沿海沙地厚荚相思人工林养分生物循环特征

用标准木法和收获法对闽东南沿海沙地8年生厚荚相思人工林N、P、K、Ca和Mg的养分含量、积累、分配和生物循环进行研究。结果表明：5种营养元素含量以树叶为最高，干材最低，各器官营养元素含量排序为N ＞ K ＞ Ca ＞ Mg ＞ P；营养元素总积累量为57921kg/hm2，各器官营养元素积累量排序为枝 ＞ 干 ＞ 皮 ＞ 叶 ＞ 根；各营养元素积累量排序为N ＞ K ＞ Ca ＞ Mg ＞ P。0~60cm土层土壤中5种养分元素含量大小排序为Ca ＞ K ＞ Mg ＞ P ＞ N，厚荚相思各器官对土壤养分的富集能力排序为叶 ＞ 根 ＞ 枝 ＞ 皮 ＞ 干。厚荚相思乔木层养分年存留量为7240kg/(hm2·a)，年吸收量为25525kg/(hm2·a)，总归还量为18285kg/(hm2·a)。5种元素利用系数和周转期均为K ＞ Ca ＞ P ＞ N ＞ Mg，循环速率为Mg ＞ N ＞ P ＞ Ca ＞ K，循环系数为072，利用系数为028，周转期为317a。厚荚相思林5种营养元素利用效率高，循环速率快，而周转期短，有利于沙质土壤肥力的恢复和生产力的维持。

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.