Abstract: This paper deals with the trophic structure and its types of arthropod community in paddy fields based on outdoor surveys and indoor experiments. In paddy field ecosystem, complex food chains and food webs may be formed because of the interspecific relations of feeding, parasitism and predatism. According to the living patterns of parasitic species in food webs, the trophic structures of arthropod commonity in paddy fields of Fuzhou suburbs can be divided into three types: 1) no link of epiparasitism in food webs; 2)some links of epiparasitism in food webs; and 3) some links of double parasitism in food webs. By using the knowledge and operation rules of graph theory, a food web can not only be described as a signed directed graph(SDG), a set, or an adjacent matrix, but also be combined with others. The method has been proved valuable in the studies of trophic relations of a complex community.

Key words: Trophic relation, Food web, Graph theory, Arthropod community, Paddy field, community structure, subalpine and alpine forest., trophic group, soil nematode