马尾松人工林微量元素生物循环的研究

STUDY ON BIOLOGICAL CYCLING OF MICROELEMENTS IN PINUS MASSONIANA PLANTATIONS

对广西中部丘陵区的 4个不同年龄阶段马尾松人工林内Fe、Cu、Zn、Mn、Pb、Ni、Cd等 7种微量元素的含量、积累、空间分配和生物循环以及它们随林分年龄的变化规律进行了研究。结果表明 :林地土壤中 ,微量元素含量以Fe最高 ,Mn次之 ,Cd最低 ,随林分年龄的增加 ,微量元素含量均呈现随土层深度增加而减少的垂直分布规律。在枯枝落叶层的分解过程中 ,Fe、Cu、Zn、Mn、Pb、Ni分解速度比Cd快。林木各器官微量元素含量大小排序为根 >叶 >枝 >皮 >干 ,微量元素在各器官中含量均以Fe >Mn >Zn >Cu >Pb >Ni >Cd为序 ,Pb、Cd在根系中含量高于其他器官。随着林龄的增加 ,微量元素含量存在明显差异 ,尤其以Fe突出。林分微量元素的总贮存量为 8 818～ 10 3 82 5kg·hm- 2 ,树皮和树干的贮存量最高 ,占总贮存量的 4 0 %～ 4 6 %。微量元素贮存量随林分生物量的增大而增加 ;4个年龄阶段林分微量元素的年吸收量分别为 3 84 6、12 5 5 8、18 75 3和13 2 34kg·hm- 2 ,年归还量分别为 2 733、9 86 6、14 86 6和 9 935kg·hm- 2 ,年存留量分别为 1 113、2 6 92、3 887和 3 2 99kg·hm- 2 。 4个年龄阶段林分微量元素总的利用系数为 0 12 7～ 0 4 36 ,循环系数分别为 0 711、0 75 1、0 786、0 793,周转期为 3 2 2

The concentration, accumulation, spatial distribution and bioloigcal cycling of 7 microelements (Fe, Cu, Zn, Mn,Pb, Ni and Cd) as well as their changes with growth of stands in Pinus massoniana plantation of 4 different age classes were studied. The results showed that concentration of Fe was the highest among 7 microelements, followed by Mn and that of Cd was the lowest in the soil. Irespetive of age classes, microelements concentration decreased with increasing of the soil depth. Microelements of Fe, Cu, Zn, Mn, Pb and Ni had a higher rate of decomposition than element of Cd in the litter floor. The order of microelements concentration in different organs of Masson Pine was as follow: root>Needle>branch>bark>stem. Regardless of organs, concentrations of 7 microelements was in the order of Fe>Mn>Zn>Cu>Pb>Ni>Cd, and concentrations of Pb and Cd in root were higher than those in other organs. Microelements concentration varied remarkedly with the stands growth, especially for Fe element. The total storage of microelements in the plantations ranged from 8 818 kg·hm -2 to 103 825 kg·hm -2 and increased with the biomass accumulation in the process of the stands growth. The storage in bark and stem was the highest and accounted for 40% to 46%. The annual absorption of microelements in 4 age classes plantations were 3 846, 12 558, 18 753 and 13 234 kg·hm -2 , respectively. The annual returns equaled to 2 733, 9 866, 14 866 and 9 935 kg·hm -2 , respectively. The annual retention were 1 113, 2 692, 3 887 and 3 299 kg·hm -2 , respectively. The microelement utilization coefficient, cycling coefficient and recycling period were estimated to be 0 127～0 436, 0 711～0 793 and 3 226～10 450 In early stage stands, microelement use efficiency in Masson Pine plantation was lower but recycling rate was higher and turnover period was shorter. Mature stands had a lower microelement recycling rate and a longer turnover period, so the trees extract more microelement from soil. Hence measures should be taken to faciltate the successional process to reach a stable zonal community.