Simulation Algorithm Of Forest Diseases And Pests Diffusion Prediction

Due to severe financial losses and ecological destruction attributed to forest diseases and pests(FDP)in China,exploiting computer to predict and simulate the spread of FDP plays an essential part in control of FDP.There are many FDP prediction methods,but these methods have disadvantages:lacking effective utilization of image data,supporting one-dimensional prediction value with limited information,only predicting the probability map of FDP,lacking information that changes over time limiting to a small scale(e.g.,a sample-plot),rather than a large scale like a forest zone.To solve the above problems,two methods are proposed to predict the spread of FDP with different focuses and the results were more intuitive through visualization.Pine wilt disease is taken as the research object.(1)A region-based simulation algorithm is proposed for the aggregation distribution in the later stage of diffusion.(2)A infectious disease dynamics method is presented due to the extremely contagious of pine wilt disease.The specific research content is as follows:(1)A large-scale region-based simulation method is designed for the diffusion of FDP.Compared to the most conventional numerical prediction,our prediction method works on two dimensions.Specifically,the FDP areas are fitted by a group of spline curves,and a defined energy function is provided to describe the difference between the contours of adjacent time.Regression method characterized by disease influencing factors is exploited to predict the spread parameters(the distance and angle),adhering to prior forestry research.After two-step corrections,the final predicted contour is obtained.Contrast with the method of cellular automata,our method is more in line with the spread law under the influencing factors,providing forestry workers with visual aids of the future situation.(2)A infectious disease dynamics method is proposed for the diffusion of FDP.Since the first method can only observe the spread area of the disease,cannot analyze the epidemic law of the disease,a method of establishing a disease spreading model is proposed.Considering the difference of disease diffusion between natural state and trunk injection,this paper builds two diffusion models: SEI' model and SEIR' model,and finally shows the spread of disease.The SEIR' model is used to simulate when there are 15% diseased trees in the constructed forest.When the removal rate of trunk injection increases from 2.5232% to 9.5477%,the proportion of diseased trees will drop from 50% to 23.5% when it is finally stable.