A Primary Study On The Diversity And PRA Of Forest Insect In Zhejiang, China

Forest is the natural resource of great importance and abundance in China, but meanwhile it is faced with the threats of diseases, pests and natural disasters. Zhejiang province is the developed region in our country, its commercial activities are very flourishing as well as merchandise exchanges, and these goings-on are very favorable for the diffusing and spreading of the harmful organisms. As a result, these activities are very threatening to the forestry production, ecological environment as well as national and international commerce. Therefore we carried out a study on the diversity and PRA of forest insect in Zhejiang province on the basis of general investigation of harmful organisms in Zhejiang province. According to the programs of State Forestry Administration, P.R.China, We studied the insect resource by selecting 10 samples of Zhejiang province thereunder different landforms from February, 2004 to October, 2004. We used the double-catercorner sampling method, the standard sample size is 30×30m~2. The results are summarized as follows:I. The results of InvestigationMore than 50,000 pieces of specimen were collected in the investigation and 32,328 pieces of specimen were identified which respectively belonged to Shaoxing, 3,138 pieces;Shangyu, 4,982 pieces;Shengzhou, 3,572 pieces;Xinchang, 2,695 pieces;Yuechegn, 3,472 pieces;Zhuji, 2,540 pieces;Fuyang, 8,321 pieces;Hangzhou, 1,581 pieces;Jingning, 2,027 pieces. The identified specimen belonged to 16 orders, 133 families, 930 species, among these there was 1 new recorded family as well as 199 new recorded species. The pest group belonged to 11 orders, 107 families (1 new recorded family included), 816 species (168 new recorded species included);The natural enemy group of pests belonged to 9 orders, 26 families, 114 species (31 new recorded species included). We studied the dominant groups of these insects in 3 different ranks.II. The research of coenoecology1 The diversity of species in different samplesWe reached the results by the analysis of species diversity, that the trend of 2 diversity indexes are coincident in each sample, the diversity indexes of species in Shangyu and Shengzhou are relatively lower than other samples', while the diversity indexes of species in Jingning and Wenling are relatively higher. The diversityindexes of species in the other 6 samples are even. As a whole, the Simpson index ￡>=0.9558, the Shannon-Wiener index H '=4.501, this indicates that the diversity indexes of species are very high in Zhejiang province, the state of ecology in Zhejiang province is very steady.2 The evenness in different samplesThe trend of Pielou evenness indexes calculated by Simpson index and Shannon-Wiener index is consistent with each other. The indexes in Shengzhou and Shangyu are relatively lower because of lacking wide spread of species. Alatolo evenness indexes are coincident with Pielou evenness indexes. As a whole, Zhejiang province has its high Pielou evenness index (JSw & ?4) meanwhile its Alatolo evenness index (￡a) is relatively lower. This is because it has many species, but the quantity of dominant spices is far more than the other species. In sum, the evenness of Zhejiang province is favorable and its dominant species are abundant.3 The hierarchical cluster analysisThe hierarchical cluster analysis indicates that Shaoxing, Yuecheng and Shangyu get together as a cluster;Shengzhou and Xinchang cluster together because of their similar terrain, hypsography and vegetation;These 5 samples get together as a further cluster;Then Fuyang, Hangzhou, Wenling, Jingning are clustered in sequently. They can take similar measures in the close-clustered samples.4 The diversity of species in different ordersThe Simpson index and the Shannon-Wiener index in different orders are coincident with each other. The indexes of diversity of Lepidoptera, Coleoptera and Diptera are relatively higher meanwhile the indexes of diversity of Homoptera, Orthoptera and Hemiptera are relatively lower.5 The evenness of different ordersThe Pielou evenness index is consistent with the Alatolo evenness index in Coleoptera, Homoptera, Orthoptera and Hemiptera. This indicates that the evenness of these four orders is favorable, and further more the difference between the dominant groups and the other groups is moderate. The Pielou evenness index is relatively higher than the Alatolo evenness index in Lepidoptera and Hymenoptera. This indicates that the evenness in the 2 orders is favorable meanwhile the dominant groups have very obvious predominance. The Pielou evenness index in Diptera is as high as Alatolo evenness index. This indicates that the evenness in Diptera is favorable but the dominant groups have less predominance.III. The results of PRA analysis1 The PRA analysis of Monochamus alternatus HopeAfter evaluating the targets and calculating, we present the value of PRA index of Monochamus alternatus Hope at last, its value is i?=2.08. We stipulate that it belongs to "the species of extremely high risk", if the R rang form 3.0 to 2.4;it belongs to "the species of high risk", if the R rang form 2.4 to 1.9;it belongs to "the species of moderate risk", if the R rang form 1.9 to 1.4;it belongs to "the species of low risk", if the R rang form 1.4 to 1.0.The hosts of Monochamus alternatus Hope are very far-ranging and its suitable environment is extensive. The lost caused by Monochamus alternatus Hope is tremendous. Further more, Monochamus alternatus Hope diffuses Bursaphelenchus xylophilus during its natural spread and the Bursaphelenchus xylophilus is very hard to eradicate once introduced in. The trees that infected by Bursaphelenchus xylophilus can only be cut off totally nowadays.2 The PRA analysis of Dendrolimus punctatus WalkerAccording to the method of assigning above, the value of PRA index of Dendrolimus punctatus Walker R=l.46, it belongs to "the species of moderate risk".Dendrolimus punctatus Walker burst out once in Zhejiang province, but afterwards it was controlled by measures such as sealing mountains pass and cultivating forest, scientific prevention and cure etc. Now the state of ecology is improving and the natural enemies of Dendrolimus punctatus Walker have boomed up, thereafter Dendrolimus punctatus Walker is not a very threatening pest in Zhejiang province these days.