Study On The Effect Of Plant Diversity On Ecological Control Of Xylotrechus Rusticus In Harbin

Poplar is the main afforestation species in the,greening city and countryside forest, farmland protection forest and road protective forest,which resulted in good social and ecological benefits.Since 1999,some areas of Heilongjiang province are suffering from Xylotrechus rusticus,not only destroyed forest-isolated area but also harmed passerby and traffic safety.Further damage of X.rusticus will effect the ecological environment seriously.X.rusticus is a kind of newly important bark pests which break out to be the disaster in the Northeast in China in recent years.It has brought great difficulties to the control of this pest because they bore into the trunk of trees.For ecological control of X.rusticus we first ascertain resistance of different breed of Poplar and other tree in the Poplar protection forest for X. rusticus by survey different sample plot of in city and countryside forest of Harbin which are pure forest,mixed forest made up by two or three kinds of Poplar,mixed forest made up by Poplar and other kinds of trees.The relation between the DTV(diversity threshold value) of artificial mixed forest and the percentage harm of X.rusticus was analyzed by applying of the theory and technology of DTV, the diversity index of Margalef D_Ma,Shannon-wiener H,Pielon J_sw and the D_v of the value accumulated of diversity as the proportion of anti-pest tree species and pest infected tree' species changed from high to low.It showed that mixed forest of multiple tree species had a obviously resistance of pest damage of stem-borer,and the forest resistance ability was largely related to the pest resistance of the tree species and the percentage of the insect-resistant tree in the mixed forest.Under certain number of tree species in the mixed forest,the model of Logistic was accorded with the relation of the harm percentage Pz and Dv.In the Logistic coefficient,the maximum of D_Ma,H and J_sw had an obviously increasing trend with,the increased tree species in the stands.In the mixed forest for 4-8 tree species,the increase of DTV followed the increase of tree species in the stands,on the contrary,the point of inflection of harm percentage L_vp decreased.When the number of tree species more than seven and more than 30 percent resistance tree make up the forest,the P_z of X.rusticus will control under the 10 percent.If more than 30 percent resistance tree make up the forest,the P_z of X.rusticus will control under the 4 percent.The plant diversity and the ratio of resistance species in Herbin city sample plots are quite high,which are up to the mustard high quality afforestation.The single afforestation species were use in city and countryside forest of Herbin,and percent of resistance specie were quite small,maybe is the main reason that X.rusticus damage.Another value of the regularity was that the selection range of tree species of mixed forest will increase with the tree species' increasing in anti-pest forest which was designed or reformed.