Studies Of Diversity Of Grasshopper Community In Loess Plateau Of Luo River District

Grasshoppers are the main agricultural pests. They have migratory instinct in large quantities and are liable to cause disasters. With the variance of ecological environment and the destruction of biodiversity in recent years, other species of grasshopper besides Locusta Linnaeus can also form disasters easily threaten both the crop and grassland growing. The disaster brought by grasshopper is one of the three natural disasters, and it affects badly the production, the life, even the survival of people. So the study about grasshopper has attracted broad attention. But up to now, there are no reports of grasshopper community in Loess Plateau of Luo River district in china. The author has researched the diversity of grasshopper community in Loess Plateau of Luo River district from May to September in 2004 and aims to provide some scientific measures for the prevention and control of grasshopper and the development of agriculture.This paper has studied the diversity of grasshopper community in this area by using species-abundance model, diversity index, clustering, ordination and stepwise regression analysis. The results are as follows:1. This experiment has collects 1647 grasshoppers, subject to 6 families 13 genera and 20 species. One genus and one species are Pamphagidae, One genus and one species are Pyrgomorphidae, 3 genera and 3 species are Catantopidae, 3 genera and 9 species are Arcypteridae, 4 genera and 4 species are Oedipodidae, and 2 genera and 2 species are Acrididae2. The distribution of grasshopper is very uneven in this area. The Palaerctic species occupies 70%, the widespread species occupies 20%, and the Oriental and endemic species occupies 5% respectively. Oedaleus infernalis Saussure is the dominant species in this area, which occupies 20% in total. Atractomor pha sinensis (B01), Chorthippus albonemus Cheng et Tu and Acrida oxycephala (Pall.) are the subdominant species. Xenocatantops humilis brachycerus (Willemse) and Chorthippus biguttulus (L.) are very few, which occupy only 0.1% and 0.06% respectively.3. The species-abundance model of different month, site and ecotype all match basically to Preston's lognormal distribution. This distribution has been hoped to appear in many communities. It reflects the constructive composing of grasshopper community and the principle that many species coexist in the community. Namely, the dominantand rare species are few, and the species in the intermediate state are rich comparatively. 4. The variational trend of diversity index in different month is the following: H' is September>August>July>June>May; Dm is September> July > August >June>May; Jsw is May > September > August > July > June; A reflects the dominance of species, so its trend is opposite to H' ; The trend of H' (GS) and PIE are the same as H". The variational trend of diversity index in different site is the following: H' is Fuxian>Ganquan>Huangling>Zhidan>Wuqi; Dm is Fuxian>Huangling>Ganquan >Zhidan>Wuqi; Jsvv is Fuxian>Ganquan> Zhidan > Wuqi > Huangling; The trend of H' (GS) and PIE are the same as H", but A is opposite. The variational trend of diversity index in different ecotype is the following: H1 is Forest>Forest-grassland>Riverside and cropland>Typical grassland; Jsw is Forest>Forest-grassland>Riverside and cropland =Typical grassland; The trend of H" (GS), PIE and Dm are the same as H", but A is opposite.5. The clustering results of different months show that the similarity of May and June, August and September are high, July is a interim from fewness to many of grasshoppers. The clustering results of different sites show that the similarity of Wuqi and Zhidan, Fuxian and Huangling are high, Ganquan closes to Fuxian and Huangling. The clustering results of different ecotype show that Forest-Forest grassland-Typical grassland is a continuous distribution, the similarity between one another is high. Riverside and cropland is another environment different absolutely from the upper ecotype.6. The results of PCA to environment factors (vegetation and climate) and grasshopper community of different ecotype and site show: The cumulative percent of two principal components of vegetation and grasshopper community of different ecotype reach respectively 92.558% and 78.566%, which occupy mass information and may represent the characteristics of the whole community. The cumulative percent of three principal components of climate and grasshopper community of different site reach respectively 96.216% and 92.058%, which also occupy mass information and may represent the characteristics of the whole community. The results of PCA are very ideal.7. The results of stepwise regression to environment factors and grasshopper community show: The vegetation factors affecting the distribution of grasshopper are the grass height diversity, the tree density, the leguminosae dominance degree, the gramineae dominance degree and the other grass dominance degree. The climate factors...