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sur le développement des zones arides et semi-arides

Titre : Population Occurrence of Predators and the Transfer-diffusion Behavior of Hippodamia Variegata in Gobi Desert of Southern Xinjiang

Auteur : 刘阳天

Grade : Master 2022

Université : Shihezi University

Résumé
Objects : To evaluate the conservation ability of Gobi desert in Tarim Basin,southern Xinjiang to predators,elaborate the mechanisms,find out which kinds of plant species plays important roles in predator conservation and demonstrate the source-sink relationship of predators between Gobi desert and cotton fields.Methods : In this study,40 sites were chosen to conduct field works from 2019-2021.We described the species composition of plants and predators within non-crop habitats of Gobi desert oases in southern Xinjiang,China,and then equally assessed whether plant-related variables（i.e.,species identity,flowering status and herbivore abundance）affect predator identity and abundance.One-way ANOVA and Duncan’s multiple comparison were performed to demonstrate the difference of predator community structure on various plant species across periods.Heatmap was used to show the population dynamics of each predator groups on various plant species cross periods.Linear regression was used to exhibit the effect of herbivore abundance to predator abundance.In addition,7 sites were chosen to observe the transfer diffusion behavior of Hippodamia variegata between Gobi desert and cotton field and investigate the effects of releasing number and distance of recapture ratio.Results : 1.The effects of plant community to predator community in Gobi desert : Species composition of plant community was investigated by visual observation.A total of 18 plant species belonging to 18 genera and 10 families were commonly encountered,with Apocynum pictum,Phragmites communis,Karelinia caspia and Tamarix ramosissima,Alhagi sparsifolia the dominant species.Sweeping method was used to investigated species composition of predator community.A total of 10405 individuals of predators,belonging to 14 taxa and 8 groups were captured with spiders and H.variegata dominant taxa.Plant traits and herbivore abundance explained up to 44%（3-44%）variation in predator community and exhibited consistent,yearround effects.The community structure of predatory natural enemies was different among various plants,and the periodic population abundance of different species of predator on various plants are different,too.Among all plant species,A.pictum had a significantly higher community structure index of resident predators in many periods.2.We detected the transfer-diffusion behavior of H.variegata,the dominant species of predators in both Gobi desert and local arable land,by marked-recapture method in early July.When 3000 individuals per site of marked H.variegata were released in Gobi desert,22 marked ladybugs were recaptured form cotton field adjacent to Gobi desert which demonstrated that individuals of H.variegata will have the transfer behavior from Gobi desert to arable land.And both the number of H.variegata released in per site and the distance between the releasing site and the sample of recapture significantly affect the recapture ratio.The relationship between distance and the recapture can be fitted in formula : y = –6.753 ln（x）+ 43.075.Significance : Our study underlines how perennial flowering plants such as A.pictum are essential to sustain predators and related ecosystem services in arid settings.And the predators harbored by these plants would transfer from Gobi desert to adjacent arable lands.This work informs the essential roles of Gobi desert to natural enemy conservation and agricultural pest management and the dominant species of predator community,H.variegata have transfer diffusion behavior between Gobi desert and arable land which could somehow provide scientific reference for sustainable management and regional control farmland pests in southern Xinjiang

Mots clés : Insect biodiversity conservation ;Desert-oasis agroecosystems ;predator;Gobi desert ;transfer and diffusion behavior ;

Présentation (CNKI)