Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.pocean.2022.102952

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Microbial products, largely the necromass, are key contributors to stable soil organic matter (SOM) in terrestrial systems, and microbial communities may differ in the stabilization. Plants can control microbial communities through litter quality and entry sites of plant inputs (above- or below-ground). However, whether soil mineral fractions (due to the characteristics such as soil texture) can also control the microbial communities, remains unclear. We conducted two model soil incubation experiments (E1 and E2) in order to simulate the four field soils. Materials included were plant materials, such as general plant inputs in soil systems, and four mineral materials derived from different field soils (i.e., “the four original field soils”), with their SOM removed by combustion. E1 was undertaken to simulate root exudate using oxalate and glucose, and E2 was undertaken to simulate plant litter using broad leaves, coniferous leaves, branches, and fine roots. The microbial (mainly bacterial) community structure from phospholipid fatty acid (PLFA) across E1 and E2 showed differences due to the mineral materials, and the differences after accounting for plant materials are similar to the difference in the four original field soils. Additionally, the abundance of bacterial PLFAs in E2 increased with silt and clay content and was correlated with the abundance of the bacterial PLFAs in the four original field soil. This study implies that even in the case of this experiment under such conditions as a broad variety of plant inputs, mineral fractions strongly influence bacterial communities, in a manner consistent with field soil systems.

DOI： 10.1007/s10533-022-00978-w

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Other Link： https://link.springer.com/article/10.1007/s10533-022-00978-w/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/ens.12519

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ens.12519

Publishing type：Research paper (scientific journal)  

Increasing atmospheric nitrogen (N) deposition in terrestrial ecosystems influences aboveground and belowground carbon (C) storage. In belowground systems, N fertilization in field experiments has often been reported to suppress soil microbial biomass and mineralization; however, the effects on soil microorganisms are not always consistent. Here, we investigated N load response of microorganisms after 2 and 5 years in organic layers and mineral soils in a temperate forest dominated by Quercus crispula using large-scale field N fertilization (9 ha, 100 kg N ha−1 year−1 for 5 years, urea) on immature volcanic ash soil (with a high buffering capacity). In the organic layers, N loading increased the total C concentration and KCl-extractable organic C content. Additionally, the amount of extractable organic C in the soil did not change after one month of laboratory incubation, possibly due to the low microbial use. These results likely indicate the accumulation of recalcitrant C (possibly due to decreased oxidase activity). Although the fungal-to-bacterial composition ratio did not change, the bacterial biomass increased by 18% and 26% in the second and fifth years, respectively, in the N-fertilized plots. Furthermore, the abundance of ammonia-oxidizing bacterial AmoA increased, which was correlated with potential nitrification. These changes may result from plant litter N content and litter quantity and subsequently change in soil environments, especially with increased soil N availability. In the mineral soils, N loading changed soil environments to a lesser extent than the organic layers; however, the fungal biomass decreased by 42% and 44% in the second and fifth years, respectively. This could be linked to a decrease in resource investment into symbionts (ectomycorrhizal fungi derived from oak roots) by underground plants. These findings suggest that in an oak-dominated forest, the influence of N loading between the organic layers and mineral soils on microorganisms varies, enhancing our understanding of belowground C dynamics.

DOI： 10.1016/j.apsoil.2022.104537

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

The relative importance of topography and vegetation in shaping local soil invertebrate communities is poorly understood. We investigated changes in the species and trait compositions of Collembola communities associated with different topography and forest types. Our study sites encompassed various topographies with different slope aspects and forest types; specifically, natural deciduous broad-leaved forests and deciduous coniferous plantations in Japan. The body length and edaphic adaptation score, which are representative of a certain life-form, were used as Collembola traits. Across a topographic gradient from south to north-facing slopes, the total biomass of Collembola was higher in dry plots than in humid plots, and the forest types did not affect either abundance, biomass, or species diversity. Variation partitioning analysis revealed that topography played an important role in determining species composition and functional traits, whereas forest types and spatial distance had minor roles. The responses of community weighted mean traits (CWMs) to environmental change were more pronounced than those of species composition. The CWM and functional diversity of body length were higher in the dry plots than in the humid plots. These changes in traits might be explained by food supply or habitat structure increasing large individuals via topography, rather than by physical stress filtering out intolerant small individuals. These results suggest that slope topography is an important determinant of the Collembola community structure in cool-temperate forest ecosystems.

DOI： 10.1016/j.pedobi.2021.150776

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Ants play important roles in trophic dynamics through their functions, ranging from herbivores to predators. However, little is known about whether the ant community modifies diet preferences and feeding habits during primary succession. We performed a bait-choice experiment and analyses of stable carbon and nitrogen isotopes (δ13C and δ15N) and radiocarbon (Δ14C) of ants at four study sites that underwent primary succession on lava flows created by four volcanic eruptions approximately 70, 100, 230, and 540 years ago in Sakurajima, Japan. The ant community increasingly preferred plant-based diets over animal-based diets as the primary succession proceeded, likely because the ants attempted to balance nutrition through compensatory feeding according to diet availability. The δ13C values showed that the ants depended largely on carbon from C4 plants at the young sites with no canopy trees. The δ15N values of ants consistently differed among the species, suggesting that each species maintained the proportion of plant- and animal-based diets during succession. The baseline-corrected δ15N values of the ants were significantly higher at the youngest site than at the older sites; this probably reflects intraguild predation or reliance on aerial prey from surrounding older sites, which exhibited a higher δ15N-baseline partly due to the colonisation of nitrogen-fixing plants. The Δ14C values show that the two ant species examined had older diet ages, by approximately 2 years, at the old sites than those at the young sites, indicating their greater dependence on the detritus food web.

DOI： 10.1111/een.13129

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Growth analysis based on tree-ring chronology is difficult in trees in aseasonal tropical rain forests, because annual growth rings may be unclear or completely absent. Fortunately, tree growth history recorded in xylem tissue is capable of providing valuable information on the responses of trees and forests to past and present environmental changes, including global warming. We have developed a new technique for aseasonal tropical forest trees which derives their growth rates from xylem Δ14C, and verified its accuracy. We also determined, from xylem δ13C, the intrinsic water-use efficiency (iWUE) in the past 50 years. We analysed changes in xylem Δ14C and δ13C in 23 canopy trees of 12 species in 6 families growing in Pasoh Forest Reserve, Malaysia; each stem diameter at breast height (DBH) was recorded 14 times from 1969 to 2011. We found a significant positive relationship between the growth rates determined by 14C dating and the past DBH data. On the other hand, leaf-internal CO2 (Ci) content did not change with increasing atmospheric CO2 (Ca). Thus, the iWUE increased significantly over the last 50 years in all the families and species tested. This study showed that the simultaneous measurements of xylem Δ14C and δ13C could reveal a long-term change in tree growth and iWUE during the past 50 years with high accuracy in various species and/or individuals in aseasonal tropical rainforests exhibiting high species diversity.

DOI： 10.1111/2041-210X.13823

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Radioisotope Association  

Analysis of carbon and nitrogen isotope ratios are now popular among many study fields mainly due to the development of EA-IRMS. It is difficult to run the tiny samples or the samples with low carbon or nitrogen concentrations with the normal EA-IRMS setting. Here we introduce the modification of EA-IRMS for the tiny samples. The analytical system with the narrow oxidation and reduction tubes allows better peak shapes for carbon and nitrogen, which increases the sensitivity of EA-IRMS. This system is now available for the users in Center for Ecological Research, Kyoto University without any big troubles in the analysis. Because the modification introduced here is not so complicated and the users can also use the normal settings whenever required, many EA-IRMS users can apply this system relatively easily.

DOI： 10.3769/radioisotopes.70.291

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Publishing type：Research paper (scientific journal)  

Native tree species are frequently unable to effectively grow in non-native tree cultivation scenarios. In the Loess Plateau, China, it is difficult to find native oak (Quercus liaotungensis) seedlings in non-native black locust forests. Black locust is an arbuscular mycorrhizal (AM) tree, but oak is an ectomycorrhizal (ECM) tree. Plants highly depend on their symbiotic mycorrhizal fungi to take up water, nitrogen (N) and other nutrients. We hypothesized that black locust forests would not provide ECM inoculum to oak seedlings, limiting their water and nutrient uptake, which would be improved by ECM inoculum. Here, we (1) sowed seeds, with or without oak forest soils, (2) transplanted seedlings collected in oak forests, with or without oak forest soils, and (3) planted seedlings germinated in autoclaved or unautoclaved oak forest soils. We measured the survival and growth rate for all three experiments, along with chemical properties, and root ECM colonization. Oak seeds sowed with oak forest soils had higher mycorrhizal colonization, leaf N concentrations and survival rate, and lower root δ13C than the seeds sowed without oak forest soils. Planting with oak forest soils also increased the survival rate of the germinated seedlings, but not the transplanted seedlings. Overall, our study suggested that the use of oak forest soils in the black locust forest to improve the water and N uptake of oak seedlings by providing the ECM inoculum, resulting in a high survival rate. Our study also implies that the method of sowing seeds was effortless and effectively compared to transplanting wild/nursery seedlings.

DOI： 10.3390/f12060669

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Aims: Topographic positions within a natural forest can considerably influence litter traits, soil microbial characteristics, and nitrogen (N) mineralization, causing plant–soil feedbacks. Despite the high abundance of coarse litter (woody debris and coarse roots) in forest ecosystems, most studies have focused on linkages between fine litter (leaves and fine roots) and N dynamics and/or the soil microbial community. Methods: We investigated the association of fine and coarse litter with soil microbial biomass, community structure, and N mineralization at upper and lower slope positions on sedimentary rocks in a temperate forest dominated by Fagus crenata. Results: Greater coarse litter abundance and litter C-to-N ratio, and lower soil microbial biomass, bacterial abundance, and N mineralization potential were found in upper positions than in lower positions. Among litter traits, coarse litter abundance and litter C-to-N ratio were the best predictors of the microbial biomass and fungal-to-bacterial dominance, possibly due to differences in climatic stress among plant communities. Microbial traits were the best predictors of N mineralization potential. Conclusions: Fine litter traits and coarse litter abundance are likely linked to soil microbial characteristics and N mineralization in natural forests with variable topography.

DOI： 10.1007/s11104-020-04759-y

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Other Link： http://link.springer.com/article/10.1007/s11104-020-04759-y/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)  

Nitrogen (N) is an essential plant nutrient, and plants can take up N from several sources, including via mycorrhizal fungal associations. The N uptake patterns of understory plants may vary beneath different types of overstory trees, especially through the difference in their type of mycorrhizal association (arbuscular mycorrhizal, AM; or ectomycorrhizal, ECM), because soil mycorrhizal community and N availability differ beneath AM (non-ECM) and ECM overstory trees (e.g., relatively low nitrate content beneath ECM overstory trees). To test this hypothesis, we examined six co-existing AM-symbiotic understory tree species common beneath both AM-symbiotic black locust (non-ECM) and ECM-symbiotic oak trees of dryland forests in China. We measured AM fungal community composition of roots and natural abundance stable isotopic composition of N (δ N) in plant leaves, roots, and soils. The root mycorrhizal community composition of understory trees did not significantly differ between beneath non-ECM and ECM overstory trees, although some OTUs more frequently appeared beneath non-ECM trees. Understory trees beneath non-ECM overstory trees had similar δ N values in leaves and soil nitrate, suggesting that they took up most of their nitrogen as nitrate. Beneath ECM overstory trees, understory trees had consistently lower leaf than root δ N, suggesting they depended on mycorrhizal fungi for N acquisition since mycorrhizal fungi transfer isotopically light N to host plants. Additionally, leaf N concentrations in the understory trees were lower beneath ECM than the non-ECM overstory trees. Our results show that, without large differences in root mycorrhizal community, the N uptake patterns of understory trees vary between beneath different overstory trees. 15 15 15

DOI： 10.3389/fpls.2020.583585

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Publishing type：Research paper (scientific journal)  

The Osumi Strait and its neighboring waters are major spawning grounds for commercially important small pelagic and coastal fish in the Pacific coastal area of Japan. Mesopelagic fish larvae are also abundant here, co-occurring with the larvae of commercial species. However, it is unknown whether these fish groups compete for prey. We examined the diet of four commercial fish groups (Engraulis japonicus, Trachurus japonicus, Triglidae spp., and Sebastiscus spp.) and two mesopelagic species (Sigmops gracilis, Myctophum asperum) during their larval stages to determine whether they had the same prey source. Morphological analysis and DNA metabarcoding of gut contents showed that the main prey species of all six fish groups were calanoid copepods. However, results from metabarcoding differed greatly from morphological analysis, showing that appendicularians were abundant in the guts of S. gracilis, M. asperum, and Sebastiscus spp. This may be because the methods differ in how they determine prey composition, with morphological analysis relying on counts of identifiable prey parts and metabarcoding being only a semi-quantitative method. In addition, appendicularians might be underestimated by metabarcoding analysis due to variation in genome size, copy number of target genes, and primer mismatches. Stable isotope analysis supported the importance of appendicularians as prey for S. gracilis, M. asperum, and Sebastiscus spp. Our results indicate that the two mesopelagic species and Sebastiscus spp. may compete for prey, but E. japonicus, T. japonicus, and Triglidae spp. occupy niches different from those of the two mesopelagic species. Our results imply that the trophic pathway via appendicularians may support the feeding of dominant mesopelagic species and enable coexistence with commercial species in the study area.

DOI： 10.1007/s00227-020-03810-x

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The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From results, a combined examination of nitrogen isotope, coliform bacteria, land-use, and geology confirmed the natural and anthropogenic origins of ammonium-nitrogen in the groundwater. In the brackish-water aquaculture region, groundwater has δ N values from +1.8 to +4.8‰ signifying that ammonium-nitrogen is derived from mineralization of organic nitrogen to ammonium. Furthermore, ammonium has a significantly positive relationship with sodium indicating the exchangeable ammonium is mobilized to groundwater via cation exchange. Meanwhile ammonium-nitrogen from anthropogenic waste was detected in agricultural and residential region. The groundwater has more varied δ N values, from −2.9 to +16.1‰, which implies attenuation of ammonium-nitrogen from several sources namely manure, mineral fertilizer, sewage, and pit latrines. Also, the presence of E. coli confirms the indication of human and animal waste contamination. However, since ammonium has no relationship with sodium, cation exchange is not feasible and ammonium-nitrogen flows into the groundwater from anthropogenic sources along with liquid wastes. 15 15 NH4 NH4

DOI： 10.3390/w13010025

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Stable nitrogen isotope ratios (δ N) of plants and soil have been used to study changes in the N cycle during ecosystem succession and retrogression. However, little is known about how δ N of soil mineral N and dissolved organic N (DON) change during retrogression, despite their potential to inform on processes contributing to N loss. Here, we examined the δ N of NH and DON together with δ N of the dominant plant species and bulk soil across a 5,000-year-old retrogressive chronosequence of forested islands in northern Sweden. The δ N of bulk soil N, NH and DON did not change greatly during retrogression, suggesting that there are no major losses of N from the system. The δ N of NH and DON was significantly correlated with that of bulk soil N across islands, indicating that bulk soil N is an important determinant of the δ N of dissolved soil N. The δ N of DON was significantly higher than those of NH and bulk soil N, probably because of the inclusion of microbial N to the DON fraction. Despite the lack of changes in δ N of soil N as retrogression proceeded, the δ N of most plant species increased. These results suggest that despite the relative importance of the three underlying mechanisms involved is unclear, the N resources of plants change in response to retrogression: they have an increasing reliance on DON, a decreasing dependence on N transferred from the mycorrhizal fungi and reduced reliance on N from surface soil layers as retrogression proceeds. 15 15 15 + 15 15 + 15 + 15 15 + 15 15 4 4 4 4

DOI： 10.1111/1440-1703.12208

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>
Accurate morphological ant mimicry by <italic>Myrmarachne</italic> jumping spiders confers strong protective benefits against predators. However, it has been hypothesized that the slender and constricted ant-like appearance imposes costs on the hunting ability because their jumping power to capture prey is obtained from hydraulic pressure in their bodies. This hypothesis remains to be sufficiently investigated. We compared the jumping and prey-capture abilities of seven <italic>Myrmarachne</italic> species and non-myrmecomorphic salticids collected from tropical forests in Malaysian Borneo and northeastern Thailand. We found that the mimics had significantly reduced abilities compared with the non-mimics. The analysis using geometric morphometric techniques revealed that the reduced abilities were strongly associated with the morphological traits for ant mimicry and relatively lower abilities were found in <italic>Myrmarachne</italic> species with a more narrowed form. These results support the hypothesis that the jumping ability to capture prey is constrained by the morphological mimicry and provide a new insight into understanding the evolutionary costs of accurate mimicry.

DOI： 10.1038/s41598-020-75010-y

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Other Link： http://www.nature.com/articles/s41598-020-75010-y

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Volcanic deposits increase soil organic carbon storage. However, little is known about the effect of volcanic deposits on forest soil nitrogen (N) dynamics and microbial communities. We explored gross and net N transformation rates and microbial community structure using a phospholipid fatty acid (PLFA) method across eight forests with soils derived from different parent material in Japan. Volcanic mineral soils had approximately three-fold greater total N and inorganic N contents and gross nitrification, ammonium immobilization, and nitrate immobilization rates that were one order of magnitude higher than in non-volcanic soils. Moreover, volcanic mineral soils had a 1.7-fold lower N turnover rate, which was estimated as net N mineralization rate per soil N. This was likely caused by a higher gross N immobilization rate, potentially due to the mineral traits of volcanic soils. Volcanic mineral soils had approximately four- and three-fold greater microbial biomass-N and bacterial PLFA contents, respectively, and the fungal:bacterial PLFA ratio was lower in volcanic mineral soils than in non-volcanic soils. Microbial community structure, analyzed using non-metric multidimensional scaling, was distinct between volcanic and non-volcanic soils, and was significantly affected by soil characteristics. This study demonstrates that aside from soil carbon storage, volcanic deposits are related to increases in soil N immobilization, N content, bacterial biomass, and N transformation rates in forest ecosystems.

DOI： 10.1016/j.soilbio.2020.108011

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Publishing type：Research paper (scientific journal)   Publisher：Arachnological Society of Japan  

DOI： 10.2476/asjaa.69.37

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DOI： 10.1007/s00040-018-0665-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

This study quantified the numbers and sex ratio of adult Sericania hidana (Coleoptera: Scarabaeidae) in a subalpine forest in 2017. Data from an area littered with coarse woody debris (CWD) created by a typhoon in 1959 were compared with those from an area where CWD had been cleared by salvage logging. Three types of traps were used: flight interception traps (FITs) with a black light, pitfall traps (PITs), and soil emergence traps (SETs). Carbon and nitrogen stable isotopes were analyzed to evaluate S. hidana diets and habitats. Overall, there were more S. hidana in the unsalvaged sites than in the salvaged sites. The FITs captured only males but SETs captured both males and females. The SETs on CWD captured more S. hidana than did SETs on soil in both the salvaged and unsalvaged sites. The PITs captured only a few individuals; thus, PITs are not suitable for studying this insect, although such traps were previously reported to capture S. hidana adults. Stable isotope analyses suggested that S. hidana feeds on a variety of plant materials, including living plants and CWD. These results suggest that CWD has long-term effects on insect populations. Soil emergence traps provide an effective method to quantitatively evaluate insect ecology, and FITs can effectively screen for the existence of insects.

DOI： 10.1111/ens.12362

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DOI： 10.1111/ens.12331

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Publishing type：Research paper (scientific journal)   Publisher：Magnolia Press  

The genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) is one of the most diversified salticid groups in Southeast Asia, with 23 species previously recorded from Borneo. Based on the collections accumulated from 2004 to 2014 in the Lambir Hills National Park, we herein describe six new species: M. amabilis sp. nov., M. hashimotoi sp. nov., M. lagarosoma sp. nov., M. leptosoma sp. nov., M. salaputium sp. nov. and M. tintinnabulum sp. nov. In addition, we describe the female of M. endoi Yamasaki &amp; Ahmad, 2013 for the first time. The male-female combination in M. amabilis sp. nov., M. tintinnabulum sp. nov. and M. endoi were confirmed by DNA barcoding.

DOI： 10.11646/zootaxa.4521.3.2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Myxomycetes are one of the major microbial predator groups found in detrital food webs within terrestrial ecosystems. They are typical inhabitants of coarse woody debris (CWD). However, the association between fungal communities and the foraging habits of myxomycetes has not been explored sufficiently in the field. Our study aimed to find community relationships between myxomycetes and fungi, a potential prey, on CWD, and the trophic status of saproxylic myxomycetes using stable isotope analysis of their sporocarps. Records of sporocarps present on 184 Pinus densiflora logs during a 3-year period listed 37 species of myxomycetes and 45 species of fungi. Ordination analysis using occurrence data of 34 dominant species (17 myxomycetes and 17 fungi) revealed their dynamic succession during log decay. Fungal dominants were clearly divided into two groups—earlier and later— and the majority of myxomycetes occurred during the middle stages of log decay between the first and second groups of fungal dominants. Species level associations between fungal and myxomycetes communities were rare. Isotopic nitrogen (δ15N) values of myxomycetes were significantly higher than those of wood-decay fungi, but few myxomycetes showed δ15N values higher than those of ectomycorrhizal fungi. Isotopic carbon (δ13C) values of myxomycetes were not significantly different from those of fungi. δ15N values of myxomycetes and fungi and δ13C of myxomycetes significantly increased with an increase in wood decay. However, these positive correlations between stable isotope profiles and wood decay disappeared after the values were calibrated by subtracting the δ15N and δ13C values of sapwood from those of myxomycetes and fungi. While saproxylic myxomycetes have long been assumed to be bacterivous, the results of this study suggest that wood-decay fungi could be an important part of their diet, and their foraging associations might be non-species specific.

DOI： 10.1016/j.soilbio.2018.03.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The soil microbial community and nitrogen (N) dynamics change seasonally due to several factors. The microbial community structure (MCS) can regulate N dynamics. However, there is insufficient information on seasonal changes in MCS and the relationship between MCS and N dynamics. We investigated MCS and N dynamics in forest soils with two different fertilities throughout a year. MCS, measured with phospholipid fatty acid (PLFA) analysis, showed a consistent seasonal trend, regardless of the fertility. Microbial indices (particularly the Saturated-/monounsaturated-PLFA ratio
Sat/mono) indicated a major PLFA shift among seasons, with temperature likely the most important factor. The fungal-/bacterial-PLFA ratio in the dormant season (December-April) was approximately 1.3 times greater than in the growing season (June-November). The trend in N dynamics showed that in summer (June-August), the gross N mineralization potential was greater than immobilization, whereas in winter (December-April), immobilization was dominant. The net mineralization potential in the growing season was approximately 1.6 times higher than in the dormant season. Moreover, a relationship was found between Sat/mono andNtransformation potentials. We highlight the microbial sensitivity to seasonal dynamics which can be associated with temperature, as well as carbon and N dynamics.

DOI： 10.3390/f9030153

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Language：Japanese  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (C-14) analysis revealed that B. chinensis has significantly younger 'diet age', the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the native range, while stable isotope analyses showed no change. These results suggest that in the introduced range B. chinensis remains a termite predator but also feeds on other consumer invertebrates with younger diet ages such as herbivorous insects. Radiocarbon analysis allowed us to elucidate cryptic dietary change associated with invasion success.

DOI： 10.1038/s41598-017-15105-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Arboreality has evolved in a wide range of taxa, but its adaptive significance has rarely been examined in natural ecosystems. Euhadra brandtii sapporo is an arboreal land snail distributed in a restricted area of Hokkaido, Japan. We hypothesized that arboreality provides the species with significant survival advantages, which we tested via field observations and experiments. A monitoring census showed that E. b. sapporo hibernates in winter in the ground litter, climbs into the canopy in early spring and returns to the ground in late autumn. This seasonal movement appears to be effective for escaping from predation by ground-dwelling carabine beetles, whose activity was high during the summer based on a pitfall-trap census. Manipulative field experiments were conducted to compare survival rates in arboreal and ground-dwelling environments. We collected 120 E. b. sapporo individuals in summer and tethered 40 in tree canopies and 80 on the ground; half those on the ground were covered by baskets to prevent predation by large animals. The survival rate after 11 days was highest in the canopy, followed by that on the ground with a basket and was lowest on the ground without a basket. Predation was the main cause of death, but some died from other causes. Similar results were obtained in autumn, except for higher survival rates of the ground treatments. Analyses of carbon and nitrogen isotope ratios suggest that the land snail uses epiphytic lichens and mosses as food resources. In conclusion, arboreality has a marked advantage in reducing mortality in E. b. sapporo and is probably supported by food availability as well. (C) 2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.anbehav.2017.02.022

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Language：Japanese   Publisher：一般社団法人 日本生態学会  

Progress in ecological studies of soil fauna includes studies of the role and effects of soil fauna on decomposition and soil carbon dynamics in relation to global environmental changes, the introduction of molecular biology approaches to such studies, feeding habit analysis using stable isotopes, trait-based analysis of community ecology, and fine-scale experimental studies on the above/below ground relationship in ecosystems. In relation to this progress, six topics were reviewed: the function of soil fauna in the decomposition process
carbon sequestration in earthworms
the process of assemblage formation in earthworms
a trait-based approach to the collembolan community
food habit analysis using stable isotopes
and soil faunal impacts on plants.

DOI： 10.18960/seitai.67.2_95

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Lignins have been used as a biomarker to explore changes in terrestrial organic matter input into lakes and to investigate past watershed vegetation. Burial of organic carbon (OC) in lake sediments, an important component of the global C cycle, is likely associated with the terrestrial OC input. However, few studies have explored changes in terrestrial C input into lakes in the last century. Furthermore, the relationship between lignin phenol compositions and watershed vegetation remains poorly examined. In this study, we examined changes in OC concentrations, OC mass accumulation rates (MAR), and lignin phenol compositions over the last century in sediments from six lakes in Japan that differ in watershed land-use and vegetation. The sediments were dated using Pb-210 and Cs-137, and showed increased OC concentrations and MARs in three lowland lakes over the last century. This pattern was not found in three mountain lakes. In one of the lowland lakes, lignin phenol concentrations normalized to OC did not change during the periods with high OC concentrations and MARs. This indicates that not only eutrophication but also enhanced terrestrial OC input could lead to greater burial of OC. The lignin phenol compositions did not show clear trends over the last century in most of the lakes examined. The ratios of syringyl to vanillyl phenols and the lignin phenol vegetation index had significant relationships with proportions of angiosperms in watershed vegetation. These results demonstrate that lignin phenols are useful in inferring recent as well as past changes in lake watershed environments. (c) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.orggeochem.2016.11.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of -19.4 +/- 0.6% and 9.4 +/- 0.6% (mean +/- SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1%, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C-3 and C-4 plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved.

DOI： 10.1038/srep33122

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Inc.  

Primary forests are known to have positive effects on the biodiversity of surrounding secondary forests. However, it is unclear whether primary forest remnants affect the feeding habits of consumers that inhabit secondary forests. Here, we examined whether the feeding habits of ants (Formicidae: Hymenoptera) belonging to four taxonomic groups (Camponotus gigas, Odontomachus rixosus, Pachycondyla spp., and Polyrhachis spp.) differed in Macaranga secondary forests with different proportions of surrounding primary forest remnants in Sarawak, Malaysia. In the secondary forests, our previous study showed that species diversity of ants significantly increased as the proportion of surrounding primary forest remnants increased. We explored feeding habits by measuring carbon and nitrogen isotope ratios (δ13C and δ15N). We also estimated the diet age of the ants, which represents the lag time between primary production and utilization by ants, by performing radiocarbon (δ14C) measurements. δ13C of ants and litter decreased with the increase in primary forest remnants, likely indicating a more closed canopy cover around the sites. Meanwhile, baseline-corrected δ15N of ants, which considered the variation in plant δ15N among study sites, or diet ages of the ants did not show significant response to the proportion of the surrounding primary forest remnants. δ13C, δ15N, and diet ages showed consistent differences among the ant taxa across different proportions of primary forest remnants. These isotopic patterns suggest that, in contrast to the effect on species diversity, surrounding primary forest remnants did not markedly affect the feeding habits of the ants that persisted in the secondary forests.

DOI： 10.1016/j.fooweb.2016.02.002

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本生態学会  

DOI： 10.18960/seitai.66.2_421

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PENSOFT PUBL  

A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to C. lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.

DOI： 10.3897/zookeys.596.8525

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DOI： 10.1007/s10310-016-0526-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL UNIV SINGAPORE, SCHOOL BIOLOGICAL SCIENCES  

To evaluate the pattern of co-occurrence between ant-mimicking jumping spiders and sympatric ants in a tropical rainforest, we sampled these arthropods and also non-mimicking jumping spiders by net-sweeping from the understory vegetation in Sabah, Malaysian Borneo. We collected the spiders and ants from a total of 594 sample points, with ants occurring in 445 points (79.4%), non-mimicking jumping spiders in 308 (51.9%), Agorius ant-mimicking spiders in 40 (6.7%), and Myrmarachne ant-mimicking spiders in 59 (9.9%). Frequencies of occurrence of non-mimicking jumping spiders showed no significant difference in relation to ant-occurrence, whereas both of the ant-mimicking spider genera occurred significantly more frequently with ants. Agorius spiders co-occurred with a wider variety of different ant genera, compared to Myrmarachne, but logistic regression analyses and a null model test showed no specific associations between Agorius spiders and the sympatric ant genera. The mimetic resemblances of Agorius spiders are considered to be much less ant-like than those of Myrmarachne spiders, because their constriction of the cephalothorax is not as obvious as in Myrmarachne. These data provide support for the multi-model hypothesis (Edmunds 2000), which predicted that a poor ant-mimic should occur in ranges of many different ants, compared to good ant-mimic.

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Language：English   Publisher：WILEY-BLACKWELL  

Insects are the most diverse organisms and often the most abundant animals in some ecosystems. Despite the importance of their functional roles and of the knowledge for conservation, the trophic ecology of many insect species is not fully understood. In this review, I present how stable carbon (C) and nitrogen (N) isotopes have been used to reveal the trophic ecology of insects over the last 30years. The isotopic studies on insects have used differences in C isotope ratios between C-3 and C-4 plants, along vertical profiles of temperate and tropical forest stands, and between terrestrial and aquatic resources. These differences enable exploration of the relative importance of the food resources, as well as movement and dispersal of insects across habitats. The C-13-enrichment (approximately 3 parts per thousand) caused by saprotrophic fungi can allow the estimation of the importance of fungi in insect diets. Stable N isotopes have revealed food resource partitioning across diverse insect species above and belowground. Detritivorous insects often show a large trophic enrichment in C-13 (up to 3 parts per thousand) and N-15 (up to 10 parts per thousand) relative to the food substrates, soil organic matter. These values are greater than those commonly used for estimation of trophic level. This enrichment likely reflects the prevalence of soil microbial processes, such as fungal development and humification, influencing the isotopic signatures of diets in detritivores. Isotope analysis can become an essential tool in the exploration of insect trophic ecology in terms of biogeochemical C and N cycles, including trophic interactions, plant physiological and soil microbial processes.

DOI： 10.1111/ens.12128

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Energy and material flows from dead organic matter, or detritus, to generalist predators have a potential impact on the food web dynamics. However, little is known about how commonly generalist predators depend on detritivorous prey, or the detritus on which the detritivores have fed in terrestrial food webs. To examine this, we measured the diet ages of terrestrial invertebrate and vertebrate consumers (&gt;30 species) at multiple trophic levels in a tropical rain forest, with a particular focus on ants and termites by using radiocarbon (C-14). Here, we defined diet age as the lag time between the primary production and the utilization by consumer organisms. The diet ages varied from 0 to &gt;50years and corresponded to known feeding habits of the consumers. Herbivores such as bees, butterflies, a frugivorous bird and bat, and nectar-feeding ants had young diet ages (0-3years). Meanwhile, detritivores such as termites had old diet ages, which increased according to the food resources in the order of litter (6years), soil (10years) and wood (19years). The diet ages of predators such as wolf spiders, hunting wasps, army ants, tree shrews and an insectivorous bat were intermediate (2-8years), indicating the dependence of many predators on detritivores. Because known dietary components of the predators include herbivores and detritivores, the intermediate ages likely indicate the coupling of energy and material flows between plant-based and detritus-based food webs. Diet ages of soil-feeding termite and army ant differed significantly, although a previous study reported that their nitrogen isotope ratios were indistinguishable despite the differing feeding habits. This indicates that radiocarbon can distinguish the two factors, trophic enrichment and the below-ground processes (humification), both of which could influence the nitrogen isotopic signatures of the terrestrial consumers. Our results show that radiocarbon would provide insights into structures of terrestrial food webs as well as time frame of energy and material flows through the webs.

DOI： 10.1111/1365-2435.12357

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Language：English   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAGNOLIA PRESS  

Pycnotarsobrentus inuiae Maruyama & Bartolozzi, gen. nov. and sp. nov. (Brentinae: Eremoxenini) is described from the Lambir Hills National Park, Borneo (Sarawak, Malaysia) based on specimens collected from Crematogaster difformis F. Smith, 1857 ant nests in the myrmecophytic epiphytic ferns Platycerium crustacea Copel. and Lecanopteris ridleyi H. Christ. A second species of Pycnotarsobrentus is known from Malaysia but is represented by only one female and consequently not yet described pending discovery of a male. Pycnotarsobrentus belongs to the tribe Eremoxenini and shares some character states with the African genus Pericordus Kolbe, 1883. No species of Eremoxenini with similar morphological modifications are known from the Oriental region.

DOI： 10.11646/zootaxa.3786.1.5

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We review the use of stable carbon isotope ratios (δ13C) and radiocarbon natural abundances (Δ14C) for stream food web studies. The δ13C value of primary producers (e.g., periphytic algae, hereafter periphyton) in streams is controlled by isotopic fractionation during photosynthesis and variable δ13C of dissolved CO2. When periphyton δ13C differs from that of terrestrial primary producers, the relative contribution of autochthony and allochthony to stream food webs can be calculated. Moreover, the variation in periphyton δ13C can reveal how much stream consumers rely on local resources because each stream habitat (e.g., riffle vs. pool, open vs. shaded) usually has a distinctive δ13C. However, periphyton δ13C often overlaps with that of terrestrial organic matter. On the other hand, periphyton Δ14C is less variable than δ13C among habitats, and reflects the Δ14C of dissolved CO2, which could be a mixture of "aged" (Δ14C &lt
0 ‰) and "modern" (Δ14C &gt
0 ‰) carbon. This is because the Δ14C is corrected by its δ13C value for the isotopic fractionation during photosynthesis. Recent studies and our data indicate that many stream food webs are supported by "aged" carbon derived from the watershed via autochthonous production. The combined use of δ13C and Δ14C allows robust estimation of the carbon transfer pathway in a stream food web at multiple spatial scales ranging from the stream habitat level (e.g., riffle and pool) to watershed level (autochthony and allochthony). Furthermore, the Δ14C of stream food webs will expand our understanding about the time frame of carbon cycles in the watersheds. © 2013 The Ecological Society of Japan.

DOI： 10.1007/s11284-012-1003-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Nitrogen (N) and carbon (C) isotopic signatures (delta N-15 and delta C-13) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.
The delta N-15, delta C-13, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden.
The delta C-13 and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, delta N-15 showed an overall decline, and delta N-15 of the feather moss and associated vascular plants diverged over time from that of atmospheric N-2.
Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in delta N-15 signature due to isotopic fractionation. The decreasing trend of delta N-15 suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition.

DOI： 10.1007/s11104-013-1667-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Tropical landscape structures have been transformed into mosaic structures consisting of small patches of primary and secondary forests, and areas of other land use. Diversity of insect assemblages is often higher in primary forests than in surrounding secondary forests. However, little is known about how the primary forests affect diversity in surrounding secondary forests in a landscape. In Sarawak, Malaysia, the typical landscape in areas from which lowland tropical rainforests had originally spread consists mainly of primary and secondary forests, with small areas of cultivation. In this study, we examined how the proportion of remnant primary forests in a landscape affects species diversity and species composition of ants and dung beetles in Macaranga-dominated secondary forests. The proportions were quantified based on remote-sensing data at various spatial scales, ranging from 100- to 5,000-m radius from each of the target forests. We found that the proportions of remnant primary forests within a 100-m radius had a significant positive effect on ant species diversity, and those within 100-, 300-, and 500-m radii significantly affected species compositions. However, the proportions of remnant primary forests had no significant relationship with dung beetle diversity, while those within 100- and 1,000-m radii had significant effects on species composition. The different responses to the remnant primary forests are likely to be related to differences in the movement and dispersal traits between the two taxa.

DOI： 10.1007/s10841-012-9544-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Nitrogen (N) and carbon (C) isotopic signatures (delta N-15 and delta C-13) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.
The delta N-15, delta C-13, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden.
The delta C-13 and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, delta N-15 showed an overall decline, and delta N-15 of the feather moss and associated vascular plants diverged over time from that of atmospheric N-2.
Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in delta N-15 signature due to isotopic fractionation. The decreasing trend of delta N-15 suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition.

DOI： 10.1007/s11104-012-1339-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Trophic fractionation of carbon and nitrogen isotopes (Delta delta C-13, Delta delta N-15) was examined using previously complied databases for food chains in Lake Biwa, Lake Baikal, and Mongolian grassland. The following two features were clarified: (1) For each ecosystem, the ratios of trophic fractionation of carbon and nitrogen isotopes (Delta delta N-15/Delta delta C-13) throughout food chain could be obtained as the slope of linear regression line on the delta N-15-delta C-13 plot. (2) Further, analysis of covariance (ANCOVA) revealed the slopes on delta N-15-delta C-13 were not significantly different among these various ecosystems and allowed us to have the regression by setting delta N-15 as the response variable: delta N-15 = 1.61 delta C-13 + [ecosystem specific constant] with standard errors of [+/- 0.41] and [+/- 9.7] for the slope and the intercept, respectively. It was suggested that the slope of the regression (or the ratio Delta delta N-15/Delta delta C-13) could be applicable to more complicated food webs in case nitrogen and carbon isotope ratios of primary producers can be assumed constant in space and time within the ecosystems. The results from simple linear regression analyses coincided well with the ANCOVA results for these ecosystems, although there was some discrepancy between the results of the two statistical analyses. Possible factors that govern the linear relationship between delta N-15 and delta C-13 along a food chain are discussed together with a new scope for the stable isotope food chain analyses.

DOI： 10.1007/s11284-012-1024-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Natural abundance of radiocarbon (C-14) has been applied to estimate the turnover time of soil carbon (C) across different climate regions. However, despite the important functional role played by soil animals in decomposition processes, little is known about variation in their C-14 concentrations across different climate regions. In this study, we measured C-14 concentrations of earthworms collected in three forests in Japan. In addition, we also reviewed C-14 data on earthworms that were previously reported. We used these data to test whether the diet ages (defined as time elapsed since C in the diet of earthworms was fixed from atmospheric CO2 by photosynthesis) differed according to feeding habits and across study sites in various climate regions ranging from cool temperate forest to tropical savanna. Multiple regression analysis showed that the diet ages of earthworms were significantly affected by both feeding habits and study sites. The diet ages of endogeic (soil-feeding) earthworms (8.3 +/- 0.4 years, mean SE) were significantly older than those of epigeic (litter-feeding) earthworms (2.6 +/- 0.5 years), with anecic (litter-/soil-feeding) earthworms (5.7 +/- 0.9 years) having intermediate diet ages. When mean diet age was compared for each feeding habit, only that of endogeic earthworms differed significantly across the sites. However, it did not necessarily become younger in warmer climate regions. These results either suggest that the degree of decomposition of soil organic matter used by earthworms differs among the study sites, or that the difference in the turnover time of Soil organic C used by earthworms across the sites is relatively small and variable due to factors other than temperature, such as soil texture and vegetation. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsoil.2012.09.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Most theories attempting to explain the coexistence of species in local communities make fundamental assumptions regarding whether neighbors exhibit competitive, neutral, or positive resource-use interactions; however, few long-term data from naturally assembled plant communities exist to test these assumptions. We utilized a 13-year experiment consisting of factorial removal of three shrub species (Vaccinium myrtillus, V. vitis-idaea, and Empetrum hermaphroditum) and factorial removal of two functional groups (tree roots and feather mosses) to assess how neighbors affect N acquisition and growth of each of the three shrub species. The removal plots were established on each of 30 lake islands in northern Sweden that form a natural gradient of resource availability. We tested the hypotheses that: (1) the presence of functionally similar neighbors would reduce shrub N acquisition through competition for a shared N resource; (2) the removal of functional groups would affect shrub N acquisition by altering the breadth of their niches; and (3) soil fertility would influence the effects of neighbor removals. We found that the removal of functionally similar neighbors (i.e., other shrub species) usually resulted in higher biomass and biomass N, with the strength of these effects varying strongly with site fertility. Shrub species removals never resulted in altered stable N isotope ratios (delta N-15), suggesting that the niche breadth of the three shrubs was unaffected by the presence of neighboring shrub species. In the functional group removal experiment, we found positive effects of feather moss removal on V. myrtillus biomass and biomass N, and negative effects on E. hermaphrotium N concentration and V. vitis-idaea biomass and biomass N. Tree root removal also caused a significant shift in foliar delta N-15 of V. myrtillus and altered the delta N-15, biomass, and biomass N of E. hermaphroditum. Collectively, these results show that the resource acquisition and niche breadth of the three shrub species are often affected by neighbors, and further that both the identity of neighbors and site fertility strongly determine whether these interactions are positive, negative, or neutral. These findings have implications for understanding species coexistence and the reciprocal relationships between productivity and species diversity in this ecosystem.

DOI： 10.1890/11-1877.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

The stable nitrogen (N) isotope ratio (delta N-15) has been used to examine the anthropogenic N input (i.e., septic water, wastewater, and manure) to aquatic ecosystems, because anthropogenic N generally has a delta N-15 signature distinct from that found in nature. Aquatic organisms and the derived organic matter such as sediments are reported to become increasingly enriched in N-15 as the human population density increases in watersheds. However, little is known about the relationship in steppe ecosystems, where the livestock population is greater than that of humans. Here, we conducted a preliminary study in the Selenga river mainstream watershed in Mongolia, which covers an area of approximately 300,000 km(2). A multiple regression analysis revealed that the delta N-15 of the riverine sediment was significantly affected by the human population density and more significantly by livestock population density. The population density, including both humans and livestock, significantly influenced delta N-15 of the macrophytic Potamogeton spp. The results showed that delta N-15 of riverine organic matter can be an indicator of the human and livestock population density, which is likely associated with the status of N cycles in livestock-dominated watersheds.

DOI： 10.1007/s10201-011-0351-7

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Language：Japanese   Publisher：日本花粉学会  

Changes in the pollen accumulation rate (PAR) of Cryptomeria japonica during the last 100 years were reconstructed based on pollen analysis of a sediment core from Lake Biwa dated by Pb-210 and Cs-137 methods. A comparison of the increases in the Lake Biwa PAR data with pollen data from afforested areas of C. japonica, planted during the 1950s, showed notable correlation. Before 1900, the PAR for C. japonica in the Lake Biwa sediment showed relatively low amounts of pollen, 900-1400 grains・cm^<-2>・year^<-1>. After 1900, the PAR increased slightly and, from 1920 to 1970, increased to between 2800-3700 grains・cm^<-2>・year^<-1>. From 1970 until the late 1970's the PAR increase continued, reaching 4200-4400 grains・cm^<-2>・year^<-1>, and further increasing by the early 1980's to 6300-7100 grains・cm^<-2>・year^<-1>. From the late 1980's and into the 1990's, the PAR showed a rapid increase from 8300 to 13400 grains・cm^<-2>・year^<-1>. Comparison of the results of the PAR data from Lake Biwa with estimated data for the mature afforested area of C. japonica suggests that recent increases of airborne pollen of C. japonica have, since the 1950's, been strongly influenced by cultivated forests of C. japonica. The PAR for the Lake Biwa sediment was also consistent with airborne pollen records of years with abundant C. japonica pollen dispersal. Notably, a comparison of the recent PAR data with a pollen analysis of sediment cores from Lake Biwa during the Quaternary period shows the quantities of C. japonica pollen during 3000-2000 cal yr BP, and during the second half of the last interglacial period, to be similar to those of PAR data after the early 1980's.

DOI： 10.24524/jjpal.58.1_5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

To examine the relationship between carbon and nitrogen stable isotope (SI) ratios (delta C-13 and delta N-15) of zooplankton, we analyzed samples collected bimonthly from March to October 2009, from the euphotic layers of the Oyashio current along the A-line in the western North Pacific. Isotopic ratios of higher trophic levels such as predatory zooplankton and/or long-lived zooplankton varied little with season, while those of short-lived zooplankton were variable on the delta N-15-delta C-13 map. We also analyzed preserved samples taken from the warm-core ring 86-B derived from the Kuroshio extension region. Although the zooplankton groups in the two regions exhibited different values in delta N-15, the delta N-15 versus delta C-13 slopes for each ecosystem do not show significant differences. Statistical analysis conducted together with previously published data from the Antarctic Ocean and the Gulf of Alaska suggested a similar delta N-15 versus delta C-13 slope throughout the four regions. We attributed this common slope to physiological aspects of feeding processes (e. g. the kinetic isotope effects inherent in the processes of amino acid synthesis). The common pattern for all four oceanic regions suggests that SIs may be used to elucidate general patterns in ecosystems and biogeochemical cycles.

DOI： 10.1093/plankt/fbr070

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER BASEL AG  

Despite the recognition of the functional role of Hymenoptera (ants, bees and wasps) and Isoptera (termites) in tropical ecosystems, their detailed feeding habits are not well known. To examine the feeding habits of these groups, we measured nitrogen (N) and carbon (C) stable isotope ratios (delta(15)N and delta(13)C) of hymenopterans (12 families, a parts per thousand yen16 genera and a parts per thousand yen32 species) and isopterans (one family and 10 species) collected in a tropical rain forest, Sarawak, Malaysia. We compared the isotopic signatures of these insects to those previously reported for other consumers collected in the same forest. The delta(15)N and delta(13)C values of these insects overlapped with those of the other consumers, indicating that they have access to diverse C and N sources in the forest. The delta(15)N values of ants and termites indicated that their feeding habits range along a continuum from herbivory (i.e. dependent on honeydew and nectar) to predation and from wood-feeders to soil-feeders, respectively. In addition, the delta(15)N values of wasps varied greatly from -0.1aEuro degrees (Braconidae sp.) to 8.6aEuro degrees (Bembix sp.), suggesting that their feeding habits also range from omnivory to predation. The ant species Camponotus gigas had delta(13)C values similar to those of invertebrate detritivores and omnivores rather than to those of invertebrate herbivores, although the diet of this species consists mostly of honeydew. This discrepancy suggests that the ant uses carbohydrates as an energy source, the isotopic signatures of which are not well retained in the body tissues. Values of both delta(15)N and delta(13)C of the predatory army ant Leptogenys diminuta and the soil-feeding termite Dicuspiditermes nemorosus did not differ significantly, indicating that both trophic level and the humification of feeding substrates can increase the isotopic signatures of terrestrial consumers.

DOI： 10.1007/s00040-011-0159-9

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Language：Japanese   Publisher：日本人類学会  

DOI： 10.1537/asj.119.9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ECOLOGICAL SOC AMER  

Despite their ubiquity, the role of ants in driving ecosystem processes both aboveground and belowground has been seldom explored, except within the nest. During 1995 we established 16 ant exclusion plots of approximately 1.1 x 1.1 m, together with paired control plots, in the understory layer of a boreal forest ecosystem in northern Sweden that supports high densities of the mound-forming ant Formica aquilonia, a red wood ant species of the Formica rufa group. Aboveground and belowground measurements were then made on destructively sampled subplots in 2001 and 2008, i.e., 6 and 13 years after set-up. While ant exclusion had no effect on total understory plant biomass, it did greatly increase the relative contribution of herbaceous species, most likely through preventing ants from removing their seeds. This in turn led to higher quality resources entering the belowground subsystem, which in turn stimulated soil microbial biomass and activity and the rates of loss of mass and carbon (C) and nitrogen (N) from litter in litterbags placed in the plots. This was accompanied by losses of similar to 15% of N and C stored in the humus on a per area basis. Ant exclusion also had some effects on foliar stable isotope ratios for both C and N, most probably as a consequence of greater soil fertility. Further, exclusion of ants had multitrophic effects on a microbe-nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web. Our results point to a major role of red wood ants in determining forest floor vegetation and thereby exerting wide-ranging effects on belowground properties and processes. Given that the boreal forest occupies 11% of the Earth&apos;s terrestrial surface and stores more C than any other forest biome, our results suggest that this role of ants could potentially be of widespread significance for biogeochemical nutrient cycling, soil nutrient capital, and sequestration of belowground carbon.

DOI： 10.1890/10-1223.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

We report on a stable isotope paleodietary reconstruction of Jomon populations in Japan during the Middle to Final Jomon period (ca. 5000-2300 years BP), focusing on dietary differences within and among populations and between regions. Carbon and nitrogen isotope analysis was performed on human and faunal bone collagen from six coastal sites along the Inland Sea in the Sanyo (Ota, Funamoto, and Tsukumo) region and along Mikawa Bay and the Pacific Ocean in the Tokai (Kawaji, Yoshigo, and lnariyama) region. We found that carbon and nitrogen isotope ratios were positively correlated, indicating that the Jomon people consumed a mixed diet of marine (shellfish and marine fish) and terrestrial (C(3) plants and terrestrial mammals) protein. In the Ota samples (n = 25, during the Middle Jomon period, 5000-4000 years BP), sex was one of the main reasons for the intra-population dietary variation. Ota males consumed greater amounts of marine food, while Ota females consumed greater amounts of terrestrial food; these dissimilar diets may have been related to the sexual division of labor. Significant inter-population dietary differences were found, which may have been related to differences in age or site location. Notably, the two coastal regions showed clear isotopic differences. Nitrogen isotope ratios of individuals from the Sanyo region were significantly higher than ratios of individuals from the Tokai region. The individuals in the Sanyo region might have consumed a diet high in aquatic foods, particularly high trophic level marine fish, whereas the individuals in the Tokai region might have consumed a lot of marine shellfish. Another possible reason for the regional isotopic difference might have been different baseline of nitrogen isotope ratios of the marine ecosystems. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jas.2010.03.002

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Language：English   Publisher：SPRINGER TOKYO  

Carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) have been used for more than two decades in analyses of food web structure. The utility of isotope ratio measurements is based on the observation that consumer delta(13)C values are similar (&lt; 1aEuro degrees difference) to those of their diet, while consumer delta(15)N values are about 3aEuro degrees higher than those of their diet. The technique has been applied most often to aquatic and aboveground terrestrial food webs. However, few isotope studies have examined terrestrial food web structure that includes both above- and belowground (detrital) components. Here, we review factors that may influence isotopic signatures of terrestrial consumers in above- and belowground systems. In particular, we emphasize variations in delta(13)C and delta(15)N in belowground systems, e.g., enrichment of (13)C and (15)N in soil organic matter (likely related to soil microbial metabolism). These enrichments should be associated with the high (13)C (similar to 3aEuro degrees) enrichment in belowground consumers relative to litter and soil organic matter and with the large variation in delta(15)N (similar to 6aEuro degrees) of the consumers. Because such enrichment and variation are much greater than the trophic enrichment generally used to estimate consumer trophic positions, and because many general predators are considered dependent on energy and material flows from belowground, the isotopic variation in belowground systems should be taken into account in delta(13)C and delta(15)N analyses of terrestrial food webs. Meanwhile, by measuring the delta(13)C of key predators, the linkage between above- and belowground systems could be estimated based on observed differences in delta(13)C of primary producers, detritivores and predators. Furthermore, radiocarbon ((14)C) measurements will allow the direct estimation of the dependence of predators on the belowground systems.

DOI： 10.1007/s11284-010-0719-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

Carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) have been used to study the structure of food webs. However, few studies have examined how a terrestrial food web can be depicted by this technique. We measured delta(13)C and delta(15)N in various consumers of four trophic groups (detritivores, herbivores. omnivores and predators), including vertebrates and invertebrates (14 orders, &gt;= 24 families). as well as canopy and understorey leaves in a tropical rain forest in Malaysia. We found that. delta(13)C and delta(15)N of the consumers differed significantly among the trophic groups. The predators had significantly, higher delta(13)C than the herbivores, and were similar in delta(13)C to the detritivores, suggesting that most. predators examined depend largely, on below-ground food webs. delta(15)N was higher in predators than detritivores by about, 3 parts per thousand. The comparison of delta(13)C in plant materials and herbivores suggests that most. herbivores are dependent on C fixed in the canopy, layers. The vertebrates had significantly higher delta(15)N and delta(13)C than the invertebrates of the same trophic group. likely reflecting differences in the physiological processes and/or feeding habits. This study indicates that stable isotope techniques can help better Understanding of the terrestrial food webs in terms of both trophic level and the linkage of above and below-ground systems.

DOI： 10.1017/S0266467409990502

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

Distinct patterns can be discerned in the extensive ritual tooth ablation found among the human skeletal remains of the Late-Final Jomon period (ca. 3200-2800 cal BP) in Japan. Based on comparative observations of sex and grave patterns in the skeletal remains, two major patterns in ritual tooth ablation, termed type 41 and type 2C, have been assigned to locals and immigrants, respectively. In order to test this hypothesis, strontium (Sr) isotope ((87)Sr/(86)Sr) analyses were performed on human skeletal remains from the Yoshigo shell mound in Aichi Prefecture, central Japan. Plants in the surrounding area were also examined to illustrate the geographic (87)Sr/(86)Sr distribution. The Sr isotopic variation in human tooth enamel ((87)Sr/(86)Sr = 0.70868-0.71028) was greater than that in human bones ((87)Sr/(86)Sr = 0.70871-0.70943). Individuals with higher Sr isotope ratios in their tooth enamel than seawater Sr values of 0.7092 can be identified as immigrants (36% of population). The presence of these isotopically identified immigrants between both type 2C and type 41 individuals does not support the previous hypothesis. The intra-population (87)Sr/(86)Sr distribution of tooth enamel of type 2C individuals showed a significantly higher mean ratio than that of type 41 individuals, suggesting a higher proportion of immigrants among the former. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jas.2009.06.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

In the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, and this involves increased nutrient limitation, and reduced aboveground and belowground ecosystem processes rates. Little is known about how the nitrogen and carbon stable isotope ratios (delta(15)N and delta(13)C) of plants, soils and consumer organisms respond to retrogression in boreal forests. We investigated a 5000 year chronosequence of forested islands in the boreal zone of northern Sweden, for which the time since lightning-induced wildfire increases with decreasing island size, leading to ecosystem retrogression. For this system, tissue delta(15)N of three abundant plant species (Betula pubescens, Vaccinium myrtillus and Pleurozium schreberi) and humus all increased as retrogression proceeded. This is probably due to enhanced ecosystem inputs of N by biological fixation, and greater dependency of the plants on organic N during retrogression. The delta(13)C of B. pubescens and plant-derived humus also increased during retrogression, probably through nutrient limitation increasing plant physiological stress. Unlike the plants, delta(15)N of invertebrates (lycosid spiders and ants) did not increase during retrogression, probably because of their partial dependence on aquatic-derived prey that had a variable delta(15)N signature. The delta(13)C of the invertebrates increased as retrogression proceeded and converged towards that of an aquatic prey source (chironomid flies), suggesting increased dependence on aquatic-derived prey during retrogression. These results show that measurement of delta(15)N and delta(13)C of plants, soils, and consumers across the same environmental gradient can provide insights into environmental factors that drive both the aboveground and belowground subsystems, as well as the linkages between them. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4095

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Zygomorphic flowers are usually more complex than actinomorphic flowers and are more likely to be visited by specialized pollinators. Complex zygomorphic flowers tend to be oriented horizontally. It is hypothesized that a horizontal flower orientation ensures effective pollen transfer by facilitating pollinator recognition (the recognition-facilitation hypothesis) and/or pollinator landing (the landing-control hypothesis). To examine these two hypotheses, we altered the angle of Commelina communis flowers and examined the efficiency of pollen transfer, as well as the behavior of their visitors. We exposed unmanipulated (horizontal-), upward-, and downward-facing flowers to syrphid flies (mostly Episyrphus balteatus), which are natural visitors to C. communis. The frequency of pollinator approaches and landings, as well as the amount of pollen deposited by E. balteatus, decreased for the downward-facing flowers, supporting both hypotheses. The upward-facing flowers received the same numbers of approaches and landings as the unmanipulated flowers, but experienced more illegitimate landings. In addition, the visitors failed to touch the stigmas or anthers on the upward-facing flowers, leading to reduced pollen export and receipt, and supporting the landing-control hypothesis. Collectively, our data suggested that the horizontal orientation of zygomorphic flowers enhances pollen transfer by both facilitating pollinator recognition and controlling pollinator landing position. These findings suggest that zygomorphic flowers which deviate from a horizontal orientation may have lower fitness because of decreased pollen transfer.

DOI： 10.1007/s00442-009-1334-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

We examined how nitrogen-stable isotopic signatures of food web components (basal resources, primary and lower consumers, and omnivores) in rivers change with increasing levels of human population density (HPD) in their watersheds. Samples were collected from 22 rivers flowing in the Lake Biwa basin, Japan. Among three potential resources at the base of food webs (epilithon, benthic and suspended particulate organic matter), the mean isotopic values (delta(15)N) of the epilithon (4.5-7.8%) were consistently higher than those of other items (1.9-4.2%) and displayed the most pronounced elevation (by 3.3%) with increasing HPD. The mean delta(15)N values of the individual taxa of lower consumers (bivalve, snail and caddisfly) tended to increase with increasing HPD, although the pattern and the extent of the elevation were highly variable among the taxa. These results suggest a taxon-specific feature in the N source (or sources) of lower consumers. Our data suggested that human activities (e.g. nutrient loading) potentially induce changes in the N baselines of river food webs. The major N source of bivalves appeared to be shifted from suspended particulate organic matter to other items with increasing HPD. Trophic levels of goby fish (Rhinogobius sp. OR) and shrimp (Palaemon paucidens), being estimated to be at 2.4-3.8 and 2.1-3.4, respectively, did not differ significantly among rivers with different HPD levels.

DOI： 10.1007/s11284-008-0489-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Many epiphytic ferns in tropical forest canopies have domatia that provide habitat for arboreal arthropods such as ants. Two species of fern that were predominantly occupied by Crematogaster difformis ants were collected from the canopy of a forest in Borneo. In the fern domatia, two cockroach species, Pseudoanaplectinia yumotoi and Blatta sp., were found to live with C. difformis. Pseudoanaplectinia yumotoi were found in large numbers and accounted for approximately 20% of the total arthropod population, while Blatta sp. comprised only 1% of the arthropods living in the domatia. Behavioural experiments were conducted to evaluate the response of C. difformis workers to newly introduced cockroaches of each species and to allospecific ant workers. Crematogaster difformis workers were highly aggressive and quickly attacked allospecific workers. Both cockroach species could fend off ant attacks; however, dead Blatta sp. were often attacked by the ants while dead P. yumotoi were infrequently bothered.

DOI： 10.1080/00222930902807734

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Deterioration of aquatic ecosystems resulting from enhanced anthropogenic N loading has become an issue of increasing concern worldwide, and methods are needed to trace sources of N in rivers. Because nitrate from sewage is enriched in N-15 relative to nitrate from natural Soils, delta N-15 values of stream nitrate (delta N-15(nitrate)) should be an appropriate index of anthropogenic N loading to rivers, as should the delta N-15 values of riparian plants (delta N-15(plant)) because they are consumers of nitrate. We determined the delta N-15 values of stream nitrate and six species of riparian macrophytes in 31 rivers in the Lake Biwa Basin in Japan. We then tested the correlation between these values and various land-use parameters, including the percentage of land used for residential and agricultural purposes as well as for natural areas. These delta N-15 values were significantly positively correlated with land use N that had a high N load (i.e., residential or agricultural use) and significantly negatively correlated with forest N. These findings indicate that (delta N-15 values of stream nitrate and riparian plants might be good indicators of anthropogenic inputs of nitrogen.

DOI： 10.1021/es801113k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured stable nitrogen (N) and carbon (C) isotope ratios, lignin-derived phenols, and fossil pigments in sediments of known ages to elucidate the historical changes in the ecosystem status of Lake Biwa, Japan, over the last 100 years. Stable N isotope ratios and algal pigments in the sediments increased rapidly from the early 1960s to the 1980s, and then remained relatively constant, indicating that eutrophication occurred in the early 1960s but ceased in the 1980s. Stable C isotope ratios of the sediment increased from the 1960s, but decreased after the 1980s to the present. This decrease in stable C isotope ratios after the 1980s could not be explained by annual changes in either terrestrial input or algal production. However, when the C isotope ratios were corrected for the Suess effect, the shift to more negative isotopic value in atmospheric CO by fossil fuel burning, the isotopic value showed a trend, which is consistent with the other biomarkers and the monitoring data. The trend was also mirrored by the relative abundance of lignin-derived phenols, a unique organic tracer of material that originated from terrestrial plants, which decreased in the early 1960s and recovered to some degree in the 1980s. We detected no notable difference in the composition of lignin phenols, suggesting that the terrestrial plant composition did not change markedly. However, we found that lignin accumulation rate increased around the 1980s. These results suggest that although eutrophication has stabilized since the 1980s, allochthonous organic matter input has changed in Lake Biwa over the past 25 years. © 2008 Elsevier B.V. All rights reserved. 2

DOI： 10.1016/j.scitotenv.2008.05.010

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Language：English   Publishing type：Research paper (scientific journal)  

We analyzed stable carbon and nitrogen isotope ratios in a sample of human and nonhuman mammal bones excavated from the Yoshigo and Inariyama shell mounds of the Late-Final Jomon periods in Aichi Prefecture, Japan, with a view to determining individual dietary differences. To investigate possible reasons for the dietary variations identified, we related isotope ratios to sex and tooth ablation patterns. At both sites, large intra-site variations in δ13C and δ15N values were found, compared with other Jomon populations previously studied, suggesting higher than usual levels of dietary variability, and at both sites there was a positive correlation between δ13C and δ15N values. The diet of the Jomon people at both these sites had two main protein sources: marine (marine finfish and shellfish) and terrestrial (C3 plants and terrestrial mammals) protein. The intra-site variability is probably explained by consumption of these resources in different proportions. Analysis of the Yoshigo shell mound data indicated that sex is one of the factors determining dietary difference. It was also found that individual differences in diet in Yoshigo males are greater than in females. This pattern was repeated in the Inariyama shell mound data. Dietary differences were found to be related to ritual tooth ablation characteristics, particularly in males. At Inariyama, type 4I ritual tooth ablation was associated with comparatively greater dependency on terrestrial resources, while type 2C tooth ablation was associated with greater dependency on marine resources. This may indicate that type 4I males engaged predominantly in hunting, and type 2C males in fishing, as a means of food acquisition. These results are possibly the earliest evidence of occupational differentiation in the Jomon people. © 2007 The Anthropological Society of Nippon.

DOI： 10.1537/ase.070703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

1. Stable nitrogen (N) isotope has been widely used to disentangle food webs and to infer trophic positions of organisms based on an assumption that the stepwise enrichment occurs along trophic levels. The enrichment of N in soil organisms with diet humification has also been reported, but the underlying mechanism has not been fully examined. 2. To examine the effect of diet humification on N, we estimated the stable N isotope ratios and diet ages of earthworms and termites. These organisms feed on organic matter with various degrees of humification, ranging from undecomposed plant materials to humified organic matter (soil organic matter), in a gallery forest and a savanna in the Ivory Coast. We defined diet age as the time elapsed since carbon (C) in the diet of earthworms and termites was fixed from atmospheric CO by photosynthesis; it was estimated by comparing the radiocarbon ( C) content of these organisms to atmospheric CO records. 3. Stable N isotope ratios increased along the humification gradient of diets, and values for earthworms and termites varied from 1.8‰ to 9.9‰ and from -1.5‰ to 15.9‰, respectively. Epigeic (litter-feeding) earthworms had younger diet ages (2-4 years), whereas endogeic (soil-feeding) earthworms generally exhibited older diet ages (5-9 years). Grass-feeding termites had young diet ages (2 years), and wood/soil-feeding termites had the oldest diet ages (c. 50 years). Soil-feeding termites were similar in diet age (7-12 years) to wood feeders (8-11 years), with the exception of one species (18-21 years) that consumes large-diameter wood. 4. A significant positive relationship was found between diet ages and stable N isotope ratios of the two groups in the savanna. This relationship held in the gallery forest when termites feeding on woody tissues were not considered. These results show that the stable N isotope ratios of organisms can increase with diet age, unless C in the diet has been stored as organic matter, such as woody tissue, that is able to age without being subject to humification processes. 5. Given that above-ground food webs are often sustained directly by material and energy flow from below-ground food webs, in addition to trophic interactions, gradual enrichment of N with the humification of below-ground diets should be considered when interpreting stable N isotope ratios of terrestrial food webs. © 2008 The Authors. 15 15 14 14 15 2 2

DOI： 10.1111/j.1365-2435.2008.01386.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO3, SO4, NO3, Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta S-34 values of SO4 in the river water converged to 0 +/- 2 parts per thousand as the SO4 concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO3 concentration increased. In particular, both the delta S-34 values (0 +/- 2 parts per thousand) and the Sr-87/Sr-86 ratios (0.7117 +/- 0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta S-34 values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable Sr-87/Sr-86 in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO3, owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO3 and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2007.08.042

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

The evolution of fungus-growing termites is supposed to have started in the African rain forests with multiple invasions of semi-arid habitats as well as multiple invasions of the Oriental region. We used sequences of the mitochondrial Coll gene and Bayesian dating to investigate the time frame of the evolution of Macrotermes, an important genus of fungus-growing termites. We found that the genus Macrotermes consists of at least 6 distantly related clades. Furthermore, the Coll sequences suggested some cryptic diversity within the analysed African Macrotermes species. The dates calculated with the Coll data using a fossilized termite mound to calibrate the clock were in good agreement with dates calculated with COI sequences using the split between Locusta and Chortippus as calibration point which supports the consistency of the calibration points. The clades from the Oriental region dated back to the early Tertiary. These estimates of divergence times suggested that Macrotermes invaded Asia during periods with humid climates. For Africa, many speciation events predated the Pleistocene and fall in range of 6-23 million years ago. These estimates suggest that savannah-adapted African clades radiated with the spread of the semi-arid ecosystems during the Miocene. Apparently, events during the Pleistocene were of little importance for speciation within the genus Macrotermes. However, further investigations are necessary to increase the number of taxa for phylogenetic analysis. (c) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.ympev.2007.07.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We measured the natural stable carbon (C) and nitrogen (N) isotope ratio patterns of collembola and the organic substrates of their habitats and potential food sources in a warm temperate coniferous forest. Based on previous studies, we classified collembola into successional classes along litter decomposition gradients: early colonizers, late colonizers, and dominants-throughout. The stable C and N isotope ratios of late colonizers exceeded those of early colonizers, and those of the dominants-throughout were intermediate between early and late colonizers, which is consistent with previous studies on two macro-invertebrates, earthworms and termites. The C and N isotopic signature differences in collembola may reflect food resource partitioning along decomposition gradients. (c) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soilbio.2007.01.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS  

The degradation of tropical forests is progressing rapidly and its ecological effects on wild animals are a global concern. We evaluated the hypothesis that small mammals in highly degraded forest occupy higher trophic levels than those in somewhat degraded forests, as indicated by diets high in consumers such as insects, in a tropical rain forest in Sarawak, Malaysia. After correcting for differences in the delta N-15 values for primary production among the study sites, the delta N-15(corrected) values for rats and mice (Muridae) differed significantly among forest types. Rats and mice in more degraded forest had higher delta N-15(corrected) values than those in less degraded or primary forest: in contrast, treeshrews (Tupaiidae) and squirrels (Sciuridae) showed no significant differences in the delta N-15(corrected) values among forest types. We found significant positive correlations between canopy openness and the delta N-15(corrected) values for one species of squirrel and two species of rats. This hypothesis was supported for small mammals that have normal dietary preferences for plants, i.e., omnivorous rodents, but not for those that normally prefer insects, i.e., treeshrews. The delta N-15 values for omnivorous mammals may be useful as an indicator of changes in food-web structure in response to forest disturbance.

DOI： 10.1139/Z07-026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIF STATE UNIV  

Mounds of the termite Amitermes laurensis in northern Queensland, Australia, are frequently invaded and occupied by the meat ant Iridomyrmex sanguineus, but their interactions remain unclear. In 1999, 68 A. laurensis mounds that were mapped and examined for the presence of the meat ants in 1998 were studied by destructive sampling, and the occupancy percentages of the termites were compared during the 2 years of meat ant occupation. The results indicate that the occupancy percentages of the termites in the intact mounds (79%) are significantly different from those in the mounds that were occupied by the meat ants in 1998 (58%), 1999 (42%), or both (20%). Although the mean vales showed apparent differences, no significant difference was observed in the occupancy percentages among the latter three cases. Our results suggest that the meat ants arc not lethal invaders of the termite mounds and that the recovery of the termite populations occurs after the meat ants abandon the mounds.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本陸水学会  

The runoff of suspended substances (SS), nitrogen, and phosphorus by enforced draining during the ploughing season was calculated from experiments in two paddy fields. The area of a paddy field was 3000m2. The total fluxes were 33 kg (SS), 85 g (total-N), and 46 g (total-P) in Field A, with a small decrease in water levels (8mm), 110kg (SS), 589 g (total-N), and146 g (total-P) in Field B with a major decrease in water levels (72mm). Furthermore, the nitrogen/ phosphorus ratios (mol ratios) of the waste water by the enforced draining were 4.1 (Field A) and 8.8 (Field B). In comparison with N/P of the phytoplankton (16), it was found that the phosphorus flowed out efficiently with the enforced draining. Increasing the supply of the phosphorus to Lake Biwa is not desirable in view of the current problems of eutrophication. The careless water management of paddy fields was a crucial factor in any plan to improve the water quality of Lake Biwa.

DOI： 10.3739/rikusui.67.105

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

We propose that diets of consumers in a food web have various ages, where age is defined as the time elapsed since carbon (C) in the diet was fixed from atmospheric CO2 by primary producers. To examine the diet ages for primary consumers in a detrital food web, we measured the radiocarbon (C-14) content of termites collected in Thailand in 1998 and 2004. Diet ages were estimated by comparing the C-14 content of samples with records of atmospheric (CO2)-C-14, which doubled in the early 1960s as a result of nuclear weapons tests and decreased after the nuclear test ban treaty. For comparison, we measured the C-14 content of bees as primary consumers in a grazing web at the same study site. Stable carbon and nitrogen (N) isotope ratios were also analysed.
The C-14 contents of the same species of termites decreased during the sampling interval, indicating that they used organic matter produced after the peak in atmospheric (CO2)-C-14. The diet ages were estimated to be 12-18, 7-13 and 5-9 years for the wood-feeder (Microcerotermes crassus), the soil-feeders (Dicuspiditermes makhamensis and Termes comis) and the fungus-grower (Macrotermes carbonarius), respectively. One colony of soil-feeder (T. comis), which nested in a fallen tree trunk, had exceptionally low C-14 content, and its diet age was estimated to be around 50 years. The two bee species had lower C-14 contents compared with the termites, and their diet ages were estimated to be 0 (Apis florea) and 2-4 years (Trigona sp.).
Stable C and N isotope ratios of termites showed similar patterns as previously reported, and no clear difference was observed between 1998 and 2004. Although the bees and the fungus-growing termite had similar stable C and N isotope ratios, their diet ages differed.
Our study suggests that radiocarbon can be used to estimate the diet ages of consumers in terrestrial food webs. Diet age should provide new insight into the trophic positions of organisms in grazing and detrital food webs and the interactions between these two webs.

DOI： 10.1111/j.1365-2435.2006.01081.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To study the deterioration of the water quality in Lake Biwa, Japan, over the last 40 years, we measured the concentrations and isotopic ratios of sulfur and strontium of water in 41 inflowing rivers and one discharging river. The concentrations of SO4 and Sr of inflowing rivers at downstream sites were generally high in the southern urban area and in the eastern area, where a large agricultural plain is situated, but low in the northern and western areas, whose watersheds are mountainous and with low population density. SO4 and Sr concentrations are also lower at upstream sites, which are closer to mountainous areas. Thus, the inflowing river receives large amounts of SO4 and Sr as it flows across the plain, where human activity levels are high. The delta(34)S or Sr-87/Sr-86 values of most eastern rivers at downstream sites are lower than those of water in Lake Biwa, and values become more uniform as the proportion of the plain area in the watershed increases. River water in other areas has higher values of delta(34)S or Sr-87/Sr-86 than the lake water. This result indicates that the decadal decrease of delta(34)S and Sr-87/Sr-86 in the lake water has been caused mainly by the increased flux of SO4 and Sr from rivers in the eastern plain. We assume that in the plain, sulfur, nitrogen, and organic compounds induced by human activities generate sulfuric, nitric, and organic acids in the water, which accelerate the extraction of Sr from bedrocks, leading to the generation of Sr in the river water in the area. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2004.10.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EVOLUTIONARY ECOLOGY LTD  

Flower orientation is an important character influencing plant fitness. Zygomorphic flowers are known to orient vertically. We conducted field experiments in which we changed the flower angle of zygomorphic Commelina communis to determine how flower orientation affects pollinator behaviour. We confirmed that Commelina flowers oriented vertically like other zygomorphic flowers. Then, we artificially prepared control, upward- and downward-oriented flowers and exposed them to natural pollinators (syrphid flies and bumblebees). We found that the frequency of approach by syrphid flies and bumblebees was not influenced by flower angle, but there were fewer landings on downward-oriented flowers than on control and upward-oriented flowers. Moreover, the upward flower orientation increased illegitimate landings (landing on the flower without touching the stigmas or mating-related anthers) compared with controls. Thus, vertical flower orientation in zygomorphic flowers serves to control pollinator landings. Our findings suggest that deviations from vertical orientation may reduce fitness in C communis by reducing the efficiency of insect-mediated pollen transfer.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We examined the crown architecture of two canopy species, Fagus crenata Blume, which is highly shade tolerant, and Quercus crispula Blume, which is less shade tolerant, in upper and lower positions on a slope in a cool-temperate forest in Japan. The purpose of this study was to investigate the relative effects of the competitive position for the light environment and developmental constraints on the crown architecture of two species that have different degrees of shade tolerance. In both species, the maximum attainable height was smaller on the upper slope than on the lower slope. The light environment brightened with increasing tree height. Trees in similar competitive position and thus similar light environments were shorter on the upper slope than on the lower slope. When we considered tree height relative to the maximum attainable height, the difference between the upper and lower slopes in the relationship of competitive position to tree height disappeared. Thus, relative tree height was a good index of the competitive position for the light environment when the trees of both slope positions were pooled. The relationships of crown depth and width to relative tree height differed between trees on the upper and lower slopes, while the relationships of crown depth and width to actual tree height were similar. This suggests that developmental constraints are more important than the competitive position in determining the crown architecture of the two species. However, variation in crown architecture was greater in Q. crispula than in F crenata, probably because of the difference in shade tolerance between the two species. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.foreco.2003.08.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING LTD  

1. To investigate whether the role of symbiotic fungi in lignin degradation and food provision differs among fungus-growing termites (four species of Macrotermes , three species of Odontotermes , Hypotermes makhamensis , Ancistrotermes pakistanicus and Pseudacanthotermes militaris ), the chemical composition of fungus combs of different ages and the chitinolytic activity in the gut of termites were analysed. In addition, the carbon stable isotope ratios (delta(13) C) in old combs, worker termite tissues and fungal nodules (aggregated conidia) were compared.
2. In Macrotermes spp., the carbohydrate : lignin ratio of the combs increased with increased comb age, but it decreased or remained the same in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris. In contrast, the chitin : carbohydrate ratio and ash content increased more over time in the combs of Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris than in the combs of Macrotermes spp.
3. Chitinolytic activity in the gut of workers was higher in O. takensis , H. makhamensis and A. pakistanicus than in M. annandalei .
4. In all species examined, the delta(13) C value increased in the sequence: old combs &lt; termites &lt; fungal nodules. Based on a two-source model of delta(13) C, the contribution of fungi to termite nutrition was considered higher in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris than in Macrotermes spp.
5. These results suggest that symbiotic fungi play different roles among fungus-growing termites. In Macrotermes spp., the main role of symbiotic fungi is to degrade lignin, so that the termites can utilize cellulose more efficiently, whereas in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris , it is to serve as a food source.

DOI： 10.1046/j.1365-2435.2003.00718.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIF STATE UNIV  

In a dry evergreen forest of Sakaerat, Thailand, five types of nests (arboreal, epigeal, hypogeal, inquiline and nests within wood) which were built by the genus Microcerotermes were observed. Morphologically, all samples collected from five nest types belonged to the same species and were identified as Microcerotermes crassus. This indicates that a single species can build different nest types in the same locality. Furthermore, the density of nests and the relative abundance were investigated. At 99 nests per plot area (165 nests per hectare), the nest abundance and the relative abundance was very much higher than in other Southeast Asian forests.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIFORNIA STATE UNIV  

The abundance and biomass of termites in dead wood were estimated in a dry evergreen forest in Thailand. Litter and dead wood were collected within ten 2 x 2 m quadrats on a 100 m transect, and then all termites in the litter and dead wood (= termites in dead wood) were dislodged. The biomass of litter and dead wood was 2.50 kg (dry weight) m(-2), of which 76% was represented by dead wood with a diameter of ! 1 cm. A total of 239 pieces of dead wood (diameter ! I cm) were collected, and 38 of them contained termites. The frequency of termites in dead wood was significantly different between pieces with a diameter of 1-5 cm and pieces with a diameter of greater than or equal to5 cm. The abundance and biomass of termites in dead wood were 1269 termites m(-2) and 3.53 g m(-2), respectively. A total of I I species, comprising Kalotermitidae, Rhinotermitidae and Termitidae, were collected; all of them belonged to the wood/litter-feeding group. Using our previous estimation for termites in the soil and data from other studies, the abundance and biomass of termites in the dry evergreen forest were estimated to be 7794 termites m(-2) and 16.7 g m(-2), of which 16 and 21%, respectively, were represented by termites in dead wood. Our study confirmed the importance of termites in dead wood in tropical seasonal forests.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING LTD  

1. Nitrogen and carbon isotope ratios and uric acid concentrations in fungus-growing termites (Isoptera: Termitidae: Macrotermitinae), sampled in Cameroon and Thailand, were determined in order to compare castes that are known to differ in behaviour and feeding habits.
2. Nitrogen isotope ratios (delta(15) N) were either not significantly changed or lower in workers compared with the diet (the fungus combs), whereas carbon isotope ratios (delta(13) C) were higher in worker termites than in the fungus combs.
3. In old workers, delta(15) N values were unexpectedly low and correlated negatively with whole-body uric acid concentrations. This indicates that older workers retain uric acid, which has a low delta(15) N value, to conserve nitrogen within the colony and, furthermore, that older colony members may ultimately be consumed by younger conspecifics.

DOI： 10.1046/j.1365-2311.2002.00414.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING ASIA  

Stable (delta(13)C and delta(15)N) and radio- (C-14, Cs-137 and Pb-210) isotopes were determined for termites that have been sampled from a dry evergreen forest in Thailand. A wood-feeding termite, Microcerotermes crassus, was separated from soil-feeders: Termes propinquus, Termes comis and Dicuspiditermes makhamensis by delta(13)C and delta(15)N values. The Termes group in Thailand had less diverse values in delta(13)C and delta(15)N than those in Australia, where the feeding habits of the 'Termes' group are more diverse. Other soil-feeding termites produced similar delta(13)C values, but a larger range in delta(15)N values. C-14-percent modern carbon (pMC) values suggest that the soil-feeding termites used younger carbon than the wood-feeding termites, and this was consistent with the termites from Cameroon, central Africa. Values of delta(13)C and C-14-pMC indicate that surface soil was used by a soil-feeding termite, D. makhamensis, in making the nest mounds, and deeper soil (10-30 cm) by a fungus-growing termite, Macrotermes carbonarius Pb-210 and Cs-137 were scarcely incorporated into the termites, although Pb-214 was recovered from the workers. The results suggest that stable- and radioisotopes are useful in the study of detritivorous animals, organic matter decomposition and ecosystem engineering.

DOI： 10.1046/j.1440-1703.2002.00479.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Tissue N and C stable isotope ratios of two sympatric termite species were investigated in relation to those of their stored food materials at two savanna sites in north-eastern Australia (Woodstock and Oak Valley). At both sites, the delta(15)N values of termite tissues and the stored food materials of the litter-feeding species Amitermes laurensis were significantly greater than their equivalents in the grass-harvesting species Drepanotermes rubriceps. In addition, the carbohydrate/lignin and C/N ratios were higher and chitin/carbohydrate ratios were lower in food materials stored in the mounds of D. rubriceps. Both sets of analyses confirmed that A rubriceps assimilates less decomposed food materials than A. laurensis. Tissue delta(13)C Values indicated that both species assimilated similar proportions of C3 and C4 plant materials at the Woodstock site, but that the workers of A. laurensis assimilated a greater proportion of C3 plant material at the Oak Valley site. The delta(15) N values of termites from the Woodstock site were significantly greater than those from Oak Valley, although the differences in order at each site were consistent between species. The results indicate that N and C stable isotope ratios must be carefully compared across habitats. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0038-0717(01)00181-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIF STATE UNIV  

Decomposition processes in the soil profile (L, F, A1 and A2 layer) in a seasonal tropical forest in Thailand was investigated and compared to the epigeal mound of the soil-feeding termite Dicuspiditermes makhamensis by CP/MAS C-13 NMR. The main characteristics of carbon structural changes during decomposition was the loss of carbohydrate and accumulation of recalcitrant aliphatic compounds. In terms of CP/MAS C-13 NMR, there is no clear difference between the carbon composition of the termite mound and that of the surface organic soil layer, suggesting that the effect of the soil-feeding termite is not very prominent on soil carbon structure.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIF STATE UNIV  

The abundance and biomass of subterranean termites were assessed in the dry evergreen forest within the Sakaerat Environmental Research Station, northeast Thailand. The samplings were carried out by pit-digging in November 1998 (during rainy season) and February 1999 (during dry season). A total of 23 species of termites, comprising 17 genera were identified. Estimated abundance was 6450 tesmites/m(2) in November and 2526 termites/m(2) in February and biomass was 10.74g/m(2) (fresh mass) in November and 5.35g/m(2) in February, although no significant difference was detected in termite abundance and biomass between rainy and dry season. In 30cm depth pit-digging, we found more than 93% of individual termites and more than 94% of total biomass within the top 20cm of soil layer in both samplings. The termite abundance and biomass within the surficial soil layer (0-10cm layer) showed no significant difference between in November and February sampling.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In order to investigate the role of the mutualistic fungus, Termitomyces sp., in the fungus-growing termite, Macrotermes gilvus, we applied CP/MAS C-13 NMR and selected proximate analyses to fungus comb of different ages and degrees of maturation. We found evidence that lignin degradation took place progressively in the fungus comb. In vitro digestibility of cellulose in old fungus comb, on which the termites feed, was approximately 3-fold higher than that in the fresh part. These results confirm the 'lignin degradation hypothesis' that the role of the mutualistic fungi is lo degrade lignin and enhance the digestibility of cellulose for the termites, suggesting the ability of the termite-fungus association to make extremely efficient use of plant material. (C) 2000 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0038-0717(99)00192-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP  

Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant wood-feeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low delta N-15 values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and delta N-15 or delta C-13 in Hospitalitermes. However, delta N-15 values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. delta C-13 values in both species were negatively correlated with C/N ratios.

DOI： 10.1080/10256010008036386

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WALTER DE GRUYTER & CO  

DOI： 10.1515/HF.1999.041

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CALIF STATE UNIV  

A hypothesis on the role of the symbiotic fungi in fungus growing termites was examined on Macrotermes carbonarius, whose fungus comb had appearance different from those of other Macrotermes species reported so far. Chemical analyses of fungus comb of M. carbonarius indicated that decline of lignin concentration within the fungus comb, which has been observed in some Macrotermes species, was not observed, but the decrease was detected between the fungus combs. This new pattern of lignin degradation confirms the hypothesis that the role of the symbiotic fungi is to degrade lignin and improve cellulose digestibility.

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DOI： 10.11519/jfsc.130.0_609

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&lt;p&gt;[in Japanese]&lt;/p&gt;

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&lt;p&gt;[in Japanese]&lt;/p&gt;

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：Forest Department Sarawak (FDS); Japan Research Consortium for Tropical Forests in Sarawak (JRCTS)  

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Other Link： http://orcid.org/0000-0001-8803-0252

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Language：Japanese   Publisher：一般社団法人日本地球化学会  

本研究では，湖沼やその集水域においての過去100年における環境変遷を地球化学的に評価する手法の開発を目的とし，北海道の羅臼湖・阿寒湖・ニセコ大沼・渡島大沼、富山県のみくりが池，長野県の木崎湖，琵琶湖の計７湖沼の湖底堆積物コアサンプルの各種元素濃度を深度（年代）ごとに誘導結合型プラズマ質量分析計（ICP-MS）で測定した。また，湖沼堆積物の起源を推定することを目的として，堆積物中のSr同位体比を表面電離型質量分析計(TIMS)で測定した。その結果，琵琶湖・阿寒湖ではP（ 最上部で共に ＞ 1000ppm ），As（ 最上部で共に ＞ 100ppm ）の濃度増加が確認され，湖底環境の嫌気化並びに湖水の富栄養化の影響が示唆された。また，Sr同位体比とSr濃度データから，ニセコ大沼ではSr同位体比の異なる二成分の混合が示唆されたが，他の湖沼においてはSr同位体比の異なる複数の成分は明確に区別されなかった。

DOI： 10.14862/geochemproc.59.0.219.0

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Language：Japanese   Publisher：一般社団法人日本土壌肥料学会  

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Language：Japanese   Publisher：一般社団法人日本土壌肥料学会  

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DOI： 10.1007/s11284-008-0517-x

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Language：Japanese   Publisher：エヌ・ティー・エス  

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Publisher：日本生態学会  

陸上熱帯生態系において、シロアリ群集は落葉・枯死木から土壌有機物にわたる様々な分解過程の有機物を利用することで分解者として重要な役割を果たしている。様々な陸上熱帯生態系におけるシロアリ機能群を評価する一つの指標として、安定炭素・窒素同位体（δ&lt;sup&gt;13&lt;/sup&gt;C・δ&lt;sup&gt;15&lt;/sup&gt;N）が用いられてきた。これらの指標はある時間断面における生産者から始まる食物連鎖での消費者の位置づけを表している。しかし、実際の食物連鎖、特に腐植食物連鎖には生産者が有機物を生産してから消費者によって利用されるまでのタイムラグとして表される時間軸が存在し、消費者が利用する有機物は様々な年齢（古さ）を持つ。&lt;br&gt;本研究ではこの時間軸の指標として、冷戦時の核実験によって生成した放射性炭素同位体（Δ&lt;sup&gt;14&lt;/sup&gt;C）を用いて、シロアリ群集の食物源の年齢の特徴を明らかにすることを目的とした。1998年及び2004年にタイ・サケラート環境研究所の乾燥常緑林において、材木食、落葉食、土壌食の食性を持つシロアリ４種を採集し、そのδ&lt;sup&gt;13&lt;/sup&gt;C・δ&lt;sup&gt;15&lt;/sup&gt;N及びΔ&lt;sup&gt;14&lt;/sup&gt;Cの値を測定した。1998年2004年のサンプル共に土壌食性シロアリ２種は材木食・落葉食性シロアリに比べ高いδ&lt;sup&gt;15&lt;/sup&gt;N値を示した。Δ&lt;sup&gt;14&lt;/sup&gt;C値は同種内では1998年より2004年のサンプルで低い値を示し、大気中の&lt;sup&gt;14&lt;/sup&gt;C O&lt;sub&gt;2&lt;/sub&gt;の1963年以降の減少を反映していると考えられた。別種間では材木食性シロアリのほうが、土壌食性シロアリよりも高いΔ&lt;sup&gt;14&lt;/sup&gt;C値を示し、その食物源の平均年齢は材木食性シロアリで12から18年、土壌食性シロアリで７から12年、落葉食性シロアリで約８年であることが推定された。また、これらの食物源の年齢について、当調査地における土壌有機態炭素の回転時間との関連で考察を行った。

DOI： 10.14848/esj.ESJ52.0.581.0

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Publisher：日本陸水学会  

水田からの排水が琵琶湖に与える影響を評価することを目的に、圃場単位において代掻き期の粗放的水管理を再現して、水田から排出される懸濁態粒子（SS）、全窒素、全リンの量を明らかにした。水深の深い水田での強制落水時に各々最大値が得られた。この結果を、東近江地域（近江八幡_から_彦根）の水田141km&lt;sup&gt;2&lt;/sup&gt;に適用すると、すべての水田で水深を深くして強制落水を行った場合、この地域から琵琶湖北湖への全窒素と全リンの負荷率はそれぞれ約2%、約9%になると見積もられた。粗放的水管理の常態化は特にリンの琵琶湖への大きな負荷源となりうることが示された。

DOI： 10.14903/jslim.69.0.187.0

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