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Sugiura Y.,Nagoya University | Kanasashi T.,Nagoya University | Ogata Y.,Nagoya University | Ozawa H.,Fukushima Prefectural Forestry Research Center | Takenaka C.,Nagoya University
Journal of Environmental Radioactivity | Year: 2016

Through the assessments of radioactive contamination after the Fukushima Dai-ichi Nuclear Power Plant (F1NPP) accident, it has been reported that some sprouts of Chengiopanax sciadophylloides (Franch. et Sav.) at the site contained radiocesium (134,137Cs) at higher concentrations than the other plants. To assess the phytoremediation properties of C. sciadophylloides for 137Cs decontamination, we aimed to quantify the 137Cs accumulation in C. sciadophylloides. We measured the 137Cs concentrations in various organs of C. sciadophylloides collected from the forest in the town of Kawamata, Fukushima prefecture, together with the concentrations of other elements [potassium (K), rubidium, 133Cs, calcium, strontium, and manganese] present. In addition, we compared the foliar concentrations of these elements in C. sciadophylloides with those in four different deciduous tree species. The mean of foliar 137Cs concentration in C. sciadophylloides was 28.1 kBq kg-1 DW, one order of magnitude higher than that found in the other species. The 137Cs concentrations were in the order of leaves > bark > wood. The wood of the treetop, leaf scars, and roots contained higher amounts of 137Cs than that of the trunk. From the distribution of 137Cs in C. sciadophylloides, we confirmed that 137Cs tends to accumulate in the young growing parts. The difference in the distribution of 137Cs and 133Cs indicated that surface uptake of 137Cs occurs. A significant correlation between K and 137Cs concentrations in each organ was found, which suggested that 137Cs in the plant body is transferred through the same pathway as K. On the other hand, there was no correlation between foliar K and 137Cs concentrations, implying that the uptake ratio of K to 137Cs was different for each individual. To determine the factors driving specific 137Cs accumulation and/or the variability of the ratio between K and 137Cs, the distribution of 137Cs and the root in soil, the difference of the expression of transporter, and the existence of mycorrhizal fungi should be considered. However, further research is required. © 2015 Elsevier Ltd.

Ozawa H.,Fukushima Prefectural Forestry Research Center | Watanabe A.,Japan Forestry and Forest Products Research Institute | Uchiyama K.,Japan Forestry and Forest Products Research Institute | Saito Y.,University of Tokyo | Ide Y.,University of Tokyo
Journal of Forest Research | Year: 2012

We attempted to evaluate the genetic diversity of long-distance transported pollen flowing over fragmented Pinus densiflora populations during a mating season. A P. densiflora clonal seed orchard, which was located in a rural area where many fragmented populations exist, was selected for pollen capture. Immigrant pollen captured by three clones having different flowering times was regarded as the pollen flowing over fragmented populations during a mating season. The genetic diversity (He) values of the immigrant pollen captured by the three clones were high (He > 0.894). The correlation of paternity (rp) values of the seeds having immigrant parent generated from the three clones were calculated to be negative. From these parameters, the pollen cloud is considered to have maintained high genetic diversity during the mating season. The genetic composition of the pollen cloud showed slight variation. The pollen captured by different trees (i. e., clonal ramets of the three clones) was significantly different based on analysis of molecular variance. Especially, the pollen pools captured by trees planted in the western side of the orchard were significantly different from the gene pool of the surrounding populations. Factors affecting this differentiation could be that the donors of the pollen transported to the orchard vary with time, as well as nonuniform dispersal of the pollen. From these results, the pollen flowing over fragmented P. densiflora populations is considered to have high genetic diversity, compensating to some extent for fragmentation. © 2011 The Japanese Forest Society and Springer.

Ozawa H.,Fukushima Prefectural Forestry Research Center | Watanabe A.,Kyushu University | Uchiyama K.,Japan Forestry and Forest Products Research Institute | Saito Y.,University of Tokyo | Ide Y.,University of Tokyo
Journal of Heredity | Year: 2013

Long-distance dispersal (LDD) of seeds has a critical impact on species survival in patchy landscapes. However, relative to pollen dispersal, empirical data on how seed LDD affects genetic diversity in fragmented populations have been poorly reported. Thus, we attempted to indirectly evaluate the influence of seed LDD by estimating maternal and paternal inbreeding in the seed rain of fragmented 8 Pinus densiflora populations. In total, the sample size was 458 seeds and 306 adult trees. Inbreeding was estimated by common parentage analysis to evaluate gene flow within populations and by sibship reconstruction analysis to estimate gene flow within and among populations. In the parentage analysis, the observed probability that sampled seeds had the same parents within populations was significantly larger than the expected probability in many populations. This result suggested that gene dispersal was limited to within populations. In the sibship reconstruction, many donors both within and among populations appeared to contribute to sampled seeds. Significant differences in sibling ratios were not detected between paternity and maternity. These results suggested that seed-mediated gene flow and pollen-mediated gene flow from outside population contributed some extent to high genetic diversity of the seed rain (HE > 0.854). We emphasize that pine seeds may have excellent potential for gene exchange within and among populations. © The American Genetic Association. 2013. All rights reserved.

Sugiura Y.,Nagoya University | Shibata M.,Nagoya University | Ogata Y.,Nagoya University | Ozawa H.,Fukushima Prefectural Forestry Research Center | And 2 more authors.
Journal of Environmental Radioactivity | Year: 2016

Radiocesium (137Cs) transfer to plants immediately after the Fukushima Dai-ichi Nuclear Power Plant accident was investigated by collecting newly emerged leaf and soil samples between May 2011 and November 2012 from 20 sites in the Fukushima prefecture. Radiocesium concentrations in leaf and soil samples were measured to calculate concentration ratios (CR). Woody plants exhibited high CR values because 137Cs deposited on stems and/or leaves were transferred to newly emerging tissues. The CR values in 2012 declined as compared to that in 2011. Exchangeable 137Cs rates in soil (extraction rate) samples were measured at five sites. These rates decreased at four sites in 2012 and depended on environmental conditions and soil type. Both CR values and extraction rates decreased in 2012. However, CR values reflected the changes in extraction rates and characteristics of each species. Amaranthaceae, Chenopodiaceae, and Polygonaceae, which had been identified as Cs accumulators, presented no clear 137Cs accumulation ability. In 2012, the perennial plant Houttuynia cordata and deciduous trees Chengiopanax sciadophylloides and Acer crataegifolium displayed high CR values, indicating that these species are 137Cs accumulators and may be considered as potential species for phytoremediation. © 2016 Elsevier Ltd.

Shinomiya Y.,Japan Forestry and Forest Products Research Institute | Tamai K.,Japan Forestry and Forest Products Research Institute | Kobayashi M.,Japan Forestry and Forest Products Research Institute | Ohnuki Y.,Japan Forestry and Forest Products Research Institute | And 6 more authors.
Soil Science and Plant Nutrition | Year: 2014

We investigated radioactive cesium (Cs) export in stream water during a typhoon flood event (No. 1204, Guchol) in a small forested headwater catchment (1.2 ha), which was contaminated by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) disaster. The experimental watershed is covered with hardwood and conifer trees. Hourly stream water samples were collected by an automatic water sampler, and turbidity was measured every 10 min. Downstream transport of radioactive Cs was recorded through the typhoon, during which the total rainfall was 168 mm. Total cesium-134 (134Cs), cesium-137 (137Cs) and suspended solid (SS) concentrations and turbidity were elevated on the rising limb of the hydrograph. When maximum rainfall intensity, maximum runoff peak were observed, and maximum radioactive Cs and SS concentrations occurred. Total 134Cs and 137Cs concentrations were 1.5 and 2.4 Bq L−1, respectively, at peak flow. However, concentrations of radioactive Cs, SS and turbidity dropped sharply on the receding limb. After filtration (0.7 μm), the concentrations of 134Cs and 137Cs were either not detectable (ND) or below 0.09 Bq L−1. Concentrations of dissolved radioactive Cs in stream water were very low, and radioactive Cs was mainly discharged with suspended materials. Total 134Cs and 137Cs exports from the study watershed were 43 and 72 Bq m−2, respectively. These exports represented approximately 0.07% of the 134Cs and 137Cs fallout around the study site (180 kBq m−2). We therefore concluded that discharge of radioactive Cs from forested headwaters was negligible even though a typhoon flood event. © 2014 Japanese Society of Soil Science and Plant Nutrition.

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