Spatiotemporal patterns in differences between the 137Cs concentrations of forest and stream litters: effect of leaching.

Forest-stream ecotones possess prominent detritus-based food webs, and 137Cs-contaminated litter can influence the contamination levels of animals inhabiting such ecosystems. The effects of leaching on contaminated litter induce greater absolute differences between the 137Cs concentrations of forest and stream litter in more contaminated sites. Because 137Cs concentrations in litter can be attenuated temporally, spatiotemporal patterns in the differences in 137Cs concentrations between forest and stream litter may vary depending on both the amount of 137Cs deposition and the passage of time. To test this hypothesis, we sampled coniferous needle and broad-leaved deciduous litter in forests and streams at seven forested headwater sites affected by the Fukushima nuclear accident 3.24 and 11.24 years after the accident. We found that 137Cs concentrations in the two litter types were one order of magnitude lower 11.24 years after the accident than 3.24 years afterwards. The absolute difference in 137Cs activity concentrations of litter between forest and stream ecosystems was higher at more contaminated sites both 3.24 and 11.24 years after the accident. The spatiotemporal changes in litter contamination provide insight into 137Cs dynamics and complex transfer in the detritus-based food webs of forest-stream ecotones.

Stomatal ozone uptake of a Quercus serrata stand based on sap flow measurements with calibrated thermal dissipation sensors.

The amount of ozone absorbed by the tree leaves is a critical factor determining the ozone effects on forest trees. Stomatal ozone uptake of a forest canopy can be estimated from the ozone concentration and canopy conductance (gc) determined by the sap-flow-based method. This method measures sap flow as a metric of crown transpiration and then derives gc. The thermal dissipation method (TDM) has been used to measure sap flow in most studies adopting this approach. However, recent studies have indicated that TDM may underestimate sap flow, especially in ring-porous tree species. In the present study, the accumulated stomatal ozone uptake (AFST) of a stand of Quercus serrata, a typical ring-porous tree species in Japan, was estimated by measuring sap flow using species-specific calibrated TDM sensors. Laboratory calibration of the TDM sensors revealed that the parameters (α and ß) in an equation converting outputs from the sensors (K) to sap flux density (Fd) were substantially larger for Q. serrata than those originally proposed by Granier (1987). The Fd measured in the Q. serrata stand using calibrated TDM sensors were significantly larger than those obtained using non-calibrated sensors. The diurnal average of gc and daytime AFST (10.4 mm s-1 and 10.96 mmol O3 m-2 month-1) of the Q. serrata stand estimated by using calibrated TDM sensors in August 2020 were similar to those of forests dominated by Quercus species estimated by micrometeorological measurements in previous studies. In contrast, the gc and daytime AFST of the Q. serrata stand estimated by non-calibrated TDM sensors were remarkably lower than those estimated by micrometeorological measurements in previous studies, indicating severe underestimation. Therefore, it is strongly recommended that sap flow sensors are species-specifically calibrated when estimating the canopy conductance and ozone uptake of forests dominated by ring-porous trees based on sap flow measurements using TDM.

Ecological resilience of physical plant-soil feedback to chronic deer herbivory: Slow, partial, but functional recovery.

Ecological resilience to ungulate overbrowsing is an important issue in forest ecosystems. After chronic herbivory, the recovery rate of understory vegetation and its related functions can be slow even with decreasing grazing intensity; thus, detecting elasticity during alternative successional trajectories is fundamental to understanding state perturbations. In this context, we focused on physical plant-soil feedback (functional interactions between plant growth and soil physical conditions) and evaluated elasticity and recovery processes according to deer density. The effects of 40 years of chronic herbivory by sika deer (average density 14.7 individuals km-2 ) on the recovery of understory plant communities and associated changes in soil physical properties in headwater catchments were assessed. Using 8 years of catchment-wide exclusion (fenced) and reduction (only culled; average 4.3 individuals km-2 ) treatments, plot sampling was conducted in 2010 (before treatment) and 2018 (after treatment). The recovery of vegetation and soil physical properties were evaluated, and functional plant-soil relationships and spatial variability were assessed to detect recovery processes during alternative successional trajectory. Woody species increased only under the exclusion treatment and the average soil bulk density was lower than that under reduction treatments. Soil bulk density was negatively correlated with root biomass in the fenced catchment, and root biomass was positively associated with woody species richness. Reduced soil bulk density (~0.5 g cm-3 ) was observed with greater root biomass and woody species richness on upper hillslopes in the deer-excluded catchment where plant coverage was minimal. Successional failure under the reduction treatment suggested slow recovery with a depressed threshold according to deer density, indicating a clockwise hysteretic response to deer density. Unlike plant coverage during the earlier period of overbrowsing, woody species root development led the recovery of functional physical plant-soil feedback; however, this was probably limited by the higher soil erosion rate in riparian areas and an under-developed herb layer. Our results highlight an alternative recovery trajectory of physical plant-soil feedback driven by an alternative plant element (woody roots) to recovery trajectory with increasing plant cover. However, riparian erosion and herb layer would still suppress recovery. Therefore, recovery might be slower at the landscape scale.

Understory biomass measurement in a dense plantation forest based on drone-SfM data by a manual low-flying drone under the canopy.

Forest is an important part of the environmental system, which has a significant impact on soil hydrological characteristics and forest landscapes, because these processes are influenced by forest management and understory vegetation. Quantitative understory vegetation biomass (UVB) measurement and estimation are vital processes in forest ecology and environmental management. However, these estimations are difficult to make on a large scale especially dense planted forest. Here, we applied catchment-scale Structure from Motion and a manually operated ultralow-flying drone under the canopy of a dense planted (2000 stems/ha) Japanese cedar/cypress plantation forest to reconstruct the understory. An understory drone survey was performed over a 1.1-ha sub-catchment to generate a canopy height model based on dense point cloud data. A biomass survey of three 16-m2 harvesting plots was conducted to compute understory vegetation volume data based on point clouds. Combined with harvested biomass data in the field, quantitative models were developed between the understory vegetation volume and biomass. Subsequently, the models were used to map spatial understory vegetation biomass distribution in the sub-catchments. Aerial photos taken by the ultralow-flying drones under the canopy yielded a high-resolution catchment-scale understory with point cloud density >10/cm2. Strong cubic model coefficients of determination (R2 = 0.75) predicted the understory vegetation biomass based on the canopy height model. The mean understory vegetation biomass was 0.82 kg/m2 and dominated by low ferns. In the present study, we successfully reconstructed the multilayered forest structure and generated understory vegetation biomass distribution models. This results also will be essential to evaluate the erosion and evapotranspiration in dense plantation forests and future environmental management.

Untangling radiocesium dynamics of forest-stream ecosystems: A review of Fukushima studies in the decade after the accident.

Forest-stream ecosystems are widespread and biodiverse terrestrial landscapes with physical and social connections to downstream human activities. After radiocesium is introduced into these ecosystems, various material flows cause its accumulation or dispersal. We review studies conducted in the decade after the Fukushima nuclear accident to clarify the mechanisms of radiocesium transfer within ecosystems and to downstream areas through biological, hydrological, and geomorphological processes. After its introduction, radiocesium is heavily deposited in the organic soil layer, leading to persistent circulation due to biological activities in soils. Some radiocesium in soils, litter, and organisms is transported to stream ecosystems, forming contamination spots in depositional habitats. While reservoir dams function as effective traps, radiocesium leaching from sediments is a continual phenomenon causing re-contamination downstream. Integration of data regarding radiocesium dynamics and contamination sites, as proposed here, is essential for contamination management in societies depending on nuclear power to address the climate crisis.

Road Dust as a Significant Radiocesium Transporter from Land to River.

This study made it clear that road dust plays an important role for Cs-137 dynamics emitted by the Fukushima Daiichi nuclear power plant accident. It was proved from the Cs-137 and heavy metals determination in road dust, drainage gutter sediment beside pavement, and riverbed sediment around the inflow point of the gutter. Road dust and drainage gutter sediment contained significantly higher concentrations of Cs-137 and Cr, Ni, Cu, Zn, Mo, Cd, Sn, Sb, and Pb than riverbed sediment. These heavy metals are typically enriched in road dust in general and originate in anthropogenic sources. Concentrations of Cs-137 and the heavy metals were higher in riverbed sediments at the inflow point of drainage than in non-inflow points. Drainage gutter sediments exhibited Cs-137 and heavy metal accumulation at the downmost of the gutter, which is the inflow point into the river. Accordingly, distribution of Cs-137 and the heavy metals concentrations were consistent with each other. Moreover, the concentrations of Cs-137 and heavy metals were correlated positively and significantly, with different proportions between sampling sites but similar between sample type and survey date. This indicates that the discharge of Cs-137 and heavy metals is characteristic of the features of the locations, such as Cs-137 and heavy metals concentrations, (micro-) topography, structure of the road and gutter, pavement area, traffic density, and so on. We conclude that road dust is a major medium of Cs-137 transport from land into aquatic ecosystems.

Assessing spatially distributed infiltration capacity to evaluate storm runoff in forested catchments: Implications for hydrological connectivity.

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 (headwaters and zero-order basins). Simulations using spatially distributed infiltration capacities showed more Hortonian overland flow compared to using uniform infiltration because of areas with low infiltration located along channels. On the other hand, no differences in runoff were apparent between spatially-distributed and uniform infiltration scenarios in larger catchments. Our study also indicates that differences in contributions of subsurface and groundwater flow at the catchment scale need to be examined based on observations and simulations in nested catchments. Our findings suggest that including detailed patterns of vegetation ground cover are important for understanding hydrogeomorphic connectivity within catchments.

Ecosystem changes following the 2016 Kumamoto earthquakes in Japan: Future perspectives.

Major earthquakes cause widespread environmental and socioeconomic disruptions that persist for decades. Extensive ground disturbances that occurred during the shallow-focus Kumamoto earthquakes will affect future sustainability of ecosystem services west of Aso volcano. Numbers of earthquake-initiated landslides per unit area were higher in grasslands than forests, likely owing to greater root reinforcement of trees, and mostly initiated on ridgelines and/or convex/planar hillslopes. Most landslides traveled short distances and did not initially evolve into debris flows; resultant sediments and wood accumulating in headwater channels can be mobilized into debris flows during future storms. Fissures along ridgelines may promote water ingress and induce future landslides and debris flows that affect residents downstream. Native grasses are at risk because of habitat fragmentation caused by ground disturbances, extensive damage to rural roads, and abandonment of traditional pasture management practices. Sustainable management of affected areas needs to consider future risk of cascading hazards and long-term socioeconomic impacts.

Developing a food web-based transfer factor of radiocesium for fish, whitespotted char (Salvelinus leucomaenis) in headwater streams.

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 137Cs 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. 137Cs 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 TTF by single prey-char showed high variability with both dilution and accumulation. TFweb is applicable for 137Cs transfer in predator-prey systems with complex food web structures of stream-riparian ecosystems.

Preventing pancreatic fistula after distal pancreatectomy: An invagination method.

Following an increase in the use of the GIA stapler for treating a pancreatic stump, more techniques to prevent postoperative pancreatic juice leakage have been required. We describe one successful case using our new technique of invaginating the cut end of the pancreas into the stomach to prevent a pancreatic fistula (PF) from occurring. A 50-year-old woman with pancreatic cancer in the tail of the pancreas underwent distal pancreatectomy, causing a grade A PF. We resected the distal pancreas without additional reinforcement to invaginate the stump into the gastric posterior wall with single layer anastomosis using a 3-0 absorbable suture. The drain tubes were removed on the third postoperative day. Although a grade A PF was noted, the patient was discharged on foot on the eleventh postoperative day. Our technique may be a suitable method for patients with a pancreatic body and tail tumor.

Fallout volume and litter type affect 137Cs concentration difference in litter between forest and stream environments.

It is important to understand the changes in the 137Cs concentration in litter through leaching when considering that 137Cs is transferred from basal food resources to animals in forested streams. We found that the difference of 137Cs activity concentration in litter between forest and stream was associated with both litter type and 137Cs fallout volume around Fukushima, Japan. The 137Cs 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, 137Cs activity concentrations in forest litter were greater with respect to the 137Cs fallout volume. The 137Cs activity concentrations in stream litter were much lower than those in forest litter when those in forest litter were higher. The 137Cs leaching patterns indicated that the differences in 137Cs 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 137Cs concentration gradient reflects to possible 137Cs transfer from lower to higher trophic animals. Our findings will improve our understanding of the spatial heterogeneity and variability of 137Cs concentrations in animals resident to the contaminated landscape.

Different cesium-137 transfers to forest and stream ecosystems.

Understanding the mechanisms of (137)Cs movement across different ecosystems is crucial for projecting the environmental impact and management of nuclear contamination events. Here, we report differential movement of (137)Cs 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 (137)Cs in stream litter was significantly lower than in forest litter, the result of (137)Cs leaching from litter in stream water. The difference in (137)Cs concentrations between the two types of litter was reflected in the (137)Cs concentrations in the animal community. While the importance of (137)Cs 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 (137)Cs through terrestrial and aquatic ecosystems, and that (137)Cs 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.

Radiocesium leaching from contaminated litter in forest streams.

In Japanese forests suffering from the Fukushima Daiichi Nuclear Power Plant accident, litter fall provides a large amount of radiocesium from forests to streams. Submerged litter is processed to become a vital food resource for various stream organisms through initial leaching and subsequent decomposition. Although leaching from litter can detach radiocesium similarly to potassium, radiocesium leaching and its migration are poorly understood. We examined both radiocesium and potassium leaching to the water column and radiocesium allocation to minerals (glass beads, silica sand, and vermiculite) in the laboratory using soaked litter with and without minerals on a water column. The mineral types did not affect radiocesium leaching from litter, but soaking in water for 1, 7, and 30 days decreased the radiocesium concentration in litter by ×0.71, ×0.66, and ×0.56, respectively. Meanwhile, the 1-, 7-, and 30-day experiments decreased potassium concentration in litter by ×0.17, ×0.11, and ×0.09, respectively. Leached radiocesium remained in a dissolved form when there was no mineral phases present in the water, whereas there was sorption onto the minerals when they were present. In particular, vermiculite adsorbed radiocesium by two to three orders of magnitude more effectively than the other minerals. Because radiocesium forms (such as that dissolved or adsorbed to organic matter or minerals) can further mobilize to ecosystems, our findings will increase our understanding regarding the dynamics of radiocesium in stream ecosystems.

Flow-preserved coil embolization using a side-holed indwelling catheter for common hepatic artery pseudoaneurysm: report of three cases.

We report three cases of hepatic artery pseudoaneurysm, which were all treated successfully using a combination of coil embolization and a side-holed 5F indwelling catheter for maintaining minimal hepatic artery blood flow with exclusion of the pseudoaneurysm. The tip of an infusion catheter was placed in the right hepatic artery and a side hole was positioned at the celiac axis. Coil embolization was then performed from the proper to the common hepatic artery using detachable coils. Hemostasis was achieved in all patients, with a final angiogram showing the hepatic arteries through the indwelling catheter. One major hepatic infarction and one focal liver abscess caused by reflux cholangitis manifested on postoperative days (PODs) 11 and 87, respectively. All patients survived and the indwelling catheter was removed on POD 136­382 without complication.

Vertical distribution of radiocesium in coniferous forest soil after the Fukushima nuclear power plant accident.

This study deals with the description of the vertical distribution of radiocaesium ((137)Cs and (134)Cs) 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 (137)Cs at the time of the soil sampling. Including the pre-Fukushima (137)Cs, 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 (137)Cs 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 (137)Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived (137)Cs was somewhat rapid.

The role of litterfall in transferring Fukushima-derived radiocesium to a coniferous forest floor.

The deposition of Fukushima-derived radiocesium via falling litter in a coniferous forest 180 km downwind immediately following the nuclear power plant accident was investigated. The litterfall contribution to the transfer of radiocesium from the forest canopy to the forest floor was determined, and this pathway was compared with hydrological pathways. The results demonstrated that during the observation period, a total of approximately 5.5 kBq m(-2) of Fukushima-derived radiocesium was deposited on the forest floor through throughfall (53%), stemflow (2.3%) and litterfall (45%) routes. The data revealed that the contributions of hydrological pathways became less important as time passed. However, the litterfall route, which transferred approximately 31% (2.5±0.6 kBq m(-2)) of the local fallout within the observation period, continued depositing radiocesium onto the forest floor.

Soil removal as a decontamination practice and radiocesium accumulation in tadpoles in rice paddies at Fukushima.

We investigated the biological accumulation of radiocesium in tadpoles [Rana (Pelophylax) porosa porosa] in rice paddies with and without decontamination practice at Fukushima. Radiocesium was accumulated in surface part of soils both in the control and decontaminated paddies one year after decontamination. Mean (134)Cs and (137)Cs concentrations in tadpoles in the control and decontaminated paddies were 3000 and 4500, and 600 and 890 Bq/kg dry weight, respectively. Radiocesium concentrations in surface soil (0-5 cm depth) and tadpoles in the decontaminated paddy were five times smaller than in the control paddy. These results suggest that decontamination practice can reduce radiocesium concentrations in both soil and tadpoles. However, at the decontaminated paddy, radiocesium concentrations in surface soils became 3.8 times greater one year after decontamination, which indicates that monitoring the subsequent movement of radiocesium in rice paddies and surrounding areas is essential for examining contamination propagation.

Human factors and tidal influences on water quality of an urban river in Can Tho, a major city of the Mekong Delta, Vietnam.

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.

The delta-shaped anastomosis in laparoscopic distal gastrectomy: analysis of the initial 100 consecutive procedures of intracorporeal gastroduodenostomy.

BACKGROUND: We developed a new method of intracorporeal gastroduodenostomy, the delta-shaped anastomosis, in which only endoscopic linear staplers are used. In this report, we present the short- and long-term outcomes of our initial experience with this procedure. METHODS: We retrospectively analyzed 100 consecutive gastric cancer patients who underwent the delta-shaped anastomosis procedure from May 2001 to November 2006. All of them underwent a laparoscopic distal gastrectomy with regional lymph node dissection. Quality of life was assessed with a questionnaire 6 months or more postoperatively, and the gastric remnant was evaluated by endoscopy one year following the surgery. RESULTS: Eight surgeons successfully performed the delta-shaped anastomosis without any conversion to laparotomy. The learning curve for all surgeons was steep and the mean time for the anastomosis was 13 min. Only one patient developed an anastomotic leak, and the leak was minor. Sixty-five patients tolerated a 1500 kcal/day soft diet at the time of discharge. The mean follow-up period was 54.9 months. Only one patient reported symptoms indicative of dumping. Two patients were diagnosed with reflux esophagitis, and approximately 70% had evidence of bile reflux, but severe gastritis of the remnant stomach on endoscopy was uncommon. CONCLUSIONS: The wide lumen of the delta-shaped anastomosis led to early, adequate postoperative oral intake without a significant incidence of dumping syndrome. The delta-shaped anastomosis is safe and simple and provides satisfactory postoperative results.

Esophageal metastasis of breast carcinoma.

Esophageal metastasis from primary breast cancer is an unusual manifestation. We recently treated a patient with dysphagia, whose breast cancer had been treated in the distant past. A 70-year-old woman had been followed regularly in our outpatient clinic for 14 years after her primary breast cancer treatment, with no apparent tumor recurrence. After 2 years absence, she consulted our clinic with progressive dysphagia. Contrast esophagography and endoscopic examination with ultrasonography revealed a protruding submucosal tumor that was histopathologically diagnosed as esophageal metastasis of breast cancer. Radiation therapy involving a total of 60 Gy in combination with aromatase inhibitor was given. The patient's dysphagia was greatly relieved, concomitant with marked improvement of the stenotic lesion on imaging. Since treatment for recurrent breast cancer is generally palliative, systemic (chemo- and/or endocrine-) therapy in combination with radiotherapy is the first-line option for esophageal metastasis of breast cancer.