Structure And Function Analysis Of Arthropod Community In Paddy Fields In Jianghan Plain

Jianghan Plain is the main rice producing area in Hubei Province,and its rice planting area accounts for 40% of the total plant area of the province.At present,there are few studies on the composition and diversity of arthropod communities in rice fields in the Jianghan Plain.The composition and diversity of arthropod community and the interaction characteristics of main pests and natural enemies are the fundamental for the development of sustainable and environmental friendly management strategies.In this study,paddy arthropods in Jiangling County,Jianli City,Qianjiang city,Honghu City,Shishou City and other counties in Jianghan Plain were systematically investigated at different growth stages of rice from 2019 to 2020.Principal component analysis,path analysis and grey correlation analysis were used to analyze the composition and diversity of arthropod species,the interaction characteristics of main pests and their natural enemies,and the ecological function of neutral insect subcommunities in paddy fields of Jianghan Plain.The specific results are as follows:1.There are 169 species of arthropods belonging to 3 classes(Insecta,Arachnida and Collembola),12 orders and 86 families.According to the feeding habit and relationship rice,the arthropod community in rice field was divided into phytophagous,predatory,parasitic and neutral four subcommunities.Phytophagous subcommunity(Ph S)has 57 species belonging to 33 families in 6 orders,predatory subcommunity(Pr S)has 50 species belonging to 30 families in 7 orders,parasitic subcommunity(Pa S)has 44 species belonging to 15 families in 2 orders,and neutral subcommunity(NS)has 18 species belonging to 16 families in 5 orders.Among the four subcommunities,the number of individuals of NS and Ph S accounted for 61.31% and 31.20% respectively,which were the main groups.The number of individuals of Pr S accounted for 4.67%,and the number of individuals of Pa S accounted for 2.82%.Dominant species of Phs in paddies are Sogatella furcifera,Haplothrips aculeatus,Cnaphalocrocis medinalis,Nephotettix bipunctatus and Nilaparvata lugens,dominant species of Pr S are Tetragnatha shikokiana,Tetragnatha nitens,Leucauge subblanda,Cyrtorhinus lividipennis,and Ischnura sp.;dominant species of Pa S are Apanteles sp.,Sympiesis parnarae,Apanteles cypris,Trichogramma japonicun,and Haplogonatopus japonicas;dominant species of NS are Chironomus sp.,Simuliidae,Culicidae,Pachycerina sp.,Collembola.2.In this study,the individual number matrix of original species is formed by taking each survey site as the row and arthropod species as the column,Standardize the original data,calculate the load and cumulative contribution rate of each principal component,and calculate the contribution rate of each major species in each principal component.The results of principal component analysis showed that: In the rice field arthropod community,the Sogatella furcifera and Nephotettix bipunctatus had the greatest effect on the first principal component;For the second principal component,the most important ones are the Orius tantillus,Paederus fuscipes,etc;The third principal component is most affected by the Cnaphalocrocis medinalis,the Laodelphax striatellus,etc.It is preliminarily concluded that the first principal component and the third principal component are the dominant phytophagous insects that have a greater impact on the rice field arthropod community,and the second principal component is the dominant natural enemies that have a greater impact on the rice field arthropod community.That is to say,the difference of arthropod community composition in rice fields is mainly determined by the number of dominant phytophagous insects and dominant predatory natural enemies3.The interaction between the main pests of rice arthropod community,the Sogatella furcifera and Cnaphalocrocis medinalis,and their natural enemies was analyzed by using the gray correlation analysis method.The correlation between the population number of Cnaphalocrocis medinalis and the population number of natural enemies is as follows:Hylyphantes graminicola > Pardosa pseudoannulata > Misumenops tricuspidatus,The results showed that the population number of the Hylyphantes graminicola was most closely related to that of the Cnaphalocrocis medinalis,and had certain control effect on Cnaphalocrocis medinalis.The correlation between the population number of Sogatella furcifera and the population number of its natural enemies is as follows: Tetragnatha nitens >Cyrtorhinus lividipennis > Paederus fuscipes,It showed that the population of Tetragnatha nitens is most closely related to the population of Sogatella furcifera,and had certain control effect on Sogatella furcifera.4.Neutral insects accounted for 61.31% of the arthropod community in rice fields,which was an important part of the arthropod community structure in rice fields;The grey correlation analysis results between different kinds of natural enemies and neutral insect populations showed that: The first three places in the order of the association degree between the number of natural enemies and the number of neutral insects are: Araneus cornutus > Tetragnatha nitens > Tetragnatha shikokiana,It showed that the population number of Araneus cornutus had the largest correlation with the number of neutral insects,that is,the occurrence number of Araneus cornutus had the closest relationship with the number of neutral insects,It has certain control effect on neutral arthropods.The order of decision coefficients in path analysis of neutral insects and phytophagous insects on predatory natural enemies was: Culicidae > Sogatella furcifera > Cnaphalocrocis medinalis > Chironomus sp.> Nilaparvata lugens > collembola.Among them,Culicidae ranked first,indicating that Culicidae played an important role in the growth and reproduction of natural enemies,could replace phytophagous pests as prey of natural enemies,and was conducive to the establishment of population of natural enemies before the occurrence of phytophagous pests,which played an important role in maintaining the stability of the rice field ecosystem.