title: Comparison of generalist predators in winter-flooded and conventionally managed rice paddies and identification of their limiting factors.
abstract: Winter-flooding of rice paddies without the application of agricultural chemicals is attracting attention as a new agricultural method for enhancing the habitat conditions of wintering waterfowl in rice paddy ecosystems throughout Japan and east Asia. Conditions in these paddies are expected to result in restoration of not only the winter habitats of waterfowl but also those of other taxonomic groups during the rice growing season. In this study, we tested whether the diversity of summer spiders--ubiquitous predators in rice paddies--was higher in the winter-flooded paddies than in the conventional ones by conducting field measurements in 31 winter-flooded and 7 conventional paddies. Limiting factors of spiders in the winter-flooded paddies were then examined. Results revealed that both the density and species richness of spiders were significantly higher in the winter-flooded paddies than in the conventional ones both before and after the insecticide application against pecky rice bug Stenotus rubrovittatus (Matsumura)(Hemiptera: Miridae) to conventional paddies. In addition, spider density and species richness in the winter-flooded paddies correlated with the availability of two prey groups--chironomids and other nematocera. These findings suggest that in the winter-flooded paddies the diversity of generalist predators is higher than in the conventional ones during the rice-growing season and that the combination of management at both the landscape and field level is likely more effective for increasing spider abundance in winter-flooded paddies.
authors.affiliation: Institute for Sustainable Agro-ecosystem Services, University of Tokyo, Midori-cho, Nishi-Tokyo, Tokyo, 188-0002 Japan.
authors.forename: Mayura B
authors.initials: MB
authors.lastname: Takada
authors.affiliation: Department of Environmental Science, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, 274-8510 Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Takagi
authors.affiliation: Rice Paddies Japan, Tajiri, Osaki-city, Miyagi, 989-4302 Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Iwabuchi
authors.affiliation: National Institute for Rural Engineering, Kannondai, Tsukuba-shi, Ibaraki, 305-8609 Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Mineta
authors.affiliation: School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.
authors.forename: Izumi
authors.initials: I
authors.lastname: Washitani
keywords: Biodiversity-friendly farming; Natural enemy; Restoration; Spiders; Waterfowl; Wetland