Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3390/f15020229

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.isprsjprs.2023.11.009

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.scitotenv.2023.164005

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1002/hyp.14947

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1039/d3em00236e

Other Link： https://pubs.rsc.org/en/content/articlehtml/2023/em/d3em00236e

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.24494/jfsh.71.0_67

Other Link： https://www.jstage.jst.go.jp/article/jfsh/71/0/71_KJ00008740524/_article/-char/ja/

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.fecs.2023.100088

Other Link： https://www.sciencedirect.com/science/article/pii/S2197562023000039

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/eap.2656

PubMed

Language：Japanese   Publisher：Society of Reconstruction Agriculture  

<p>In May 2020, street dust, bryophytes (mainly mosses) and Sumatran fleabane (Asteraceae family) were collected from the south exit of Shinjuku Station to the Imperial Palace, mainly along Route 20 in Tokyo and were analyzed radioactive cesium in an attempt to reveal the distribution of radioactive cesium around urban road sides environment. The highest concentration of radioactive cesium in this area at the time of the survey was 3,020 Bq kg^-1 dry weight of ¹³⁷Cs in street dust, suggesting the existence of potential hotspot areas in Tokyo. Among four types of samples analyzed, mosses rhizosphere soils, street dust, mosses, and shoot of Sumatran fleabane, in that order, showed the highest concentrations. The variability of concentrations varied among samples. Among the four types of samples, the roadside dusts, Sumatran fleabane, rhizosphere soil, and mosses showed the greatest variability, in that order. From these results, it was concluded that mosses and their rhizosphere soils accumulate radioactive cesium at high and stable concentrations and that their use for monitoring is effective. In the survey area, a peculiarly high concentration was found in front of Shinjuku Gyoen, and relatively high levels of radioactive cesium were also detected in Shinjuku 3-chome, Yotsuya Station overpass, and in front of Hanzomon. The roads at those sites were relatively narrow, suggesting that local geographical conditions may have played a role in the accumulation.</p>

DOI： 10.57341/jras.2.2_28

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jenvman.2022.114862

PubMed

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/hyp.14611

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Understanding the factors influencing Cs-137 concentrations in freshwater salmonids is crucial for reviving inland fisheries in polluted regions. We studied seasonal variations of Cs-137 concentration in charr (Salvelinus leucomaenis) through uptake and metabolism in forested headwaters at Fukushima and Gunma sites. Charr consumed both terrestrial and aquatic animals, and terrestrial prey was predated more in summer at both sites. The Cs-137 concentrations in litter, which is a dominant basal food resource of both forest and stream ecosystems, differed between forest and stream due to Cs-137 leaching effect on litter submerged in streams. The concentration difference in both litter and prey was greater at Fukushima site than at Gunma site. The estimated prey Cs-137 concentration at Fukushima site peaked in summer when terrestrial preys are most available, whereas it remained relatively constant at Gunma site because of the small difference of Cs-137 concentrations in between terrestrial and aquatic preys. The specific metabolic rate of charr was commonly changed with stream water temperature, greatest in summer, and lowest in winter at both sites. Because both prey Cs-137 concentrations and specific metabolic rates peaked in summer, the combination of uptake and metabolism at Fukushima site largely negated seasonal Cs-137 fluctuations in charr, whereas specific metabolic rate fluctuations could be the major determinant of charr Cs-137 concentrations at Gunma site. Our results suggested that Cs-137 concentrations in prey items, whose seasonality are varied due to initial Cs-137 fallout volume, were expected to be an important determinant for Cs-137 concentrations in charr.

DOI： 10.1111/1440-1703.12266

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/fwb.13811

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/fwb.13811

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>　To improve the prediction accuracy of numerical simulation models of water and sediment transport phenomena in mountainous catchments, we discuss extraction methods of the governing processes, and important site conditions and external forces affecting the governing processes. Results show a relationship between catchment area and water and sediment discharges, as derived from observations conducted at multiple locations within a catchment, can be typed according to differences in the spatial distribution of governing processes and controlling conditions. Elucidating relations between the catchment area and water and sediment discharges at multiple locations within the catchment might reveal the governing processes and controlling conditions of water and sediment transport phenomena. Based on these analyses, we discussed issues and approaches reflecting the observed information related to the spatial distribution of water and sediment discharge in the numerical prediction models. Results revealed (1) the importance of longitudinal observations at multiple streams in a catchment for ascertaining characteristics of the spatial distribution of water and sediment discharges. This study also clarified (2) the importance of cataloging spatial distribution of site conditions and, (3) processes that are and are not be expressible solely by topography, Furthermore, we argued (4) a method of modelling processes that cannot be determined solely by topography.</p>

DOI： 10.3178/jjshwr.34.192

CiNii Research

DOI： 10.3390/w13091313

Web of Science

DOI： 10.1016/j.geoderma.2020.114547

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

We examined the characteristics of landslides triggered by the 2016 Kumamoto earthquake (Mw = 7.0: focal depth=10.0 km) in forests and grasslands within two affected watersheds (Tokosegawa: 6.9 km(2) and Nigorigawa: 6.1 km(2)) in southwestern Japan. We identified 190 landslides using aerial photographs and analyzed their sizes by geographic information system (GIS). Field investigations were conducted to obtain landslide depth, volume and residual sediment for 38 selected landslides (21 in forests and 17 in grasslands). The minimum area of detected landslides in grasslands (400 m(2)) was smaller than in forests (1000 m(2)), probably because of reduced detectability of landslides under tree cover. The ratio of total area occupied by landslides for a given range of slope gradient in the watersheds increased from 3.2% on gentle grassland slopes (10-15 degrees) to 15.5% on steep (>45 degrees) slopes, whereas the maximum landslide-area ratio in forest sites (7.4%) occurred on relatively gentle slopes (25-30 degrees). Estimated landslide volume ranged from 27 to 9622 m(3), based on mean depth of each landslide measured around individual landslide scars. Moreover, the volumetric ratio of landslide deposit volume to total landslide volume exceeded 100% for 48% of the landslides within forests and 35% of the landslides within grasslands. Our findings show that land cover had extensive and recognizable effects on the characteristics of landslides and resulting in-channel sediment accumulations. Resetting sediment dynamics after earthquakes associated with different land cover distributions needs to be considered within watersheds. (c) 2019 John Wiley & Sons, Ltd.

DOI： 10.1002/esp.4781

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

We assessed spatial distribution of infiltration capacity under forest canopies to simulate runoff processes in a steep small catchment in Japan. High resolution LiDAR data were used to assess light availability to understory vegetation, which in turn was converted into an understory vegetation cover ratio. Spatially distributed infiltration capacities based on data from field rainfall-runoff experiments were incorporated into the TopoTube model using a relationship between infiltration capacity and vegetation cover. Effects of spatial distribution of infiltration capacity and its influence on hydrological connectivity and runoff processes were examined based on numerical simulations in the following three infiltration scenarios for seven natural storms: (1) spatially distributed infiltration capacity; (2) uniform infiltration capacity using the weighted mean of the spatial distribution in the drainage basin; and (3) uniform infiltration capacity using the arithmetic mean of field measurements. Although saturated subsurface flow dominated storm runoff in all simulations, Hortonian and saturated overland flow were significant for storm runoff response in smaller catchments (headwate

DOI： 10.1016/j.scitotenv.2019.02.453

Web of Science

PubMed

Language：Japanese   Publisher：JAPANESE SOCIETY OF REVEGETATION TECHNOLOGY  

DOI： 10.7211/jjsrt.44.489

CiNii Research

Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

DOI： 10.3178/jjshwr.31.560

CiNii Research

DOI： 10.1002/hyp.13246

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>　Examining the patterns of spatial variability of runoff and sediment transport is necessary for understanding hydrologic and geomorphic processes in watersheds. Knowledge of water and sediment transport behaviors in various catchment areas can improve the process-based representation of numerical models. We reviewed the relations between drainage areas and various properties of runoff and sediment transport comprehensively, particularly addressing spatial-scale dependence and spatial heterogeneity. Results show that patterns of increases and decrease of water and sediment amounts occurred relative to the catchment area, although other properties showed no distinctive relation to catchment areas, partly because of a lack of measured data. Most earlier studies specifically examined either spatial-scale dependence or spatial heterogeneity. Properties such as peak specific discharge showing clear spatial-scale dependence should be controlled by mechanisms that change with the spatial scale. Properties such as specific discharge during base flow showed spatial heterogeneity. Results suggest that mechanisms controlling base flow did not change much with the spatial scale for the measured ranges of catchment areas. Heterogeneous properties of landscapes exerted strong effects on those properties.</p>

DOI： 10.3178/jjshwr.31.219

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>　We reviewed the treatment of spatial scales in numerical models of runoff and sediment transport to elucidate current problems and to identify avenues for future research. We specifically examined the following questions: (1) Which spatial scale is used in existing modeling and how was it decided? (2) What spatial information was used? (3) Do the governing equations differ with spatial scale? Results show that the smallest spatial scale in distributed models was determined by the spatial resolution of spatially distributed information used in modeling, although lumped models were applicable at any scale. Some physical parameters used in modeling, aside from elevation, land use and vegetation cover, were not based on field-based information. Results demonstrate that the governing equations differ depending on locations within the watershed (i.e., hillslopes and channels) presenting different processes for runoff and sediment transport. Nevertheless, no report of the relevant literature describes a study with changed governing equations along with the changes in spatial scales. We also reviewed modeling studies of how we should treat the effects of spatial scale in runoff modeling, which revealed that they had reported minimum and the maximum spatial scales for lumping runoff mechanisms and the relative importance of spatial data used as input and parameters, although no attempts have been reported for a change in governing equations with spatial scale. We were unable to find similar studies of sediment runoff modeling. In summary, we suggest improvement of these findings and their use for modeling rainfall runoff and sediment transport mechanisms for better hydrological science.</p>

DOI： 10.3178/jjshwr.31.245

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

<p>　Findings for spatial patterns of runoff and sediment transport at selected observation sites were summarized to elucidate processes controlling scale dependence and spatial heterogeneity of their catchment areas. We selected Fudoji and Kiryu watersheds in Shiga for runoff generation and Tanzawa in Kanagawa and Saru watersheds in Hokkaido for sediment transport. Regarding runoff generation, variation of concentration of specific chemical species (i.e. silica) suggested various flow paths from weathered bedrock layer to soil layer in small catchments, although variation tapered with increased catchment area because of the mixing of several flow components. Sediment transport also varied spatially depending on the catchment characteristics. Variation tapered with increased catchment area. Moreover, increased storage components and decreased ratios of sediment source areas to the total catchment area for larger drainage areas decreased the sediment transport with catchment areas in some catchments. Landscape legacies of sediment supply, storage, and transport can contribute to increased sediment yields in larger catchments.</p>

DOI： 10.3178/jjshwr.31.232

CiNii Research

Language：English   Publisher：John Wiley and Sons Ltd  

Spatial variability of throughfall (TF) isotopic composition, used as tracer input, influences isotope hydrological applications in forested watersheds. Notwithstanding, identification of the dominant canopy factors and processes that affect the patterns of TF isotopic variability remains ambiguous. Here, we examined the spatio-temporal variability of TF isotopic composition in a Japanese cypress plantation, in which intensive strip thinning was performed and investigated whether canopy structure at a fine resolution of canopy effect analysis is related to TF isotopic composition and how this is affected by meteorological factors. Canopy openness, as an index of canopy structure, was calculated from hemispherical photographs at different zenith angles. TF samples were collected in a 10 × 10 m experimental plot in both pre-thinning (from July to November 2010) and post-thinning (from May 2012 to March 2013) periods. Our results show that thinning resulted in a smaller alteration of input δ18O of gross precipitation, whereas the changes in deuterium excess varied in both directions. Despite the temporal stability of spatial patterns in TF amount, the spatial variability of TF isotopic composition was not temporally stable in both pre- and post-thinning periods. Additionally, after thinning, the isotopic composition of TF was best related to canopy openness calculated at the zenith angle of 7°, exhibiting three different relationships, that is, significantly negative, significantly positive, and nonsignificant. Changes in meteorological factors (wind speed, rainfall intensity, and temperature) were found to affect the relationships between TF δ18O and canopy openness. The observed shifts in the relationships reveal different dominant factors (partial evaporation and the selection), and canopy water flowpaths control such differences. This study provides useful insights into the spatial variability of TF isotopic composition and improves our understanding of the physical processes of interception through canopy passage.

DOI： 10.1002/hyp.11475

Web of Science

Scopus

Language：English   Publisher：Springer Tokyo  

We examined the cesium-137 (137Cs) contamination of river food webs in a gradient of initial fallout deposition (net density estimates 2.5–3.5 months after the Fukushima Daiichi Nuclear Power Plant accident in March 2011), in Fukushima Prefecture, Japan. Litter, aquatic insects, and salmonid fish were collected in five headwater stream reaches (watershed-average fallout density, 368.1–1398.4 kBq/m2) for the measurement of 137Cs concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in June 2014. The stable isotope ratios suggested that the detrital food chain was a dominant energy pathway in rivers originating from a basal resource (litter) to primary (aquatic insects) and secondary (fish) consumers. The 137Cs concentration decreased with an increase in the trophic level, with the highest value for litter (10930 ± 5381 Bq/kg, mean ± SD), the lowest for fish (2825 ± 2451 Bq/kg), and the intermediate one for dominant (numerically and biomass-wise) detritivorous insect, Ephemera japonica McLachlan (4605 ± 1970 Bq/kg). 137Cs concentrations of three trophic levels were linearly predicted by the initial fallout amount of 137Cs. The evacuation of the gut contents of E. japonica during field experiments led to a reduction in their 137Cs concentration by approximately 50% within 1–2 day(s) without loss of body weight. This suggested that a substantial portion of 137Cs contamination of E. japonica was derived from highly contaminated fine solids deposited in depositional habitats at a disproportionately high density. Overall, the initial fallout amount of 137Cs was helpful in roughly predicting the contamination levels of headwater river-riparian ecosystems with the detrital food chain as a dominant energy pathway. Long-term monitoring of the dynamics and fates of 137Cs associated with fine organic and inorganic particulates appears important for better prediction of 137Cs contamination of food webs in forested headwater streams.

DOI： 10.1007/s11355-017-0328-8

Web of Science

Scopus

Language：English   Publisher：Springer Tokyo  

This study examined 137Cs detachment from needle litter of Japanese cedar (Cryptomeria japonica) through leaching and decomposition in a headwater stream located 45 km from Fukushima Daiichi Nuclear Power Plant. We placed litter bags in pools and riffles and removed them after 4, 15, 75, 150, and 240 days. The 137Cs activity concentration in litter collected after 4 and 15 days was 48–72 % of the initial 137Cs activity concentration in litter. The 137Cs activity concentration in litter after 240 days in the pools decreased by 26 %, while that in litter of riffles decreased by 9 % compared with the initial 137Cs activity concentration. The dry weight of litter became 71 and 86 % of initial weight after 75 days, and from 32 to 51 % after 150 days. The decay coefficient of litter (k = 0.0060) in the riffles was 1.6-fold higher than that in the pools (k = 0.0037). The greater decrease in litter weight with longer submergence time was possibly associated with a combination of leaching and decomposition, in particular in litter that was submerged for 100 days in the water column. The difference in the rate of decomposition and 137Cs detachment from litter between the riffles and pools was due to the substrate and flow conditions at the litter bag sites. Examining the different patterns of 137Cs detachment from litter among channel morphologies is necessary for comprehending the mechanisms of 137Cs accumulation in aquatic biota. The findings of this study suggest that elucidating leaching and decomposition processes in litter of stream channels is important for understanding 137Cs dynamics in forested headwater ecosystems.

DOI： 10.1007/s11355-017-0337-7

Web of Science

Scopus

Language：English   Publisher：Springer Tokyo  

DOI： 10.1007/s11355-017-0345-7

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Understanding integrated hydrological phenomena in catchments is difficult because of the fragmented nature of soil physical and hydrological data, given these are typically derived from pedons or small plots. Runoff plot and lysimeter or pedon-scale studies do not capture the complexity of surface and subsurface flowpaths in hillslopes. Because pedon/plot scale results are not easily transferable to hillslope and catchment scales, theoretical and empirical approaches to quantify hydrological dynamics based on such 'point-scale' data tend to over- or underestimate parameters and fluxes. Unit area sediment flux measured during storms typically (but not always) decreases from small plots to hillslopes owing to sediment deposition and re-infiltration of overland flow in localized areas. At broader scales, re-entrainment of previously stored sediment complicates this generalization, as may the development of rill and gully systems, facilitated by overland flow concentration. Quantifying mass wasting and sediment interactions in channels presents different temporal and spatial challenges, and must be assessed at the catchment scale. Process-based scaling requires an over-arching integration of different hydro geomorphic concepts and approaches. Nested catchment studies, where processes are monitored at different scales, represent an opportunity to elucidate the diverse spatial and temporal patterns of water and sediment behaviour. The spatial scale dependence inherent in many pedology and catchment hydrology studies can be overcome by incorporating hydrogeomorphic, pedological, and connectivity concepts that demonstrate how soil hydraulic parameters, geomorphic controls, and water/sediment routing change from plot to hillslope to catchment scales. The resulting self-organization generates spatial and temporal dependencies and provides a paradigm to better understand, model, and assess management effects on water and sediment fluxes and pathways in the continuum from plots to catchments.

DOI： 10.1016/j.earscirev.2017.10.010

Web of Science

DOI： 10.1016/j.landurbplan.2017.05.017

Web of Science

DOI： 10.1016/j.foreco.2017.07.036

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Thinning resulted in evapotranspiration decrease and caused the relative contributions of each component to evapotranspiration to become very close.
To increase the understanding of forest management to control water cycles, we examined the effect of 50% strip thinning on evapotranspiration (ET) and its partitioning into canopy interception (E (i)), tree transpiration (E (t)), and forest floor evaporation (E (f)) in a Japanese cypress (Chamaecyparis obtusa Endl.) plantation. Intensive measurements were employed to monitor each component of ET during the pre- and post-thinning periods. The results showed the annual E (t) was the dominant component of ET followed by E (i), whereas E (f) was the smallest component in both periods. Thinning has significant impact on the process of ET partitioning. In such that it decreased from 42.3 to 33.7% in E (i)/ET and from 45.0 to 34.9% in E (t)/ET, and increased from 12.7 to 31.4% in E (f)/ET on an annual scale. The relative contributions of each ET component to the whole ET became more or less the same after thinning. Additionally, the monthly E (i)/P (g) had relative stable values in both pre- and post-thinning periods, contributing significantly to the ET/P (g) during heavy rainfall conditions. After thinning, ET decreased by 21.4% from 629.3 to 494.8 mm during the growing season and by 20.4% from 979.8 to 780.1 mm at the annual scale, demonstrating that thinning results in an increase in water availability in the forested watershed. This study can improve the understanding of forest water budget in response to thinning and aid in development of appropriate forest management practices accordingly.

DOI： 10.1007/s00468-017-1555-1

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Land use composition and patterns influence the hydrological response in mountainous and forest catchments. In plantation forest, management operations (FMO) modify the spatial and temporal dynamics of overland flow processes. However, we found a gap in the literature focussed on modelling hydrological connectivity (HC) in plantation forest under different FMO. In this study, we simulated HC in two steep paired forest subcatchments (K2 and K3, 33.2 ha), composed of Japanese cypress (Chamaecyparis obtusa Endl.) and Japanese cedar (Cryptomeria japonica D. Don) plantations (59% of the total area) against a tree thinning intensity of 50% at different time. Additionally, construction of new skidding trails and vegetation recovery was simulated on five thinning-based scenarios that covered a 40-month test period (July 2010 - October 2013). As a future scenario, six check-dams located in the main streams were proposed to reduce sediment and radionuclide delivery. An updated version of Borselli's index of runoff and sediment connectivity was run, using the D-infinity flow accumulation algorithm and exploiting three 0.5-m resolution digital elevation models. On the basis of the pre-FMO scenario, HC increased at catchment scale owing to tree thinning and the new skidding trails. This change was more noticeable within the area affected by the FMO, where HC increased by 11.4% and 10.5% in the cypress and cedar plantations in K2 respectively and by 8.8% in the cedar plantation in K3. At hillslope plot and stream scales, the evolution in the values of HC was less evident, except the increment (by 5.4%) observed in the streams at K2 after the FMO. Progressive vegetation recovery after the FMO triggered a slight reduction of connectivity in all compartments of both subcatchments. Forest roads and especially skidding trails presented the highest values of HC, appearing as the most efficient features connecting the different vegetation patches with the stream network. The spatial and temporal evolution of HC over the five past scenarios correlated well with the observed changes in runoff yield, as well as with the available values of rainfall interception and throughfall before, during, and after the FMO. The simulation of the proposed scenario recommends the construction of check-dams as effective landscape features to somewhat reduce HC and thus to decrease the sediment and radionuclide delivery rates from the two subcatchments.

DOI： 10.1016/j.geomorph.2017.05.006

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We developed a food web-based transfer factor (TFweb) to study contaminant movements from multiple prey items to a predator based on the dietary contributions of prey items with their respective contamination levels. TFweb was used to evaluate the transfer of Cs-137 into whitespotted char (Salvelinus leucomaenis) from the trophic structure of a stream riparian ecosystem in headwater streams draining a Japanese cedar forest. We also examined the applicability of this method by comparing sites with different contamination levels but similar surrounding environments in Fukushima and Gunma. All samples were collected from August 2012 to May 2013. The dietary contributions from both aquatic and terrestrial prey items to whitespotted char were analyzed using stable carbon and nitrogen isotope ratios. Cs-137 activity concentrations in char ranged from 704 to 6082 Bq kg(-1)-dry in Fukushima and from 193 to 618 Bq kg(-1)-dry in Gunma. Dominant prey taxa such as mayflies (Ephemera japonica), spider crickets (Rhaphidosphoridae gen. spp.), and freshwater crabs (Geothelphusa dehaani), each of them accounted for 3-12% of the fish diet, based on lower and upper estimates, respectively. TFweb ranged from 1.12 to 3.79 in Fukushima and from 1.30 to 4.30 in Gunma, which suggested bioaccumulation from prey items to predator. Widely used ecological parameters TFs by media-char and ITF by single prey -char showed high variability with both dilution and accumulation. TFweb is applicable for Cs-137 transfer in predator-prey systems with complex food web structures of stream-riparian ecosystems. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2017.02.020

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Hydrology and Water Resources  

We performed a field experiment on throughfall, stemflow, and bamboo culm flow to estimate interception in a deciduous broadleaf forest with different stand structures by separately removing the overstory and understory vegetation. The study area is occupied by oak (Quercus serrata) and chestnut (Castanea crenata) with an understory of chino bamboo (Pleioblastus chino). We established three plots for vegetation control, including an overstory plot (removal of understory), a bamboo plot (removal of overstory), and a control plot (both overstory and understory remained). Throughfall amounts relative to precipitation were 61% in the control plot, 54% in the overstory plot, and 31% in the bamboo plot. Average stemflow in control and overstory plots was 3% of precipitation. The significant difference in throughfall for the bamboo plot may have been caused by the high density of understory vegetation. A large portion of intercepted water is transferred to the ground as bamboo culm flow in the understory beneath the canopy in the control plot and in the bamboo plot. Our experiment highlighted the significance of understory vegetation in altering hydrological processes from canopy to understory vegetation.

DOI： 10.3178/hrl.11.181

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

It is important to understand the changes in the Cs-137 concentration in litter through leaching when considering that Cs-137 is transferred from basal food resources to animals in forested streams. We found that the difference of Cs-137 activity concentration in litter between forest and stream was associated with both litter type and Cs-137 fallout volume around Fukushima, Japan. The Cs-137 activity concentrations in the litter of evergreen conifers tended to be greater than those in the litter of broad-leaved deciduous trees because of the absence of deciduous leaves during the fallout period in March 2011. Moreover, Cs-137 activity concentrations in forest litter were greater with respect to the Cs-137 fallout volume. The Cs-137 activity concentrations in stream litter were much lower than those in forest litter when those in forest litter were higher. The Cs-137 leaching patterns indicated that the differences in Cs-137 activity concentration between forest and stream litter could change with changes in both fallout volume and litter type. Because litter is an important basal food resource in the food webs of both forests and streams, the Cs-137 concentration gradient reflects to possible Cs-137 transfer from lower to higher trophic animals. Our findings will improve our understanding of the spatial heterogeneity and variability of Cs-137 concentrations in animals resident to the contaminated landscape. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2016.07.030

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This study revealed the influence of change in forest canopy structure by forest management practice for throughfall generation and canopy water interception process. Throughfall and stemflow were observed in a mature Japanese cypress (Chamaecyparis obtusa) plantation before and after thinning. Decreased stem density (from 2400 to 1300treesha(-1)) and basal area (from 107.6 to 60.4m(2)ha(-1)) resulted in an increase in the throughfall fraction (from 58% to 79%) and decreases in the stemflow fraction (from 14% to 8.6%) and the canopy interception loss fraction (from 27% to 12%). Thinning also decreased spatial variability in throughfall and smoothed temporal persistence of throughfall among sampling points or rainfall events. These results were supported by the change in the throughfall balance between direct throughfall and released throughfall. The proportion of direct throughfall of incident rainfall changed from 0.16 to 0.42 owing to an increase in canopy gap. The distribution ratio of released throughfall from intercepted rainwater by canopy changed from 50% to 64% because of a decrease in foliage; this led to lower water storage in the canopy (from 1.83 to 0.82mm), and thus less precipitation was needed to saturate the canopy. Consequently, the amount of throughfall increased and less precipitation was needed to stabilize the water flow path during the post-thinning period. This study contributes to knowledge of differential canopy wetting processes and spatiotemporal heterogeneity of throughfall distribution in response to specific silvicultural prescription. Copyright (c) 2015 John Wiley & Sons, Ltd.

DOI： 10.1002/eco.1636

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Understanding the mechanisms of Cs-137 movement across different ecosystems is crucial for projecting the environmental impact and management of nuclear contamination events. Here, we report differential movement of Cs-137 in adjacent forest and stream ecosystems. The food webs of the forest and stream ecosystems in our study were similar, in that they were both dominated by detrital -based food webs and the basal energy source was terrestrial litter. However, the concentration of Cs-137 in stream litter was significantly lower than in forest litter, the result of Cs-137 leaching from litter in stream water. The difference in Cs-137 concentrations between the two types of litter was reflected in the Cs-137 concentrations in the animal community. While the importance of Cs-137 fallout and the associated transfer to food webs has been well studied, research has been primarily limited to cases in a single ecosystem. Our results indicate that there are differences in the flow of Cs-137 through terrestrial and aquatic ecosystems, and that Cs-137 concentrations are reduced in both basal food resources and higher trophic animals in aquatic systems, where primary production is subsidized by a neighboring terrestrial ecosystem. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.envpol.2015.11.025

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Nutrient concentrations in stream water, rainfall, throughfall, stemflow, surface flow and ground water were compared before, during and after strip thinning (intensive 50%) in plantation forested watersheds in Tochigi, Japan. Influences were evaluated comparing four thinning-applied and two reference basins for 1 year before, 6 months during and 1 year after the thinning. Results show that this strip thinning significantly increased dissolved total phosphorus, total phosphorus and dissolved organic carbon (0.01, 0.04 and 0.53 mg l(-1), respectively) during the thinning period and dissolved total nitrogen and total nitrogen (0.34 and 0.46 mg l(-1), respectively) after the thinning in stream waters relative to the unthinned basins. The increased phosphorus during thinning indicated ground disturbances by the strip thinning, with a concomitant increase in dissolved organic carbon. Changes in biotic and abiotic conditions resulted in increased nitrogen after the thinning, particularly in the dissolved pool. Changes in hydrological processes due to thinning, for example, a change in flow distributions (less high nutrient stemflow and more low nutrient throughfall) and an increase in water discharge in stream water, possibly weakened the direct influences of thinning on nutrient concentrations. Copyright (C) 2015 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.10570

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We examined the effect of strip thinning on rainfall interception (Et) in a 32-year-old Japanese cypress plantation in central Japan. Strip thinning was conducted in the catchment in October 2011; that removed 50% of the stems. The gross precipitation (Pg), throughfall (TF) and stemflow (SF) were monitored in a 12-m x 13-m plot before and after thinning. Et was calculated as the difference between Pg and the sum of TF and SF. The interception processes were illustrated using the revised Gash model with quantifying interception parameters. The results showed that the Gash model successfully predicted Et on a rainy-season basis in both pre- and post-thinning periods. Thinning altered the interception components whereas the largest part during and after rainfall accounted for similar proportion in both periods. Additionally, after thinning, the annual TF rate was increased from 61.4% to 73.0%, whereas the annual SF rate was decreased from 9.8% to 6.1%, and the annual E-i rate was decreased from 28.7% to 20.8%. The summarized findings of previous studies indicate that the degree of decline in the Ei caused by thinning is related to Pg and the thinning ratio. These results provide useful information for understanding the changes in interception processes induced by thinning, and for acquiring a more accurate forecast of the effects of forest management practices on water resources in the watershed. The response in rainfall partitioning to strip thinning can also help us to acquire an integrated understanding of the changes in canopy water balance under different forest practices. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhydrol.2015.04.023

Web of Science

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Objective: This study examined the interrelations among vegetative cover and biomass, soil macronutrient levels, and soil erosion in northern Vietnam.
Methods: We selected ten dominant land-use types in a hilly area of western Hanoi including bare soil, agriculture (cassava or lemon grass), shrub land, five types of plantation forest, and indigenous forest. We measured the understory biomass, litter biomass, canopy openness, soil moisture content, soil pedestal height, soil hardness, soil bulk density,Cs-157 and Pb-210(ex) activities, and soil carbon and nitrogen on three 1 m(2) plots for each land-use type. Soil erosion was calculated from both pedestal heights and radionuclides. Multivariate statistical analysis was used to identify the key factors controlling soil erosion and nutrient accumulations.
Results: Understoty biomass ranged from 2 to 375 g m(-2), and this tended to be higher in most of the forest types and shrubland than in cassava and lemon grass. In contrast, the amount of ground cover varied more by forest type than between the agricultural land uses and forest lands. The height of soil pedestals indicated that short-term soil erosion was negligible when understory biomass was greater than 130 to 150 g m(2). Cs-137 was only detected in the cassava plots, whereas Pb-210(ex). indicated widely different erosion rates across the land uses, with lower values in the agricultural lands and two types of forest plantations, although this may be due to soil management practices. Both the correlation and principal component analyses showed that soil organic carbon and nitrogen were positively correlated to understory biomass and strongly and inversely influenced by bulk density. Soil erosion as indicated by soil pedestal height was strongly and inversely controlled by ground cover, litter, and understory biomass. Soil erosion was also heavily influential to soil chemical richness and bulk density.
Conclusions: Ground vegetation cover and the resultant soil erosion processes altered the production and accumulation of SOC, while forest cover did not always result in high soil fertility or low erosion. A simple characterization of forest or non-forest is not sufficient to calculate carbon and nutrient stocks, or assess erosion risk.
Practice: Understory biomass of at least 130 g m(-2) and high ground cover are essential for reducing soil erosion and sustaining short- and long-term soil productivity. Implications: Rapidly developing areas in Southeast Asia, including hilly areas in North Vietnam, need to maintain understory biomass and ground cover for soil and nutrient conservation. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.geoderma.2014.05.011

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

This study deals with the description of the vertical distribution of radiocaesium (Cs-137 and Cs-134) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol + Of) holds 52% (5.3 kBq m(-2)) of the Fukushima-derived and 25% (0.7 kBq m(-2)) of the pre-Fukushima Cs-137 at the time of the soil sampling. Including the pre-Fukushima Cs-137, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushima-derived Cs-137 at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble Cs-137. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived Cs-137 was somewhat rapid. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2014.06.017

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.scitotenv.2014.05.034.

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In this study, we focused on water quality in an urban canal and the Mekong River in the city of Can Tho, a central municipality of the Mekong Delta region, southern Vietnam. Water temperature, pH, electrical conductivity, BOD5, CODCr, Na+, Cl-, NH4 (+)-N, SO4 (2-)-S, NO3 (-)-N, and NO2 (-)-N for both canal and river, and tide level of the urban canal, were monitored once per month from May 2010 to April 2012. The urban canal is subject to severe anthropogenic contamination, owing to poor sewage treatment. In general, water quality in the canal exhibited strong tidal variation, poorer at lower tides and better at higher tides. Some anomalies were observed, with degraded water quality under some high-tide conditions. These were associated with flow from the upstream residential area. Therefore, it was concluded that water quality in the urban canal changed with a balance between dilution effects and extent of contaminant supply, both driven by tidal fluctuations in the Mekong River.

DOI： 10.1007/s10661-013-3421-y

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/hyp.10129

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Stream temperature was recorded between 2002 and 2005 at four sites in a coastal headwater catchment in British Columbia, Canada. Shallow groundwater temperatures, along with bed temperature profiles at depths of 1 to 30cm, were recorded at 10-min intervals in two hydrologically distinct reaches beginning in 2003 or 2004, depending on the site. The lower reach had smaller discharge contributions via lateral inflow from the hillslopes and fewer areas with upwelling (UW) and/or neutral flow across the stream bed compared to the middle reach. Bed temperatures were greater than those of shallow groundwater during summer, with higher temperatures in areas of downwelling (DW) flow compared to areas of neutral and UW flow. A paired-catchment analysis revealed that partial-retention forest harvesting in autumn 2004 resulted in higher daily maximum stream and bed temperatures but smaller changes in daily minima. Changes in daily maximum stream temperature, averaged over July and August of the post-harvest year, ranged from 1.6 to 3 degrees C at different locations within the cut block. Post-harvest changes in bed temperature in the lower reach were smaller than the changes in stream temperature, greater at sites with DW flow, and decreased with depth at both UW and DW sites, dropping to about 1 degrees C at a depth of 30cm. In the middle reach, changes in daily maximum bed temperature, averaged over July and August, were generally about 1 degrees C and did not vary significantly with depth. The pre-harvest regression models for shallow groundwater were not suitable for applying the paired-catchment analysis to estimate the effects of harvesting. However, shallow groundwater was warmer at the lower reach following harvesting, despite generally cooler weather compared to the pre-harvest year. Copyright (c) 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.9673

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

We conducted a field monitoring experiment examining throughfall in Japanese cypress plantations located in Tochigi Prefecture, eastern Japan. A set of 20 tipping-bucket rain gauges and throughfall collectors were placed in a lattice-like distribution throughout a 10× 10-m experimental plot to investigate the effect of the forest canopy on the spatial variability of throughfall. The isotopic composition of throughfall and open rainfall were analyzed and compared for each rainfall event. A clear relationship between throughfall rate and the radial distance to the nearest tree trunk was observed when the influence of wind was negligible
however, such a systematic pattern of throughfall was not observed during rainfall events that occurred during windy conditions. The δ18O and δD values in throughfall varied considerably, reflecting different rainwater flow paths in the saturated canopy. The analysis of stable isotope ratios in the throughfall and its comparison with isotopic composition of rainwater hitting the canopy can help elucidate the interception processes in the forest canopy. © 2013 Elsevier B.V.

DOI： 10.1016/j.jhydrol.2013.09.028

Scopus

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.1002/eco.1249

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The Fukushima Daiichi nuclear power plant accident resulted in extensive radioactive contamination of the surrounding forests. In this study, we analyzed fallout Cs-137, Cs-134, and I-131 in rainwater, throughfall, and stemflow in coniferous forest plantations immediately after the accident. We show selective fractionation of the deposited radionuclides by the forest canopy and contrasting transfer of radiocesium and I-131 from the canopy to the forest floor in association with precipitation. More than 60% of the total deposited radiocesium remained in the canopy after 5 month of the initial fallout, while marked penetration of the initially deposited I-131 through the canopy was observed. The halflives of Cs-137 absorbed in the cypress and cedar canopies were calculated as 620 days and 890 days, respectively for the period of 0-160 days. The transfer of the deposited radiocesium from the canopy to the forest floor was slow compared with that of the spruce forest affected by fallout from the Chernobyl nuclear reactor accident. Citation: Kato, H., Y. Onda, and T. Gomi (2012), Interception of the Fukushima reactor accident-derived Cs-137, Cs-134 and I-131 by coniferous forest canopies, Geophys. Res. Lett., 39, L20403, doi:10.1029/2012GL052928.

DOI： 10.1029/2012GL052928

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER BASEL AG  

Data from a paired-catchment study in south coastal British Columbia, Canada, were analyzed to assess the thermal effects of clearcut harvesting with no riparian buffer on a fish-bearing headwater stream. The approach used time series of daily mean water temperatures for East Creek (control) and A Creek (treatment), both before and after harvest. Statistical models were developed to predict (a) what the temperatures would have been in the post-harvest period had harvesting not occurred, and (b) what temperatures would have been in the pre-harvest period had harvesting already occurred. The Wisconsin Bioenergetics Model was used to simulate growth of coastal cutthroat trout (Oncorhynchus clarki clarki) for the first year following fry emergence using the predicted and observed stream temperatures to generate scenarios representing with-harvest and no-harvest thermal regimes. A Monte Carlo approach was used to quantify the effects of uncertainty associated with the regression models on predicted stream temperature and trout growth. Summer daily mean temperatures in the with-harvest scenario were up to higher than those for the no-harvest scenario. Harvesting-induced warming reduced growth rates during summer, but increased growth rates during autumn and spring. In the with-harvest scenario, trout were 0.2-2.0 g (absolute weight) smaller throughout the winter period than in the no-harvest scenario. However, the bioenergetic simulations suggest that trout growth may be more sensitive to potential changes in food supply following harvesting than to direct impacts of stream temperature changes.

DOI： 10.1007/s00027-011-0238-z

Web of Science

Language：Japanese   Publishing type：Research paper (other academic)   Publisher：Japan Society of Erosion Control Engineering  

DOI： 10.11475/sabo.65.1_01

CiNii Research

DOI： 10.1002/hyp.8086

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

Upscaling and the effect of slope length on the sediment production are important issues in hillslope hydrology. This study investigated the effect of slope length at a steep forested site between 2006 and 2010 using erosion plots and neighboring sediment traps. The hillslope had high litter cover but sparse understory due to overgrazing by wild deer. Sediment transport increased for short distances (5 m to 10 m), then decreased over the hillslope (> 10 m). In plots this effect was due to organic litter accumulation. Organic litter production declined progressively along the hillslope continuum. When accumulated organic litter altered the microtopography, sediment production declined more with increase in slope length. Heavy precipitation events did not change the pattern of these scale effects. These results demonstrate that the slope length effect had inconsistent controls on sediment transport due to variations in soil surface conditions of the landscape. Such variations in the slope length effect cause uncertainty in sediment flux estimations in steep forested landscapes.<br>

DOI： 10.3178/hrl.5.16

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

We examined the effect of forest thinning on overland flow generation on hillslopes covered by a Japanese cypress plantation in central Japan. We established hillslope plots in two small catchments for monitoring overland flow generation. Plot 1 was a treatment plot in which 58.3% of stems were removed, whereas plot 2 remained untreated as a control. Overland flow generation was examined using (1) time-trend analysis that compared overland flow to precipitation 2 years pre- and 2 years post-thinning in plot 1 and (2) a paired-plot approach that compared the treated hillslope plot to the control hillslope plot. The latter approach was more reliable for identifying treatment effects than time-trend analysis because it minimizes effects of climate variables such as precipitation. Unlike our initial hypothesis for decreasing overland flow after thinning, paired-plot analysis indicated that after thinning, mean overland flow increased 7.4% (corresponding to 2.1 mm) in response to individual storms and 4.8% (corresponding to 7.9 mm) based on monthly data. Although the increased overland flow is likely associated with reduced canopy interception, the reduction of canopy interception after the thinning was estimated to be greater than the increases in overland flow. Therefore, sonic of the increased throughfall was infiltrated into the soil matrix. Such changes in hillslope-scale runoff in response to thinning alter the distribution of water in the surface and subsurface layers of forested headwater basins. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/eco.135

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The contributions and relationships of erosion by splash and overland flow over a steep slope in a Japanese beech forest in plots with different percentages of ground cover were examined. Three erosion plots (2 m wide x 5 m long) with average understory coverage of 1%, 45%, and 94% were installed. Sediment transported by rain splash and by overland flow was sampled separately. For the plots with sparse, moderate, and high understory coverage, the average proportions of splash soil to total soil erosion during the monitoring period were 16%, 32%, and 18%, respectively. A significant correlation between the amount of splash soil and precipitation was found in the plots with 1% and 45% understory coverage, whereas no statistical relationship was identified for the plot with high understory coverage. At the sparse ground cover plot showing the largest sediment movement, the contribution of splash transport decreased with increasing precipitation. The amount of sheetwash erosion was significantly correlated with the amount of splash soil under the condition of sparse ground cover. This relationship was more pronounced during high precipitation events and the rainy season. Splash contribution to the sediment transport was in the range of 0.8%-76.7%. 2.8%-81% and 2.1%-60.8% for plot with high, moderate and low ground cover, respectively. The sparse ground cover showed the largest variation of splash and sheetwash contribution in soil erosion. This variability was due to variation in ground cover and soil surface wetness condition which led to a variation of detachment and non-linear relationship of sheetwash splash. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catena.2010.11.005

Web of Science

Language：English   Publisher：SPRINGER TOKYO  

Despite continued interest in stream water temperature (Tw) analysis, there are few studies of Tw response to rainfall events at forested watersheds. We examined 61 sets of data on Tw for 21 rainfall events at 16 watersheds with various slope gradients (from 0.08 to 0.56) in four regions of Japan from June 2004 to December 2005. The investigation focused on the changes of specific discharge (Delta Qs) and Delta Tw at medium-sized watersheds (0.5-100 ha). The results clearly demonstrated different flow patterns expressed by Qs vs. Tw hysteretic loops. Those were clockwise in Period I (April-September) and counterclockwise in Period II (October-March), except for lower slope gradient at Aichi, where counterclockwise loops were observed in both periods. These differences in hysteretic loops could be explained by the differences in Tw and in response times to rainfall between surface/subsurface and groundwater flows. The response times were probably determined by the slope gradient and the vertical level of groundwater. We also found that the changes in air temperature (Delta Ta) influenced Delta Tw to a lesser degree than Qs. The average rainfall intensities in Period I and Period II (9.3 +/- A 1.7 and 5.4 +/- A 0.2 mm/h, respectively) affected the average values of Delta Qs and Delta Tw (6.62 +/- A 4.08 mm/h and 1.7 +/- A 0.4A degrees C; 0.85 +/- A 0.68 mm/h and 0.9 +/- A 0.3A degrees C, respectively). This indicates that slope gradient and Qs influenced Delta Tw by changing the relative proportions of flow paths. In addition, the water table changes influenced the percentage of groundwater flow to the stream.

DOI： 10.1007/s10201-009-0296-2

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

We examined short-term responses of macroinvertebrate drift associated with experimental sediment flushing in a headwater. Increases in the drifting abundances of Ephemeroptera and Plecoptera coincided with increases in bed load yield rather than peaks in discharge or suspended sediment concentrations. The approach and arrival of a sediment wave may provide a physical cue that initiates the escape of benthic macroinvertebrates. Because fine bed load sediments, with diameters &lt; 4 mm, tended to accumulate on and in the substrate matrix, such sedimentation affected the benthic macroinvertebrates residing on and in the substrate, increasing the number of macroinvertebrates in the drift. Therefore, the decreases observed in the densities of most macroinvertebrate taxa following sediment flushing were probably associated with sediment deposition and the resulting escape of macroinvertebrates from benthic habitats. The magnitudes of the decreases in macroinvertebrate density were lower at sites located 200 m downstream from the sediment sources than at sites located 20 m downstream. The results from this experimental flushing study suggest that bed load movement and resulting sediment accumulation alter macroinvertebrate drift patterns and cause decreases in the abundances of benthic macroinvertebrates in headwater streams.

DOI： 10.1007/s11355-010-0107-2

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Intensive field observations as well as monitoring of discharge, water quality, and soil erosion have been conducted in forest plantations in order to identify the effects of forest cover and management practices on runoff generation, sediment transport, and downstream environmental issues. Five experimental catchments, each with rather uniform lithology, were established in both managed and unmanaged plantations of Japanese cypress and cedar, as well as broadleaf forests. Field monitoring was conducted from sub-plots (e. g. splash cups) to small hillslope plots (0.5 x 2 m) to large hillslope-scale plots to first order streams (0.1-4 ha) and finally to larger catchments (&gt;4 ha) in a nested structure. Remote sensing techniques were employed to identify broad scale forest stand and soil surface conditions. As part of this integrated study, these field-based monitoring and remote sensing techniques provide information for modelling runoff generation and developing adaptive management schemes with respect to catchment-scale water resources. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.7548

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1139/F09-186

Language：English   Publishing type：Research paper (scientific journal)  

CiNii Research

Language：Japanese   Publisher：Japan Forest Conservation Association  

DOI： 10.20820/suirikagaku.53.6_77

CiNii Research

DOI： 10.1002/hyp.7440

Web of Science

DOI： 10.1029/2008WR007270

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We conducted field monitoring of bedload transport rate associated with experimental sediment release in a natural channel to clarify behavior of the supplied sediment on mixed size bed. Observation of bedload rate at two sites along the 30 m channel reach revealed that downstream migration of finer particles delay compared with coarser particles. Ratio of the bedload sediment that deposited during the migration was higher for finer sediments. These behaviors of the mixed size particles were clear during passage of the sediment wave without changes in water discharge. Flashing peak of discharge that caused artificially by opening of the dam gate did not destroy channel bed structure including steps and pools formed by coarser sediments, and only small amount of bedload was mobilized. Both reach scale channel features including steps, pools, and riffles as well as fine scale features (i.e., armour coat) likely increased critical shear stress of particles and decreased bedload rate during our experiment. Extreme sediment supply induced two types of sediment deposition; (1) filling the pools in reach sales and (2) the intrusion of fine particles into the coarser sediment that formed an armour layer. The all grain size fractions can deposit as type (1) when shear stress of stream water is not enough to entrain bedload particles, while deposition type (2) occurs when finer sediment pass over channel bed on which armour coat is well-developed. Deposition of finer sediment into coarser sediment that forms armour coat is affected by grain size distribution of bed surface sediment. Thus, impact of the sediment supply on downstream channel depends on both bedforms and grain size distribution of bed surface sediment over which the supplied sediment pass. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catena.2008.12.015

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

In order to gain insight into the effect of watershed conditions on fluctuations in stream water temperature, we statistically analyzed water temperature data for 1 year, using root mean square (Rms) and harmonic (A Amplitude, phi delay time) methods. The average values of delay time (days) between air and water temperatures (T (a) and T (w)) of small (&lt; 0.5 ha), medium (0.5-100 ha) and large (&gt; 100 ha) watersheds were 4.53 +/- A 0.82 days, 11.83 +/- A 3.88 days and 4.45 +/- A 1.52 days, respectively. Fluctuations in stream water temperature expressed by Rms (Rms T (w)/Rms T (a)) and harmonic methods (A -T (w)/A -T (a)) in the medium-sized watersheds with moderate slope gradients were 0.37 +/- A 0.09 and 0.56 +/- A 0.14, respectively. These values increased in the larger watersheds with low slope gradients, including five large rivers covered by various landscapes, with their averages of 0.53 +/- A 0.09 and 0.78 +/- A 0.09, respectively, indicating the influences of solar radiation and heat transfer processes. In the smaller watersheds with high slope gradients, these values were 0.73 +/- A 0.02 and 0.87 +/- A 0.03, respectively, suggesting that shorter passage time affected water temperatures. With respect to forest type, these values at badly managed hinoki forest watersheds (0.45 +/- A 0.04 and 0.73 +/- A 0.07) were larger than those at broadleaf forest (0.34 +/- A 0.04 and 0.51 +/- A 0.12) and well-managed hinoki forest (0.33 +/- A 0.04 and 0.51 +/- A 0.07) watersheds, indicating different proportions of flow paths.

DOI： 10.1007/s10201-008-0258-0

Web of Science

Language：Japanese   Publisher：Japanese Society of Soil Physics  

We examined effects of soil water repellency on hydrological processes in various scales from small plot to catchment in a Japanese cypress plantation. We measured soil water repellency and infiltration rate along a hillslope transect, and monitored overland flow at small plots (1 × 2 m) with sparse and dense fern cover and a large plot (8 × 25 m) and stream discharge at the outlet of a small catchment (0.43 ha). Strong water repellency in surface soil horizon was partially associated with Hortonian over-land flow, which volume potentially depended on sever-ity of water repellency. Relationships between matric po-tential and soil water content indicate that changes in the soil water repellency and consequently runoff coefficient of overland flow could occur during a single storm event. Greater amounts of overland flow at small plots compared to ones at large plot suggests that overland flow generated in hillslope was discontinuously transferred. Higher infil-tration rate at the bottom of hillslope likely caused little contribution of overland flow on catchment runoff. Despite the substantial overland flow generated in hillslope due to soil water repellency, water repellency was not a dominant factor accelerating runoff directly at the small catchment scale.

DOI： 10.34467/jssoilphysics.111.0_9

CiNii Research

DOI： 10.1007/s11355-008-0044-5

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Overland flow generation was monitored. in large plots (8 x 25 m) on four hillslopes in a 4.9-ha catchment in Mie Prefecture, Japan. Three Japanese cypress (hinoki, Chamaecyparis obtusa) treatments (including three different understory conditions) and one deciduous forest treatment were studied. For all plots, including deciduous hillslopes, we observed overland flow even for small storm events (&lt;10 mm in total precipitation). The mean runoff coefficients in dense Japanese cypress plots with sparse understory were highest (13.0%) followed by dense Japanese cypress with fern ground cover (6.7%), and coefficients in managed cypress and deciduous forest were 3.6% and 1.2%, respectively. The runoff coefficients tended to be higher during storms that were preceded by dry conditions. High soil water repellency initially occurred in Japanese cypress forests between the titter and mineral. soil horizon and might have been partly responsible for overland flow generation. During storms with total precipitation &gt;180 mm, runoff from Japanese cypress plots with dense fern understory exhibited a delayed and higher peak associated with return flow. The dominance of hillslope-scale flow contribution to catchment runoff was also affected by changes in the dominance of overland flow and return flow. Understory vegetation cover and the availability of a titter layer altered the amount of overland flow, which was mediated by soil water repellency and soil moisture. Observations at the hillslope scale are essential for conceptualization of runoff mechanisms and pathways in forested headwaters. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhydrol.2008.07.045

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A comprehensive investigation on all dissolved nitrogen and phosphorus components at both local and regional scales in the headwaters from forested watersheds is valuable to improve our understanding of the factors controlling water quality. Here, we investigated the baseflow concentrations of dissolved nitrogen and phosphorus components, N:P ratio, and their associations with region and vegetation type in forested headwaters in fives regions of Japan. We found that inorganic nitrogen and phosphorus were the dominant components in the 26 temperate forested streams, rather than organic forms. There were significant positive correlations between the concentrations of N and P components. Furthermore, the regional patterns of the concentrations of nitrate, dissolved inorganic P (DIP), and dissolved total N (DTN) and P (DTP) were similar. Our results suggest that the regional patterns of the concentrations of N and P components should be related to the regional atmospheric deposition of both N and P nutrients. We also found that the nitrate and DTN concentrations were higher in man-made evergreen conifer (EC) than those in the natural deciduous broadleaf (DB). in contrast, the DIP and DTP concentrations in EC were lower than those in DB. The uniformly higher NT ratio in EC-than in DB-forested streams for each region suggest that EC-forested streams could be more affected by P-limited than DB-forested streams when N inputs from atmospheric sources increased. (c) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2008.04.045

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Both scaling effect and connectivity of overland flow were examined in steep hillslopes covered by (1) Japanese cypress (hinoki, Chamecyparis obtusa) plantations with sparse understory vegetation, (2) hinoki plantations with fern understory vegetation, and (3) deciduous forests. Two sizes of plots were installed for monitoring overland flow: small (0.5 x 2 m) and large hillslope scale (8 x 24-27 m). For all hillslopes, measurable amounts of overland flow occurred during storms. Runoff coefficients of large plots (0.1-3%) were consistently smaller than those of small plots (20-40%). Estimated runoff flow lengths at the hillslope scale were based on runoff coefficients from small plots and were used to calculate runoff volume from large plots. Then we compared the differences between observed and estimated runoff volumes of large plots. Estimated runoff from large plots was smaller than observed runoff in hinoki slopes with sparse understory vegetation. Greater amounts of observed compared to estimated overland flow suggest that more runoff occurred from hillslopes with sparse understory. In contrast, estimated overland flow was larger than observed runoff from the deciduous forest, implying greater opportunities for infiltration compared to hinoki hillslopes. Comparison of estimated versus observed overland flow for successive 5 min intervals during storms indicates that runoff networks expand upslope during short and intense precipitation periods. Our examination and comparison of storm runoff from small and large plots facilitate better understanding of runoff mechanisms, scaling effects in hillslopes, and connectivity of the overland flow network.

DOI： 10.1029/2007WR005894

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Morphologic and hydrologic properties of head-cut gullies formed in meandering bends of a gravel-bed river in northern Japan were examined to investigate their topographic development. head-cut gullies had incised to 2 in below the floodplain surface and had perennial seepage outflows. Because no surface runoff was observed across the meandering necks, we hypothesized that hyporheic flow erosion cutting into the down-river edge of the meandering necks is one factor for the development of head-cut gullies. Several topographic features caused by sapping and piping erosion were observed within the head-cut gullies. A tracer experiment and examination of the water table, water chemistry, and water table responses in wells on the floodplain and within the head-cut gully revealed that significant preferential hyporheic flow occurred between coarse cobble and fine sediment layers of the floodplain materials. During a storm event, water tables around the head-cut gully quickly responded to changes in the water table of the stream channel; this result also suggests that hyporheic flow occurred across the meandering bends. Hyporheic flow around the head-cut gullies had higher hydraulic conductivities and preferential flow paths that may relate to buried beds of paleochannels. An erosion model suggests that it is unlikely that hyporheic flow alone had enough energy to account for all the soil erosion. Thus, a combination of hyporheic flow (sapping erosion) and channel erosion (bank erosion) appeared to contribute to the formation of the head-cut gullies. Hyporheic flow is an important component in the geomorphic evolution of channels and the floodplain in a gravel-bed river. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catena.2007.10.004

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Extensive reforestation using Cypress, Pinus and Cedar has widely taken place in Japan since early 1960s in attempt to fulfill national wood demands and control soil erosion. In 2004 one small headwater mountainous reforested watershed encompasses 4.8 ha was established in Mie Prefecture in Japan to monitor the hydrological response. Frequently and automatically collected values of discharge and suspended sediment concentration were examined for the main outlet and five other stations, spanning from June 2004 to July 2006. In the present study, the different functional linear and non-linear sediment rating curves analytical methods were employed in the investigation of ordinary and some transformed flow discharge-suspended sediment concentration relationships for the study watershed using from 48 to 162 simultaneous discharge-sediment records (2004-2006).
According to the results of statistical analyses using different criteria and out of many types of regression functions and data transformation, power rating curve by least square regression on fourth root transformed flow discharge and suspended sediment concentration data performed well. Contrary to what is oft-reported, the best fitted rating curves to the entire data collected for each individual station excessively overestimated the suspended sediment concentration in the study area by 113-430%. The temporal and magnitude stratification of flow discharge and sediment data, flow components separation as well as employing bias correction factor did not improve the relationship, while better estimates were obtained when power regression was applied to the fourth root transformed data separated based on their locations on rising and falling limbs of hydrographs. Results also showed a complex suspended sediment concentration and flow discharge relationship in different subwatersheds of the study reforested watershed reflecting the effect of different physical local characteristics, sediment availability, contribution of various hydrologic cycle components, and subtle variation of soil hydrophobicity on runoff generation and consequently sediment supply. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.geoderma.2007.11.008

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Forest areas have been identified as important sources of nonpoint pollution in Japan. The managers must estimate stormwater quality and quantities from forested watersheds to develop effective management strategies. Therefore, stormwater runoff loads and concentrations of 10 constituents (total suspended solids, dissolved organic carbon, PO4-P, dissolved total phosphorus, total phosphorus, NH4-N, NO2-N, NO3-N, dissolved total nitrogen, and total nitrogen) for 72 events across five regions (Aichi, Kochi, Mie, Nagano, and Tokyo) were characterised. Most loads were significantly and positively correlated with stormwater variables (total event rainfall, event duration, and rainfall intensity), but most discharge-weighted event concentrations (DWECs) showed negative correlations with rainfall intensity. Mean water quality concentration during baseflow was correlated significantly with storm concentrations (r = 0.41-0.77). Although all pollutant load equations showed high coefficients of determination (R-2= 0.55-0.80), no models predicted well pollutant concentrations, except those for the three N constituents (R-2=0.59-0.67). Linear regressions to estimate stormwater concentrations and loads were greatly improved by regional grouping. The lower prediction capability of the concentration models for Mie, compared with the other four regions, indicated that other watershed or storm characteristics should be included in the prediction models. Significant differences among regions were found more frequently in concentrations than in loads for all constituents. Since baseflow conditions implied available pollutant sources for stormwater, the similar spatial characteristics of pollutant concentrations between baseflow and stormflow conditions were an important control for stormwater quality. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2007.09.045

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

There is a growing opinion that poorly managed plantation forests in Japan are contributing to increased storm runoff and erosion. Here we present evidence to the contrary from runoff plots at two scales (hillslope and 0.5 x 2 m plots) for several forest conditions in the Mie and Nariki catchments. Runoff coefficients from small plots in untended hinoki forests were variable but typically higher than from better managed or deciduous forests during small storms at Nariki; at Mie, runoff during small events was highly variable from all small plots but runoff coefficients were similar for hinoki plots with and without understory vegetation, while the deciduous plot had lower runoff coefficients. Storm runoff was less at the hillslope scale than the plot scale in Mie; these results were more evident at sites with better ground cover. During the largest storms at both sites, differences in runoff due to forest condition were not evident regardless of scale. Dynamic soil moisture tension measurements at Nariki indicated that during a large storm, flow in the upper organic-rich and root-permeated soil horizons was 3.2 times higher than measured overland runoff from a small hinoki plot with poor ground cover and 8.3 times higher than runoff from a deciduous forest plot. On the basis of field observations during storms, at least a portion of the monitored 'Hortonian overland flow' was actually occurring in this near-surface 'biomat'. Therefore our field measurements in both small and large plots potentially included biomat flow in addition to short-lived Hortonian runoff. Because overland flow decreased with increasing scale, rill erosion did not occur on hillslopes. Additionally, runoff coefficients were not significantly different among cover conditions during large storms; thus, the 'degraded' forest conditions appear not to greatly enhance peak flows or erosion potential at larger scales, especially when biomat flow is significant. Copyright (C) 2007 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.6876

Web of Science

DOI： 10.1007/s10310-007-0017-9

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Recent studies have suggested that soil water repellency can be one of the important factors affecting hydrological processes on headwater catchments. In Japan, water repellency is known to occur under Japanese cypress (Chamaecyparis obtusa) forests, a typical plantation type in Japan, however, previous studies have not evaluated the severity of water repellency and its effects on surface runoff generation. To quantify water repellency and its effects, this study combined the critical surface tension (CST) test with a new spraying experiment in which the infiltration rates of water and ethanol solutions sprayed over 0.09-m(2) plots were compared. Long-term intensive hydrological observations of surface runoff from 2-m(2) plots, soil water potential, and soil water content were conducted concurrently.
The spraying experiment revealed that strong water repellency in surface soils, as quantified by the CST test, caused Hortonian overland flow despite the high conductivity measured under saturated hydrophilic conditions. Generally, the surface runoff coefficient for a storm event was negatively correlated with initial soil moisture conditions. However, during a period of successive storm events separated by short intervals, the coefficient decreased gradually even when the initial moisture conditions were similar. indicating a weakening of water repellency by repeated wetting. On the other hand, a drying period r with long inter-rainfall intervals and increasing air temperature was associated with increases in the surface runoff coefficient. These results suggest that the water repellency and the resultant surface runoff depended on the history of rainfall at the site. Relationships between soil water potential and soil water content indicate that changes in the soil water repellency and consequently surface runoff coefficient could occur during a single storm event. Copyright (c) 2007 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.6749

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC AMER FORESTERS  

We focus on headwater streams originating in the mountainous terrain of northern temperate rain forests. These streams rapidly descend from gradients greater than 20% to less than 5% in U-shaped glacial valleys. We use a set of studies on headwater streams in southeast Alaska to define headwater stream catchments, link physical and biological processes, and describe their significance within watersheds. We separate headwater stream systems into four units that have distinct hydrologic and geomorphic processes that link terrestrial processes to aquatic systems. Headwater streams collect, process, and transport material downstream. Physical and biological processes in headwater streams are complex and closely tied to terrestrial processes. Steps and step pools formed by large wood are keystone structures that link physical processes to biological processes and increase channel complexity. Large and coarse wood debris dams form in-channel step structures and act as valves that regulate the downstream flow of material. A large amount of inorganic and organic sediment is stored in step structures, which may be biological hotspots in headwater streams. Step pools formed by large woody debris are critical habitat for Dolly Varden (Salvelinus malma), juvenile coho salmon (Oncorhynchus kisutch), steelhead (O. mykiss), and cutthroat trout (O. clarkii) in reaches with gradients from less than 4% to those greater than 10%. Landslides and debris flows are the dominant channel-altering processes in headwater streams and remove the step profile. Management activities that increase the number and frequency of channel disturbance events in headwater streams can have important and long-term consequences throughout a watershed.

Web of Science

Language：Japanese  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

[ 1] A 6-year study documented the effects of clear-cut harvesting with and without riparian buffers ( 10 m and 30 m wide) on headwater stream temperature in coastal British Columbia. The experiment involved a replicated paired catchment design. Pretreatment calibration relations between the treatment and control streams were fitted using time series of daily minimum, mean, and maximum temperatures. Generalized least squares (GLS) regression was used to account for autocorrelation in the residuals. While water temperature in streams with 10 and 30 m buffers did not exhibit marked warming, daily maximum temperature in summer increased by up to 2 degrees - 8 degrees C in the streams with no buffer. The effectiveness of the buffers may have been maximized by the north-south orientation of the streams, which meant that the streams would be well shaded from late morning to early afternoon by the overhead canopy, even under the 10 m buffer. The variation in response for the no-buffer treatments is consistent with the differences in channel morphology that influence their exposure to solar radiation and their depth. Relations between treatment effect and daily maximum air temperature suggested that recovery toward preharvest temperature conditions was occurring, with rates appearing to vary with stream and by season.

DOI： 10.1029/2005WR004162

Web of Science

Language：Japanese   Publisher：THE JAPANESE FORESTRY SOCIETY  

DOI： 10.11519/jjsk.47.0_10

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS  

Factors (riparian stand condition, management regimes, and channel properties) affecting distributions of wood, detritus (leaves and branches), and sediment were examined in headwater streams draining young-growth red alder (Alnus rubra Bong.) - conifer riparian forests (&lt; 40 years old) in southeast Alaska. More riparian red alder were found along streams affected by both timber harvesting and mass movement than in streams affected by timber harvesting alone. Young-growth stands produced little large wood material (diameter &gt;= 10 cm) and had little effect on altering the size distribution of functional large wood in channels, although more alder wood pieces were found in streams with greater numbers of riparian alder trees. Legacy wood pieces (&gt; 40 years old) remained in channels and provided sites for sediment and organic matter storage. Despite various alder-conifer mixtures and past harvesting effects, the abundance of large wood, fine wood, and detritus accumulations significantly decreased with increasing channel bank-full width ( 0.5-3.5 m) along relatively short channel distances (up to 700 m). Changes in wood, detritus, and sediment accumulations together with changes in riparian stand characteristics create spatial and temporal variability of in-channel conditions in headwater systems. A component of alder within young-growth riparian forests may benefit both wood production and biological recovery in disturbed headwater stream channels.

DOI： 10.1139/X05-272

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The amount of sediment, wood, and detritus (leaves and small branches) accumulations were examined in four headwater tributaries subjected to different treatments (unlogged, logged with riparian buffer, and logged with no buffer) 16 and 40 months after timber harvesting in the Bukit Tarek Experimental Watershed, Peninsular Malaysia. Sediment transport from hillslope logging roads and skid trails resulted in large sediment storage in the stream channels. Riparian reserves appear to mitigate logging impacts to streams; however, more sediment was found in a tributary channel with a 20-m buffer than an unlogged channel because some of the nearby roads and skid trails were connected to the stream. Sediment storage in channels declined within 40 months after logging in catchments with and without riparian buffers. Vegetation recovery on skid trails and logging roads reduced both sediment supply and delivery. The volume of large wood was 1.5 to 2-times greater in the stream without riparian reserves than the stream of an unlogged catchment or in a stream with a riparian buffer. No consistent change in detritus accumulations was found among streams in 2001 and 2003, although more detritus was present in 2003 in all streams. The effects of logging and the effectiveness of riparian buffers appear to depend on the hydrologic connections between hillslopes and headwater streams. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.foreco.2005.12.016

Web of Science

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

This study examined the thermal regime of a headwater stream within a clear-cut. The stream had a complex morphology dominated by step-pool features, many formed by sediment accumulation upstream of woody debris. Maximum daily temperatures increased up to 5 degrees C after logging, and were positively associated with maximum daily air temperature and negatively with discharge. Maximum daily temperatures generally increased with downstream distance through the cut block, but decreased with distance in two segments over distances of tens of metres, where the topography indicated relatively concentrated lateral inflow. Localized cool areas within a step-pool unit were associated with zones of concentrated upwelling. Bed temperatures tended to be higher and have greater ranges in areas of downwelling flow into the bed. Heat budget estimates were made using meteorological measurements over the water surface and a model of net radiation using canopy characteristics derived from fisheye photography. Heat exchange driven by hyporheic flow through the channel step was a cooling effect during daytime, with a magnitude up to approximately 25% that of net radiation during the period of maximum daytime warming. Heat budget calculations in these headwater streams are complicated by the heterogeneity of incident solar radiation and channel geometry, as well as uncertainty in estimating heat and water exchanges between the stream and the subsurface via hyporheic exchange and heat conduction. Copyright (c) 2005 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.5733

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Hydrogemorphic linkages related to sediment transport in headwater streams following basin wide clear-cut logging on Prince of Wales Island, southeast Alaska, were investigated. Landslides and debris flows transported sediment and woody debris in headwater tributaries in 1961, 1979, and 1993. Widespread landsliding in 1961 and 1993 was triggered by rainstonns with recurrence intervals (24 h precipitation) of 7.0 years and 4.2 years respectively. Occurrence. distribution, and downstream effects of these mass movements were controlled by landform characteristics such as channel gradient and valley configuration. Landslides and channelized debris flows created exposed bedrock reaches, log jams, fans, and abandoned channels. The terminus of the deposits did not enter main channels because debris flows spread and thinned on the unconfined bottom of the U-shaped glaciated valley. Chronic sediment input to channels included surface erosion of exposed till (rain splash, sheet erosion, and freeze-thaw action) and bank failures. Bedload sediment transport in a channel impacted by 1993 landslides and debris flows was two to ten times greater and relatively finer compared with bedload transport in a young alder riparian channel that had last experienced a landslide and debris flow in 1961. Sediment transport and storage were influenced by regeneration of riparian vegetation, storage behind recruited woody debris, development of a streambed armour layer, and the decoupling of hillslopes and channels. Both spatial and temporal variations of sediment movement and riparian condition are important factors in understanding material transport within headwaters and through channel networks. Copyright (C) 2004 John Wiley Sons, Ltd.

DOI： 10.1002/hyp.1366

Web of Science

DOI： 10.1029/2003WR002440

Web of Science

DOI： 10.1016/S0169-555X(02)00338-0

Web of Science

DOI： 10.1641/0006-3568(2002)052[0905:UPADLO]2.0.CO;2

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1139/cjfr-31-8-1386

Total pages：634   Responsible for pages：399－413   Language：English Book type：Scholarly book

DOI： https://doi.org/10.1007/978-981-16-9554-4

Total pages：197   Responsible for pages：169-184   Language：English Book type：Scholarly book

DOI： https://doi.org/10.1007/978-981-16-3671-4

Total pages：504   Responsible for pages：133–158   Language：Japanese Book type：Scholarly book

Total pages：694   Language：Japanese Book type：Dictionary, encyclopedia

Total pages：372   Responsible for pages：95–120   Language：Japanese Book type：Scholarly book

Total pages：248  

Responsible for pages：161-247   Language：English Book type：Scholarly book

Responsible for pages：73-85   Language：Japanese Book type：Scholarly book

Responsible for pages：55-84   Language：English Book type：Scholarly book

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