| Jiangxi is a key forest region in southern of China.Masson pine(Pinus massoniana Lamb.)is widely distributed in Jiangxi Province.It is an important timber tree species and a pioneer ecological tree species for afforestation in barren hills.In recent years,however,this tree species is suffering attacked from the Japanese pine sawyer beetle,Monochamus alternatus Hope(Coleoptera,Cerambycidae).More importantly,this beetle can transmit pine wood nematode(Bursaphelenchus xylophilus(Steiner et Buhrer)Nickle),which causes pine nematode disease(PND)and the death of pines.In order to understand the population dynamics of this beetle in Jiangxi and its influencing factors,in this paper,the population fluctuation,developmental and damaged characteristics,as well as the vertical distribution were conducted from three factors of latitude,fire and insect disaster.These results will provide an important guiding significance for the integrated management of this beetle.The results showed as follows:1.Effects of latitude on population dynamics of M.alternatusAdult population dynamics of M.alternatus were monitored through setting up monitoring point and installing the attractant trap in pure stands of Masson pine at Quannan,Nankang,Wan’an,Nancheng,Wanli and Fuliang along the latitude gradient of about 1° in Jiangxi province.The results showed that the initial occurrence periods of M.alternatus in Jiangxi were from late March to early May,and were obviously delayed with the increase of latitude.The final appearance periods of this beetle were from early October to early December,and were obviously advanced with the increase of latitude.The occurrence period of adults M.alternatus lasted for 5-9 months and decreased significantly with the increase of latitude.Adult activity peak period gradually postponed and the peak number transited from 2 to 1 with the increase of latitude.The population density of M.alternatus were larger in central Jiangxi than that in southern or northern Jiangxi.The sex ratio of this beetle was1: 0.74-0.87,showing biased female and no difference was found in different latitude of Jiangxi province.There was an obviously positive correlation between trapping amounts of this beetle and mortality of Masson pine.2.Effects of latitude on development and life history of M.alternatusThe growth and development of M.alternatus were observed through the method of cutting the top lure wood and covering with nylon gauze.The results showed that different proportions of adults emerged in the same year of laying eggs in the south of Nancheng,while adults emerged in the following year of laying eggs in the north of this county.The proportion of adult emergence in that year decreased significantly with the increase of latitude.This parameter decreased significantly with the delay of egg-laying time when compared in the same latitude.The proportion of adult emergence in following year showed opposite results.Comparing the developmental duration from egg to adult emergence of M.alternatus,the individual average developmental duration was 110.66～122.01 d when emerged in the same year of laying eggs,and 330.61～366.01 d when emerged in the following year of laying eggs,showing prolonged and shorten slightly with the increase of latitude,respectively,but no difference was found in developmental duration.The life history observation of M.alternatus in different latitudes of Jiangxi Province showed that this beetle experience two generations a year in the south of Nancheng,while only one generation a year in the north of this county.3.Effects of latitude on damage characteristics of M.alternatusVertical distribution of the oviposition scars,entrance holes and emergence holes of M.alternatus and the relationship between the number of those parameters and tree height were analyzed by investigating the lure Masson pines.The results showed that the number of oviposition scars,entrance holes and emergence holes displayed positive correlation with tree height.The proportion of oviposition scars in middle-lower of trunk was over 30.66%,and higher significantly than that in other parts of trunk in different latitude areas.However,the proportion of oviposition scars in the same part of trunk did not change with latitude.The natural larval entrance holes were 66.74% ～ 73.90% and no difference was found in different latitude areas.The proportion of larval entrance holes was the highest in middle-lower of trunk(>32.27%)and the lowest in upper of trunk(<4.17%).These significant differences were found in different latitude areas,even same part among different latitudes.The natural adult emergence holes were 52.24% ～ 69.45% and no difference was found in different latitude areas.However,the proportion of emergence hole in the middle-lower of trunk(> 31.99%)were also significantly higher than that in other parts of trunk.4.Effects of wild fire on the population of M.alternatus the mortality and infested rates of P.massoniana damaged by M.alternatus,larval population density and vertical distribution of M.alternatus in the fire area after the forest fire were investigated to ascertain the role of the wildfire on the population distribution of M.alternatus.The results showed that the mortality rate of Masson pine in the fire area was 58.65%,the infested rate of Masson pine damaged by M.alternatus was 37.88%,the average density was 36.96 larvae/tree,which was significantly higher than that of the control group.The vertical distribution of larva in the middle-lower of trunk and middle trunk was 76.4%,while in the control group,the distribution was mostly in the middle trunk with 46.21%.The density of M.alternatus larvae was positively correlated with tree height in the fire area and non-disaster forest area,and the spatial patterns of M.alternatus larvae on these two treatments was aggregation distribution.These results demonstrated that after forest fire,the population of M.alternatus showed increase trend,and the vertical distribution in the Masson pine displayed upwards.These results provide important reference for the post disaster restoration of P.massoniana fire forest.5.Effects of insect disaster on the population of M.alternatusWe investigated the population dynamics of Japanese pine sawyer beetle,M.alternatus in Masson pine forests after attacked by pine caterpillar,Dendrolimus punctatus Walker through establishing sample plots.The results showed that with the increasing damage of Masson pine P.massoniana attacked by D.punctatus,the tree mortality significantly increased from 9.57% to 22.86%,the percentage of pine trees containing M.alternatus was between 90.60% and 95.83%,and no difference was found in different treatments,and the average larval population density of M.alternatus significantly increased from 20.58 larvae/tree to 41.11 larvae/tree.About 70% of the larvae of M.alternatus were obviously concentrated in the middle-lower and middle parts of trunk,but no difference in the proportion of larvae in the same part was found among the trees with different damaged degrees attacked by D.punctatus.These results demonstrated that the Masson pine trees are more favorable to damage by M.alternatus after attacked by D.punctatus. |
PDF Full Text Request