Establishment And Analysis Of Structural Equation Model Of Wheat Aphid Ecosystem

Aphids are the main pests that harm the growth of wheat,but the growth rate of aphids is affected by many factors such as the environment and natural enemies.The complex interaction relationships bring great difficulties to the state description of the wheat aphid populations,which also brings great challenges to management of the aphids.The structural equation model shows significant advantages in dealing with complex multivariate relationships.In view of the above,three structural equation models of wheat aphid population state are proposed using the field survey data in ecological system of the wheat aphid populations for 32 years and the corresponding ecological explanations are given,which reveals the change law of wheat aphid populations in different environments and provides the theory basis for pest management.The specific contents are as follows:1.Considering the influence of the climatic on the wheat aphid populations,the structural equation model of the wheat aphid populations is proposed by choosing the wheat aphid population and the climate factor as the endogenous latent variable with observation variables such as the aphids per hundred plants and the exogenous latent variable with observation variables such as the temperature,respectively.Using the AMOS24.0 software,the fitness between the model and the data is tested,and the reasonable paths are determined.Finally,the model parameters are estimated and compared,the climatic influence on the wheat aphid populations is analyzed.2.On the basis of the above model,the structural equation model of the wheat aphid population is proposed by choosing natural enemy factor as the exogenous latent variable with observation variables such as the spider populations.According to confirmatory factor analysis method,the natural enemy influence on the wheat aphid populations is discussed.3.Considering the comprehensive effects of multiple factors on the wheat aphid populations,a structural equation model with multiple exogenous latent variables is proposed.On the one hand,the corresponding comprehensive effect is discussed using confirmatory factor analysis method.On the other hand,the mediating effect of the model is analyzed by Bootstrap,the direct and indirect effects of the climate on the wheat aphid population state are studied.