The Influence Of Atmospheric Dynamic Conditions On The Migration Of Brown Planthopper In China And The Prediction Of Its Impact Of Climate Chang

Brown planthopper(BPH,Nilaparvata lugens [St?l])is one of the most damaging rice pests in East Asia and Southeast Asia,characterized by aggregation,long-distance migration,outbreak,and internationality.As a small insect with a low self-propelled flight speed,the BPH can complete a migration circle of thousands of kilometers annually with the assistance of atmospheric dynamic conditions,e.g.,atmospheric circulation and weather systems,covering the Indochina Peninsula,China,Korea,Japan,and other regions.However,there are few studies on the influence mechanism of atmospheric dynamic conditions on the BPH migration based on different migration types in academia,also the predictive exploration and possible causes of BPH outbreaks under the different climate change backgrounds in the future.Therefore,taking the rice planting area of southern China as the main study area,the Chinese BPH light-trap catches number from 1979 to 2017,the Korean BPH light-trap catches data in 2016,the CMIP6 Scenario MIP(Coupled Model Intercomparison Project Phase 6,Scenario Model Intercomparison Project)climate scenario data,the process analysis method based on atmospheric dynamic condition,the composite analysis method,and the trajectory simulation method of HYSPLIT(Hybrid Single Particle Langrangian Integrated Trajectory)model are used in this paper.Based on the above-mentioned data and methods,the following works are mainly carried on in this study:(1)explore and interpret the differences and similarities of the influence mechanism of atmospheric dynamic conditions between the overland migration and the overseas migration of BPH,(2)use a self-defined quantitative research method(i.e.,the REM method,“Response variable processing,Explanatory variables processing,and Modeling”)to establish atmospheric-dynamics-based outbreak models of BPH in rice planting area of southern China,and(3)predict the outbreak situation and analyze the causes of BPH in the rice planting area of southern China under the different climate change scenarios in the future.The main conclusions are as follows.1.There are similarities and differences in the influence of atmospheric dynamic condition on the overland migration and overseas migration of BPH.The main difference is that the overall risk of BPH overseas migration is much higher than that of BPH overland migration,and the coordination of atmospheric dynamic conditions is more severe for the former.It is attributed to the overland migration of BPH population can go through multiple migrations to reach their intended destinations,while the overseas migration is the “one-off” migration.The similarities are mainly shown in two aspects:(1)the both migration types experience the process of “gradual immigration,peak immigration,and gradual emigration” of BPH population;(2)the number of BPH light-trap catches between the upstream and downstream pest occurrence areas is mutually influenced and correlated.2.Although there are differences in the specific forms for the effects of atmospheric dynamic conditions on the overland migration and the overseas migration of BPH,there is no essential difference in the influence mechanisms of atmospheric dynamic conditions on them from the macroscopic point of view,and they are homogeneous.The influence mechanism of atmospheric dynamic condition on the BPH migration is shown as follows.First,the change of atmospheric circulation situation in East Asia leads to the change of permanent or semipermanent weather systems in the middle-lower troposphere.Then,the dynamic balances between these weather systems directly determine the atmospheric dynamic situation of secondary weather systems in East Asia.Finally,the 3D atmospheric dynamic environment constructed by the secondary weather systems affects the take-off,high-altitude migration,and landing of BPH migration.3.It is feasible to establish an objective and quantitative analysis method that can meet the requirements of the cross disciplines like insect migration and have interpretability,based on the study for the influence mechanism and variable screening as systematic as possible.The REM method defined in this paper is a possible solution.The models of BPH outbreak in the rice planting area of southern China established by the REM method is effective.4.Under the different backgrounds of climate change,the outbreak level of BPH in the rice planting area of southern China will generally increase in the future,and the risk of serious outbreaks of BPH in the Yangtze River-Nanling Mountains Region is much higher than that in the northern South China and the lower Yangtze River Valley.The main reason for the generally increasing outbreaks level of BPH in the rice planting area of southern China in the future is the significant southwesterly extension of the West Pacific subtropical high(WPSH)under the background of climate change with the uncontrolled emission.The difference in the distribution of wind-precipitation fields in East Asia,caused by this southwesterly extension,is the main reason for the significant difference in the BPH outbreaks among different rice planting areas in southern China in the future.5.The implementation of mandatory emission-reduction measures will significantly reduce the high-level outbreaks risk of BPH in the rice planting area of southern China,mainly due to the mandatory emission reduction weakens the southwesterly expansion trend of the WPSH system,and thus slows the process of the emergence of a wind-precipitation field distribution conducive to migration over East Asia.