Study On Root Distribution And Accumulation Of Nickel With Caragana Korshinskii Under Heavy Metal Stress

Taking the 5-year-old Caragana korshinskii under the soil replacement of planting hole,direct planting,covering soil 30cm,50cm,80cm different planting methods in ecological restoration experimental field of tailings in Jin-chuan as the research object, the paper studied on the absorption feature and laws of each organ of Caragana korshinskii to Ni in the response of root to the heavy metal stress and in different planting measures by using soil coring method, discussed the relationship between soil and element of Ni in the plant and the process of transportation and accumulation and the law of internal and external cycle of Ni in the plant.To fill in the research blank of?root distribution under heavy metal stress.Meanwhile in order to Use Caragana plants which provide theoretical basis for remediation of heavy metal pollution.It provided the helpful reference on restoration and reconstruction of mining wasteland in arid and semiarid regions. The mainly results showed that:1. The content of Ni in ecological restoration experimental field of tailings in Jin-chuan experimental field decreased with the increasing of soil thickness and increased with the increasing of soil depth. The comparison results of Ni contend is soil replacement of planting hole >direct planting>covering soil 30cm>covering soil 50cm> covering soil 80cm. Compared with the soil background value, the content of Ni is over standard seriously. Compared with soil environmental quality standardⅢ, only the district of 80cm covering soil measured up to standard and others is over standard seriously which is 4.74～9.20 times than standard.2. Under Heavy Metal Stress, the root length and the effective root length of Caragana korshinskii in horizontal direction is mainly focus on 0～50cm, and in vertical direction mainly focus on 0～60cm which the maximum length is 0～30cm and the length decreased with the depth since the 30cm. In five planting measures, the order of the total root length and the effective root length density in unit area are covering soil 50cm> covering soil 80cm> covering soil 30cm> soil replacement of planting hole >direct planting.?3.Under Heavy Metal Stress in varying degrees, the order of the root biomass of Caragana korshinskii is covering soil 50cm> covering soil 30cm> soil replacement of planting hole> covering soil 80cm >direct planting. In horizontal direction, the root biomass of Caragana korshinskii distribution in the distance of 100cm from trunk; in vertical direction, the root biomass of Caragana korshinskii decreased with the depth of soil lay increasing; it focused on 0～50cm of soil lay and existing certain functional relationship with the depth of soil lay; the order of the root biomass in different diameter class is nakane(2.0mm≤DR < 8.0mm) >rootlet(1.0mm≤DR <2.0mm)>hair root(DR<0.5mm)>fine root(0.5mm<DR<1.0mm)4. The distribution of effective root density decreased with the increasing of soil thickness. From the distribution of weighted mean, the order of effective root weight density is covering soil 30cm>covering soil 50cm> covering soil 80cm> soil replacement of planting hole >direct planting. Dry weight of effective root distribute in the distance of 1m from the trunk in horizontal direction; effective root weight density was a trend in decreasing with the depth increasing of soil lay and focused on 0～60cm of lay.5. The contend of Ni in root and flower of Caragana korshinskii is larger, but it is less in leaf and stem. The content of Ni in root decreased with the increasing of diameter and increased with the increasing of soil layers depth and appeared maximum in the best primary(70cm～90cm).6. Under Heavy Metal Stress in varying degrees, the uptake of Caragana korshinskii to Ni decreased in certain degree with the increasing of soil thickness and the order of the uptake is covering soil 30cm> soil replacement of planting hole >direct planting> covering soil 80cm>covering soil 50cm. In each organ, the uptake of root is higher than any other organs and the minimum is stem, leaf and flower. Generally speaking, the uptake of Caragana korshinskii of growing covering soil 30cm to Ni is more than the one of the measures of thicker covering soil and direct planting measures, which is the best planting measure of Caragana korshinskii restoration of tailings reservoir in Jin-chuan.7. The order of enrichment coefficient of each organ of Caragana korshinskii to Ni is root>flower>leaf>stem. In each experimental plot, the enrichment coefficient ofⅢis significant higher than others,Ⅴis second andⅤis minimum. 8. The order of transfer coefficient of Ni under Heavy Metal Stress in varying degrees is covering soil 80cm>covering soil 50cm >direct planting> soil replacement of planting hole>covering soil 30cm. The order is flower>leaf>stem in different parts of Ni, the transfer coefficient is less than 1 and this plant is a type of root hoarding plant.9. From the retention ratio of root to Ni, in covering soil 30cm, enrichment of root Ni is more and it transferred seldom toward the aerial part of stem, leaf and flower and the retention ratio of root is up to 85.24%; then the retention ratio of soil replacement of planting hole, direct planting and covering soil 50cm is 76.92%,4.96%,61.93% respectively; in covering soil 80cm, the lagging effect of root to Ni is weaker and the retention ratio is 47.27% which is much more in transferring from root to above-ground.10. Not all relationship is a positive correlation between the absorption of Caragana korshinskii to Ni and the content of soil Ni. The dependence is quite large inⅠdistrict of absorptive capacity of Caragana korshinskii leaf to Ni for soil environment and the correlation coefficient is 0.993 which is very significant(p<0.01); the effect is large inⅤdistrict that soil environment for enrichment of Caragana korshinskii stem to Ni and the correlation coefficient is 0.766 which is significant(p<0.05); the relationship had a negative correlation between enrichment ability of Caragana korshinskii stem and leaf to Ni and concentration of soil Ni in some district and the other correlation are not up to significantly(p<0.05).