Analysis Of Influential Factors Of Oak Pest Threat And Its Occurrence Degree In The Main Distribution Areas Of Oaks In China

In China,Quercus resources are abundant and important,which has high economic,ecological and social values.In order to protect and develop Quercus resources,it is necessary to learn about the pest species and their infestation rate.However,there is little knowledge of systematic research about oak pests in China.Therefore,the species of Quercus pests were investigated by field experiment and indoor artificial rearing so as to get the present situation of oak pests and provide basic data for prevention and control of oak pests in China.During the investigation,it was found that Fentonia ocypete Bremer not only occurred in a wide range,but also severely in some areas.Thus,from climate,host plant,the stand,site,and other aspects,analysis of the key factor,affecting natural population of F.ocypete,was made to reveal its occurrence law.In addition,there are many foreign pests that threaten oak trees in China.Among them,Agrilus bilineatus(Weber)has occurred in many regions,and is constantly spreading.Therefore,the distributional model of potential habitat of A.bilineatus in China was made using the MaxEnt model.The results are as follows:(1)There are 26 survey plots,including Beijing,Heilongjiang,Jilin,Liaoning,Hebei and so on.In total,165 species of oak pests were identified.According to different damage characteristics,the species can be divided into four major groups:defoliating insects,sap-sucking insects,acorn feeders,and wood-boring insects.The number of defoliating insects are significantly more than other species,accounting for 57.58%.The manifestation degree of pests in different regions is obviously different,and the dominant species are also different.Among them,Massicus raddei(Blessig&Solsky),F.ocypete,Trichagalma serratae Ash and Mechorhis ursulus Roelofs have caused severe damage in some areas of northeast China,north China and central China.In addition,it was found that Carpatolechia yangyangensis Park is the newly recorded species of Quercus trees.According to the investigation results,the number of Palaearctic species and Eurytopic species are relatively consistent,significantly more than the number of Oriental species.(2)According to the results,the factors such as temperature,altitude,host species are positively correlated with the occurrence of F.ocypete.The principal component analysis was evaluated on the biological factors affecting the population fluctuation of F.ocypete.It was found that the forests with large canopy density and complex structure were favorable for the occurrence of F.ocypete.The results of the principal component analysis of the abiotic factors demonstrated that mean annual temperature,elevation and annual extreme high temperature were positively correlated with the occurrence of F.ocypete.(3)When the MaxEnt model was used to predict the potential distribution area of A.bilineatus,it was found that AUC of the training data and testing data were 0.989,indicating that the predicted result had achieved the level of excellence.The result showed that the suitable geographical distribution areas of A.bilineatus under contemporary climatic conditions are mainly southeastern China.The high-level suitable distribution region are eastern Zhejiang,southern Jiangsu,eastern Anhui,southern Hubei,central Hunan and other regions;The moderate suitable distribution region are central Zhejiang,southern Jiangsu,central and western Anhui,eastern Hubei,eastern Hunan,western Jiangxi.The analysis of Jackknife showed that the driest seasonal rainfall(bio17),the seasonal variation standard deviation of temperature(bio4),and the maximum temperature in the warmest month(bio5)were the main climatic factors affecting the distribution of A.bilineatus.