Relationship between microtopography and spatial distribution patterns of summer chafer Amphimallon solstitiale (L.) in Xinjiang grasslands
To clarify the spatial distribution pattern of the significant pest summer chafer Amphimallon solstitiale (L.) in different microtopographies of the Xinjiang grasslands,the checkerboard sampling method was employed to sample different microtopographic regions of the Yili grasslands. The number of A. solstitiale larvae was recorded,and their spatial distribution patterns were analyzed by using nine aggregation indices (the diffusion coefficient C,clumping index I,diffusivity index Iδ,negative binomi-al distribution index K,Cassie index CA,mean crowding m*,patchiness index m*/m,Lαindex,and Z in-dex) along with two regression models (the Iwao m*-m regression model and Taylor's power law). The cause of aggregation was analyzed using the aggregation meanλ,and a sampling technique was estab-lished based on Iwao's theoretical sampling number model and Kuno sequential sampling model. The results showed that the population density of A. solstitiale larvae diminished as the elevation increased in the Yili grasslands. Nine aggregation indexes and Taylor's power law suggested that A. solstitiale lar-vae followed an aggregated distribution pattern. Microtopography influenced the level of aggregation represented by aggregation indices and Iwao m*-m regression model;for example,the degree of aggre-gation for five aggregation indices (C,I,m*,Lα,and Z) tended to decrease as the elevation increased. In contrast,the four aggregation indices,K,CA,m*/m,and Iδ,showed that the degree of aggregation of the larvae initially rose and then fell with rising elevation. Larvae in the plains and toe slopes showed a uni-form distribution pattern according to the Iwao m*-m regression model. The aggregation meanλindicat-ed that the aggregation behavior of A. solstitiale larvae in the four microtopographies was caused by ex-ternal factors. Based on the number of A. solstitiale larvae,Iwao's theoretical sampling number model and Kuno's sequential sampling model were established to obtain the theoretical sampling number and the critical cumulative number of larvae. When the permissible error D was 0.2 and the population den-sity was 6 larvae/0.09 m2,the theoretical sampling number was 49 sample squares;when the permissi-ble error D was 0.2 and 40 sample squares were investigated,the critical cumulative population was 33.22 larvae. The findings indicated that the spatial distribution type of A. solstitiale larvae in Yili grass-lands followed an aggregated distribution pattern. While microtopography influenced population densi-ty,it did not alter the spatial distribution pattern.
Amphimallon solstitiale (L.)grasslandspatial distribution patternsampling techniqueaggregation distributionterrain
万方数据
维普
