喀斯特城市杨树人工林微量元素的生物循环

对喀斯特城市25年生杨树人工林内Cu、Fe、Zn、Mn、Ni、Pb、Co、Cd微量元素的含量、积累、空间分配和生物循环进行了研究。结果表明,林地土壤中,微量元素含量Fe最高,Mn次之,Cd最低,且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,Pb、Ni、Mn、Cd、Cu、Co、Zn分解速度比Fe快。林木各器官微量元素含量为细根>树叶>粗根>树皮>树枝>大根>根桩>干材,Cu在叶中高于其他器官。林分微量元素的总贮量为14.086 kg.hm^-2,微量元素在各器官中贮存量排序为Mn>Zn>Cu>Fe>Cd>Co>Pb>Ni,树干和树皮的贮存量最多,占总贮存量的43.4%。林分微量元素的年吸收量为3.079 kg.hm^-2,年归还量为2.663 kg.hm^-2,年存留量为0.417 kg.hm^-2,总利用系数为0.219,循环系数为0.865,周转期为5.29年,林分对土壤中Cd的吸收能力强,微量元素的生物分解率均高于生物迁移率。杨树林分中微量元素具有较大的循环速率和较短的周转期,而且林分对养分的稳定性、自我调节能力和培肥土壤的能力强,有利于林地生产力维持。

Contents and cycling of microelements in Karst urban poplar plantations

The concentration, accumulation, spatial distribution and bioloigcal cycling of 8 microelements (Cu, Fe, Zn, Mn, Ni, Pb, Co and Cd) in 25-year old Populus tremula plantation in Karst city were studied. The results showed that concentration of Fe was the highest among 8 microelements, followed by Mn and that of Cd was the lowest in the soil, and microelements concentration decreased with increasing of the soil depth. Microelements of Pb, Ni, Mn, Cd, Cu, Co and Zn had a higher rate of decomposition than element of Fe in the litter floor. The order of microelements concentration in different organs of Populus tremula was as follow: fine root> leaf > coarse root > bark > branch > large root > stake > stem, and concentrations of Cu in leaf were higher than those in other organs. The total storage of microelements in the plantations was 14.086 kg?hm-2, and the storage of 8 microelements in different organs of Populus tremula was in the order of Mn>Zn>Cu>Fe>Cd>Co>Pb>Ni. The storage in stem and bark was the highest and accounted for 43.4%. The annual absorption of microelements in the plantations was 3.079 kg?hm-2, and the annual returns equaled to 2.663 kg?hm-2, and the annual retention was 0.417 kg?hm-2. The microelement utilization coefficient, cycling coefficient and recycling period were estimated to be 0.219, 0.865 and 5.29. Cd absorbency of Populus tremula plantation was strong, and the biological decomposition rates of microelement were higher than migration rates. Populus tremula plantation had a higher microelement recycling rate and a shorter turnover period, and it could make nutrient stability, self-adjustment and soil fertilization, which contribute to maintaining forest productivity.