Arthropod communities of paddy rice fields in the western hilly and mountainous area of You City: Effects of settlement environment and farming method on population density and species diversity
2010
Adati, T., Tokyo Univ. of Agriculture (Japan) | Ishikawa, T. | Okajima, S.
In two settlements, Obuti and Yosiura, in the western hilly and mountainous area of Zyoetu City, Niigata, Japan, arthropod communities of paddy rice fields, which were grown by conventional and organic farming methods, were investigated. Among the total sample, 70% of the population was identified as rice pests, while natural enemies and other arthropods occupied 16% and 14%, respectively. Among the pests, plant- and leaf-hoppers were the most dominant and proportions of moths and beetles followed. Among the natural enemies, spiders were the most dominant. Other arthropods included springtails as majority and some chironomids. Annual and seasonal changes of arthropod densities were observed in the respective settlements and farming methods. Such changes were significant also in plant- and leaf-hoppers, the green rice caterpillar (Naranga aenescens) and spiders. Two-way analysis of variance indicated that densities of five species and eight species groups, including the whitebacked rice planthopper, Sogatella furcifera, differed with the settlement. On the other hand, densities of two species and six species groups, including spiders, differed with the farming method. Their densities, except for one species group, were higher in organic farming than conventional farming. Diversity index (H') of pests was higher at Obuti than Yosiura, and in organic farming than conventional farming. No difference in diversity index of natural enemies was observed between the settlements or farming methods. Spiders seem to be used as indicator species for evaluating impact of farming methods on paddy field ecosystem because their density was higher in organic farming plots and seasonal change of their population dynamics was constant.
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