Study On The Spray Seeding On Loess Slope And Plant Community Characteristics And Pest Control

The research on slope greening is the key national technical demand and important for theoretical and practical development. In this case, four plant communities were established in Pingliang from 2007 to 2010 to study the features, development, species diversity and pest control of community with orthogonal experimental design by measuring the biomass. The main results are as follows:1. The importance order of affecting factors was spay seeding technique > grass species composition > fertilizers. The guest soil was the main factor and followed by the grass species composition while the same factor was compared. And the difference among treating factors was significant at 0.05 level.Four plant communities were established including CⅠ( Festuca rubra + Poa annua + Carex heterostachya -Leapedeza bicolor) , CⅡ( Leymus secalinus + Carex rigescens-Ajiania gmalinii + Ajiania anethoides), CⅢ(Medicago sativa + Carex heterostachya + Chenopodium glaucum - Ajiania gmalinii) and CⅣ(Festuca arundinacea + Poa angustifolia + Carex rigescens + Agrostis stolonifera).2. The main characteristics of established communities could be described as follows: The dominants were gramineous, feverfew and legumes and the species composition greatly varied. The performance of spray seeding grass species was greatly different. The order of least area ranking of four communities was CⅡ> CⅢ> CⅣ> CⅠ. The maximum communality of family, genus and species among communities occurred between CⅡand CⅢ. And the minimum communality occurred between CⅠand CⅡ. The maximum communality of grass synusia, gramineous and feverfew occurred between CⅡand CⅢ. The order of relative frequency was CⅡ> CⅢ> CⅠ> CⅣ. The chamaephyte, hemicryptophyte and geophyte were the main component of each synusia, in which, the hemicryptophyte and geophyte were dominant in CⅡand CⅢ.The result indicated that the species number of community was related to the experiment treatments. The species composition of communities establish through spay seeding was relatively complex. Although the community was at the early development stage, the plant species were gradually replaced by native species. The more species number, the greater least area. The similarity of plant composition and habitat between CⅡa nd CⅢwas high and it was low between CⅠa nd CⅡ. The bunch grass, sedge and perennial subshrub were the dominants in each community. The development of community established through spray seeding was similar with the community in recovering abandoned arable land, it means that the habitat was in restoring period and the plant in spray seeded community played the pioneer role.3. The average density, frequency and coverage of grasses in wet spray seeded communities (CⅠand CⅣ) were high and it indicated their importance, and CⅣdeveloped batter than CⅠ. As for the guest soil spray seeded communities (CⅡand CⅢ), 10 plant species performed batter and CⅢwas better than CⅡ. In terms of community function, the slope protection effect of CⅡⅣand CⅢwas satisfied.4. The order of richness andαindex of 4 communities was CⅡ>CⅢ>CⅣ>CⅠ. The order of evenness index was CⅠ>CⅣ>CⅢ>CⅡ. This ranking pattern reflected the organizing level, slope protection effect and community stable ability.5. The analysis on richness, evenness andαindex of main synusia indicated that grass synusia and gramineous species played an important role in communities. However, the diversity of young community was not high because of developing time and it would be more diverse in future.6. The dissimilarity among communities andβindex analysis indicated that the order of Cody index among 4 communities wasⅠ-Ⅱ>Ⅲ-Ⅳ>Ⅰ-Ⅳ>Ⅱ-Ⅳ>Ⅰ-Ⅲ>Ⅱ-Ⅲ. And the order of similarity among communities wasⅡ-Ⅲ>Ⅱ-Ⅳ>Ⅰ-Ⅲ>Ⅲ-Ⅳ>Ⅰ-Ⅱ. The analysis on dissimilarity of species composition andβindex could explore the replacing degree and habitat difference among synusia and communities.7. Totally 7025 pest specimen, belonging 8 subject, 22 family, 35 genus and 39 species. In which, the armyworm in cutworm family was the dominant pest.8. The pest in slope protection community could be divided into 5 density gradients. The relationship between control efficiency and peat density was positive (r=0.9771) by using same dose of 4.5% cypermethrin EC (53.55 ml/1000m~2). The highest control efficiency was only 62.84%, which means that the dose was low.9. The result of control experiments with different doses indicated that the control efficiency was also related to the concentration of cypermethrin EC (r=0.9754).10. The virulence of 4.5% cypermethrin EC to mixed pest population could be described as y = 2.2476 + 5.1118 x, and the suitable concentration could be simulated according to this model.