An experiment was conducted to study the accumulation and biological cycling of nutrient elements (N, P, K, Caand Mg) in Eucalyptus urophyllaxE. grandis plantations based on the data from site-specific observation for 4. S yean in Jiepai Branch of Gaofeng Forest Farm, Guangxi Province. Results show that the nutrient contents are different in various organs, which are highest in the leaves, followed by bark, branch, and stem. The total storage of nutrient elements in the plantations ranged from 452.19 to 850.54 kg/hm2 and increased with biomass accumulation. The storage of nutrient elements accounted for 70.92% -80.73% of the total for the arbor layer, 13.84% -22.99 % for the understory vegetation layer, and 4. 63% -6.48% for the litter layer. The annual net accumulation of nutrient elements in E. urophyllaxE. grandis plantations of four stand ages ranged from 150.72 to 224. 93 kg/( hm2 · a) , and that in the stem decreased with stand age. The change in annual net accumulation of various nutrients in the same organ was similar to that in various organs. The annual net accumulation of Ca or K was highest, followed by N, Mg or P. The annual amounts of nutrient element absorption of E. urophyllaxE. grandis plantations of four stand ages of 1.5, 2.5, 3.5, and 4.5 years were 282.62, 298.81, 241.46 and 204.95 kg/( hm2· a) , the annual returns were 68.83, 73.88, 63.42, and 54.23 kg/( hm2 · a), the cycling coefficients were 0.88, 0.53, 0.39, and 0.30, and the recycling periods were 4.66, 7.61, 9.83, and 12.51 years, respectively.%根据广西高峰林场界牌分场4.5a的定位观测与分析,对1.5 ～4.5年生尾巨桉人工林的5种营养元素(N、P、K、Ca和Mg)的积累和生物循环特征进行了研究.结果表明:尾巨桉不同器官营养元素质量分数存在明显差异,以树叶营养元素质量分数最高,其次是树皮和树枝,最低是树干；1.5 ～4.5年生尾巨按人工林营养元素积累量为452.19 ～ 850.54 kg/hm2,随生物量的增加而增大,其中乔木层营养元素积累量占70.92％～80.73％,林下植被层占13.84％ ～ 22.99％,地表现存凋落物层占4.63％ ～6.48％；林分营养元素年净积累量为150.72 ～224.93kg/(hm2·a),其中干材年净积累量随林龄增加而减少,同一器官各营养元素年净积累量与各器官营养元素积累量变化顺序一致,即为Ca或K＞N＞Mg或P;1.5、2.5、3.5、4.5年生各林分营养元素年吸收量分别为282.62、298.81、241.46和204.95 kg/( hm2·a),年归还量分别为68.83、73.88、63.42和54.23 kg/(hm2·a),循环系数分别为0.88、0.53、0.39和0.30,周转期分别为4.66、7.61、9.83和12.51 a.
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