Arthropod Communities Reestablishment And The Niche Of Main Groups In Kiwifruit Orchards

In recent years, with the expansion of cultivation and increase of tree-age, the arthropod communities in kiwifruit orchards have been founded gradually, and the pest damage was also getting worse increasingly. The progress of community reestablishment was reflected by the changes of arthropod communities, such as, more species, more complicated composition, more serious detriment. In order to know the progress of community reestablishment and succession, the systematical investigation of arthropod communities in both wild and cultivated (three-year, nine-year and 14-year) kiwifruit orchards was carried out through the time-space substitution method in this study. Then, the structures, dynamics and succession of the communities was analyze according to that. Results as followed:1. The basic characteristics of arthropod communities in kiwifruit orchards.Approximately 90 species were identified, which belonged to three classes, 15 orders and 74 families. The differences in community diversity index, evenness and dominance among orchards were significant (P<0.05). The community stability of the wild kiwifruit orchard was the highest followed by the nine years and 14 years of kiwifruit orchards, with the three years kiwifruit orchard having the lowest. The diversity index, evenness and dominance of arthropod community in wild kiwifruit orchard changed smoothly, while in cultivated orchards changed sharply. The diversity index and evenness of all the kiwifruit orchards were highest in July, the dominance were also lowest in July. Therefore, in wild ecosystem, the groups interact and restrict each other, the structure of community is complicated, and stable. While in man-made ecosystem, the primary succession isn't stable, with single structure, the structure of secondary succession is complicated, with more species.2. The compositions and main components of arthropod communitiesMain species groups in the arthropod communities were discrepant in the four types of kiwifruit orchards. There was considerable variation in the number of different species groups. The proportions of different species groups in the wild kiwifruit orchard were similar, with natural enemies and neutral insects taking a larger proportion, however, in cultivated orchards, species groups that are considered as pest occupied a larger scale in the community. The dominant factors were obviously different in different kiwifruit orchards and more complicated with the increase of tree-age. For example, passing spiders and neutral insects, phytophagous groups had been the dominant factors from predatory and parasitic species groups initially. With the increasing of tree-age, the percentages are getting homogeneous.3. The dynamics of arthropod communitiesThe arthropod communities in all the kiwifruit orchards were occurred during the period from May to September. The peak of arthropod community in wild kiwifruit is June, while July in cultivated orchards. However, the dominant species groups in orchards were different, the hawthorn spider mites (Tetranychus Viennensis) outbreak in July in cultivated orchards, and Microgramme spp. outbreak in August and September. As for 14 years orchard, May and October were the outbreak period for the leafhoppers (Cicadellidae) and fruit flies (Drosophila melanogaster) respectively. Farmers should control them in proper time.4. The spatial-temporal niche of main species groupsThe differences of main groups niches in these four orchards were significant. The niches of spider (Araneida), ants (Formicidae) and flies were large, which could represent their strong competence. The relationship of predatory and competition between leafhoppers and ladybirds (Coccinellidae), spiders and Microgramme spp., spiders and hawthorn spider mites, hawthorn spider mites and Microgramme spp., Microgramme spp. and gall midge (Cecidomyiidae) were obvious due to the large niche overlap between them. It could be demonstrated from the above results that, in the course of changing from wild kiwifruit orchard to man-made ecosystem, the hawthorn spider mites and leafhoppers had been the dominant groups by occupying the niche; the microgramme spp. and gall midges had become the dominant pest group with the increase of tree-age.In this study, the reestablishment and succession of arthropod communities in kiwifruit were researched through the combination of the structural dynamic of community with niche theory, which could provide the evidence for improvement of fruit quality and protection of ecological system.