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To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (Tb) was estimated. The concentration of ¹³⁷Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the ¹³⁷Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of ¹³⁷Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days.

Understanding the pathways of 137Cs transfer to spiders as generalist predators is useful to assess the long-term recycling of 137Cs through the food chain in forest ecosystems. Approximately 6.5 years after the Fukushima Dai-ichi Nuclear Power Plant accident, we collected spider samples at two different habitats (in a forest interior and along a river) in a forest and determined their 137Cs activity concentrations and stable carbon and nitrogen isotope ratio values (δ13C and δ15N). Across the locations, 137Cs was detected in all spiders, indicating that a significant fraction of the deposited 137Cs is still bioavailable. The geometric means of the transfer factor (Tag) values were 1.3 × 10−3 m2 kg−1 and 0.8 × 10−3 m2 kg−1 for the spiders in the forest interior and along the river, respectively. There were no significant differences in the 137Cs activity concentration and Tag value between the locations. In contrast, the δ13C and δ15N for the spiders were significantly different between the locations, indicating different food resources of the spiders. The preliminary results indicate that the transfer of 137Cs to spiders can be a useful indicator of 137Cs recycling in forest ecosystems, but the transfer pathways remain difficult to identify because of high variability.

Surface albedo of snow and ice is substantially reduced by inorganic impurities, such as aeolian mineral dust (MD) and black carbon (BC), and also by organic impurities, such as microbes that live in the snow. In this paper, we present the temporal changes of surface albedo, snow grain size, MD, BC and snow algal cell concentration observed on a snowpack in northwest Greenland during the ablation season of 2014 and our attempt to reproduce the changes in albedo with a physically based snow albedo model. We also attempt to reproduce the effects of inorganic impurities and the red snow algae (Sanguina nivaloides) on albedo. Concentrations of MD and red snow algae in the surface snow were found to increase in early August, while snow grain size and BC were found to not significantly change throughout the ablation season. Surface albedo was found to have decreased by 0.08 from late July to early August. The albedo simulated by the model agreed with the albedo observed during the study period. However, red snow algae exerted little effect on surface albedo in early August. This is probably owing to the abundance of smaller cells (4.9×104 cells L−1) when compared with the cell abundance of red snow reported by previous studies in the Arctic region (∼108 cells L−1). The simulation of snow albedo until the end of the melting season, with a snow algae model, revealed that the reduction in albedo attributed to red snow algae could equal 0.004, out of a total reduction of 0.102 arising from the three impurities on a snowpack in northwest Greenland. Finally, we conducted scenario simulations using the snow albedo model, coupled with the snow algae model, in order to simulate the possible effects of red snow blooming on snow albedo under warm conditions in northwest Greenland. The result suggests that albedo reduction by red snow algal growth under warm conditions (surface snow temperature of +1.5 ∘C) reached 0.04, equivalent to a radiative forcing of 7.5 W m−2 during the ablation season of 2014. This coupled albedo model has the potential to dynamically simulate snow albedo, including the effect of organic and inorganic impurities, leading to proper estimates of the surface albedo of snow cover in Greenland.

Surface albedo of snow and ice is substantially reduced by inorganic impurities, such as aeolian mineral dust (MD) and black carbon (BC), and also by organic impurities, such as microbes that live in the snow. In this paper, we present the temporal changes of surface albedo, snow grain size, MD, BC, and snow algal cell concentration observed on a snowpack in northwest Greenland during the ablation season of 2014 and our attempt to reproduce the changes in albedo with a physically based snow albedo model. We also attempt to reproduce the effects of inorganic impurities and the red snow algae (Chlamydomonas nivalis) on albedo. Concentrations of MD and red snow algae in the surface snow were found to increase in early August, while snow grain size and BC were found to not significantly change throughout the ablation season. Surface albedo was found to have decreased by 0.08 from late July to early August. The albedo simulated by the model agreed with the albedo observed during the study period. However, red snow algae exerted little effect on surface albedo in early August. This is probably owing to the abundance of smaller cells (4.9 × 104 cells L^-1) when compared with the cell abundance of typical red algal snow (~ 108 cells L−1). The simulation of snow albedo until the end of the melting season, with an algal growth model, revealed that the reduction in albedo attribute to red algae could equal 0.004, out of a total reduction of 0.102 arising from the three impurities on a snowpack in northwest Greenland. Finally, we conducted scenario simulations using the snow albedo model, coupled with the algal growth model, in order to simulate the possible effects of red algal blooming on snow albedo under warm conditions in northwest Greenland. The result suggests that albedo reduction by red snow algal growth under warm conditions (surface snow temperature of +1.5 °C) reached 0.04, equivalent to a radiative forcing of 7.5 W m−2 during the ablation season of 2014. This coupled albedo model has the potential to dynamically simulate snow albedo, including the effect of organic and inorganic impurities, leading to proper estimates of the surface albedo of snow cover in Greenland.

To understand the behavior of radioactive cesium (134Cs+137Cs) in terrestrial invertebrates, chronological changes in the concentration of radioactive Cs in arthropods from different trophic levels were investigated after the Fukushima Daiichi Nuclear Power Plant accident. In addition, the level of radioactive Cs in earthworms, representing the detritivores, was also investigated. The median radioactive Cs concentration in the rice grasshopper (Oxya yezoensis) and the Emma field cricket (Teleogryllus emma) was 0.46 and 0.15 Bq/g fresh weight (fw) in 2012, respectively, which dropped continuously to 0.05 and 0.01 Bq/g fw in 2016. In contrast, no significant reduction in radioactive Cs concentration was observed in the Joro spider (Nephila clavata) in which the concentration was 0.31 Bq/g fw in 2012 and remained at 0.14 Bq/g fw in 2016. The comparison of radioactive Cs concentration at each trophic level showed that the amount in detritivorous earthworms was 85 times higher than in herbivorous grasshoppers. This suggests that detritus food web could be a primary pathway for migration of radioactive Cs through food webs.

Snow and ice algal communities were investigated on four glaciers in the Suntar-Khayata Mountain Range in eastern Siberia in Russia over three melting seasons from 2012 to 2014. Two taxa of green algae and five taxa of cyanobacteria were observed on the glaciers. The algal community was dominated by green algae: Ancylonema nordenskioldii in the lower bare ice area and Chloromonas sp. in the upper snow area. The total algal bio-volume showed altitudinal variation, ranging from 0.03 to 4.0 mL m−2, and was greatest in the middle of the glaciers. The altitudinal variations in the algal community were similar on all studied glaciers, suggesting that they are typical in this region. Observations over the three years revealed that there was no significant change in the community structure, but a significant change in the total biomass. Since the mean summer air temperature was significantly higher in 2012 when algal biomass was greater, the difference in algal biomass among the years is probably due to the duration of surface melting. The community structure on the studied glaciers is similar to those on glaciers in Arctic and sub-Arctic regions.

Little is known about the effect of soil disinfection on bacterial communities. Soils were treated with an effective chemical fumigant chloropicrin and biofumigant mustard greens (Brassica juncea). While mustard greens did not affect the soil bacterial community structures very much, chloropicrin greatly reduced soil biomass and bacterial species richness. Chloropicrin also influenced the bacterial community structure, making the phylum Firmicutes dominant by occupying about 75%. In more than two months, the proportion of Firmicutes was reduced to the basal level, and the phyla Bacteroidetes and Proteobacteria became dominant. Since mustard greens worked as carbon sources for soil reduction, soils were treated with wheat bran and a low concentration of ethanol. Soil reduction with wheat bran and ethanol did not influence the soil bacterial community structures. Beta diversity analyzed by Principal Coordinate Analysis showed that bacterial communities in the soils except chloropicrin-applied soils formed a cluster. All together, biofumigant mustard greens, a probable substitute for chloropicrin, were demonstrated to cause much less damage on soil bacterial community than chemical chloropicrin.

Although an estimation of forest biomass is essential for the development of a carbon storage baseline in the ''Reducing Emissions from Deforestation and Deg- radation in Developing Countries'' scheme, few have been conducted in logged-over rain forests of Southeast Asia. We measured the aboveground and belowground biomass in logged-over mixed dipterocarp forests growing on an infertile soil with bleached white sand (Sabal) and on a clay and nutrient-rich soil (Balai Ringin) in Sarawak, Malaysia. We established four 0.5-ha plots on each site and calcu- lated the biomass. Basal area and stand density of large trees (diameter at breast height, DBH C 10 cm) were

Cryoconite granules are aggregations of microorganisms with mineral particles that form on glacier surfaces. To understand the processes by which the granules develop, this study focused on the altitudinal distribution of the granules and photosynthetic microorganisms on the glacier, bacterial community variation with granules size and environmental factors affecting the growth of the granules. Size-sorted cryoconite granules collected from five different sites on Qaanaaq Glacier were analyzed. C and N contents were significantly higher in large (diameter greater than 250 μm) granules than in smaller (diameter 30–249 μm) granules. Bacterial community structures, based on 16S rRNA gene amplicon sequencing, were different between the smaller and larger granules. The filamentous cyanobacterium Phormidesmis priestleyi was the dominant bacterial species in larger granules. Multivariate analysis suggests that the abundance of mineral particles on the glacier surface is the main factor controlling growth of these cyanobacteria. These results show that the supply of mineral particles on the glacier enhances granule development, that P. priestleyi is likely the key species for primary production and the formation of the granules, and that the bacterial community in the granules changes over the course of the granule development.

This study discusses soil fertility under perennial cash crop farming (para rubber, Hevea brasiliensis ; black pepper, Piper nigrum ; oil palm, Elaeis guineensis ) conducted by local farmers and an oil palm estate in an upland area of Sarawak, Malaysia, in comparison with the surrounding secondary forests. In the farmlands of the local farmers, rubber farming was conducted without fertilizer application, while 2–5 t ha −1 of NPK compounds were applied annually on pepper farms. Soils under rubber farming were acidic with poor nutrient contents, resembling soils in secondary forests. In pepper farms, soils were less acidic and showed high nutrient contents, especially with respect to available P and exchangeable Ca. This trend became stronger with increasing farming duration. Fertilizers applied around pepper vines appeared to migrate and spread across the fields. Bulk density and hardness of surface soils were higher in pepper farms than in secondary forests, indicating soil compaction due to field works. In the oil palm estate, annual fertilizer application rates were moderate at 0.4–0.8 t ha −1 of NPK compound fertilizers. However, the soil properties in the oil palm estate were similar to those of the small-scale pepper farms. Close to the bases of the palms where fertilizers usually are applied, the contents of exchangeable Ca and available P were high. Nutrient uptake by the dense root systems of the palms seemed to prevent excessive loss of nutrients through leaching. Loss of soil organic matter and deterioration of soil physical properties were brought about by terrace bench construction, but the soils seemed to recover to some extent over time. In conclusion, technologies such as intercropping and the appropriate allocation of different crops to specific locations as well as the proper selection and dosage of fertilizers should be developed and adopted to improve fertilizer efficiency and prevent water pollution due to fertilizer wash-off from farmlands.

Patterns of woody regeneration in terms of species composition and diversity were studied in a 37-year-old teak plantation established on degraded mixed deciduous forest (MDF) at Mae Yuak Plantation Station, Ngao District, Lampang Province, Northern Thailand. In order to assess the role of plantations in regeneration of woody tree species within the plantation, the understorey floristic structures and composition were evaluated fifteen 20 m × 20 m plots at three sites differing in topographic position, stand structure and distance from natural forest. The average density and species richness of woody regeneration in the plantation was 556.7 stem ha −1 and 9.6 species plot −1 , respectively. The Shannon–Wiener index was 2.47–2.68, and Sorensen's index of similarity between plantation and the adjacent MDF was 0.38–0.55. A total of 334 woody regeneration individuals were found in 0.6 ha of teak plantation, representing 37 species, with Leguminosae the most common family. Pterocarpus macrocarpus Kurz (Leguminosae) showed the highest density of 73.3 stem ha −1 . The eight most dominant species were P. macrocarpus , Dalbergia oliveri Gamble, Croton roxburghii N.P. Balakr, Xylia xylocarpa (Roxb.) Tuab., D. cultrate Graham ex Benth., Wrightia arborea (Dennst.) Mabb., Schleichera oleosa (Lour.) Oken and Morinda tomentosa Heyne ex Roth. The proximity to the natural forest, seed dispersal characteristics and site qualities influenced woody regeneration. These results show teak plantations could be effective tools in rehabilitating degraded MDF in Northern Thailand.

The role of arbuscular mycorrhizal fungus (AMF) on biotransformation of arsenic (As) in the rhizosphere of sunflower (Helianthus annuus L.) was studied in a rhizobag system with As-contaminated soil. The treatments consisted of a combination of two levels of AMF (Glomus aggregatum) inoculation (–AM and +AM) under sterile and non-sterile soil conditions (S and NS). Each treatment was designated as –AM/S, –AM/NS, +AM/S and +AM/NS. Sunflower seedlings were cultured in the rhizobag for 6 weeks. Rates of root AMF colonization in +AM treatments were approximately 40% and 0% in –AM/S treatment. The AMF inoculation reduced As toxicity symptoms and improved plant growth. Shoot As, but not the root As, concentrations were reduced by AMF inoculation. Shoot and root P concentrations increased in +AM treatments regardless of soil sterilization. Analyses of water soluble (WS) As in the soils at the end of the cultivation indicated that the amount of WS-arsenite (AsIII) was higher in the central compartment com...

The effects of burning strength in shifting cultivation on the early stage of secondary succession in tropical rain forest was investigated at four sites (Sabal, Balai Ringin, Niah, and Bakam) in Sarawak, Malaysia. The number and growth (diameter, height, and biomass) of germinated seedlings were measured in experimental shifting cultivation plots in which the burning strength varied between 0, 100, 200, and 300 t/ha at Sabal, Balai Ringin, and Niah and 0, 20, and 100 t/ha at Bakam. Species composition of germinated tree and herbaceous seedlings was surveyed, and a germination test of buried seed was conducted at Niah and Bakam. The number of germinated seedlings decreased with increasing burning strength, whereas seedling growth was promoted by burning. During the first year, growth was best in the intermediate burning strength plots, whereas during the second year, growth was best in the most strongly burned plots. Species composition differed between unburned and burned sites. Site-specific factors such as original stand biomass, soil properties, and invasion of exotic species also affected germination and growth. Buried seeds in the Ao layer were killed by burning, and nearly all seeds in the 0-5 cm layer were killed in the plots with the highest burning strength (> 100 t/ha). On the basis of our findings, we conclude that in shifting cultivation systems burning promotes vegetation recovery when the burning strength is properly managed.

To clarify the extent of radioactive contamination in a broad environment of Fukusima, in and around farming lands and residential areas, the amount of radionuclides in the Japanese grasshopper, Oxya yezoensis, the Emma field cricket, Teleogryllus emma, the wasp spider, Argiope bruennichi, and the Joro spider, Nephila clavata, was investigated. Radioactive cesium was detected in all arthropods collected from survey sites in Fukushima. The highest radioactive cesium (134Cs and 137Cs) concentration of approximately 4.7 × 102 Bq/kg (wet weight) was detected from the grasshopper. The amount of radionuclides tended to rise in agreement with the space radiation dose rates in the survey sites. The spiders, which are classified at higher trophic levels on the food chain, therefore demonstrated correspondingly higher levels of cesium concentration, suggesting that bioaccumulation of radioactive cesium was occurring.

Effects of arbuscular mycorrhiza (AM) and phosphorus (P) application on arsenic (As) toxicity were studied in a rhizobox system with As-contaminated soil collected from Shimane Prefecture, Japan. The treatments consisted of a combination of two levels of AM (Glomus aggregatum) inoculation (−AM and +AM) and two levels of P application (−P and +P at 30 mg P kg−1). Sunflower (Helianthus annuus L.) seedlings were cultured in rhizoboxes for 6 weeks. Rates of root AM infection in +AM treatments were about 40% regardless of P application. AM inoculation as well as P application reduced As toxicity symptoms, most clearly so in the +AM−P treatment. Plant growth was highest in the +AM + P treatment. Shoot As concentrations were slightly reduced by AM inoculation but enhanced by P application. Shoot P concentration in the +AM−P treatment was similar to that of +P treatments and was higher than in −AM−P. Analyses of rhizosphere soils at the end of the cultivation period indicated that P application increased water-soluble As (WS−As) in all compartments while AM inoculation increased WS−As in the central compartment only. Both the WS−arsenite [WS−As(III)] and the dominant form, arsenate [WS−As(V)], showed gradients toward the root surface. Dimethylarsine (DMAA) was detected in the +AM treatments only. To our knowledge, this is the first report of the occurrence of DMAA in the mycorrhizosphere. AM inoculation increased WS−P similarly as +P treatments did and promoted acid phosphatase activity in the soil. In conclusion, AM inoculation alleviated the effects of As toxicity by improving P nutrition without increasing As concentrations in the shoots. Moreover, AM appeared to be involved in the transformation of soil inorganic As into less toxic organic forms.

Sustainability of the local shifting cultivation practice in the mountainous region of Northern Laos was investigated. Due to low fertility of the soils derived from shale and its strongly weathered and acidic nature in the eastern side of the Nam Khan River watershed, shortening of the fallow period to produce enough amount of upland rice for the local population would not be sustainable any more. On the other hand, the eroded materials from limestone range were added to the soils in the western side of watershed which made the soil more fertile. Based on the calculated population capacity by Carneiro's equation, a system with 2- or 3-year fallow for 1-year cultivation can be the maximum to afford the current population. To make the shifting cultivation system more sustainable, introduction of fallow system with a tree species, paper mulberry (Broussonetia papyrifera) could be a good option to be proposed.

The effects of steam sterilization (SS) on soil microbial properties including metabolic diversity of the microbial communities were examined in a greenhouse compared with those of two fumigants, methyl bromide (MB) and chloropicrin (CP). The numbers of fungi decreased in all the treatments. Nitrifiers, both ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, were severely affected by the SS and CP treatments, resulting in their virtual disappearance. The decrease in the levels of microbial biomass C and N after the treatments suggested that the SS and CP treatments eradicated the microorganisms more effectively than the MB treatment and that the influence of the former persisted until the end of the experiment, 4 months after the treatments. Accumulation of NH4-N was observed after the SS and CP treatments mainly due to the partial decomposition of the dead microorganisms and the marked decrease in the number of ammonium-oxidizing bacteria. The richness and average well color development...

In spite of the significant increase in the frequency and extent of fire occurrence in Indonesia recently, little information is available about the immediate, short-term, and long-term effects of fire on soils. To investigate the effects of wildfires on the dynamics of T-C, T-N, available P, pH, exchangeable bases, and cation exchange capacity (CEC) of Ultisols from South Sumatra Indonesia, surface soils of an unburnt 9-year old Acacia mangium plantation and of A. mangium plantations burnt in 1995, 1997, 1998, and 2000 were sampled in triplicate consecutively from December 1998 until December 2000. The values of T-C, T-N, available P, pH, and exchangeable bases significantly increased immediately after the fire while the levels of Al saturation and CEC significantly decreased. Soil nutrients were still accumulated 1 year after the fire but by the end of the second year, they were depleted and returned to the pre-fire levels. Although fallowing aggraded the burnt sites, the nutrient levels in the...

[This corrects the article DOI: 10.1371/journal.pone.0112510.].

Tropical regions are not well represented in glacier biology, yet many tropical glaciers are under threat of disappearance due to climate change. Here we report a novel biogenic aggregation at the terminus of a glacier in the Rwenzori Mountains, Uganda. The material was formed by uniseriate protonemal moss gemmae and protonema. Molecular analysis of five genetic markers determined the taxon as Ceratodon purpureus, a cosmopolitan species that is widespread in tropical to polar region. Given optimal growing temperatures of isolate is 20-30 °C, the cold glacier surface might seem unsuitable for this species. However, the cluster of protonema growth reached approximately 10 °C in daytime, suggesting that diurnal increase in temperature may contribute to the moss's ability to inhabit the glacier surface. The aggregation is also a habitat for microorganisms, and the disappearance of this glacier will lead to the loss of this unique ecosystem.

To investigate the dynamics of micronutrients in the rhizosphere under the application of sterile and non-sterile arbuscular mycorrhizal inoculum, sunflower plants were grown in a rhizobox system. When the non-sterile mycorrhizal inoculum was supplied in the central compartment of the rhizobox, concentration of N, P, K, Mg, Fe, and Zn in the shoots increased without reducing the plant growth. Analyses of the rhizosphere soil showed an increase in the amount of water soluble Fe in addition to that of P, and a higher activity of phosphomonoesterase. Fractionation of P in the rhizosphere soil indicated a decrease in the amount of Fe-P. Neither the excretion of low-molecular-weight organic acids specific to the treatment nor the increase in amounts was observed. These results suggested that the enzymes originated from arbuscular mycorrhiza and/or mycorrhizal roots caused the dissolution of Fe-P with a resultant release of both Fe and P.

In order to understand the influence of the Fukushima Daiichi nuclear power plant accident on the ecosystem in hilly and mountainous areas of Fukushima Prefecture, chronological changes in the levels of radiocesium in arthropod species were investigated. From 2012 to 2014, arthropods from different trophic levels were sampled and the air radiation dose rates at the sampling sites were analyzed. The air radiation dose rates showed a significant and constant reduction over the 2 years at the sampling sites in Fukushima. The median radiocesium concentration (134Cs + 137Cs) detected in the rice grasshopper, Oxya yezoensis, and the Emma field cricket, Teleogryllus emma, dropped continuously to 0.080 and 0.078 Bq/g fresh weight, respectively, in 2014. In contrast, no significant reduction in radioactive contamination was observed in the Jorô spider, Nephila clavata, in which the level remained at 0.204 Bq/g in 2014. A significant positive correlation between radiocesium concentration and the air radiation dose rate was observed in the rice grasshopper, the Emma field cricket and the Jorô spider. The highest correlation coefficient (ρ = 0.946) was measured in the grasshopper.

A pot culture experiment was conducted using a Cu-spiked soil to compare the effects of the application of ethylenediamine-N,N′-tetraacetate (EDTA) and [S,S]-ethylenediamine-N,N′-disuccinate (EDDS), a biodegradable chelating agent, on the soil Cu distribution, Cu uptake by brown mustard and on the metabolic activity of the soil microorganisms for substrate utilization. Seedlings of brown mustard were planted in the pots fitted with hollow fibers for soil solution suction, and cultivated for 12 weeks. Solutions of chelating agents with pH 6.0 at a concentration of 1.0 mmol kg−1 soil were supplied on the 35, 43, and 51 d after transplanting (total 3.0 mmol kg−1). The addition of EDTA and EDDS enhanced plant Cu uptake by 2.9 and 1.8 times compared with the uptake of the control plants which were grown without chelating agent supply. However, EDTA addition caused a significant growth reduction compared with the control, while the application of EDDS did not reduce the dry matter yield of the plants. The conce...