第2代杉木人工林微量元素的积累、分配及其生物循环特征

Accumulation, distribution and biological cycling of microelements in a second rotation Chinese fir plantation

利用定位观测取得的数据 ,对第 2代杉木人工林 4种微量元素 ( Fe、Mn、Cu、Zn)的积累、空间分布及其生物循环进行了研究。结果表明 :杉木林生态系统中 4种微量元素总贮量为 30 72 89.70 8kg/ hm2 ,其空间分布表现为土壤层 >乔木层 >死地被物层 >草本层 >灌木层。土壤层中微量元素的贮量占绝对优势 ,4种微量元素贮量的排序为 Fe>Mn>Zn>Cu。杉木中 4种微量元素的积累量为 35 .971 kg/ hm2 ,排列顺序为 Mn >Fe >Zn >Cu,各器官中微量元素积累量排列顺序为树叶 >树根 >树枝 >树干 >树皮。杉木林生态系统中 4种微量元素的年存留量为 4.1 0 8kg/ ( hm2 · a) ,年归还量为 - 2 .2 0 9kg/ ( hm2 · a) ,其中凋落物归还量为 1 .2 5 7kg/ ( hm2·a) ,淋溶归还量为 - 3.446kg/ ( hm2·a) ,杉木林冠针叶、枝及树干对 Zn元素具有较强的吸附能力 ,年吸收量为 2 .0 84kg/ ( hm2 · a) ,尽管杉木对微量元素吸收数量不大 ,但为净吸收的。 4种微量元素的吸收系数排序为 Mn>Cu>Fe>Zn;利用系数的排序为 Cu>Fe>Mn>Zn;循环系数的顺序为 Zn>Fe>Mn>Cu;周转期大小顺序为 Mn>Cu>Fe>Zn。因此 ,该系统中 Zn、Fe存留比例较小 ,周转期短 ,流动性较大 ,而 Mn、Cu则相反 ,存留比例较大 ,周转期长 ,流动性较小。

This study investigated the accumulation, distribution and biological cycling of four microelements (Fe, Mn, Cu, Zn) in a second rotation Chinese fir plantations at the Huitong Ecological Station, Hu′nan Province of China. The quantities of micronutrients in the system could be ranked in the following order: Fe (303558.9 kg/hm 2) > Mn (1783.7 kg/hm 2) > Zn (1672.0 kg/hm 2) > Cu (275.2 kg/hm 2). The greatest pool of micronutrients was in the soil, and the next largest pool was in overstorey trees. The smallest pool was found in understorey plants. In the soil, Fe was evenly distributed in different layer whereas Zn was mainly concentrated at 0~45 cm depth. The concentration in the distribution of Mn and Cu in the 45~60 cm depth layer indicated adsorption processes at that depth. The overstorey trees of Chinese fir had accumulated Fe 12.70 kg, Mn 22.34 kg, Cu 0.24 kg/hm 2 and Zn 0.69 kg/hm -2. Obviously, the highest accumulation was observed for Mn and the lowest was found for Cu. The amounts of micronutrients in different parts of overstorey trees decreased in the order of leafs > roots > branches > stem > bark. Microelements storage in understorey plants and litter was up to 2.16 kg/hm 2 of Fe, 3.12 kg/hm 2 of Mn, 0.05 kg/hm 2 of Cu and 0.18 kg/hm 2 of Zn. Microelements in understoery plants and litter constituted an important nutrient pool in Chinese fir plantations. The annual microelement accumulation reached Fe 1.50, Mn 2.50, Cu 0.03 and Zn 0.08 kg/hm 2. The annual returns to soil were Fe 7.99,Mn 6.77, Cu 0.15 and Zn -17.04 kg/hm 2, of which litterfall contained Fe 0.22, Mn 1.00,Cu 0.004 and Zn 0.029 kg/hm 2 and leaching Fe 7.70, Mn 5.76, Cu 0.15 and Zn -17.07 kg/hm 2, respectively. The aboveground tree components in Chinese fir plantations had a strong capacity to accumulate Zn. The total annual uptakes of the four elements were 9.49 kg/(hm 2·a) of Fe, 9.27 kg/(hm 2·a) of Mn, 0.30 kg/(hm 2·a) of Cu and -16.97kg/(hm 2·a) of Zn. Although the amount of uptake was very low, it was a net uptake. The uptake coefficient, utilization coefficient, cycling coefficient and turnover period of 4 microelements followed the order of Mn > Cu > Fe > Zn, Cu > Fe > Mn > Zn, Zn > Fe > Mn > Cu, and Mn > Cu > Fe > Zn, respectively. The biological cycling of Zn and Fe was characterized by low retention, short turnover periods and fast flow rates, while that of Cu and Mn was characterized by high retention, long turnover periods and slow flow rates. These results provide some basic information for soil nutrient manipulations and further research of biological cycling in Chinese fir plantations