Above Ground Biomass Production and Nutrient Cycling of Middle age Plantation of Acacia mangium

Above-ground biomass production,net primary productivity,nutrient accumulation and distribution in different tree components,litterfall amount and it’s decomposition and nutrient biological cycling of 5 to 6 years old plantation of Acacia mangium are presented in this paper. Biomass of 5 and 6 years old plantations were 65.0 and 77.3 t/hm2. Net primary productivity of the plantation from 5 to 6 years old was 19.9 t/hm2. N accumulation by tree component,understorey and litter on forest floor was 525.45 kg/hm2 at the age of 5 years and 590.24 kg/hm2 at the age of 6 years. P and K accumulations were 24.50 and 263.10 kg/hm2 at the age of 5 years,and 23.87 and 309.66 at the age of 6 years. Average litterfall of the plantation in 2 years and 3 months was 4.87 t/hm2. From 5 to 6 years old,cycling rate of N,P,K,Ca and Mg were 60.5%,233.0%,44.6%,60.7% and 47.5% respectively in the plantation. Results indicate that P deficiency was a main limit for the plantation productivity.