TABLE CONTENTS

How Different or Similar are Nematode Communities in Paddy and
Upland Rice Fields
Okada, H. (1), W. Abe (2), M. Komatsuzaki (3) & M. Hiroki (4)
(1) National Institute for Agro-Environmental Sciences, 3-1-3, Kan'nondai, Tsukuba-city, Ibaraki, 305-8604,
Japan; (2) University of Toyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; (3) Ibaraki University, 3-21-
1, Chuou, Ami-machi, Inashiki-gun, Ibaraki, 300-0393, Japan; (4) National Institute for Environmental Studies,
16-2, Onogawa, Tsukuba-city, Ibaraki, 305-8506, Japan.
Paddy field (PF) is now attracting worldwide attention as a valuable land use for biodiversity
conservation and as a land use with significant greenhouse gas emission, as well as being
important for food production. Nematodes may play an important role in soil food-web and
ecosystem function in paddy, as both microbial feeders and prey for soil and aquatic animals.
Thus, we characterized nematode community structure in paddy before, in and after flooding,
with adjacent upland rice fields (UF) as a reference site. It is generally accepted that in PF,
bacteria dominate over fungi but decomposition is slow due to low oxygen concentration
during flooding. We also expect that greater physicochemical changes due to flooding affect
ecosystem status to maintain an r-selected nematode community. In this context, we analyzed
community structures using multivariate and index approaches. For indices, we hypothesized
that each of Maturity, combined Maturity, Structure, Channel and Enrichment Index would
be lower in PF. In the flooded period, however, our hypothesis was confirmed only for
Channel Index. Distinctive occurrence of Rhabdolaimus, Tobrilus and monhysterids, and
greater occurrence of dorylaimids in PF seemed to be responsible for the deviation. Other
than such differences, we found that total nematode density and plant feeder frequency were
lower when flooded in paddy. Interestingly, some common taxa in UF and other terrestrial
habitats, such as Acrobeloides and Filenchus, still occur under water in flooded paddy. We
also discuss how nematode communities different between PF and UF, before and after
flooding and discuss nematode community dynamics in PF.
5 th International Congress of Nematology, 2008 6