In order to explore relationships betweenthe occurrence of Bipectilus zhejiangensis moth in the bamboo shoot and soil chemical characteristics and depth. Two plots of bamboo forest damaged by the moth were selected to perform this study in 2007 in Shaowu, Fujian.Soil beneath the damaged bamboo shoots were divided into 3 depth levels (0 20cm, 20 40cm and 40 60cm) in each 60 cm × 60 cm plot, and were labeled as Layer 1, 2 and 3 from the surface. Soil samplings from each level were composited to test for pH, total N content and seven other soil parameters. Discriminant analysis technique was used to analyze each layer, 1,2-layer combination, 2,3-layer combination and 1,2,3-layer composition. The results indicated that:
(1) Layer 1 had significant organic matter with the most effective combination discriminant of the total nitrogen content and instant potassium; Layer 2was not significant in single index, but the most effective combination discriminant were still total nitrogen content and instant potassium. Layer 3 had significant single parameter of organic matter, the most effective combination discriminant were instant potassium and organic matter. Levels of importance on the target groups were not identical. The individual indicator was significant in the portfolio which had great impact on the group, but not completely decisive. Combination indicator played a more important role than the individual indicator.
(2)Layer 1 discriminant function can be used to correctly classify Layer 2 and Layer 3. Layer 2 discriminant function can be used to correctly classify Layer 3, but not to Layer1. Layer 3 can not be used to correctly classify Layer1 and Layer2. Discriminant function had forward classifying to the lower layer with a certain degree of accuracy, but hadn't reverse classifying to the upper layer. From the surface to bottom layer, the damage level increased with the total nitrogen content and decreased with instant potassium content.
(3)Discriminant analysis of 1,2-layer combination and 2,3-layer combination showed that Significance in single indicator changed, but the combination of the index didn't. The most effective indicators of 1,2-layer combination were still total nitrogen content and instant potassium. 2,3-layer combination had the same indicator in single layer which were still total N content and instant potassium, which illustrates again that the physical and chemical properties of soil affect the damage level from surface to bottom layer.
(4) Compared with the results of variance analysis and multiple comparisons, discriminant analysis reflects not only the single indicator statistically significant in a group, but also the importance of index portfolio. This result indicates that significance of single indicator could not differentiate decisively between groups. Therefore, we conclude that the physical and chemical properties of soil could affect the occurrence of B. zhejiangensis from surface to bottom layer, and the damage level increases with the increase of total nitrogen and the decrease of instant potassium Using discriminant analysis method to identify the relations between the occurrence of B. zhejiangensis and soil was superior to variance analysis and multiple comparisons.