Preliminary Study On The Relationship Between Occurrence Of Dendroctonus Valens And Community Species Diversity In The Early Stage Of Invasion

Dendroctonus valens LeConte 1860(Red Turpentine Beetle,RTB)is originally widespread in North America As one of the invasive alien species in Chinese natural ecosystem,RTB has caused serious damages to Pinus tabuliformis.Since invading into Shanxi province of China in 1980s,RTB has spread rapidly and caused serious losses in economy and ecology.The study site is located in Heilihe National Nature Reserve,Ningcheng County,Inner Mongolia.There are large-scale of natural pine forests.This nature reserve,a new distribution area in the northward spread of RTB,are still in the early stage of invasion of RTB.This study focuses on the character of plant and insect community in the forests under the attack of RTB.Furthermore,we investigated the natural enemies of RTB and the effects of artificial disturbance on environment' attacked by RTB.The main results are as follows:1.We selected four regions of Dabagou,Xidaliang,Yuanbaogou,and Toudaocha where under the threat from RTB.We set 3 plots in each area.We found that the percentage of insect-infected trees was significantly negatively correlated with canopy density.The canopy coverage of the plot attacked seriously by RTB was less than 0.6.Disturbing intensity of stump and fallen wood(IDISF)was positive correlated with the percentage of insect-infected trees in Yuanbaogou and Toudaocha.2.The areas attacked seriously by RTB had low quantity of litter-layer insects.The proportion of the individual quantity of Staphylinidae in the quantity of ground-dwelling beetles had highly significant differences between the plots harmed seriously and harmed slightly.The species diversity,species richness and species evenness of Carabidae in plots attacked seriously by RTB were also higher than those in plots attacked slightly by RTB.Carabus smaragdinus,Dinothenarus chrysocomus and Platydracus sp.could be used as the bioindicator of environment where RTB prefers after further confirmed.Principal component analysis(PCA)and cluster analysis were used to analyze the quantity of four common Litter-layer insects species in Yuanbaogou,Toudaocha,Dabagou and Xidaliang.We found that the environment of some plots in Xidaliang was similar to that in Yuanbaogou and Toudaocha.Therefore,we need pay more attention to the Xidaliang,and despite RTB occurred not very seriously at present.3.Formica sp.and Clerus dealbatus were found as natural enemies of RTB.But according to the results of video monitoring,Formica sp.could not prey high active RTB,and Clerus dealbatus were rarely seen in the wild.So based on the present results,they were not efficient enough to control RTB in naturel.This research studies the stand feature attacked by RTB in early stage,which provided a reference for the monitoring and warning in early period and the prevention of RTB.In addition,the survey of the natural enemies and the effect of artificial disturbance on environment attacked by RTB provided references for the integrated management of RTB in Nature Reserve.