| The thesis firstly summarized the research progress of arthropod community and function of spider community in rice field. Based on some IPM practice, and on the progress in this area, the thesis compared some parameters of arthropod community in three types of rice field (organic rice field (ORF), organic rice field with ducks release (ODR), conventional chemical control rice field (CCF)), such as arthropod community structure, intrinsic rate of increase of functional guilds, community turnover value, and etc. Research on the effects of water on predacious function of rice field spider was also conducted in the present paper. The results were as follows:This paper compared abundance, richness, community turnover and mean intrinsic increase rate of three sub-communities (natural enemy, neutral insect and pest) in arthropod community in three types of rice field, including organic rice field(ORF), releasing duck in organic rice field(RDF) and conventional chemical control rice field(CCF). Link numbers of three sub-community were calculated. Spiders were lumped into top and immediate species according to the nature of their predation. Regression relationship between link numbers and intrinsic rates of increase of two sub-community (pest and natural enemy) was constructed. Results showed that richness of arthropod community increased with time until 72 days after transplanting. The relationship between community turnovers and time was fitted by a parabola in three types of rice fields. The order of the lowest value of community turnover in each rice field was CCF 33.98,74.1d; ODR 33.90,79.1d; ORF 33.49,54.0d. Community turnovers of ORF and CCF were negatively related to population size of pest. While abundance and richness of arthropod community until 72 days after transplanting is ORF>ODR>CCF. The intrinsic rate of increase of neutral insects is higher in ORF (0.0665) than in CCF (0.0652 and ODR (0.0509). Likewise, natural enemies were greater in ORF (0.0352) than in ODR (0.0243) and CCF (-0.0132). Inversely, insect pests were greater in CCF (0.0478) than in ODR (0.0.0199) and ORF (0.0198). The order of total link numbers is ORF (6623348)>ODR (249821 7)>CCF (1363372), and the mean link numbers per natural enemy is ORF (5627.3)>ODR (3652.4)>CCF (2279.9), indicating that ORF had a more robust ecosystem than CCF. There were linear correlations between the intrinsic rate of increase of insect pests and naturalenemies, and the increase rate of link numbers. The slope between the intrinsic rate of increase of pests and the increase rate of link numbers for ORF or ODR was 214% and 233% greater than that of CCF. The slope between the intrinsic rate of increase of natural enemy and the increase rate of link numbers of ORF was 151% and 89.4% higher than that of ODR and CCF, respectively.Predation capacity by spider group to planthoppers under two conditions, in presence and absence of water in rice fields, was studied using method of pulse sampling and planthoppers killed by insecticide during 2000-2001. The relationships between number of planthopper preyed (NPP), percentage of planthopper preyed (PPP), and with spider density and with mean crowding of planthopper were analyzed by the data of predation capacity. In addition, functional responses of Pirata subpiraticus and Oedothorax insecticeps to planthopper in presence and absence of water were also conducted in laboratory. The results showed that PPP decreased with the increase of mean crowding of planthopper. At the same crowding, NPP in presence of water was higher than that in absence of water. The relationship between NPP in presence of water and Pirata japonicus density was fitted by a parabola. NPP was maximum when the Pirata japonicus density was 1.4 per hill, but the above relationship was linear when there was no water on the field. Influence of water on NPP by Micryphantidae was not clear. The functional response experiments showed that NPP of Pirata subpiraticus in presence of water was higher than in absence of water. NPP in presence of wat... |
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