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824 Ergebnisse:

High-resolution serial sampling for nitrogen stable isotope analysis of archaeological mammal teeth
Journal of Archaeological Science (2016)
Eric J. Guiry, Joseph C. Hepburn, Michael P. Richards

We present the results of an archaeological application of a rapid method for high-resolution stable nitrogen isotope (δ15N) measurements of time-series samples of tooth dentine. Over 250 analyses of samples of untreated dentine powder taken at continuous millimeter intervals along the growth axis of archaeological pig tusks were compared to results from a subset of tandem δ15N measurements of extracted and purified tooth collagen from the same teeth. Samples were also taken at 0.25 mm depth intervals to test the effect of depth with respect to temporal resolution of diet. Results show that δ15N measurements of untreated dentine powder from well-preserved archaeological teeth provide: 1) broadly comparable δ15N values to extracted and purified collagen, and 2) a rapid method of assessing dietary change over much shorter time intervals than is possible using extracted collagen. Analyses also show that large changes in δ15N values can occur across the thickness of a tooth due to the inclusion of multiple growth layers and/or secondary dentine, which results in a significant time−averaging lag in dietary representation, as demonstrated by samples that analyze collagen from the full width of the tooth wall. This method will also be useful for initial prescreening of samples to select for specimens of interest before undertaking further, more rigorous, sample pre−treatment and measurement.

High retention of (15) N-labeled nitrogen deposition in a nitrogen saturated old-growth tropical forest.
Global change biology (2016)
Geshere Abdisa Gurmesa, Xiankai Lu, Per Gundersen, Qinggong Mao, Kaijun Zhou, Yunting Fang, Jiangming Mo

The effects of increased reactive nitrogen (N) deposition in forests depend largely on its fate in the ecosystems. However, our knowledge on the fates of deposited N in tropical forest ecosystems and its retention mechanisms is limited. Here, we report the results from the first whole ecosystem (15) N labeling experiment performed in a N-rich old-growth tropical forest in southern China. We added (15) N tracer monthly as (15) NH4 (15) NO3 for one year to control plots and to N-fertilized plots (N-plots, receiving additions of 50 kg N ha(-1) yr(-1) for 10 years). Tracer recoveries in major ecosystem compartments were quantified four months after the last addition. Tracer recoveries in soil solution were monitored monthly to quantify leaching losses. Total tracer recovery in plant and soil (N retention) in the control plots was 72% and similar to those observed in temperate forests. The retention decreased to 52% in the N-plots. Soil was the dominant sink, retaining 37% and 28% of the labeled N input in the control and N-plots, respectively. Leaching below 20 cm was 50 kg N ha(-1) yr(-1) in the control plots and was close to the N input (51 kg N ha(-1) yr(-1) ), indicating N-saturation of the top soil. Nitrogen addition increased N leaching to 73 kg N ha(-1) yr(-1) . However, out of these only 7 and 23 kg N ha(-1) yr(-1) in the control and N-plots, respectively, originated from the labeled N input. Our findings indicate that deposited N, like in temperate forests, is largely incorporated into plant and soil pools in the short term, although the forest is N-saturated, but high cycling rates may later release the N for leaching and/or gaseous loss. Thus, N cycling rates rather than short term N retention represent the main difference between temperate forests and the studied tropical forest. This article is protected by copyright. All rights reserved.

Exogenous nutrients and carbon resource change the responses of soil organic matter decomposition and nitrogen immobilization to nitrogen deposition.
Scientific reports (2016)
Ping He, Song-Ze Wan, Xiang-Min Fang, Fang-Chao Wang, Fu-Sheng Chen

It is unclear whether exogenous nutrients and carbon (C) additions alter substrate immobilization to deposited nitrogen (N) during decomposition. In this study, we used laboratory microcosm experiments and (15)N isotope tracer techniques with five different treatments including N addition, N+non-N nutrients addition, N+C addition, N+non-N nutrients+C addition and control, to investigate the coupling effects of non-N nutrients, C addition and N deposition on forest floor decomposition in subtropical China. The results indicated that N deposition inhibited soil organic matter and litter decomposition by 66% and 38%, respectively. Soil immobilized (15)N following N addition was lowest among treatments. Litter (15)N immobilized following N addition was significantly higher and lower than that of combined treatments during the early and late decomposition stage, respectively. Both soil and litter extractable mineral N were lower in combined treatments than in N addition treatment. Since soil N immobilization and litter N release were respectively enhanced and inhibited with elevated non-N nutrient and C resources, it can be speculated that the N leaching due to N deposition decreases with increasing nutrient and C resources. This study should advance our understanding of how forests responds the elevated N deposition.

Resource subsidies from adfluvial fishes increase stream productivity
Freshwater Biology (2016)
Nicholas E. Jones, Robert W. Mackereth

Anadromous fishes are well known to shape the structure and function of recipient ecosystems by introducing nutrients and rich organic matter from the ocean. In contrast, the importance of potamodromous migrations, confined to freshwater, and the subsidies they provide to stream ecosystems has received much less attention. Our objective was to determine the importance of excretion, eggs, milt, and carcasses as nutrient and energy sources from a large population (82 449 suckers) of migrating longnose (Catostomus catostomus) and common white (Catostomus commersonii) suckers into a small (wetted width c. 10 m) oligotrophic river system. We hypothesise that the adfluvial suckers provide a large material subsidy that increased the productivity of the Cypress River and that this resource subsidy rivals or exceeds those delivered by other native and non-native fishes (e.g. Pacific salmonids). In total there was an estimated 5635 kg of eggs, 2025 kg of milt, and 1 kg of carcasses from suckers that spawn in the Cypress River. Relative to other mainly non-native fishes, suckers provided 92% of the annual egg biomass and 95% of the milt. Suckers, however, only provided <1% (1 kg) of the annual carcass biomass, whereas, pink salmon provided 50% (600 kg). Overall, suckers provided 84% and 78% of the annual subsidies of N and P, or 212 and 14 kg respectively. Ambient NH4 concentrations in the river were consistently below that predicted from excretion equations suggesting that microorganisms may have rapidly taken up much of the released ammonium. Downstream of the falls, epilithon biomass was over nine times more abundant, benthic invertebrate densities were approximately two times higher, and fish biomass was eight times greater compared to upstream. There were no upstream–downstream differences in substrate organic matter biomass. Fishes downstream of the falls had higher δ13C and δ15N values than biota upstream of the falls consistent with the anticipated effect of lake derived subsidies. Using stable isotopes values and a mixing model, we estimated that sucker eggs comprised 25–58% of the diet of stream fishes during the growing season. Suckers provided a large subsidy, greater than all other fishes, without mass mortality and significantly enhanced the productivity of the recipient river system. Stable isotopes revealed that subsidies were incorporated into the stream food web. Differences between salmon and sucker subsidies related to the type, magnitude, timing, and the life history of the donor highlight the potential importance of spawning migrations of adfluvial suckers, and other potamodromous fishes, in streams and rivers around the world.
Schlagworte: C , N , ec , EA

Use of stable carbon isotope ratios to determine the source of cypermethrin in so-called natural plant extract formulations used for organic farming.
Isotopes in environmental and health studies (2016)
Hiroto Kawashima, Takuro Kariya

Some natural plant extract formulations (NPEFs, also referred to as essential oils) used in organic farming have been shown to contain synthetic pesticides. We obtained samples of four NPEFs (Muso, Hekiro, Kensogen-Ten, and Nurse Green) that were contaminated with the synthetic pyrethroid cypermethrin, and we used gas chromatography coupled with combustion, cryofocusing, and isotope ratio mass spectrometry to determine the stable carbon isotope ratios (δ(13)C) for the cypermethrin in the four NPEF samples, as well as in ten cypermethrin reagents and two commercial pesticide formulations (Agrothrin emulsion and Agrothrin water-dispersible powder). Our goal was to identify the source of the cypermethrin in the NPEFs. Cryofocusing markedly sharpened the cypermethrin peak and thus improved the accuracy and precision of the determined δ(13)C values. The δ(13)C values (± SD) of the 16 cypermethrin samples ranged from -28.3 ± 0.2 to -24.5 ± 0.2 ‰. Surprisingly, the four NPEFs showed similar δ(13)C values (-26.8 to -27.3 ‰), suggesting that the cypermethrin in all the samples came from the same source (either the same chemical reaction or the same primary material). This possibility was supported by previously published results. In addition, the δ(13)C values of the two commercial pesticides were similar to the values for the NPEFs, suggesting that the commercial pesticides had been diluted and sold as NPEFs.

Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian–Spathian boundary in the Bac Thuy Formation, Vietnam
Palaeogeography, Palaeoclimatology, Palaeoecology (2016)
Toshifumi Komatsu, Reishi Takashima, Yasunari Shigeta, Takumi Maekawa, Huyen Dang Tran, Tien Dinh Cong, Susumu Sakata, Hung Doan Dinh

The Smithian–Spathian boundary is indicated by the first occurrence of the ammonoid Tirolites cf. cassianus in the Olenekian Bac Thuy Formation, northeastern Vietnam. The boundary is intercalated within organic-rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the An Chau and Nanpanjiang Basins on the South China Block. In Lang Son area, three conodont zones, Novispathodus ex gr. waageni, Novispathodus ex gr. pingdingshanensis, and Icriospathodus collinsoni, are recognized in the formation. The Smithian–Spathian boundary is intercalated within N. ex gr. pingdingshanensis conodont Zone. The positive excursion inδ13C with values increasing from around −2.3‰ to +5.7‰ was recorded in the uppermost Smithian Xenoceltites variocostatus ammonoid beds and N. ex gr. pingdingshanensis conodont Zone. The δ13C values decrease across the Smithian–Spathian boundary. These δ13C isotopic patterns are correlated with well-known positive excursions around the Smithian–Spathian boundary globally.

Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species.
Plant biology (Stuttgart, Germany) (2016)
Marco M Lehmann, Frederik Wegener, Roland A Werner, Christiane Werner

Leaf respiration in the dark and its isotopic composition (δ(13) CR ) contain information about internal metabolic processes and respiratory substrates. δ(13) CR is known to be (13) C enriched compared to potential respiratory substrates, in particular shortly upon darkening during the light enhanced dark respiration (LEDR). This phenomenon might be driven by respiration of accumulated (13) C enriched organic acids, however, studies on δ(13) CR during LEDR and potential respiratory substrates simultaneously are rare. We determined δ(13) CR and respiration rates (R) during LEDR, as well as δ(13) C and concentrations of potential respiratory substrates using compound-specific isotope analyses. The measurements were conducted along the diel cycle in several plant species under different environmental conditions. δ(13) CR and R patterns during LEDR were strongly species-specific and showed an initial peak, which was followed by a progressive decrease in both values. The species-specific differences in δ(13) CR and R during LEDR may be partially explained by the isotopic composition of organic acids (e.g. oxalate, isocitrate, quinate, shikimate, malate), which were (13) C enriched compared to other respiratory substrates (e.g. sugars and amino acids). However, the diel variations in both δ(13) C and concentrations of the organic acids were generally low. Thus, additional factors such as the heterogeneous isotope distribution in organic acids and the relative contribution of the organic acids to respiration are required to explain the strong (13) C enrichment in leaf dark-respired CO2 . This article is protected by copyright. All rights reserved.

Distribution and storage of crop residue carbon in aggregates and its contribution to organic carbon of soil with low fertility
Soil and Tillage Research (2016)
Shuangyi Li, Xin Gu, Jie Zhuang, Tingting An, Jiubo Pei, Hongtu Xie, Hui Li, Shifeng Fu, Jingkuan Wang

Long-term intensive cultivation leads to the decrease of soil organic carbon (SOC) and soil fertility. Crop residue amendment to soil is documented as an effective measure to increase SOC and improve soil productivity. However, there is limited information on the turnover and storage of crop residue carbon (C) in soil aggregates after the residue is added to soil with low fertility. The objectives of this research were to investigate the distribution and storage of residue C in soil aggregates and its contribution to different physical fractions of SOC, and to quantify the turnover of residue C in soil with low fertility. Soil samples added with 13C-labelled maize straw residue were put into carborundum tubes for two-year long in-situ incubation. Soil aggregates were separated by wet sieving and then physically fractionated. During the whole incubation process, 12–15% of residue C was stably distributed to 2000–250 mm aggregates, while the percentage of residue C distributed to microaggregates (<250 mm) increased with incubation time. The contribution of residue C to particulate organic C (POC) fractions decreased from average 63% on day 60 to average 43% on day 720 and that to mineral-associated organic C (mSOC) fraction increased from average 23% on day 60 to average 28% on day 720. More than 50% of fine POC (fPOC) was derived from residue C, especially 71% in microaggregates on day 360. Within aggregates, the percentages of residue C distributed to free light organic C (fLOC) and coarse POC (cPOC) reduced and these to fPOC and mSOC strengthened with incubation time. Mean residence time (MRT) of residue C was shortened with the increase of the aggregate sizes. MRT of mSOC was longer compared to other SOC physical fractions. These results suggest that microaggregates could provide favorable conditions for microbial activities and conduce to fPOC accumulation in a low fertility soil amendment with crop residue.

Water quality and hydrogeochemistry of a basin and range watershed in a semi-arid region of northern New Mexico
Environmental Earth Sciences (2016)
Benjamin Linhoff, Patrick Longmire, Michael Rearick, Denis McQuillan, George Perkins

Hundreds of domestic wells in northern New Mexico, have concentrations of U, As, and NO3 − that exceed the Environmental Protection Agency’s (EPA) maximum contaminant level (MCL) for drinking water consumption. As part of a case study in groundwater quality, we collected groundwater samples from 749 domestic wells throughout the eastern half of the Española Basin. All water samples were analyzed for major ions, trace metals, and alkalinity. Selected samples were also analyzed for stable isotopes of O, H, and N. Of the wells we measured, 15, 173, and 99 had respective NO3 −, U, and As concentrations that exceeded the EPA’s MCL. Total dissolved solids (TDS), U, and HCO3 − were elevated in the Sangre de Cristo mountain block and around the town of Nambé. Our findings suggest that roll-front U deposits and devitrification of volcanic ash result in elevated U near Nambé, while weathering of granitic rocks accounts for high U in the mountain block. Arsenic concentrations were high in much of the study area with the exception of the Santa Fe metro region and the mountain block. Elevated As concentrations can be explained by devitrification of volcanic ash, anion exchange with clays, and mixing with hydrothermal fluids. In wells with high NO3 − concentrations, analysis of N isotopes are consistent with contamination from domestic wastewater effluent. Our findings suggest that the geochemistry of the region is largely influenced by local geology while groundwater contamination from domestic water treatment and wastewater effluent is an emerging issue
Schlagworte: H , N , O , ge , EA

Priming by Hexanoic Acid Induce Activation of Mevalonic and Linolenic Pathways and Promotes the Emission of Plant Volatiles
Frontiers in Plant Science (2016)
Eugenio Llorens, Gemma Camañes, Leonor Lapeña, Pilar García-Agustín

Hexanoic acid is a short natural monocarboxylic acid present in some fruits and plants. Previous studies reported that soil drench application of this acid induces effective resistance in tomato plants against Botrytis cinerea and Pseudomonas syringae and in citrus against Alternaria alternata and Xanthomonas citri. In this work, we performed an in deep study of the metabolic changes produced in citrus by the application of hexanoic acid in response to the challenge pathogen Alternaria alternata, focusing on the response of the plant. Moreover, we used 13C labeled hexanoic to analyze its behavior inside the plants. Finally, we studied the volatile emission of the treated plants after the challenge inoculation. Drench application of 13C labeled hexanoic demonstrated that this molecule stays in the roots and is not mobilized to the leaves, suggesting long distance induction of resistance. Moreover, the study of the metabolic profile showed an alteration of more than two hundred molecules differentially induced by the application of the compound and the inoculation with the fungus. Bioinformatics analysis of data showed that most of these altered molecules could be related with the mevalonic and linolenic pathways suggesting the implication of these pathways in the induced resistance mediated by hexanoic acid. Finally, the application of this compound showed an enhancement of the emission of 17 volatile metabolites. Taken together, this study indicates that after the application of hexanoic acid this compound remains in the roots, provoking molecular changes that may trigger the defensive response in the rest of the plant mediated by changes in the mevalonic and linolenic pathways and enhancing the emission of volatile compounds, suggesting for the first time the implication of mevalonic pathway in response to hexanoic application.