Distribution Pattern Of Agrilus Planipennis In The Stem And Forests And Diffusion Path And Main Meteorological Influence Factors

Urban afforestation has developed rapidly with the development of ecological construction and its associated ecological benefits.As the deputy administrative center of Beijing,Tongzhou has introduced various tree species suitable for the northern climate as a part of the “Million Acres of the Plain Afforestation Project” launched by Beijing in 2012.Ash trees have been introduced in large quantities and planted extensively,and Fraxinus pennsylvanica has been the main tree species planted.However,in recent years,the occurrence of emerald ash borers in this region has affected afforestation efforts.Here,we evaluated the damage status of ash trees.We studied the occurrence characteristics and population spatial patterns of the affected stands under different degrees of damage through study of 12 sample areas(36 sample plots)in the Tongzhou plain forests.The emergence holes,mines and pupal cells formed by damage to the trunks of trees were systematically studied,and three-dimensional constructions were made.We also analyzed trends in the occurrence of emerald ash borers in China over the past 16 years and identified the main meteorological factors that affected their distribution.Our study produced several major findings.Firstly,emerald ash borers occurred at high densities in the Tongzhou district of Beijing,and all ash forests in the surveyed area were damaged to different degrees,with a stand damage rate of 100%.Ash trees planted in the early stage of this area were more seriously damaged because they had no coevolutionary history with the insects carried by seedlings transferred from plain afforestation in recent years.Secondly,the spatial distribution of the early damaged stands in this area was affected by the transfer of artificial seedlings and was completely determined by anthropogenic factors.As the degree of damage increased,the spatial distribution of emerald ash borers was affected by their biological habits.Indeed,their spatial distribution in the heavily damaged forest was highly affected by their habits.Thirdly,the large-scale occurrence of emerald ash borers was related to the establishment of ash forest in this region.Given the seriousness of the hazard and their ability to stay concealed,the introduction of ash seedlings should be strictly limited to areas where emerald ash borers do not occur,and ash seedlings should not be planted in pure forest.Fourthly,the straight edge of the "D" type emergence hole was in the same direction as the adult's back and was related to the direction of the insect body in the pupal cell.There was no significant difference between the diameter at breast height of the damaged wood,the number of emergence holes and the length and width of mines.The size and shape of the pupal cells were similar to the size and shape of the adult body,which were in the shape of a long strip with a wide and narrow side and with a sharp point.Based on the multi-level and multi-angle photographic images of the emergence holes,mines and pupal cells,the 3D construction and animation design were completed in the Sketch Up environment.Fifthly,the occurrence area data provided by the National Forestry and Grassland Administration Forest and Grassland Pest Control Station revealed that the pest was mildly and moderately abundant in Tianjin and Liaoning in the early stage.The abundance of this pest in the Beijing-Tianjin-Hebei region has significantly increased in recent years,including the occupation of a large area in Beijing and Hebei.Sixthly,Pearson correlation analysis showed that monthly average temperature and sunshine hours were positively correlated with the occurrence of emerald ash borers(r > 0),and monthly average relative humidity and average wind speed were negatively correlated with the occurrence of emerald ash borers(r < 0).Average temperature in June and September(r = 0.4361,P = 0.027;r = 0.4421,P = 0.023),sunshine hours in December(r = 0.4229,P = 0.041),average relative humidity in September(r=-0.586,P=0.0013),and average wind speed in April and October(r =-0.4159,P = 0.031;r =-0.4201,P = 0.029)had comparatively greater impacts.In this paper,the occurrence area and changes in the presence of the emerald ash borers in tree trunks,as well as affected stands with different degrees of damage and different regions,were studied through characterization of the spatial distribution of emerald ash borers.Correlations between the occurrence area and meteorological factors were used to analyze the main meteorological influencing factors.Reasonable explanations were proposed for the selection of ash species as well as seedling and afforestation mode,and scientific guidance was provided for the monitoring of emerald ash borers and the prevention of their deleterious effects.