ON STAND DENSITY MANAGEMENT AND LONG-TERM PRODUCTIVE OF CHINESE FIR (CUNNINGHAMIA LANCEOLATA) PLANTATION Dynamics of understory vegetation biomass in successive rotations of Chinese fir (Cunninghamia lanceolata) plantations Carbon and nitrogen dynamics of decomposing foliar litter in a Chinese fir (Cunninghamia lanceolata) plantation exposed to simulated nitrogen deposition