The aim of this study was to assess the interaction between Daphnia similis and various organisms related to the rice paddy ecosystem. We selected several organisms that are likely to prey on D. similis and evaluate predation rate as well as responses of D. similis to the chemical compounds exuded by these organisms. As a result of predation experiment, larval dragonfly (Anax parthenope) and Triops longicaudatus were clearly shown decreasing abundances of D. similis. Especially, Triops longicaudatus was observed higher feeding rates on D. similis than larval dragonfly. Chemical compounds from the vertebrates such as fish (Misgurnus anguillicaudatus, Pseudorasbora parva, Micropterus salmoides) and tadpole of frog (Rana nigromaculata) did not affect the life history of Daphnia. However, a potential predatory fish P. parva induced significantly longer tail spine in Daphnia. In addition, among the invertebrates (T. longicaudatus, A. Parthenope, Micronecta spp., Palaemon paucidens), chemical compounds exuded by T. longicaudatus induced shorter body and significantly longer tail spine in D. similis.

The value of rice-fields is being graded down in Korea because it has been estimated only from the size. The purpose of this study is to suggest a management plan in which the location and the size of valuable rice-fields for conservation are based on the results of appraising the worth of ecosystem services of rice-fields in Chungcheongnam-do region. The study is as follows; ①selecting the indicators for evaluating the ecosystem services of rice-fields considering both general functions and special functions in the regional environment conditions, ②classifying the grades of rice-fields in ecosystem service values, ③suggesting the location and the size of valuable rice-fields for conservation, ④calculating the total economic value of the ecosystem services of rice-fields. The results of this study are that the valuable rice-fields’ locations for conservation are the grade I rice-fields and their total area is 100,000ha. Also, the value of the ecosystem services of rice-fields in Chungcheongnam-do region was equivalent to 32.8 trillion won. This amount is over 18 trillion won more than the amount obtained if the total rice-fields in Chungcheongnam-do region were to be transformed to other land-use types. The value of ecosystem services should be considered in the future when appraising the worth of rice-fields, and methods of estimating the ecosystem services of rice-fields need to be developed with a more objective and suitable index.