Spatial and Temporal Distribution of Pine Wood Nematodes in Yiling District Based on GIS

[Objectives]This study was conducted to accurately understand the spatial distribution of the outbreak of pine wood nematode disease,explore its spatial laws,and provide a more scientific and efficient analysis and decision-making basis for the prevention and management of pine wood nematode disease.[Methods]Taking the GIS management of Bursaphelenchus xylophilus tree felling in Yiling District as an example,the spatial positions of epidemic wood in the two years from 2019 to 2020 were collected.The spatial data management function of ArcGIS software was used to collect point and surface layers.Spatial information maps were drawn by spatial visualization,trend surface,spatial autocorrelation,nearest neighbor distance index and spatial-temporal clustering analysis of kernel density,so as to intuitively understand the evolution of spatial pattern trend of pine wood nematode disease,and to explain the variation raw and diffusion characteristics of pine wood nematode disease.[Results](1)Under the control measures,the affected pine forests and epidemic sites(subcompartments)decreased in the following year,the spread of the epidemic was still spreading,which was spreading from the central to the western and northern regions.The distribution of the plane epidemic sites was sparse from high concentration.The new epidemic sites occurred in a jump,and the number of affected pine trees was high.The outbreak was concentrated in a certain area,and the risk was high.The natural transmission and diffusion would coexist for a long time.(2)The epidemic trend of pine nematode in the two years was in the east and west,with a high value in the east,and the trend line was almost straight line.The outbreak of pine nematode showed cone-shaped central point aggregation and spread.(3)The spatial and temporal clustering characteristics of the epidemic show spatial clustering in the overall pattern,high clustering of pine victims caused by the spread of the epidemic source and clustering distribution pattern of epidemic points.(4)In the two years,the damaged pine trees were searched within the range of 5 km by using the distance threshold.The kernel density maps showed that the damaged pine trees in 2019 were more serious than those in 2020.The result of density map was consistent with the nearest neighbor distance index,and the damaged pine forests were mainly concentrated.(5)The epidemic situation of B.xylophilus disease in this region has a certain number of epidemic sites and a wide distribution area,the epidemic situation is difficult to eradicate in a short time.On the comprehensive measures,we should increase the clearing of epidemic trees,block the spread of the epidemic situation in the new areas,reduce the epidemic sites,regulate the density of pine trees by forest management,reduce the density of Monochamus alternatus and establish a broad-leaved forest ecosystem.[Conclusions]The study provides assistive technology support for the prevention and control of pine wood nematode disease.