遠藤 いず貴

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.

© 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.

<p>2011年3月11日に宮城県沖で起きた東北地方太平洋沖地震および地震に伴う津波に起因する福島第一原子力発電所の事故は、環境中への大量の放射性物質の放出をもたらした。森林では、林冠に付着した¹³⁷Csの大半は降雨や落葉によって地面に移行するものの、一部は表面吸収や経根吸収によって樹体内に留まることが明らかとなっている。そして、このような¹³⁷Csの滞留と循環は、生態系の構造や構成樹種など様々な要因によって変化すると予想される。そこで本研究では福島県内のスギ人工林と広葉樹二次林において、林冠を構成する葉と枝が持つ¹³⁷Csの挙動を明らかにすることを目的とした。調査は、福島県伊達市霊山町上小国川上流に生育する広葉樹二次林と隣接したスギ人工林で行った。2012年から2015年にかけて毎年1回、広葉樹二次林に優占するコナラの成木個体とスギ個体の伐倒調査を行い、枝葉を採取して¹³⁷Cs濃度を計測した。その結果、両樹種において枝葉の¹³⁷Cs濃度は2013年以降に急速に減少することや、調査期間を通じて枝よりも葉の方が、¹³⁷Cs濃度が高いことなどが示された。</p>

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.

森林域から下流域への将来的な放射性セシウムの流出やその影響を予測するためには，森林内での放射性セシウムの動態を明らかにする必要がある．本研究では，土壌表層での空間線量率の測定を継続的に実施することで，斜面上に成立した落葉広葉樹林での放射性セシウムの移動を検討した．調査地は福島県伊達市霊山町上小国川上流に位置する．林内に設置した約50 m×27 mのプロット内にほぼ等間隔で160点の測定点を設け，地表と地表から10 cmの空間線量率を2013年5月～2014年12月の間に5回測定した．プロット内外には複数の土砂トラップと定点撮影カメラを設置し，表土・リターの移動もモニタリングした．結果として，侵食を伴う顕著な土砂移動は生じなかったが，夏期・冬期ともに地形条件による局所的な表土・リターの移動が見られた．測点による空間線量率のばらつきや変化の差が大きいという結果はこのような移動形態に対応すると考えられる．斜面下部に位置するプロット全体での空間線量率の変化は自然減衰を考慮した逓減曲線に概ね従うが，やや大きな値を示し，顕著な土砂移動が無い場合にも，森林斜面における放射性セシウムの移動が生じる可能性があることが示唆された．

森林から河川を通して¹³⁷Csが流出するメカニズムを明らかにするには、洪水時の浮遊砂（SS）の挙動と共に捉え、SS濃度との対応関係を調査する必要がある。本論では洪水時における経時的な採水に基づき、SS濃度と¹³⁷Cs濃度の対応関係について考察した。調査は福島県伊達市霊山町上小国川の最上流の森林集水域で行った。洪水時の採水は2013年6月から合計7回、自動採水器を用いて行った。SSはガラス繊維濾紙（GF/F孔径0.7μm）を用いて捕集し、¹³⁷Cs濃度はゲルマニウム半導体検出器を用いて測定した。洪水時に、流量増加に伴いSS濃度、¹³⁷Cs濃度ともに上昇することが示された。しかし、SS濃度と¹³⁷Cs濃度の経時変化は必ずしも一致せず、SS濃度とSS中の¹³⁷Cs濃度には負の相関が見られることがわかった。つまり、洪水時の流量増加に伴うSS濃度上昇により、単位重量あたりのSSに含まれる¹³⁷Cs量が低下することが示された。この現象は洪水時の流量増加時の掃流力、侵食力の増大に伴って、１）SSの粒径組成が変化すること、２）SSの供給源が変化することの影響であると考えられる。

森林内における将来の放射性セシウムの分布や蓄積を知る上で、リターの分解に伴う放射性セシウム(Cs)の土壌への移行は重要な情報である。本研究では、林床に設置したリターバッグの重量変化からリターの分解速度を求め、分解に伴う放射性Csの濃度変化を調べた。<br> 調査は、福島県伊達市霊山町上小国川上流に位置する落葉広葉樹-アカマツの混交林2プロットとスギ人工林1プロットで行った。細かいメッシュと粗いメッシュの2タイプのリターバッグ内に、2012年秋に落葉した各プロットの葉を詰め、1プロットにつきランダムに5カ所に設置した。リターバッグは2012年11月に設置し、2014年4月まで約3ヶ月に1度回収して、重量と放射性Cs濃度を測定した。<br> リター分解への菌類の関与や樹種の異なる森林間での分解過程の違いを考察した。

福島第一原発事故で放出された放射性セシウム（Cs）は、3年が過ぎてその大半が森林土壌に移行したと考えられるが、その後の森林土壌内におけるCsの挙動、特に樹木根のCsの吸収については量や経路など多くの点が未だ不明である。そこで本研究はこれまで細根生産量、分解量の測定のための手法だったイングロースコア法を用いて樹木根におけるCs吸収を把握する方法を考案し、その有効性について検討した。<br>実験は福島県伊達市のスギ人工林で行った。現地のCsを含む土壌(+Cs)と、京都のスギ林のCsを含まない土壌(-Cs)を詰めた長さ20cmのイングロースコアを10本ずつ準備し、2013年6月に試験地に埋設した。1年後の2014年6月にコアを回収し、土表表層から0-3cm、3-10cm、10-20cmの3深度に分けて土壌と新規に伸びた根系を分別した。+Csのコア内にあった土壌の平均Cs濃度は4232±2807Bq/kgと、-Csの土壌中の平均Cs濃度1446±1217Bq/kgの約3倍も高く、この手法により根系の土壌環境を制御することが出来たと判断された。また植物根中の平均Cs量についても、+Csで1331±574Bq/kg、-Csで423.2±235Bq/kgと土壌と同じく約３倍であり、根系は土壌からCsを吸収すると予想された。

【背景と目的】福島第一原発事故後降下した放射性セシウムは、現在も森林内に多く蓄積している。放射性セシウムは粘土粒子などに吸着されやすく、それらが浮遊砂として河川を通して流下することが考えられる。本研究の目的は森林からの放射性セシウムの流出機構を明らかにし、流出量を正確に把握することである。特に洪水時において河川中の浮遊砂濃度が上昇することが知られており、放射性セシウム濃度もそれに対応して上昇することが考えられる。【方法】調査は福島県伊達市霊山町上小国川の最上流の森林集水域で行った。平水時の試料水の採取は2012年7月より月1回、洪水時の採水は2013年6月から10月にわたって計5回の洪水イベントを自動採水器を用いて行った。ガラス繊維フィルターGF/Fを用いて懸濁物を捕集し、その中の放射性セシウムをゲルマニウム半導体検出器で測定した。【結果】平水時において、放射性セシウムは殆ど検出されなかった。浮遊砂濃度と懸濁態セシウム濃度には正の相関がみられ、洪水時において、流量増加中は浮遊砂濃度と懸濁態セシウム濃度は流量の増加より先に上昇し、流量低下時には流量の低下より先に浮遊砂濃度と懸濁態セシウム濃度は低下した。

モンゴル国マンダルゴビ地域では、多年生イネ科草本のAchnatherum splendens (以下、アクナテラム)群落が災害時に家畜の生存を左右するKey-resourceと考えられている。本研究ではアクナテラム群落の成立要因を明らかにすることを目的として、水と養分の利用特性に着目し、同所に存在する他種と比較した。 植物の吸水源を特定するために、土壌水、地下水、雨水と植物体中の水の酸素と水素の安定同位体比を比較した。アクナテラムは乾燥時に地下30 cm以上深くから水を利用していたが、降雨後には地表面付近の水も利用することが分かった。同所に生育するアカザ科の一年生植物は、地下浅い水を利用していることが示唆された。長期的な水利用効率の指標となる炭素安定同位体比の結果から、アクナテラムは同所に生育する他の種に比べて水利用効率が高かった。アクナテラムが優占するプロットは、塩生植物が優占するプロットに比べ植物のT/R比が大きく、水や栄養条件が良いことが考えられた。アクナテラム群落の成立に水利用特性が関与しており、群落の成立によって群落外と比べ水や養分の保持を有利にしている可能性がある。

モンゴル国マンダルゴビ地域では、多年生イネ科草本のAchnatherum splendens (以下、アクナテラム)群落が災害時に家畜の生存を左右するKey-resourceと考えられている。本研究ではアクナテラム群落の立地特性を明らかにすることを目的として、アクナテラム群落を含む複数の群落間で植生構造と地形及び土壌の化学性を比較した。調査は、塩類が集積している低地から、斜面上部に向かって4本のトランセクトラインを設置し、斜面傾度に伴い変化する植物群落について、出現種、被度を記録するとともに、土壌の化学性（EC, pH）を調査した。 塩類集積が見られる低地ではKalidium, Halogeton等の塩生植物が優占する群落が成立し、低地に続く段丘上で、アクナテラム優占群落が出現した。さらに斜面を上がると、アクナテラム群落からStipa., Alium., Artemisia 等が優占する植物群落へ変化した。土壌の化学性からアクナテラム群落の立地特性をみると、アクナテラム群落はEC：15～170 の範囲内、PH：7.69～8.92 の範囲内に成立することが明らかとなった。

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.