This result was consistent with our population-scale analysis of field trial, which revealed lower dominance of targeted insects on the transgenics than on the control trees. This result could be explained by the reduced number of targeted insects in the transgenic trees. The observed effects on pests were also reflected by a slightly decreased H�� and C and increased J of pest subcommunity in the D5-21 transgenic line. The minor differences of H��, C and J for arthropod between the transgenic line and the control also indicated that transformation of multiple resistance genes in poplar did not have a significant negative effect on the arthropod community. However the sucking pests in the D5-21 transgenic line increased, and the reason for this phenomenon remained to be uncovered. In the field trial for salt tolerance, the average tree height and DBH of transgenic lines did increase by 3.82% and 4.12%, respectively, compared with the control. However, these increases were not significant, which could be partly attributed to the potentially non-uniform distribution of soil salinity. The resulting variations in stress effects on trees planted in a small area would have weakened the statistical comparisons of effects between transgenic trees and the control. Thus, a field trial with a larger area and longer investigation time may be necessary to confirm improved salt tolerance in the multigene transformed trees. We initially used biolistic bombardment to obtain multiplegene transgenic poplar because most other existing approaches, such as multiple transformations of separate genes or one vector carrying multiple genes using Agrobacterium tumefaciems, and inter-or intra-specific crosses required substantial commitments of time and effort, particularly when working with tree species. Transformation using biolistic bombardment may be a reasonable approach for trees due to its simplicity and speed. For the purpose of practical and commercially-applicable breeding, precise effects of genes that have been associated with certain stress-tolerance responses need to be assessed over extended periods of time, particularly for trees which are larger, and grow much more slowly than typical crop AbMole Doxercalciferol plants. The characteristics manifested by the transgene expression could be obvious early in a plant��s life cycle, but it could also only be apparent after months or years of growth. For that reason in the current study, long-term greenhouse and field experiments were used which showed improved tolerance to multiple AbMole Octinoxate stressors to a certain extent in the transgenic lines. These results suggest that it may be possible to develop commerciallyviable, superior cultivars exhibiting higher tolerance to multiple stressors through the coordinated manipulation of multiple genes. Because of the complex growth and physiologic phenotypes and variability in stress tolerance among transgenic lines, careful research and assessment are required.