| The problem of environment and ecology which caused by mining activities has threat human survive and social economic development seriously. Wasting and occupying lots of land resources and causing soil heavy mental pollution, thus it arouses great attention today. Phytoremedation is considered the best way to solve this problem, but in addition to choosing suitable plantation, understand and master plantation nutrient, utilization efficiency and nutrient cycling character seemed more important. Therefore, we studied soil, plantation nutrient content and nutrient bio-cycle based on3different aged Koelreuteria bipinnata in Xiangtan manganese mine. The results indicated that:(1) The highest macro element content in soil was Ca, and next was Mg, the lowest was P, but after9years later, K in soil was reached4.22g/kg, becomes the highest; the content of Fe, Mn in soil was the highest in micro element, and next was Zn and Pb; nutrient elements showed no consistent regularity varied with soil depth; the sequence of total micro elements in3-and9-year soil was Fe>Mn>Zn>Pb>Ni>Cu>Co>Cd, but in5-year it was Fe>Mn> Pb>Zn>Cu>Ni>Cd> Co.(2) Macro elements in litter floor has no magnitude difference, and they all showed Litter>Fermentation>Humus. The content of Mn in micro elements was higher than others, and next is Fe, flowed by Zn and Pb, the lowest was Cd, there has magnitude difference between Fe, Mn and Co, Ni, Cd. What is more, total micro element in litter floor showed Litter>Fermentation>Hurmus in3-and9-year, but in5-year, they increased with decomposition, except for Mn and Co.(3) The content of macro element in different aged tree organs was between127.32g/kg and158.45g/kg, and they have no significant difference among different age, the sequence of macro element was N>K>Ca>Mg>P; the content of micro element was between3375.44mg/kg and6432.83mg/kg, and they have significant difference among different age (p<0.05). The sequence of all aged micro element was Fe>Mn>Zn>Pb>Ni>Co, except for Cu and Cd. The highest nutrient content in all aged tree organs was leaves, and the opposite was stem, others varied with tree age.(4)Micro elements storage was from85.33kg/ha to1046.38kg/ha, micro element was between0.71and65.55kg/ha, and they all increased significantly varied with growth. From the point of different element, the storage of N was the highest in macro element, from19.83kg/ha to86.77kg/ha, accounted total macro element storage for34.96%-43.48%, P was the lowest, about3.79kg/ha to23.20kg/ha, accounted total macro element storage for2.22%-4.44%; the highest storage in micro element was Mn and Fe, from0.65kg/ha to54.85kg/ha, accounted total micro element storage for75.70%-91.55%, and the lowest were Co, Ni and Cd. Furthermore, the storage of nutrient elements in organs varied with element and tree age.(5) Annual net accumulation of macro element was from20.69kg/(ha·a) to103.82kg/(ha·a), and from1.16kg/(ha·a) to6.97kg/(ha·a) in micro element, and they all increased with stand age. The retention for different elements was varied with tree age, N and Ca in3-year tree was the highest in macro element, and next was K, the lowest was Mg and P, but macro element retention has similarities between5-year and9-year tree, they all showed N>K>Ca>Mg>P. The highest annual net accumulation in micro element was Mn and Fe, the accounted82.00%-93.75%, but the proportion showed wavelike decrease with tree age increase. The sequence for aretention of micro element in3-year tree was Mn>Fe>Zn>Pb>Cu>Co>Ni>Cd, and in5-and9-year, except the different order for Zn and Pb, others was Mn>Fe>Cu>Cd>Co>Ni. Retention in organs showed that, above ground was higher than under ground, except for3-year tree.(6) The absorption for macro element was between38.63kg/(ha·a) to201.06kg/(ha·a), and N was the highest, P was the lowest; the absorption for micro element was from0.38kg/(ha·a) to9.81kg/(ha·a), and Mn, Fe was the highest, Co, Ni was the lowest. Retention amount for macro element was between17.93kg/(ha·a) and89.56kg/(ha·a), and it from0.22kg/(ha·a) to2.84kg/(ha·a) in micro element, moreover, the retention amount for different elements varied with tree age.The utilization coefficient for Koelreuteria bipinnata tree varied with element and tree age. Utilization coefficient for macro element was between0.14and0.53, and decreased with stand age, but it was between0.15and0.98for micro element; cycling coefficient for macro element was from0.29to0.42, and from0.28to0.62for micro element, utilization coefficient and cycling coefficient were all decreased with tree age increase. The recycling period was different for macro and micro element, it needs4.85a to33.86a for macro element, and2.09a to28.10a for micro element. In addition, there has difference for bio-absorption coefficient in different aged trees, it varied with stand age, and with stand age increasing, bio-decomposition coefficient gradually less than bio-migration coefficient for macro element, but for micro element, it was opposite. |
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