Jpn. J. Environ. Entomol. Zool. 24（４）：187− 198（2012） 環動昆 第 24 巻 第４号：187 − 198（2012） 原 著 Effects of hydrological modifications and nature restoration projects on ground beetles along the Yodo River, Osaka Prefecture, Japan Takahiro Fujisawa and Minoru Ishii Entomological Laboratory, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan （Received：October 29, 2012；Accepted：December 14, 2012） Abstract Hydrological modifications to the Yodo River of Osaka Prefecture, Japan, have been drastically changed the riverine environment, since dam construction and extensive excavation began in 1971. More recently, riverine restoration projects involving excavation of major beds designed to prevent them from drying out have recently been conducted. A field survey of carabid ground beetle assemblages using unbaited pitfall traps was conducted in the Yodo River riverbed from April to December 2009 to elucidate the influence of both hydrological modification and nature restoration activities on the assemblages. Ground beetles were captured for two weeks each month at 13 sites. Also, we measured four environmental parameters, riverbed conditions（minor or major beds）, submergence duration, soil moisture and median soil particle diameter, at each site. A total of 8,697 ground beetles belonging to 65 species were captured during the surveys. Generalized linear mixed model analysis showed that the abundance of nine species, such as Oodes vicarius, Pterostichus eschscholtzii and Pterostichus prolongatus, was positively correlated with the existence of minor beds and submergence duration or soil moisture, while that of 10 other species, such as Carabus yaconinus, Lesticus magnus and Synuchus nitidus, was negatively correlated with existence of minor beds, soil moisture rate and/ or submergence duration. Results of detrended correspondence analysis indicate that most of the former nine species and the latter 10 species were ordered at higher and lower scores of the axis 1, respectively. Also, ground beetle assemblages of major and minor beds were well separated by the ordination along axis 1. The results of this study demonstrate that hygrophilous species and the species preferring less disturbed environments characterize minor and major beds, respectively. Possibly, the nature restoration projects favored hygrophilous species by enlarging minor beds, which resulted in maintenance of heterogeneity of ground beetle habitats in the riverbeds. Key words：Carabid beetle, Detrended correspondence analysis, Generalized linear mixed model, Major bed, Minor bed, Submergence channelization and dredging for flood control（Ward, Introduction 1998；Poff et al., 2007）. The habitat homogeneity in river environments has created a major loss of Rivers serve as important landscape features to biodiversity globally（Hauer and Lorang, 2004；Poff et aquatic and terrestrial animals and plants, which al., 2007；Vörösmarty et al., 2010）. provide them with various types of habitats such The Yodo River, the largest river in the northern as intermittently flooded wetlands and floodplains area of Osaka Prefecture, central Japan, has with environmental gradients（Ward, 1998；Ward characteristic landscapes such as a large reed et al., 1999；Bunn and Arthington, 2002）. However, community in the riverbed called locally known human management of river hydrology has caused as “Udono”（Koyama, 1988, Nishino, 2009）. River heterogeneity of these habitats to decline with the regulation works have heavily modified the Yodo River construction of river regulation works such as dams, riverbed since 1971；ground water levels have fallen Corresponding author：[email protected] ― 187 ― Takahiro Fujisawa and Minoru Ishii as major beds dried after extensive excavation and the ground beetles have been decreasing as a result of construction of dams and weirs has been carried out to river regulation works and massive development of stabilize the water level（Koyama, 1999；Aya, 2004； residential zones in and around the river system. Our Nishino, 2009）, and many recreation areas including previous study（Fujisawa et al., 2012）also proved that golf courses have been built on major beds（Aya, the abundance of hygrophilous ground beetles has 2004）. These works probably exerted considerable decreased in the Udono riverbed because of the river influence on riverine terrestrial ecosystems of the regulation works. Yodo River. For example, the reed community declined However, nature restoration projects, involving because terrestrial plants such as kudzu, Pueraria lobata excavation of major beds to prevent them from drying, Ohwi, invaded the riverbeds at Udono（Koyama, 1999）. have recently been carried out at Udono（Koyama, 1999； Ground beetles serve as effective bio-indicators when Aya, 2004；Nishino, 2009）. In this study, we compared used to evaluate environmental changes of terrestrial ground beetle assemblages in the major and minor ecosystems（e.g. Thiele, 1977；Lövei and Sunderland, riverbeds along the Yodo River, to elucidate the influence 1996；Ishitani, 1996；Rainio and Niemelä, 2003）. As of nature restoration projects as well as river regulation for riverbeds, many studies of ground beetles have projects on the characteristics of the assemblages. clarified the influence of human disturbance（Ishii et al., 1996；Lee and Ishii, 2010；Follner et al., 2009）, Study Sites and Methods flood events（Gerisch et al., 2006）, and river restoration （Jähnig et al., 2009）on beetle assemblages. In the Yodo Field surveys using unbaited pitfall traps were River, Yasui et al.（2011）reported that bembidiine made at 13 sites named 1–6, 7a, 7b and 8–12 in the Fig. 1 Location of 13 study sites（closed circle：major bed, open circle：minor bed）in the Yodo River riverbed, central Japan. Contour interval：200 m. ― 188 ― Effects of hydrological modifications and nature restoration projects on ground beetles along the Yodo River, Osaka Prefecture, Japan Yodo River riverbed in Osaka and Kyoto Prefectures Site 6：A minor bed on the right bank of the Yodo from April to December in 2009（Fig. 1）. Plastic River at Takatsuki City located about 1.9 km upstream cups（7 cm diameter, 10 cm depth）with five 2–3 mm of the Hirakataohashi Bridge where the river was diameter holes in the bottom for drainage were used about 200 m wide. A reed community covered this site, for trapping. Ten traps were placed in a row at about dominated by M. sacchariflorus, P. karka and S. canadensis, 3 m intervals for two weeks a month and emptied which was completely flooded in autumn of 2009；no twice, at one and two weeks after trap placement. traps were placed at Site 6 at that time. Thus ground beetles were sampled a total of 18 times Site 7a：The right bank of the Yodo River at at all the sites except for Sites 7a, 7b and 10. Only 10, Takatsuki City located about 30.6 km upstream of the 16, and 16 samples were collected at Sites 7b, 10 and estuary. This site and Sites 7b, 8 and 9 were located Site 7a, respectively, because of flooding. Also, because in the Udono, the largest reed community in the Yodo some traps were lost during the sampling period, the River, in an area where the river was about 150 m total number of traps collected ranged from 145 to 179 wide. A grassland community dominated by P. australis, at all the sites except for Site 7b, where 91 traps were M. sacchariflorus and P. karka covered this site. This collected. The location and environment of each site site was regarded as a minor bed because a nature follows. restoration project had been completed at this site, Site 1：A minor bed on the right bank of the Yodo where riverbeds had been excavated in 2007 to prevent River at Osaka City located about 0.1 km upstream of drying after which the area became submerged every the Sugawarashirokitaohashi Bridge where the river year. From late July to late August and for a few days was about 200 m wide. A reed community covered this in October 2009, the site was inundated so no traps site, dominated by Phragmites australis（Cav.）Trin. were placed at Site 7a at this time. Also, a prescribed ex Steudel, Phragmites karka（Retz.）Trin. ex Steud, fire burned this site in March 2009. Miscanthus sacchariflorus（Maxim.）Benth. and Bidens Site 7b：This site was added in a minor bed about frondosa L.. 10 m upstream of Site 7a from August 2009 as an Site 2：A major bed on the left bank of the auxiliary to Site 7a. This site on sandy ground had Yodo River at Moriguchi City located about 1.5 km been created by excavation of a major bed and was downstream of the Torigaiohashi Bridge where the poorly covered by Aeschynomene indica L. and Conyza river was about 300 m wide. A reed community canadensis（L.）Cronq.. covered this site, dominated by P. karka, Solidago Site 8：A major bed on the right bank of the canadensis L. and Trichosanthes cucumeroides Maxim.. Yodo River at Takatsuki City located about 31.0 km Site 3：A major bed on the left bank of the Yodo upstream of the estuary where the river was about River at Hirakata City located about 1.3 km upstream 150 m wide. A community dominated by P. australis, of the Yodogawashinbashi Bridge where the river was M. sacchariflorus, P. karka and Humulus japonicus Sieb. et about 200 m wide. A reed community covered this site, Zucc. covered the site. Also, a prescribed fire burned dominated by M. sacchariflorus, P. karka and P. lobata. this site in March 2009. Site 4：A minor bed on the right bank of the Site 9：A major bed on the right bank of the Yodo River at Takatsuki city located about 2.7 km Yodo River at Takatsuki City located about 32.0 km downstream of the Hirakataohashi Bridge where upstream of the estuary where the river was about the river was about 200 m wide.