Shibetsu River Research Articles

Changes in Denitrification Potentials and Riverbank Soil Bacterial Structures along Shibetsu River, Japan

Riverbank soil ecosystems are important zones in terms of transforming inorganic nitrogen (N), particularly nitrate (NO3−-N), in soils to nitrous oxide (N2O) gases. Thus, the gasification of N in the riverbank soil ecosystems may produce a greenhouse gas, N2O, when the condition is favourable for N2O-producing microbes. One of the major N2O-producing pathways is denitrification. Thus, we investigated the denitrification potentials along Shibetsu River, Hokkaido, Japan. We sampled riverbank soils from eight sites along the Shibetsu River. Their denitrification potentials with added glucose-carbon (C) and NO3−-N varied from 4.73 to 181 μg·N·kg−1·h−1. The increase of the denitrification after the addition of C and N was negatively controlled by soil pH and positively controlled by soil NH4+-N levels. Then, we investigated the changes in 16S rRNA bacterial community structures before and after an anaerobic incubation with added C and N. We investigated the changes in bacterial community structures, aiming to identify specific microbial species related to high denitrification potentials. The genus Gammaproteobacteria AeromonadaceaeTolumonaswas markedly increased, from 0.0 ± 0.0% to 16 ± 17%, before and after the anaerobic incubation with the excess substrates, when averaged across all the sites. Although we could not find a significant interaction between the denitrification potential and the increase rate of G. AeromonadaceaeTolumonas, our study suggested that along the Shibetsu River, bacterial response to added excess substrates was similar at the genus level. Further studies are needed to investigate whether this is a universal phenomenon even in other rivers.

Significance of the stable foundations provided and created by large wood for benthic fauna in the Shibetsu River, Japan

Restoration is needed to recover biodiversity in many lowland rivers under threat by human activities. It is commonly believed that stable large wood provides a suitable habitat for benthic fauna in lowland rivers with an unstable riverbed of fine sediment, as the wood creates benthic habitat via riverbed stabilization. In the present study, we installed large wood in the riverbed to test the stabilization effect on benthic fauna and to assess the differences in composition of macroinvertebrates between the large wood itself (branches) and the riverbed stabilized with the wood. Current velocity near the riverbed was substantially decreased by installing large wood. Abundance and richness of macroinvertebrates in the riverbed with large wood were significantly higher than those in riverbed without wood. Larval lampreys were also found in the riverbed but only with large wood present. Macroinvertebrate compositions differed between the stable riverbed and the branches. Chironominae (midges) was the most dominant taxon in all habitats, collector-gatherer mayflies Paraleptophlebia and Ephemerella were abundant in stable riverbed habitats, and collector-filterers such as Simulium, Cheumatopsyhce, and Hydropsyche in addition to the mayflies were also abundant in branch habitats. This study showed that large wood not only serves as habitat for benthic fauna but also creates habitat via riverbed stabilization. In lowland river restoration, installing large wood could have a significant effect on the provision and creation of stable habitats for benthic fauna.

Integrated Effects of Land Use and Topography on Streamflow Response to Precipitation in an Agriculture-Forest Dominated Northern Watershed

Based on statistical analysis, baseflow separation and wavelet analysis, this research was carried out in Shibetsu River Watershed (SRW), Eastern Hokkaido, Japan, to investigate the integrated effects of land use and topography on streamflow response to precipitation. The agriculture-dominated sub-watershed (AW) showed coupled flat topography/agriculture characteristics, the forest-dominated sub-watershed (FW) had coupled steep topography/forest characteristics, and the mixed agriculture-forested sub-watershed (AFW) had mixed flat topography/agriculture and steep topography/forest characteristics. Precipitation variability is characterized by 6-months and 1-year periods. Coupled forest land/steep topography of the FW can increase surface runoff due to forest surface soil water repellency and steep slope, and might receive more external water and higher precipitation that resulted in the highest baseflow and total streamflow compared with other sub-watersheds. Coupled forest land/steep topography can cause higher monthly streamflow variability than coupled agricultural land/flat topography. The FW streamflow is characterized by 3–4 months, 6 months, and 1-year periods. The AW streamflow is only characterized by 3–4 months and 6 months periods. Coupled agricultural land/flat topography produced similar magnitude of baseflow during snowmelt season (March–May) and rainfall season (July–September), which resulted in the losing of annual periodicity in AW streamflow. The coupled forest land/steep topography can increase synchronicity in precipitation and streamflow at annual and monthly scales than coupled agricultural land/flat topography, except in 2007 under wet antecedent conditions when pasture land has lower rainfall interception and lower surface soil infiltration capacity. The coupled forest land/steep topography can increase time lags between precipitation and streamflow compared to coupled agricultural land/flat topography.

The significance of meandering channel to habitat diversity and fish assemblage: a case study in the Shibetsu River, northern Japan

This study examined the structure and function of habitats for fish, the contribution to fish populations, and the effects of channel modification on habitats and fish populations in the lowland meandering Shibetsu River, northern Japan. Electrofishing and environmental measurements were conducted in bank areas of habitats constituting natural meandering and modified reaches. All types of habitats in a meandering reach highly contributed to the fish population(s). In particular, the contributions of lateral and wood habitats to fish populations were generally high, despite the low spatial extent of these habitats. The modified reach was simplified and had fewer types of habitats with uniform currents, and there was a low abundance of most fish within these habitats. Abundance of each fish group (taxa) was negatively affected by the changes in the habitats and/or channel shortening (i.e., decrease in the absolute abundance of habitat) due to river modification, which was implemented during 1950–1978. This study suggests that the recovery of all the habitat types is important in meander restoration and that the changes in habitat types and abundance should be examined in monitoring meander restoration and channel shortening.

Comparison of Langmuir and Freundlich adsorption equations within the SWAT-K model for assessing potassium environmental losses at basin scale

Potassium (K) is an important nutrient for agricultural crop growth. Adsorption of K in soil involves fertilizer optima for enhancing crop productivity and efficient nutrient management. Adsorption is often necessary to predict K transport and losses, such as solid/liquid distribution in soil, plant uptake, and transportation with water and suspended sediments. Based on the Soil and Water Assessment Tool (SWAT), the SWAT-K model has been developed to quantify daily K losses and budget at watershed scale. In this study, Langmuir and Freundlich adsorption equations were both applied and compared in the SWAT-K model to predict K adsorption in the soil and K losses in the volcanic Shibetsu River Watershed (672km2, Hokkaido, Japan). Both the Langmuir and Freundlich adsorption equations well fitted the solid/liquid distribution of K in soil. The Freundlich and Langmuir equations showed similar performances to fit the measured data of K sorbed to soil (R2=0.91 for both cases) and Freundlich equation showed slightly better performances of dissolved K load in stream than Langmuir equation (Nash-Sutcliffe efficiency coefficient (ENS)=0.66 and 0.60, respectively). Overall, Langmuir and Freundlich equations predicted similar K budgets, including soil K surplus with a difference of 1.2%. The uncertainty related to the choice of the adsorption equation is negligible. Hence, both Langmuir and Freundlich adsorption equations are recommended to predict the K adsorption in soil and in-stream K load when using the SWAT-K model in watershed similar to the study case. Their applicability deserve to be tested in other agricultural watersheds characterized by different soils.

Assessing potassium environmental losses from a dairy farming watershed with the modified SWAT model

Potassium (K) was intensively used to optimize agricultural crop yield. Potassium losses should be accurately quantified for efficient nutrient management. However, no hydrologic model had been developed yet to quantify daily K losses at watershed scale. The Soil and Water Assessment Tool (SWAT) model was modified (named SWAT-K) by including the main K dynamic processes (solid–liquid distribution in soil and stream, plant uptake, and transportation with water flow and soil erosion) to simulate stream K load and K budget at the watershed scale. The SWAT-K was tested on the dairy farming Shibetsu River Watershed (672km2), Eastern Hokkaido, Japan. The solid–liquid distribution coefficient for K in suspended sediment was 10mlg−1. Langmuir equation was fitted to describe the solid–liquid distribution of K in soil, which derived an affinity constant of 0.046LmgK−1 and was used directly in SWAT-K. The fitted Langmuir equation also derived an adsorption maximum for K in soil. The adsorption maximum for K in soil normalized for clay content ranged from 4 to 20gKkg−1, and the fitted value of 15.5g Kkg−1 was used in SWAT-K. The SWAT-K satisfactorily predicted the daily dissolved K load at watershed outlet, and estimated an annual dissolved K load of 27.3kgKha−1year−1. The simulated pasture K yield of 36.1 (±2.5) kgKha−1year−1 was close to the observed data of 38.0 (±3.1) kgKha−1year−1. Then the model was used to quantify K budget at watershed scale. The simulated dissolved K leaching was 15.1kgKha−1year−1, and simulated soil K surplus of 75.1kgKha−1year−1 was much higher than plant uptake of 28.4kgKha−1year−1. The large amount of leaching and soil storage indicated that agricultural K input might be excessive and reducing the K application was recommended.

Sex differences in metabolic rate and swimming performance in pink salmon (Oncorhynchus gorbuscha): the effect of male secondary sexual traits

AbstractDo secondary sexual traits, such as large dorsal hump and hooked snout, decrease the swimming efficiency of male pink salmon during freshwater migration? This is the first study to address the effects of secondary sexual traits in pink salmon on oxygen uptake and swimming capacity. We conducted a laboratory experiment using a swimming respirometer and a field study using electromyogram (EMG) telemetry in the Shibetsu River, Hokkaido, Japan. We compared the relationship between MO2 (mg O2·kg−1·h−1) and swimming velocity U (m·s−1) in male and female fish, and also investigated the effects of morphological traits (secondary sexual characters) on the relationship between MO2 (mg O2·kg−1·h−1) and swimming velocity U (m·s−1). Additionally, we compared energy costs and swimming behaviour during upstream migration between male and female pink salmon. The laboratory experiment revealed that MO2 exponentially increased with increasing U; this increase was described by MO2 = 167.9e1.23U for males and 144.9e1.14U for females. Linear mixed models found that hump height and the upper jaw length in males significantly and positively affected the relationship between MO2 and U; no effect was found in females. The field study found that swimming velocity for both sexes estimated from EMG calibration was lower than optimal swimming velocity (Uopt) calculated from the laboratory experiment. We suggest that pink salmon in the Shibetsu River do not swim at the optimal swimming velocity because of the short migration distance involved (20 km).

Estimating sediment and particulate organic nitrogen and particulate organic phosphorous yields from a volcanic watershed characterized by forest and agriculture using SWAT model

The study was conducted in the Shibetsu River watershed (SRW), Hokkaido, Japan, in order to examine the possibility of using the soil and water assessment tool (SWAT) to provide an understanding of sediment and particulate organic nitrogen (PON) and particulate organic phosphorous (POP) yields between 2003 and 2008. The SRW is a non-conservative catchment (the surface catchment lying on a continuous impervious horizon) and it is recognized that it receives external groundwater (EXT) from other watersheds. The EXT yield from each hydrologic response unit (HRU) was added to streamflow in the SWAT model. Simulated daily sediment and PON and POP yields from the SWAT model showed a strong agreement with the observed values. The simulated annual sediment yield ranged from 5 to 45 tonnes.km−2.yr−1 (annual mean of 24 tonnes.km−2.yr−1). Annual PON yield ranged from 0.1 to 0.3 tonnes.km−2.yr−1 (annual mean of 0.18 tonnes.km−2.yr−1). Annual POP yield ranged from 0.01 to 0.03 tonnes.km−2.yr−1 (annual mean of 0.02 tonnes.km−2.yr−1). Snowfall, snowmelt and rainfall seasons contributed about 10, 20 and 70% respectively to total sediment and associated PON and POP yields. The SWAT model identified that sub-basins located in the upper part of the watershed were critical source area of land surface erosion. This research demonstrates the ability of the SWAT model to estimate sediment and associated PON and POP yields, and to improve the understanding of soil erosion mechanisms at catchment scale receiving external water.

Spatial variation of denitrification potential of grassland, windbreak forest, and riparian forest soils in an agricultural catchment in eastern Hokkaido, Japan

Riparian forest soils have a high denitrification potential (DP), but the effect of their spatial distribution on DP within a catchment has rarely been assessed. To provide insights into this effect, we evaluated the spatial distribution of DP and its control factors in the Shibetsu River Catchment (SRC), eastern Hokkaido, Japan. Soil samples from August 2008 were used in the lab to determine the DP (using the acetylene inhibition method) of grassland, windbreak forest, and riparian forest soils in the SRC. Soil DP ranged from 0.001 to 64mgNkgsoil−1d−1 and followed a log-normal distribution. Soil DP was highest in the surface peat soil of a low-elevation riparian forest. The land-use type and soil depth both significantly affected soil DP, with higher DP in riparian forests and surface soils. Soil DP increased with increasing soil moisture content and water-extractable soil organic carbon (WESOC). The clay, moisture, and WESOC contents in the surface soils decreased significantly with increasing elevation, resulting in increased soil DP in low-elevation riparian forests. The stream NO3− concentration was significantly correlated with the upland (grassland and cropland) proportion (%) of the catchment's area, and the ratio of stream NO3− concentration to this proportion tended to be lower in low-elevation areas, indicating higher NO3− denitrification. We conclude that low-elevation riparian forest soils have a higher DP due to the higher moisture, clay, and WESOC contents of their soils, and that these factors control riverine NO3− export in the SRC.

Influence of Agricultural Activity on Nitrogen Budget in Chinese and Japanese Watersheds

AbstractTo analyze the effect of agricultural activity on nitrogen (N) budget at the watershed scale, a comparative study was conducted at two Japanese watersheds, the Shibetsu River watershed (SRW) and Upper-Naka River watershed (UNRW), and one Chinese watershed, the Jurong Reservoir watershed (JRW). The total area and the proportion of agricultural area (in parentheses) of the watersheds were 685 (51%), 1 299 (21%), and 46 km2 (55%) for SRW, UNRW, and JRW, respectively. The main agricultural land use in SRW was forage grassland, while paddy fields occupied the highest proportion of cropland in UNRW (11% of total area) and JRW (31% of total area). The farmland surplus N was 61, 48, and 205 kg N ha−1 year−1 for SRW, UNRW, and JRW, respectively. The total input and output for the whole watershed were 89 and 76, 83 and 61, and 353 and 176 kg N ha−1 year−1 for SRW, UNRW, and JRW, respectively. The proportion of discharged N to net anthropogenic N input was 31%, 37%, and 1.7% for SRW, UNRW, and JRW, respectively. The two watersheds in Japan showed similar proportions of discharged N to those of previous reports, while the watershed in China (JRW) showed a totally different characteristic compared to previous studies. The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies, which was an underestimated N sink at the landscape scale.

Influence of prey variables, food supply, and river restoration on the foraging activity of Daubenton’s bat ( Myotis daubentonii) in the Shibetsu River, a large lowland river in Japan

To conserve the foraging habitat of Daubenton’s bat ( Myotis daubentonii) in a large lowland river, we investigated the influence on this bat of prey variables (number or biomass) and insect origin (aquatic or terrestrial). We tested the hypothesis that river restoration (re-meandering) conducted in the Shibetsu River, northern Japan, enhances foraging habitat quality by increasing the abundance of aquatic insects. From June to September 2004, flying insects were collected using Malaise traps in restored and channelised reaches in the Shibetsu River. Bat activity was recorded by bat detectors placed near the Malaise traps in each of the two reaches. Foraging activity of Daubenton’s bat was more strongly related to the number of insects than to biomass, and to adult aquatic insects than to terrestrial insects. The high dependence of Daubenton’s bat on aquatic prey was attributed to the fact that aquatic insect numbers were always higher than those of terrestrial insects. Contrary to the hypothesis, Daubenton’s bat was more active in the channelised reach than the restored reach in all months except June, and it synchronized its foraging activity with the seasonal distribution of adult aquatic insects. However, the study was undertaken just two years after restoration and the riparian vegetation had not yet established itself. Our results demonstrate the importance of aquatic insect abundance for Daubenton’s bat throughout the seasons in large lowland rivers. A further decrease in aquatic insects, associated with progressive anthropogenic alteration of river environments, undoubtedly exerts a harmful influence on the conservation of this species.

標津川の再蛇行化が一次生産過程に及ぼす影響の評価

本研究では河川における平面形状の違いが物質・エネルギーの動態に及ぼす影響を把握することを目的として，標津川の再蛇行化を取り上げ，一次生産速度に及ぼす影響を直線区間と蛇行区間の比較から明らかにし，その要因を分析した．観測結果から，蛇行区間における一次生産速度は直線区間と比較して大きかった．河床付着物中のChl.a が蛇行区間で有意に大きかったことから，両区間における一次生産速度の差は蛇行区間における高い底生藻現存量に起因していると考えられた．また，河床表層を占める河床材粒の粒径は，蛇行区間では瀬・淵構造の発達に伴い相対的に大きく，砂の面積占有率は直線区間で大きかった．更に，蛇行区間では湾曲の影響により，砂は平常時においても掃流状態で流下していたのに対し，蛇行区間では掃流砂が横断方向に偏った分布を有し，横断面の一部でしか確認できなかった．底生藻の現存量が直線区間で相対的に小さく，一次生産速度が減少したのも，このような河床環境の違いを反映したものと考えられた．

Migratory behaviour of adult chum salmon, Oncorhynchus keta, in a reconstructed reach of the Shibetsu River, Japan

Abstract During 2004–2006, 30 adult chum salmon, Oncorhynchus keta (Walbaum), were tagged with electromyogram (EMG) transmitters and depth/temperature loggers and tracked along both the channelised and reconstructed segments of the Shibetsu River, Japan to assess the effects of the river re‐meandering construction on upstream migration. Holding time of chum salmon in the reconstructed segment was longer than in the channelised segment. Further, greater diversity of physical condition in water velocity was observed in the reconstructed segment in 2005. Swimming speeds decreased during holding and often exceeded the critical swimming speed (Ucrit). It appears that the physical characteristics developed in the reconstructed segment may be suitable for holding of chum salmon. Further, swimming speed exceeding Ucrit prior to holding may be exhaustive so holding behaviour may be important for muscle recovery as well as for efficient swimming to reduce the energetic cost during upstream migration.

River restoration for macroinvertebrate communities in lowland rivers: insights from restorations of the Shibetsu River, north Japan

Because of human impacts, lowland rivers are among the most degraded running water ecosystems, with their floodplains being the center of human activity. Recently, many programs to restore running water ecosystems have been undertaken using various methods in streams and rivers of North America, Europe, and Far East Asia. However, research and knowledge on the effects of river restoration in lowland rivers are limited around the world. The restoration project involving the first reconstruction of a meandering channel in Asia has been conducted in a lowland river section of the Shibetsu River, northern Japan. We review the geomorphologic and hydraulic characteristics of lowland rivers and their environments for macroinvertebrates and discuss approaches to restoring macroinvertebrate communities in lowland rivers, using insights from the restoration project in the Shibetsu River. It is concluded that the recovery of macroinvertebrate assemblages in channelized lowland rivers requires the implementation of restoration methods to create stable substrates.

Methods for and fish responses to channel remeandering and large wood structure placement in the Shibetsu River Restoration Project in northern Japan

The Shibetsu River Restoration Project intends to reestablish a historic meander pattern by connecting a 3.5-km channelized reach with a series of oxbow lakes that were previously isolated by channel straightening. Prior to full-scale construction, a remeandering experiment (pilot) was conducted upstream of the project segment to assess the methods for and ecological responses to channel remeandering. Large wood (LW) structures were also installed in the experimental remeandering reach. The channel remeandering project with LW placement in a large lowland river is the first undertaken in Asia, and it has rarely been undertaken elsewhere. In this report, we present an overview of the Shibetsu River Restoration Project and the methods for and fish responses to channel remeandering and LW placement in the experiment.

Upstream migration of adult chum and pink salmon in the Shibetsu River

The migratory behavior and swimming patterns of anadromous upstream migratory fish have been poorly described in the Shibetsu River in eastern Hokkaido, Japan. In this 2004 study, we used electromyogram (EMG) transmitters and depth/ temperature (DT) loggers to compare the upstream migratory behavior of adult male chum salmon (Oncorhynchus keta) and pink salmon (O. gorbuscha) in the canalized and reconstructed segments of the Shibetsu River, where a part of canalized section was preliminary reconstructed meander to restore a more natural section. The EMG transmitter and DT logger were externally attached to the left side of the body, below the front edge of the dorsal fin. Fish of both species often migrated along the riverbanks and near the bottom of the water column, sometimes engaged in holding behavior, which was defined as cessation of swimming during their upstream migration for 5 minutes. Modal swimming depth calculated by DT loggers for chum salmon (0.2–0.4 m) was shallower than pink salmon (0.6–0.8 m). Further, modal swimming speeds measured by calibrated EMG for chum salmon (0.2–0.4 BL s−1) were slower than pink salmon (1.2–1.4 BL s−1). Pink salmon swam faster as well as in relatively deeper than chum salmon, suggesting that they expend more energy than chum salmon in the reconstructed segment. Based on these results, it seemed likely that the upstream migration behavior of chum and pink salmon was different with species-specific strategies.

Responses of macroinvertebrate communities to river restoration in a channelized segment of the Shibetsu River, Northern Japan

AbstractThe effects of restoration of channel meandering and of groyne structures on physical variables and river‐dwelling macroinvertebrates were examined in a lowland river, the Shibetsu River in Northern Japan. The lowland segment of the Shibetsu River, which previously meandered, was straightened by channelization and groynes installed on some portions of the channelized reach. In 2002, the channelization works were partly reversed to improve the degraded river ecosystem.Physical environment variables and macroinvertebrate community structure and composition were compared among reconstructed meanders and channelized reaches with and without groynes. The shear stress of the river edge in reconstructed meanders and groyne reaches was lower than that in a channelized reach. In addition, the edge habitat near the stream bank created by the reconstructed meander and groyne reaches had higher total density and taxon richness of macroinvertebrates than those of the channelized reach. Restoration provided a relatively stable edge habitat, contributing to the recovery of macroinvertebrate communities in such channelized lowland rivers. The placement of groynes can be an effective method of in‐stream habitat restoration for macroinvertebrates. Copyright © 2006 John Wiley & Sons, Ltd.

Upstream migration of chum salmon through a restored segment of the Shibetsu River

Abstract – A segment of the Shibetsu River was restored to reconstruct the ecological condition of the previously canalized river stretch to a more natural, meandering state. In this study, we investigated the upstream migration of chum salmon (Oncorhynchus keta) using radio transmitters to track the horizontal position of fish and data loggers to detect the vertical swimming depth of fish, simultaneously. The monitored salmon travelled near the bottom of the water column and along the riverbanks, and tended to hold in deep, slow current areas in the canalized river. In the restored segment, the fish swam at more shallow depths and against stronger currents. Although the three tracked fish all reached the confluent point and chose to enter the restored segment, they did not remain in the segment for long. This indicates that the restored area facilitates the upward migration of the chum salmon.

A hierarchical approach to ecosystem assessment of restoration planning at regional, catchment and local scales in Japan

A hierarchical approach to restoration planning at the regional, catchment and local scales is proposed and examined. Restoration projects limited to a local scale and focused on habitat improvement for individual species ended in failure, which has led to the recognition that there is a need for ecosystem-based management at the landscape level. The first landscape-level restoration in Japan is under way in the Kushiro and Shibetsu River Basins, in northern Japan. However, public consensus on these large-scale restoration projects has not yet matured and there are very few projects that have progressed even as far as mapping to classify intact and disturbed ecosystems. Classification of habitat quality using physical and biological indicators appears to be the core element of analysis of ecological degradation at the regional scale (100–1,000 km2). This mass-screening process is critical to identify areas in potential need of restoration. The causes and mechanisms of ecosystem degradation are then examined at the catchment scale (10–100 km2) by linking material flows and habitat conditions. Direct environmental gradient analysis is useful to determine cause and effect relationships between species and habitat quality. Finally, we recommend implementation of field experiments with a clear hypothesis at the local scale (0.01–1 km2). At this stage, key variables causing degradation of the target ecosystem are manipulated to verify the hypothesis. Based on the results of local-scale analyses, the possibility of restoration success can be evaluated, which directs us to practical schemes for future restoration projects at larger scales.

Shibetsu River Restoration Project:

Shibetsu River Restoration Project: