Studies On Relationships Between Plant Composition And Occurrence Of Insect Pests In City Parks

City parks have important ecological functions, which are called the “lung” and “kidney”of cities. They play important roles in improving city’s ecological environment and keeping theecological balance. Meanwhile, city parks also provide citizens playground. However, theself-regulation ability of the existing city park ecosystems is relatively low. Impropermanagement measures of city parks may cause frequent outbreak of pests, especiallypiercing-sucking insect pests, wood borers and underground insect pests, which greatly affectthe sustainable development of the city park ecosystems. In order to improve theself-regulation abilities of the city park ecosystems and protect the ecological environment inthe city parks, in this study, taking Yuetan Park, Xuanwu Park and Wanshou Park in theXicheng District as sample plots, various factors affecting the pest-outbreak in parks wereinvestigated. These findings will help to effectively prevent and control pest-outbreak,decrease the cost of pest control, reduce the environmental pollution and provide a theoreticalbasis for city park pest management.The main results of this study are as follows:1. There is a close correlation between the richness of insects in plant community in parksand the species of the plants, especially the species of ground cover plants. The species andnumber of insect pests, natural enemies and neutral insects in native plants are more than thosein exotic plants; most natural enemies and neutral insects stayed in ground cover plants, butdifferent kinds of natural enemies and neutral insects have different preference, therefore, thespecies richness of ground cover plants directly affecting the species richness of naturalenemies and neutral insects.2. Rational composition of tree, shrub and grass helps to improve the self-regulationability of the park ecosystem against insect pests. The coverage of tree, shrub and grass inWanshou park were42.8%,36.9%and25.85%, while the vegetation coverage in Yuetan park and Xuanwu park were50.9%,9.1%,71%, and41.5%,13.8%,87.5%, respectively. Therefore,in Wanshou park, the vegetation coverage, insect community diversity and evenness of wholetemporal dynamic fluctuated slightly with better stability of community.3. The species and number of natural enemies and neutral insects in buffalo grass (Buchlodactyloides) and lilyturf grass (Liriope spicata) lawn are around twice those in annualbluegrass (Poa annua). And the species of insect pests were also decreased sharply. Thus thebuffalo grass and lilyturf grass are more beneficial to the improvement of insect diversity in theplant community in parks, comparison to annual bluegrass in lawns.4. Most natural enemies and neutral insects fed on the honey in the flowers of nectarplants, as a result, nectar plants could effectively attract natural enemies and neutral insects,thus improving the self-regulation ability of the park ecosystems. The coverage of chaste tree(Vitex negundo var. heterophylla) in Wanshou park (29.5%) were much higher than that inYuetan park and Xuanwu park (3.3%and1.3%), and the species and number of naturalenemies were also more than that in Yuetan park Xuanwu park.5. Reducing the use and the frequency of pesticides could significantly increase thespecies and number of natural enemies and neutral insects in park ecosystems. In2012, theusage and frequency of chemical pesticides were decreased in Wanshou park, as a result, thespecies and quantity of natural enemies and neutral insects increased significantly.Through correlation analysis, it can be concluded that the number of pests and naturalenemies in parks are mainly related to the diversity of shrubs and the richness of trees, and theoccurrence of insect community are related to the richness of plants, the diversity of groundcover plants and shrubs and the coverage of shrubs.