Abstract:

A field survey was carried out by sampling using pitfall trapping method to investigate diversity of topsoil layer dwelling arthropods in organic and conventional fields in Suning of Hebei and Gaotang and Caoxian of Shandong in the North China Plain. Comparison analysis was made of diversities at three taxonomic levels, such as the suborder of Arthropod, the sub-family of Coleopetera and the sub-species of Carabidae, structural composition and distribution of different arthropod communities, relative to farming pattern, organic or conventional, so as to evaluate effect of organic farming on biodiversity in farmlands and determine whether difference exists between evaluations using bio-indicators different in taxonomic level.  Results show that (1) in Caoxian County, organic fields were higher than conventional fields in abundance of Arthropods at all the three taxonomic levels; in Gaotang County, it was so only in abundance of the suborder of Arthropods and in Suning County, no big difference was found in abundance of Arthropods at all the three taxonomic levels between the two farming patterns. (2) in terms of richness of Arthropods, significant differences were found between the two farming patterns at the taxonomic levels of the sub-family of Coleoptera Families and the sub-species of Carabidae in Caoxian County only; besides, in terms of community structure, significant difference was found only in Caoxian County, partial difference in Gaotang County and nothing significant in Suning County. On the whole, organic fields are much higher than conventional fields in biodiversity of the three groups of arthropods and differences exist between the two farming patterns in structure of arthropod communities in the topsoil layer. However, the differences between the two vary with region and taxonomic level, which may be attributed to the number of years the fields have been under organic management. Evaluations of biodiversity in organic and conventional fields using bio-indicators based on different taxonomic levels may differ slightly, but basically consistent in general trend, indicating that it is more advisable to use bio-indicators based on high taxonomic level, e.g. the suborder of Arthropods or the sub-family of Coleoptera, to indicate effect of organic farming on environment, so as to reduce difficulty in classification and raise working efficiency. But bio-indicators based on the taxonomic level of sub-species of Carabid are more sensitive to difference in bio-diversity.

Key words: Arthropod, Coleopera, Carabidae, Biodiversity, Bioindicator, Environment assessment