厚荚相思人工林营养元素生物循环的研究

Biological Cycling of Nutrients in Acacia crassicarpa plantation

对1.5～4.5年生厚荚相思人工林5种营养元素(N、P、K、Ca和Mg)的含量、积累、分配和生物循环以及它们随林分年龄的变化趋势进行了研究.结果表明,厚荚相思人工林不同器官中营养元素含量排序大致为树叶＞于皮＞树枝＞树根＞干材,林木各器官中营养元素含量均以N最高,其次是Ca,然后是K和Mg,P最低;厚莫相思人工林营养元素贮存量依次为145.00～611.70 kg/hm2,随生长过程中生物量的增加而增大;不同器官微量元素贮存量的分配随林分年龄的增长发生变化,1.5年生时营养元素贮量主要集中在树叶和树枝,2.5～4.5年生时营养元素贮量则主要集中在树干和树根;林分营养元素年净积累量为96.66～135.93 kg/(hm2·a),林木各组分营养元素年净积累量总的变化趋势以树干最高,树皮最低,年吸收量为116.50～258.10 kg/(hm2·a),年归还量分剐为19.83,117.21,114.83,122.17 kg/(hm2·a),利用系数分别为0.80,0.78,0.55和0.42,循环系数分别为0.17,0.49,0.48和0.47,周转期分别为7.34,2.64,3.73,5.01年.

The concentrations,accumulation,distribution and biological cycling of 5 nutrient elements(N,P,K,Ca and Mg) from 1.5-year-old to 4.5-year-old Acacia crassicarpa plantations were studied.The results show that the nutrient concentrations in various organs was in the order of leaves > bark > branch > root > stem.In plant,concentration of N was the highest among the five elements,followed by Ca and K and Mg,while P was the lowest in various organs of A.crassicarpa plantation.The total storage of nutrient elements in the plantations ranged from 145.00 kg/hm2 to 611.70 kg/hm2 and increased with the biomass accumulation in the process of the stands growth.The distribution of nutrient accumulations in A.crassicarpa varied with different stands growth stages, most nutrient elements accumulated in leaves and branches at 1.5-year-old stage,while they gradually moved gradually in stem and root from 2.5-year-old to 4.5-year-old.Nutrients element annual net accumulations in four ages of A.crassicarpa plantation were 96.66 kg/(hm2·a),117.21 kg/(hm2·a),114.83 kg/(hm2·a) and 135.93 kg/(hm2·a),respectively.Comparison of nutrients annual net accumulation in different organs was in the order of stem or leaves > branches > roots or bark.Changes in annual net accumulation of various nutrients in the same component was similar to that in various components.The annual absorption of microelements in four age classes plantations were 116.50～258.10 kg/(hm2 ·a).The annual returns equaled to 19.83 kg/(hm2 ·a),117.21 kg/(hm2 ·a),114.73 kg/(hm2 ·a) and 122.17 kg/(hm2·a),respectively.The nutrient utilization coefficients were 0.80,0.78,0.55 and 0.42,respectively.The cycling coefficient were 0.17,0.49,0.48 and 0.47.The recycling periods were 7.34 a,2.64 a,3.73 a and 5.01 a,respectively.