Spatial Distribution Pattern of Gall on Populus szechuanica var.tibetica Leaves

TANG Xiaoqin; LU Jie

doi:10.15933/j.cnki.1004-3268.2017.04.017

Abstract：In order to reveal the harm of aphid and distribution features of gall on Populus szechuanica var.tiebtica leaves in Xizang Gongbu Nature Reserve,based on field survey data,spatial distribution pattern of gall on P.szechuanica leaves was studied by diffusion coefficient C,Morisita index I,Cassie index Ca,mean crowding M*,Lloyd patchiness index,negative binomial parameter K,Iwao regression analysis,and Taylor power index.The results showed that the occurrence rate of gall on P.szechuanica leaves was 25.36％ for the upper left,24.30％ for the lower left,24.98％ for the upper right,25.36％for the lower right.The occurrence rates on the left and right were 49.66％ and 50.34％,respectively.The gall occurrence rates on P.szechuanica leaves was about 25％ in different directions.Three to seven galls existed on P.szechuanica leaves by aggregation.The relationship between gall number level(x) and gall appearance frequency(y) was y =-2.150 3x2 + 23.159x-7.309 1 (R2 =0.818 4).The gall number of level 6 was the most,accounting for 22.15％ of the total.The spatial distribution parameters of gall showed that the spatial distribution pattern of gall on P.szechuanica leaves was aggregation type,but the aggregation intensity was little.The individual clump size of gall increased with gall density increasing,and the average value of individual group index was 7.20.The Iwao M*-M model of spatial distribution pattern was M* =1.059 9m +0.523 4(R2 =0.993 9) for gall on P.szechuanica leaves,and the Taylor power model was logS2 =1.043 41ogm + 0.043 7 (R2 =0.996 4).The galls showed aggregation distribution by the two models.In a word,the occurrence rates of gall on P.szechuanica leaves were near in different azimuth,but they showed aggregation distribution.This distribution pattern of gall related to not only environmental factors but also gall biological characteristics.