Biological Cycling of Nutrients of Acacia crassicarpa Plantation in Coastal Sandy Area

Standardtimber and harvesting methods were used to study the concentration, accumulation, distribution and biological cycling of the nutrient elements (N, P, K, Ca and Mg) in an 8yearold Acacia crassicarpa plantation on a sandy coastal plain soil in southeast Fujian Province, China. The results showed that nutrient contents in the leaves were the highest among those in different organs, with the lowest in the stems. The total nutrient accumulation was 57921kg/hm2. In this plantation, concentration of N was the highest among the five elements, followed by K, Ca, Mg and P. The nutrient accumulation of various organs was ranked as branches ＞ stems ＞ barks ＞ leaves ＞ roots in the pure plantation of Acrassicarpa, and the nutrient accumulation of the five elements were ranked as N ＞ K ＞ Ca ＞ Mg ＞ P. Nutrient contents of 0-60cm depth of soil was rank as Ca ＞ K ＞ Mg ＞ P ＞ N, the accumulation coefficients of nutrient elements of different organs was leaves ＞ roots ＞ barks ＞ branches ＞ stems. Annual net nutrient accumulation, return and absorption were 7240kg/(hm2·a), 18285kg/(hm2·a), and 25525kg/(hm2·a), respectively. The utilization coefficient and the recycling period of five nutrient elements were ranked as K ＞ Ca ＞ P ＞ N ＞ Mg, the cycling coefficient were ranked as Mg ＞ N ＞ P ＞ Ca ＞ K in this plantation. The nutrient cycling coefficient, the utilization coefficient and the recycling period were 072, 028, and 317a, respectively. The cycling coefficient was high, but recycling period was shot, which was conducive to the recovery of sandy soil fertility and productivity maintenance in the Acrassicarpa plantation.