Studies On The Structures Of Arthropod Communities In Corn Fields In Huaibei Region

Basing on investigating the structure of arthropod community in spring and summer corn field in Huaibei district, the dynamic variation of general arthropod community was studied with fuzzy cluster analysis, and the relationship between pests and natural enemies was studied with gray relation analysis and niche overlapping and similarity. The results were as follows:1.Analysis of anti-Ostrinia furnacalisThe damaging severity and occurrence frequency of Ostrinia furnacalis varied with the varieties of corn at the same cultivation condition. The occurrence rate of the secondary Ostrinia furnacalis was the lowest in the No.8 of Hongda corn, with no fresh channel and occurrence density of one eggmass per 100 plants. Meanwhile, the occurrence rate was the highest in the No.1 of Qidan corn, with 17 fresh channels and 3 eggmass per 100 plants.2.The species kinds and amount of arthropod communityThe kinds of phytophagous and rapacious arthropod in spring corn field were 18 and 13 respectively, and those in summer corn field were 19 and 16 respectively. The dominant pests in the 2 kinds of corn field were colaphellus spp., tetranychus cinnabarinus and rhopalosiphum maidis, and the amount of colaphellus spp. and tetranychus cinnabarinus were more than rhopalosiphum maidis in spring corn field, while the amount of rhopalosiphum maidis was higher than the two other in summer corn field. The dominant natural enemies of spring corn pests were erigonidium graminicolum, propylea japonica and harmonia axyridis, which mainly existed at the early growth period of corn; and those of summer corn pests were erigonidium graminicolum, harmonia axyridis and theridion octomacutatum, which mainly existed at the late growth period of corn.3. Speciality analysis of arthropod communityThe relative abundance of the general community and subcommunity of dominant pests of spring corn were 0.7298 and 0.8945 respectively, and those of summer corn were 0.8355 and 0.9733 respectively, which revealed that attribute of the subcommunity was mainly influenced by general community. The diversity of 3 kinds of arthropod community in spring corn field and the subcommunity of natural enemy in summer corn field was high, while that of general community and subcommnunity in summer corn field was low, just of 0.3852 and 0.6544 respectively.4. Index main features and dynamics of community The number of arthropod species in spring maize was first overall growth and then declined,and the total number of summer maize species changed little early, rapid increase in the later. Peak pest populations in maize field advantage in the early growth of spring corn, summer corn as late growth stage. Fluctuations in the number and the number of natural enemies of insect pests have a certain following effect From jointing stage to big trumpet, the diversity index was bigger in spring corn. Although the advantages of maize pests because of the number of the late surge led to uniformity decreased, but increased species richness decreased evenness up so late in the diversity index increased.5.Cluster analysis of community dynamicsBased on a comprehensive feature such as community property in individuals, species number, richness, evenness, abundance and diversity, etc, the spring maize total arthropod community and pest sub-community were divided into five categories and the predatory natural enemy sub-community was divided into three categories; the summer maize total arthropod community, pest sub-communities, predator sub-community were divided into 4 categories. Three communities in the cluster showed good results for spring and summer maize arthropod community structure in the characteristics of each growth period.6. Correlation analysis on the major natural enemies and pestsTemporal niche breadth of Rhopalosiphum maidis,Tetranychus cinnabarinus,Colaphellus spp.in spring corn fields were 1.8233,1.0141,1.1072,in the summer corn fields,those were 1.8233,1.0141,1.1072.There were biggest Niche breadth (0.9445),Correlation (0.7771) and the Similarity index (0.9897) between Colaphellus spp.and Theridion octomacutatum in spring corn fields,and R. maidis and Chrysoperla sinica had the biggest Niche breadth,Correlation,the Similarity index in the summer corn,the datas were 0.7490,0.9741,0.9669.