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Effect Of Forest Structure On The Number Of Dendrolimus Superans In Primary Forest Of Changbai Mountain

Posted on:2022-08-04Degree:MasterType:Thesis
Country:ChinaCandidate:C H SunFull Text:PDF
GTID:2493306491957209Subject:Physical geography
Abstract/Summary:PDF Full Text Request
The occurrence of forest diseases and insect pests is closely related to the forest structure.In recent years,the primeval forests of Changbai Mountain have been seriously damaged by Dendrolimus superans.The forest structure of the primeval forest is diverse,and the Dendrolimus superans pests have obvious spatial differences.It is an ideal place to study the impact of forest structure on the pest population density.In order to clarify the relationship between forest structure and Dendrolimus superans population density,and to provide the basis for the prevention and control of Dendrolimus superans in Changbai Mountain Nature Reserve,this study explored the different effects of forest spatial structure parameters and community structure indexes on Dendrolimus superans population change through sample plot investigation,and the following conclusions are obtained:There are obvious differences in the incidence of Dendrolimus superans in different types of forests.The incidence of Dendrolimus superans in Spruce-fir coniferous forests is the heaviest,followed by the Larix olgensis forests,and the Pinus koraiensis broadleaf mixed forests have the least incidence.Different spatial structure indexes have different correlations with the density of Dendrolimus superans population: the mingling degree is negatively related to the density of the insect population.The lower the mingling degree,the simpler the composition of the tree species,the more likely to be pests;the neighborhood comparison is positively related to the density of the insect population.Trees with low growth dominance and poor resistance are more susceptible to pest interference;uniform angle is positively correlated with insect population density.The more the spatial pattern of host tree species,the more severe the threat of insect pests;the competition index and insect population density of each forest type are both significant relevance,tree vigor is closely related to competitive pressure.The density of trees is high,and competition for space and light is fierce,and its own resistance is affected,which is easy to cause pests.There are obvious differences in the influence of community structure indexs on the population density of Dendrolimus superans: the higher the Shannon-Wiener index,the richer the species diversity in the forest,the more complex the community composition function,the stronger the ability to resist pest interference,and the richness Margalef index has the same impact as it;the higher the Berger-Parker index of dominance,the greater the proportion of dominant species of Dendrolimus superans,which is likely to lead to aggravation of pests;the evenness of Pielou index is less correlated with insect population density and has no significant impact;forests with low canopy density are more affected by pests than forests with good canopy density.Increasing the canopy density is beneficial to reduce the insect population density;juvenile forests and overmature forests are more disturbed by pests than other forests,and forests of moderate age have stronger resistance to insects.The main influencing factors of larch caterpillars in different forest types are different,and different control measures should be adopted.The neighbourhood comparison of diameter breast height of Pinus koraiensis broadleaf mixed forest has the greatest influence on population density of Dendrolimus superans,followed by diversity index,competition index,canopy density and abundance index.Therefore,increasing the dominance of forest growth,reducing competition pressure,enriching species diversity,and accelerating stand canopy density have a certain effect on controlling the Dendrolimus superans disaster in the forest;the main influencing factors of Dendrolimus superans in Spruce-fir coniferous forest are uniform angle,forest age,neighbourhood comparison of diameter breast height,mingling degre and canopy density.Therefore,in order to prevent the further development of insect pests in the forest,measures can be taken to reduce the accumulation and distribution of forest trees,create suitable conditions to promote the growth and development of young trees,improve the growth advantages of trees,strengthen forest stands,and reduce forest density;the mingling degree,diversity index,dominance index,competition index and canopy density are the main factors affecting the population of Dendrolimus superans in the Larix olgensis forest.It is possible to prevent and control Dendrolimus superans disasters in forests by enhancing the mixing of tree species,enriching biodiversity,reducing the proportion of the dominant species of Larix olgensis,thinning disadvantaged forest trees to relieve competition pressure and increasing forest canopy density.
Keywords/Search Tags:primary forest of Changbai Mountain, Dendrolimus superans, forest spatial structure, biodiversity, stand factor
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