Izuki ENDO

The long-term behaviour of radiocaesium (Cs-137) activity concentrations in forest ecosystems and their downstream impacts remain important issues in the deciduous broadleaf forests of Fukushima, Japan following the Fukushima Daiichi Nuclear Power Plant accident. To predict Cs-137 cycling and discharge in the forest ecosystem, it is important to understand the spatial dynamics of the Cs-137 inventory and transport along hillslopes. Therefore, we observed the spatial distribution of the Cs-137 inventory and Cs-137 transport via sediment and litter of a deciduous forest hillslope in Fukushima, Japan in 2016 and 2017 and examined how the spatial distribution of Cs-137 inventory was formed using a mass balance model. In 2017, the Cs-137 activity concentration was significantly greater in the downslope riparian area (455 kBq/m(2)) than in the upslope ridge area (179 kBq/m(2)). Annual Cs-137 transport within litter and sediment contributed <0.5% to the current Cs-137 inventory and cannot explain the current spatial variation of Cs-137 inventory on the hillslope. The mass balance model results showed that if the initial Cs-137 deposition was distributed uniformly in 2011, the spatial distribution of the hillslope Cs-137 inventory was influenced mainly by the movement of leaf litter with a high Cs-137 activity concentration.

Abstract The diverse socio-cultural conditions in Indonesia can make it difficult to develop sustainable micro-hydro power (MHP) generation in rural areas. However, the existing framework of sustainable development indicators to assess MHP sustainability does not include indicators for locations with traditional characteristics. This study aimed to develop indicators related to the specific cultural features for evaluating the sustainability of MHP generation. The identification of indicators was accomplished through field investigations and literature studies. Thirty-one experts in the Delphi method validated the indicators. The results revealed three indicators related to specific traditional characteristics and importance to the sustainability of MHP generation, i.e., electricity-supported cultural activities, customary rules of environmental protection, and directive of a traditional leader. These indicators can be elaborated with the existing framework and expected to increase sustainability assessment efforts for MHP generation in remote locations.

Litter usually drops to the ground, but some is retained within the canopy. Mass and CO2 efflux from retained litter may play a significant role in carbon cycling in tropical rainforests where emergent trees with complicated canopy structures are observed. This study aimed to show vertical variation in the mass and CO2 efflux (R-litter) of the retained litter and examined its contribution to carbon cycling in a Bornean tropical rainforest. The retained litter was collected from six 40 m tall columns with a radius of 1.6 m using an 85 m tall crane at six subplots. Dry mass and R-litter were measured in the laboratory. The mass of the retained litter from the sampling points ranged from 0.35 g to 187.0 g, and R-litter of the retained litter (42.4 +/- 43.4 mg CO2 kg(-1) h(-1)) was significantly lower than that of the soil surface litter (85.9 +/- 39.2 mg CO2 kg(-1)h(-1)) because of the lower water content in the retained litter. The mean mass of the retained litter measured from the ground to the canopy was 40.6 +/- 22.2 g m(-2). The greatest mass was observed at a height of 0-2 m. The ratio of the retained litter mass to the soil surface litter mass ranged from 1.0% to 11.5% with a mean of 5.2%, suggesting that litter retained within the canopy can contribute to carbon storage in this forest. On the other hand, R-litter did not differ with height, and the ratio of R-litter to aboveground autotrophic respiration was less than 1%. This study is the first to show that the litter retained within the canopy can sporadically be a moderate hot spot for C storage, but it is not a significant source of released CO2.

The sustainable development of micro-hydropower (MHP) plants is a challenge for rural electrification in developing countries, especially in Indonesia, which has diverse ethnic groups, cultures, and traditions in several isolated locations due to its complex terrain. The uniqueness of a social situation in a location can affect the sustainable electrification development. This study aimed to assess the sustainable development of MHP plants in the Kasepuhan Ciptagelar, which has unique traditions and cultural characteristics. The assessment was conducted using the sustainable development indicator (SDI) method, the Ilskog method, which can include social, economic, environmental, technical, and institutional dimensions. Data were collected through field investigations and qualitative dialogs to understand the culture and ways of thinking. The results of the Ilskog method analysis revealed that the environmental dimensions had the highest scores, whereas economic dimensions had the lowest scores, indicating that the cultural background of the Kasepuhan Ciptagelar impacted the SDI scores. This was attributable to the decision of Kasepuhan’s traditional leader, which strengthened the community commitment to renewable energy use. However, the cultural background adversely impacted monetary income to sustain MHP plants. This study proposed that community innovation and microcredit availability could improve productive activities, resulting in better economic conditions to sustain MHP plants.

<title>Abstract</title> <sec> <title>Background and Aims</title> Condensed tannin (CT) is an important compound in plant biological structural defence and for tolerance of herbivory and environmental stress. However, little is known of the role and location of CT within the fine roots of woody plants. To understand the role of CT in fine roots across diverse species of woody dicot, we evaluated the localization of CT that accumulated in root tissue, and examined its relationships with the stele and cortex tissue in cross-sections of roots in 20 tree species forming different microbial symbiotic groups (ectomycorrhiza and arbuscular mycorrhiza). </sec> <sec> <title>Methods</title> In a cool-temperate forest in Japan, cross-sections of sampled roots in different branching order classes, namely, first order, second to third order, fourth order, and higher than fourth order (higher order), were measured in terms of the length-based ratios of stele diameter and cortex thickness to root diameter. All root samples were then stained with ρ-dimethylaminocinnamaldehyde solution and we determined the ratio of localized CT accumulation area to the root cross-section area (CT ratio). </sec> <sec> <title>Key Results</title> Stele ratio tended to increase with increasing root order, whereas cortex ratio either remained unchanged or decreased with increasing order in all species. The CT ratio was significantly positively correlated to the stele ratio and negatively correlated to the cortex ratio in second- to fourth-order roots across species during the shift from primary to secondary root growth. Ectomycorrhiza-associated species mostly had a higher stele ratio and lower cortex ratio than arbuscular mycorrhiza-associated species across root orders. Compared with arbuscular mycorrhiza species, there was greater accumulation of CT in response to changes in the root order of ectomycorrhiza species. </sec> <sec> <title>Conclusions</title> Different development patterns of the stele, cortex and CT accumulation along the transition from root tip to secondary roots could be distinguished between different mycorrhizal associations. The CT in tissues in different mycorrhizal associations could help with root protection in specific branching orders during shifts in stele and cortex development before and during cork layer formation. </sec>

© 2019, Springer Nature Switzerland AG. Aims: Root phenology patterns in tropical regions are poorly understood because limited data are available. Using the root scanner method, the aims of this study were to clarify 1) the temporal phenology of root production and decomposition, 2) the spatial variability of the root phenology, and 3) the contribution of different root diameter classes to root production and decomposition. Methods: Image acquisition was conducted monthly from April 2014 to May 2015 at five sites in a Bornean tropical rainforest. The projected area and length of root production and decomposition were derived manually from images using image-processing software and were grouped into 0.5-mm-diameter intervals. Results: The spatial distribution of root production and decomposition differed among the sites. Monthly projected root length indicated that the number and timing of peak root production and decomposition differed with each site. A substantial proportion of root production and decomposition was dominated by very fine roots (<0.5 mm diameter). Conclusions: The scanner method was useful to monitor the root phenology at the root system scale though the scanner images cover only a portion of the root systems of mature trees. Different patterns of root phenology among the sites might be associated with the high diversity and the indistinct seasonality of the Bornean tropical rainforest.

AimsTropical forests contribute significantly to the stability of global carbon (C) balance; however, little is known about root litter decomposition in tropical rainforests. In this study, we aimed to (1) characterise the effect of soil depth, root diameter and soil organisms on root litter decomposition and (2) estimate the contribution of root decomposition to soil carbon dioxide (CO2) efflux in a tropical rainforest in Malaysian Borneo.MethodsWe incubated soil chambers with fine and coarse root litterbags at varying soil depths. Soil chambers were covered with nets of different mesh sizes, and CO2 efflux was monitored from the top of each soil chamber during the incubation.ResultsOur results showed that coarse roots decomposed faster than fine roots. There was no impact of soil depth, but soil animals and fungi had a significant impact on coarse root decomposition from 398days after the start of the experiment. Soil CO2 efflux increased linearly with C loss from root decomposition, indicating that 40% of the CO2 efflux originates from root litter.ConclusionsThe variation in root decomposition rates suggests the possible role of root litter in soil C storage and emission in a tropical rainforest.

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Clarifying the dynamics of fine roots is critical to understanding carbon and nutrient cycling in forest ecosystems. An optical scanner can potentially be used in studying fine-root dynamics in forest ecosystems. The present study examined image analysis procedures suitable for an optical scanner having a large (210 mm x 297 mm) root-viewing window. We proposed a protocol for analyzing whole soil images obtained by an optical scanner that cover depths of 0-210 mm. We tested our protocol using six observers with different experience in studying roots. The observers obtained data from the manual digitization of sequential soil images recorded for a Bornean tropical forest according to the protocol. Additionally, the study examined the potential tradeoff between the soil image size and accuracy of estimates of fine-root dynamics in a simple exercise. The six observers learned the protocol and obtained similar temporal patterns of fine-root growth and biomass with error of 10-20% regardless of their experience. However, there were large errors in decomposition owing to the low visibility of decomposed fine roots. The simple exercise revealed that a smaller root-viewing window (smaller than 60% of the original window) produces patterns of fine-root dynamics that are different from those for the original window size. The study showed the high applicability of our image analysis approach for whole soil images taken by optical scanners in estimating the fine-root dynamics of forest ecosystems.

Aboveground biomass is often restricted by water availability; therefore, water acquisition strategies have important roles in determining biomass volume and distribution under arid conditions. In cold Asian rangelands, the large tussock grass Achnatherum splendens is the most important forage for maintaining livestock under severe winter conditions. However, A. splendens distribution is restricted to the middle of the slopes of ephemeral streams, making it difficult to manage winter foraging. To understand the mechanisms behind the specific distribution and maintenance of a large A. splendens biomass under arid conditions, we established four typical vegetative plots along a riverside slope with different A. splendens density levels and elevations: river bottom with no A. splendens, riverbank with a large A. splendens community, upper slope with an isolated A. splendens community, and flat plain with no A. splendens. We measured the soil pH and electric conductivity (EC) of the plots and investigated the vertical biomass and root distribution of A. splendens. We also investigated the water source for the A. splendens communities using isotope techniques. The soil pH was not different among plots, while the soil EC was significantly higher in the river bottom because of salt accumulation. However, low soil EC levels were found under the A. splendens communities. In the ground below the A. splendens communities, plant stems were buried deeply. The belowground biomass and buried stem depths decreased at the sites of the isolated A. splendens communities in the upper slope. The aboveground biomass of A. splendens increased as the stem burial depths and, therefore, the adventitious roots depths increased. The water source of A. splendens was estimated to be at a depth of more than 30 cm. Thus, A. splendens prefers a habitat with a low level of soil salinity and a high level of water availability, which may increase with the sand burial depth because of the increasing accessibility of a substantial water source in the deeper soil layer. Sand burial may affect the water acquisition strategy and maintenance of large biomasses of tussock grass species that act as important winter forage in cold Asian rangelands.

To investigate the contribution of soil animals to the cesium-137 (Cs-137) concentration change in the course of the litter decomposition process, we conducted litter bag experiments in forest sites located about 50km northwest from the Fukushima Dai-ichi Nuclear Power Plant. To control the influence of soil animals of different size, two different mesh sizes of litter bags (fine and coarse mesh) were used. Litter bags were placed in three different types of forests: (1) broad-leaved forest, (2) Japanese red pine mixed broad-leaved, and (3) Japanese cedar plantation, for the period from November 2012 to April 2014. Through the whole period, litter was decomposed to 60-70% from the initial dry weight. We found no significant difference between the mesh sizes. The litter Cs-137 concentration and the relative Cs-137 amount in each sampling time from initial Cs-137 amount (relative Cs-137 amount) in broad-leaved and mixed broad-leaved forests increased from the initial. In both forest types, Cs-137 concentration in coarse mesh showed higher than the fine mesh. In cedar plantation, relative Cs-137 amount in both mesh sizes did not differ from the initial value. We assumed that enhancement of the activity of microbes by the mesofauna contributed to an increase in the amount of Cs-137 in the litter. Although we could not deny the effect of mesh size of the litter bag, the activity of soil organism could be one of the factors that lead to an incremental increase of the Cs-137 amount in the litter layer.

The nuclear accidents at Chernobyl and Fukushima released large amounts of Cs-137 radionuclides into the atmosphere which spread over large forest areas. We compared the Cs-137 concentration distribution in different parts of two coniferous forest ecosystems (needle litter, stems and at different depths in the soil) over short and long term periods in Finland and Japan. We also estimated the change in Cs-137 activity concentrations in needle and soil between 1995 and 2013 in Southern Finland based on the back calculated Cs-137 activity concentrations. We hypothesized that if the Cs-137 activity concentrations measured in 1995 and 2013 showed a similar decline in concentration, the Cs-137 activity concentration in the ecosystem was already stable in 1995. But if not, the Cs-137 activity concentrations were still changing in 2013. Our results showed that the vertical distribution of the Cs-137 fallout in the soil was similar in Hyytiala and Fukushima. The highest Cs-137 concentrations were observed in the uppermost surface layers of the soil, and they decreased exponentially deeper in the soil. We also observed that Cs-137 activity concentrations estimated from the samples in 1995 and 2013 in Finland showed different behavior in the surface soil layers compared to the deep soil layer. These results suggested that the Cs-137 nuclei were still mobile in the surface soil layers 27 years after the accident. Our results further indicated that, in the aboveground parts of the trees, the Cs-137 concentrations were much closer to steady-state when compared to those of the surface soil layers based on the estimated declining rates of Cs-137 concentration activity in needles which were similar in 1995 and 2013. Despite its mobility and active role in the metabolism of trees, the Cs-137 remains in the structure of the trees for decades, and there is not much exchange of Cs-137 between the heartwood and surface layers of the stem. (C) 2016 Elsevier Ltd. All rights reserved.

© The Author(s) 2016. The accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 emitted 1.2 × 1016 Bq of cesium-137 (137 Cs) into the surrounding environment. Radioactive substances, including 137 Cs, were deposited onto forested areas in the northeastern region of Japan. 137 Cs is easily adsorbed onto clay minerals in the soil; thus, a major portion of 137 Cs can be transported as eroding soil and particulate organic matter in water discharge. Dissolved 137 Cs can be taken up by microbes, algae, and plants in soil and aquatic systems. Eventually, 137 Cs is introduced into insects, worms, fishes, and birds through the food web. To clarify the mechanisms of dispersion and export of 137 Cs, within and from a forested ecosystem, we conducted intensive monitoring on the 137 Cs movement and storage in a forested headwater catchment in an area approximately 50 km from the Nuclear Power Plant. Two major pathways of 137 Cs transport are as follows: (1) by moving water via dissolved and particulate or colloidal forms and (2) by dispersion through the food web in the forest-stream ecological continuum. The 137 Cs concentrations of stream waters were monitored. Various aquatic and terrestrial organisms were periodically sampled to measure their 137 Cs concentrations. The results indicate that the major form of exported 137 Cs is via suspended matter. Particulate organic matter may be the most important carrier of 137 Cs. High water flows generated by a storm event accelerated the transportation of 137 Cs from forested catchments. Estimation of 137 Cs export from the forested catchments requires precise evaluation of the high water flow during storm events. The results also suggested that because the biggest pool of 137 Cs in the forested ecosystem is the accumulated litter and detritus, 137 Cs dispersion is quicker through the detritus food chain than through the grazing food chain.

Since the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, large areas of the forests around Fukushima have become highly contaminated by radioactive nuclides. To predict the future dynamics of radioactive cesium (Cs-137) in the forest catchment, it is important to measure each component of its movement within the forest. Two years after the accident, we estimated the annual transportation of Cs-137 from the forest canopy to the floor by litterfall, throughfall and stemflow. Seasonal variations in Cs-137 transportation and differences between forests types were also determined. The total amount of Cs-137 transported from the canopy to the floor in two deciduous and cedar plantation forests ranged between 3.9 and 11.0 kBq m(-2) year(-1). We also observed that Cs-137 transportation with litterfall increased in the defoliation period, simply because of the increased amount of litterfall. Cs-137 transportation with throughfall and stemflow increased in the rainy season, and Cs-137 flux by litterfall was higher in cedar plantation compared with that of mixed deciduous forest, while the opposite result was obtained for stemflow. (C) 2015 Elsevier Ltd. All rights reserved.

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Background and Aims Root caps release border cells, which play central roles in microbe interaction and root protection against soil stresses. However, the number and connectivity of border cells differ widely among plant species. Better understanding of key border-cell phenotype across species will help define the total function of border cells and associated genes.Methods The spatio-temporal detachment of border cells in the leguminous tree Acacia mangium was investigated by using light and fluorescent microscopy with fluorescein diacetate, and their number and structural connectivity compared with that in soybean (Glycine max).Key Results Border-like cells with a sheet structure peeled bilaterally from the lateral root cap of A. mangium. Hydroponic root elongation partially facilitated acropetal peeling of border-like cells, which accumulate as a sheath that covers the 0- to 4-mm tip within 1 week. Although root elongation under friction caused basipetal peeling, lateral root caps were minimally trimmed as compared with hydroponic roots. In the meantime, A. mangium columella caps simultaneously released single border cells with a number similar to those in soybean.Conclusions These results suggest that cell type-specific inhibitory factors induce a distinct defective phenotype in single border-cell formation in A. mangium lateral root caps.

Aluminum (Al) is a harmful element that rapidly inhibits the elongation of plant roots in acidic soils. The release of organic anions explains Al resistance in annual crops, but the mechanisms that are responsible for superior Al resistance in some woody plants remain unclear. We examined cell properties at the surface layer of the root apex in the camphor tree (Cinnamomum camphora) to understand its high Al resistance mechanism. Exposure to 500 mu M Al for 8 d, more than 20-fold higher concentration and longer duration than what soybean (Glycine max) can tolerate, only reduced root elongation in the camphor tree to 64% of the control despite the slight induction of citrate release. In addition, Al content in the root apices was maintained at low levels. Histochemical profiling revealed that proanthocyanidin (PA)-accumulating cells were present at the adjacent outer layer of epidermis cells at the root apex, having distinctive zones for cell division and the early phase of cell expansion. Then the PA cells were gradually detached off the root, leaving thin debris behind, and the root surface was replaced with the elongating epidermis cells at the 3- to 4-mm region behind the tip. Al did not affect the proliferation of PA cells or epidermis cells, except for the delay in the start of expansion and the accelerated detachment of the former. In soybean roots, the innermost lateral root cap cells were absent in both PA accumulation and active cell division and failed to protect the epidermal cell expansion at 25 mu M Al. These results suggest that transient proliferation and detachment of PA cells may facilitate the expansion of epidermis cells away from Al during root elongation in camphor tree.