藏青杨虫瘿的空间分布格局

摘要

为明确蚜虫在西藏工布自然保护区藏青杨(Populus szechuanica var.tibetica)叶片上的危害特征及其产生虫瘿的分布特点,基于野外调查数据,应用扩散系数(C)、Morisita指数(I)、Cassie指标(Ca)、平均拥挤度(M *)、Lloyd聚块性指标、负二项参数(K)、Iwao回归分析法、Taylor幂指数法对该区藏青杨叶片上虫瘿空间分布格局进行研究.结果表明,藏青杨叶片左上虫瘿出现率为25.36％、左下为24.30％、右上为24.98％、右下为25.36％,叶片左边为49.66％、右边为50.34％;藏青杨不同方向叶片上虫瘿出现的比率均在25％左右.藏青杨叶片上虫瘿主要以3～7个聚集的形式存在.虫瘿出现频次(y)与虫瘿数量级别(x)的拟合曲线为y=-2.1503x2 +23.159x-7.309 1(R2 =0.8184).6级虫瘿数量最多,占总虫瘿数的22.15％.由虫瘿空间分布参数可知,藏青杨叶片上虫瘿空间分布呈聚集型,但虫瘿聚集强度不大.总体上虫瘿个体群大小随虫瘿密度的增加而增大,个体群指数L值平均大小为7.20.经拟合,虫瘿空间分布格局Iwao M*-M回归模型为M*=1.059 9m+0.523 4(R2=0.993 9),Taylor模型为logS2=1.043 41ogm+ 0.043 7(R2=0.996 4),两模型均判定为聚集分布.综上,虫瘿在藏青杨不同方位的出现率相近,但在叶片上均呈聚集分布,虫瘿的聚集除与环境因素有关外,也与其生物学特性相关.%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.