Determination of trophic levels of marine fish in the Yellow Sea and northern East China Sea using nitrogen stable isotope (δ^(15)N) analysis of otoliths

Fish otolithδ^(15) N(δ^(15) N_(oto))is a demonstrated source of information of dietary history for marine fi sh as it is available iN_(oto)lith archives and sedimentary deposits unlike white muscle tissue(WMT).WMT and stomach content data are insufficient for trophic level(TL)data of past fi shes which is important for the changes of marine fi shery resources over long time scales.To determine the correlation betweenδ^(15) N_(oto) and fi sh WMTδ^(15) N(δ^(15) N_(wmt))and the feasibility of usingδ^(15) N_(oto) in characterizing the TLs of marine fi shes,we conducted nitrogen stable isotope analysis(SIA)in the otolith and WMT of 36 marine fi sh species sampled from the Yellow Sea and northern East China Sea in 2011-2014.Bothδ^(15) N_(oto) andδ^(15) N_(wmt) were analyzed using an elemental analyzer coupled with an isotope ratio mass spectrometer(EA-IRMS).Multiple otoliths were combined to make each otolith measurement and were analyzed as-is without a carbonate dissolution pre-processing step.δ^(15) N_(oto) andδ^(15) N_(wmt) comparisons for species in the Yellow Sea and northern East China Sea are currently lacking and would be helpful for both regional studies and for increasing the number of species for whichδ^(15) N_(oto) andδ^(15) N_(wmt) have been compared.Additionally,to determine the relative accuracy of trophic level calculated usingδ^(15) N_(oto),we compared TL calculated fromδ^(15) N_(oto) to traditional trophic level metrics calculated usingδ^(15) N_(wmt).The results showed a positive and highly signifi cant correlation(R=0.780,P<0.001)betweenδ^(15) N_(oto) andδ^(15) N_(wmt).Trophic level estimation using WMT(TL wmt)and otolith(TL oto)showed congruence in our study,which is not entirely surprising given thatδ^(15) N_(oto) was regressed againstδ^(15) N_(wmt) and the resulting regression coefficient was used to convertδ^(15) N_(oto) toδ^(15) N_(wmt) prior to calculating TL oto.This conversion was required in order to be consistent with previousδ^(15) N_(wmt)-based calculations of TL for comparison.TL oto calculations resulted in TL values that were largely within 5%-10%of TL values calculated withδ^(15) N_(wmt).Our fi ndings show thatδ^(15) N_(oto) is a feasible technique for characterizing the TLs of marine fi sh and can also assist in food web and marine ecosystem studies.

Application of ^15N Stable Isotope Labeling Technology in Sugarcane Nitrogen Research

Nitrogen is one of the essential nutrient elements for plant growth,which plays an important role in the growth and development of sugarcane. The whole growth cycle of sugarcane needs a large amount of nitrogen. Increasing the application of nitrogen can improve the yield of sugarcane,but it will also cause environmental pollution. Therefore,how to control or reduce the application of nitrogen fertilizer while continuously increasing sugarcane yield,reduce the increase of sugarcane production cost and environmental pollution caused by excessive application of nitrogen fertilizer has become an important scientific problem faced by sugarcane industry in China.^15N stable isotope labeling technology has been applied to many crops as a nitrogen research tool. In order to better understand the demand of nitrogen fertilizer in soil-cane system,this paper reviewed nitrogen allocation in plants,nitrogen loss,nitrogen recycling and endogenous nitrogen fixation of sugarcane based on^15N stable isotope labeling technology used in the nitrogen uptake and utilization,providing a theoretical basis for the improvement of sugarcane nitrogen use efficiency and the efficient nitrogen fertilizer management of sugarcane.

Absorption spectra and isotope shifts of the(2, 0),(3, 1), and(8, 5) bands of the A^2Π_u-X^2Σ_g^+ system of ^(15)N_2^+ in near infrared

The high-resolution absorption spectra of the （2,0）,（3,1）,and （8,5） bands of the A^2Π^u-X^2∑g^＋ system of ^15N2^＋ have been recorded by using velocity modulation spectroscopy technique in the near infrared region.The rotational constants of the X^2∑g^＋ and A^2Πu states of ^15N2^＋ were derived from the spectroscopic data.The isotope shifts of these bands of the A^2Πu-X^2∑g^＋ system of ^14N2^＋ and ^15N2^＋ were also analyzed and discussed.

Trace element geochemistry and stable isotopic(δ^(13)C andδ^(15)N)records of the Paleocene coals,Salt Range,Punjab,Pakistan

The Paleocene coals of the Salt Range in the Punjab Province of Pakistan have great economic potential;however,their trace element and stable isotopic characteristics have not been studied in detail except for a few sporadic samples.In this study,a total of 59 coal samples of which 14 are obtained from open cast mines have been investigated for elemental composition andδ^(13)C-δ^(15)N isotopic signatures.Average contents of trace elements such as Co,Cr,Cu,Pb,Sr,Th,U,V,and Zn are 7.4,41.7,11.2,12.5,90.2,4.0,1.9,128,and 31.1 mg/kg,respectively.These values,when compared with the World Coal Clarke values,were relatively higher in low-rank coals in comparison with Clarke values for brown coals.Likewise,As(20.4 mg/kg),Co(6.6 mg/kg),Cr(22.4 mg/kg),Cu(^(13).3 mg/kg),Pb(19.2 mg/kg),Sr(^(15)4.7 mg/kg),Th(2.5 mg/kg),V(47.8 mg/kg),and Zn(75.1 mg/kg)were significantly higher in the sub-bituminous to bituminous coals of the Salt Range.Mineralogical analysis,based on X-ray diffraction and energy dispersive X-ray spectroscopy,revealed that the studied samples contain illite,kaolinite calcite,gypsum,pyrite,and quartz.Elemental affinity with organic and inorganic phases of coals calculated by an indirect statistical approach indicated a positive association of ash content with Ag,Al,Co,Cr,Cs,Cu,Mn,P,Rb,Pb,Th,U,and V,suggesting the presence of inorganic components in studied coals.However,As,Fe,Sr,and Zn exhibit negative correlations that imply their association with the organic fraction.Theδ^(13)C andδ^(15)N isotopic range and average−24.94‰to−25.86‰(−25.41‰)and−2.77‰to 3.22‰(0.96‰),respectively,reflecting 3C type modern terrestrial vegetation were common in the palaeomires of studied coal seams.In addition,the trivial variations of 0.92‰and 0.45‰among^(13)C and^(15)N values can be attributed to water level fluctuations and plant assemblies.

^(15)N自然丰度法在生态系统氮素循环研究中的应用

稳定性同位素技术是现代生态学研究中的一门新兴技术，在生态学研究的诸多领域都展示了广阔的应用前景。其中，稳定性同位素１５Ｎ自然丰度法近年来在生态系统氮素循环研究中发挥了和正在发挥着极为重要的作用。首先简述了自然生态系统氮素循环诸过程中的１５Ｎ同位素分馏机制。然后，在此基础上，综述了１５Ｎ自然丰度法的基本原理与方法，列举了近年来此法在生物固氮及氮素转化过程研究中的一些应用实例，并预测了该方法在国内氮素循环研究中的应用前景。

^(15)N示踪技术在湿地氮素生物地球化学过程研究中的应用进展

稳定性同位素技术是现代生态学研究中的一门应用技术,它几乎在生态学研究的各个领域都有着广泛的应用。其中15N技术由于具有示踪和区分氮素物质的源与去向等优越性而在生态系统氮循环研究中发挥了极为重要的作用。文章主要从湿地氮素的输入过程、转化过程以及归趋过程三方面综述了该技术在当前国内外湿地氮素生物地球化学过程研究中的应用进展,特别指出当前基于该技术的湿地氮素生物地球化学过程研究尚缺乏一定的系统性、深入性和广泛性。最后,文章就该技术在湿地氮素生物地球化学过程研究中的应用前景进行了展望研究。

^(15)N同位素稀释法研究固氮菌接种对甘蔗生物固氮的影响

利用15N同位素稀释法,研究接种固氮菌klebsiella L03对甘蔗品种B8和ROC22的生物固氮的影响。结果表明:B8的固氮百分率最高为31.28%Ndfa,从苗期开始就显著高于ROC22,分蘖期和伸长初期的固氮量和固氮百分率与ROC22相比差异达到极显著水平。B8和ROC22的根、茎、叶都可发生固氮,以伸长初期(60d)叶片中的固氮能力最强。接种L03能显著提高B8和ROC22各器官的含氮量,其中对ROC22叶片和B8茎的含氮量提高作用最明显。不同甘蔗品种、相同品种的不同器官甚至相同器官的不同生长时期固氮作用有很大差异。

稳定性同位素^(15)N在我国农业研究中的应用

对近年来稳定性同位素15N在农业研究中的应用及所取得的成就进行了综述 ,并展望了稳定性同位素15N在农业科学研究方面应用的发展前景。

用^(15)N同位素稀释法研究沸石对氮肥利用率的影响

通过15N示踪研究不同沸石水平处理对玉米氮肥利用率的影响。结果表明 :( 1 )沸石和肥料混合使用促进了玉米的生长 ,第一茬玉米氮肥利用率以 0 7g kg土沸石用量为最高 ,其次是 1g kg土 ;( 2 )第二茬玉米的氮肥利用率则是以 0 1 %的沸石用量最高 ,其次是 0 1 3 %的沸石用量水平 ,与对照相比 ,沸石处理使两茬玉米的氮肥利用率分别提高了 2 3 2 %～ 3 3 1 % ;( 3 )沸石处理可以显著降低土壤中氮肥的损失 ,与对照相比 ,降低率达 2 5 9%～3 0 6% 。

^(15)N同位素示踪技术研究辣椒器官氮素分配特性和基质氮素运移规律

为探究日光温室蔬菜基质栽培氮肥在栽培基质中运移和累积规律及其在辣椒植株各器官中吸收和分配特性。以辣椒(品种:陇椒10号)为试验材料,利用K^(15)NO_3同位素示踪法,将K^(15)NO_3分别标记于栽培基质剖面向下5～10 cm和15～20 cm深处,并设2个灌水下限60%(W60)和80%(W80),研究了日光温室基质栽培辣椒的生物量、辣椒各器官对氮素吸收与分配及栽培基质中氮素的运移规律。结果表明,60%灌水下限条件下较80%灌水下限显著增加了辣椒植株总生物量和氮的吸收量。在空间分布上,^(15)N标记施肥深度越深,则辣椒植株对^(15)N利用率下降;同时,^(15)N在基质层(0～20 cm)中的累积量也明显下降,损失量显著增加。其中60%灌水下限条件下基质中^(15)N的损失量少于80%灌水条件,且^(15)N在5～10 cm处的损失量较少,此时,减小了基质层15～20 cm处^(15)N的向下迁移量,并增加了60%灌水下限条件下辣椒植株各器官对全氮的吸收利用率。因此,W60F5处理可以提高辣椒植株的总生物量和氮肥的吸收量,减弱基质深层氮素向下运移量,有利于辣椒植株更好地吸收与利用,且辣椒植株各器官生物积累量与氮肥吸收量依次为叶>果>茎。

Tree-ring δ^(15)N of Qinghai spruce in the central Qilian Mountains of China:Is pre-treatment of wood samples necessary?

A knowledge of the tree-ring stable nitrogen isotope ratio(δ^(15)N)can deepen our understanding of forest ecosystem dynamics by indicating the long-term availability,cycling and sources of nitrogen(N).However,the radial mobility of N blurs the interannual variations in the long-term N records.Previous studies of the chemical extraction of tree rings before analysis had produced inconsistent results and it is still unclear whether it is necessary to pre-treat wood samples from specific tree species to remove soluble N compounds before determining theδ^(15)N values.We compared the effects of pre-treatment with organic solvents and hot ultrapure water on the N concentration andδ^(15)N of tree rings from endemic Qinghai spruce(Picea crassifolia)growing in the interior of the central Qilian Mountains,China,during the last 60 a.We assessed the effects of different preparation protocols on the removal of the labile N compounds and investigated the need to pre-treat wood samples before determining theδ^(15)N values of tree rings.Increasing trends of the tree-ring N concentration were consistently observed in both the extracted and unextracted wood samples.The total N removed by extraction with organic solvents was about 17.60%,with a significantly higher amount in the sapwood section(P<0.01).Theδ^(15)N values of tree rings decreased consistently from 1960 to 2019 in both the extracted and unextracted wood samples.Extraction with organic solvents increased theδ^(15)N values markedly by about 5.2‰and reduced the variations in theδ^(15)N series.However,extraction with hot ultrapure water had little effect,with only a slight decrease in theδ^(15)N values of about 0.5‰.Our results showed that the radial pattern in the inter-ring movement of N in Qinghai spruce was not minimized by extraction with either organic solvents or hot ultrapure water.It is unnecessary to conduct hot ultrapure water extraction for the wood samples from Qinghai spruce because of its negligible effect on the removal of the labile N.Theδ^(15)N variation trend of tree rings in the unextracted wood samples was not influenced by the heartwood-sapwood transition zone.We suggest that theδ^(15)N values of the unextracted wood samples of the climate-sensitive Qinghai spruce could be used to explore the ecophysiological dynamics while focusing on the long-term variations.

Effect of Alternate Bearing Phenomenon and Boron Foliar Application on Nitrogen-15 Uptake,Translocation and Distribution in Mango Tree(cv.Zebda)

The objectives of this investigation are to study nitrogen uptake,translocation,accumulation and distribution in mango tree organs using labeled nitrogen(^(15)N)and to understand the mechanism of boron action in increasing fruit yield in the off-year.A field experiment was conducted using fifteen-year-old mango trees(cv.Zebda)grown at Al Malak Valley Farm,El-Sharkeya Governorate-Egypt.Treatments included the application of(^(15)NH4)2SO4,“in the on-year”,at a rate of 50 g nitrogen/tree through the stem injection technique.While boron was sprayed on the same trees“in the off-year”at the following rates:0.0(control),250 and 500 mg·L^(-1).The authors hypothesize that boron and nitrogen act synergistically to increase mango fruit yield in the off-year.Results indicated that the highest ^(15)N uptake and accumulation in the on and off-years was observed in the upper(young leaves).When boron was applied at 250 mg·L^(-1),in the off-year,the upper(young leaves)recorded the highest ^(15)N uptake and accumulation(%^(15)Ndff=13.93)relative to the other two leaf categories and those of the on-year.In the on-year fruit accumulated higher ^(15)N than leaf or bud.In the off-year,bud exhibited the highest ^(15)N accumulation without boron application,while leaves exhibited the highest ^(15)N with boron application.The highest%^(15)Ndff in all tree organs was observed at 250 mg·L^(-1) boron rate.Boron increased nitrogen uptake,translocation and accumulation in mango tree organs.A synergistic relationship was observed between boron and nitrogen which led to an increase in fruit yield in the off-year.

Stable isotopes in aquatic food web of an artificial lagoon in the Hangzhou Bay,China

Stable isotope values, δ13C and δ15N, were determined for four primary producers and 19 dominant consumers in a small artificial lagoon located in Hangzhou Bay. Based on these results the major pathways for energy flow and trophic structure of the artificial lagoon ecosystem were characterized. The mean δ13C values for the 19 consumers ranged from -22.99‰ to -14.24‰. Apart from so-iny mullet Liza haematocheila, the other 18 consumers had intermediate δ13C values between those of epibenthic microalgae and particulate organic matter (POM). The results of a multiple source linear mixing model (IsoSource model) indicated that 50% or more of the organic carbon in the tissues of most consumers was derived from epibenthic microalgae. This indicated that these primary producers were the main food source fueling the lagoon food web. The mean δ15N values for the 19 consumers varied between 4.93‰ and 12.97‰ and indicated four trophic levels in the lagoon. Four macroinvertebrates and zooplankton represented the primary consumers, whilst the other 14 consumers occupied the secondary and tertiary consumer levels. The 19 consumers were divided into three trophic guilds (detritivores/suspension feeders, omnivores and carnivores).

Estimation of Biological Nitrogen Fixation Capacity by Sugarcane Using 15N

[ Objective] The study aimed to reveal the biological nitrogen fixation capacity by sugarcane from Brazil under the ecological conditions of Guangxi, and to provide reference for study on the biological nitrogen fixation capacity by sugarcane and related generalization and application. [ Method] The ^15N isotopic fertilizer was solely applied on plants of three sugarcane cultivars planted in greenhouse with no other fertilizer forms applied, meanwhile virus-free stem seedling was regarded as control, to measure their biological nitrogen fixation capacity using ^15N isotope. [ Result ] The nitrogen fixation rate of B8 from Brazil reached 26.91%, while Guitang 11 and RIC16 presented no or poor nitrogen fixation capacity. [ Conclusion] The sugarcane eultivar B8 from Brazil showed some nitrogen fixation capacity under the ecological conditions of Guangxi.

15N同位素在华北冬小麦夏玉米氮营养来源研究中的应用

小麦-玉米一年两作是华北平原最主要的种植方式之一,对保障国家粮食安全至关重要。阐明该种植体系作物氮营养来源定量组成对区域养分资源管理、施肥制度优化、作物营养状况调控都具有十分重要的意义。15N作为氮元素的一种稳定同位素,其示踪技术在农田氮肥去向,作物氮营养来源等农业生产领域得到广泛应用。本文主要概述了15N同位素技术在研究当季施入化肥氮、前茬残留化肥氮、播前土壤固有硝态氮对华北冬小麦-夏玉米氮营养贡献中的具体应用方法、实例及相关研究结果,并对叶面肥氮、还田秸秆氮、大气沉降氮等其他氮营养来源的研究进行了展望,以期为该种植体系养分资源管理以及施肥制度优化提供理论参考。

Use of ^(15)N stable isotope to quantify nitrogen transfer between mycorrhizal plants

Aims Mycorrhizas(fungal roots)play vital roles in plant nutrient acquisition,performance and productivity in terrestrial ecosystems.Arbuscular mycorrhizas(AM)and ectomycorrhizas(EM)are mostly important since soil nutrients,including NH+4,NO
3 and phosphorus,are translocated from mycorrhizal fungi to plants.Individual species,genera and even families of plants could be interconnected by mycorrhizal mycelia to form common mycorrhizal networks(CMNs).The function of CMNs is to provide pathways for movement or transfer of nutrients from one plant to another.In the past four decades,both ^(15)N external labeling or enrichment(usually expressed as atom%)and ^(15)N naturally occurring abundance(d^(15)N,&)techniques have been employed to trace the direction and magnitude of N transfer between plants,with their own advantages and limitations.Important Findings The heavier stable isotope ^(15)N is discriminated against 14N during biochemical,biogeochemical and physiological processes,due to a greater atomic mass.In general,non-N2-fixing plants had greater d^(15)N values than N2-fixing(;0&)ones.Foliar d^(15)N often varied by 5 to 10&in the order:non-mycorrhizas/AMs>EMs>ericoid mycorrhizas.Differences in d^(15)N(&)or ^(15)N(atom%)values could thus provide N transfer information between plants.A range of between 0 to 80%of one-way N transfer had been observed from N2-fixing mycorrhizal to non-N2-fixing mycorrhizal plants,but generally less than or around 10%in the reverse direction.Plant-to-plant N transfer may provide practical implications for plant performance in N-limited habitats.Considering that N translocation or cycling is crucial,and the potential benefits of N transfer are great in both agricultural and natural ecosystems,more research is warranted on either oneway or two-way N transfers mediated by CMNs with different species and under field conditions.

利用^(15)N示踪技术研究木荷与马尾松幼苗叶片对NO_(2)的吸收与分配

大气氮氧化物(NOx=NO+NO_(2))随着干沉降进入森林生态系统时,会首先接触森林冠层。森林乔木能通过叶片吸收多少NO_(2)以及对吸收的NO_(2)是如何分配的,目前尚不清楚。该研究利用15N稳定同位素示踪技术,对中国南方常见乔木树种木荷(Schima superba)和马尾松(Pinus massoniana)幼苗在黑暗和光照两种条件下进行了^(15)NO_(2)静态箱熏蒸实验,检测并分析了两种植物的15N回收率以及吸收的NO_(2)在植物各组织中的分配结果。结果显示:植物主要通过气孔吸收NO_(2),木荷和马尾松在黑暗条件下整体分别能回收10.3%±5.9%和20.4%±7.0%^(15)NO_(2),在光照条件下整体分别能回收35.9%±5.4%和68.2%±7.6%^(15)NO_(2)。两种植物各组织中的平均干质量15N回收率均表现为叶>枝>干>根,大部分吸收的NO_(2)在短时间内都留在叶片中,木荷和马尾松叶片15N回收率占比在黑暗条件下分别为72%和49%,在光照条件下分别为91%和96%。本研究的结果表明森林乔木对NO_(2)的吸收不可忽略,森林乔木吸收NO_(2)这一过程在森林生态系统氮收支中起着十分重要的作用。

Nitrate and Ammonium Leaching in Variable-and Permanent-Charge Paddy Soils

A variable-charge （VC） and a permanent-charge paddy soil （PC） were selected to study nitrate-N （NO3^--N） and ammonium-N （NH4^＋-N） leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls （CK）, ^15N-labeled （NH4）2SO4 （NS）, and milk vetch （NV） applied at a rate equivalent to 238 kg N ha^-1 to unplanted lysimeters, totaling six treatments in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3^--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added ^15N respectively; and 〉 85% of leached NO3-N came from of the total inorganic N in leachate. Moreover, NH4^＋-N native N in the soil. In the case of VC, NH4^＋-N made up to 92% leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3^--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3^--N leaching during the drained season in permanent-charge paddy soils and NH4^＋-N leaching in variable-charge soils deserve more attention for regional environmental control.

Symbiotic nitrogen fixation in black locust (Robinia pseudoacacia L.) seedlings from four seed sources

We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.

The role of green manure nitrogen use by corn and sugarcane crops in Brazil

Three assays were developed from April 3, 1995 to October 10, 2005. The work with corn was conducted in a greenhouse, using velvet bean (Mucuna aterrima) and sunn hemp (Crotalaria juncea) as green manure with 15N labeling of either shoots or roots, in two soils with contrasting textural classes. The mineralization of N from legume plants incorporated into the two soils was investigated too. This work included two green manures: velvet bean and sunn hemp, and the common bean (Phaseolus vulgaris) residues. Nitrogen from the velvet bean accounted for a greater proportion of the soil inorganic N;shoots were responsible for most of N accumulated. Common bean residues caused immobilization of inorganic N. The leguminous species added were intensively and promptly mineralized, preserving the soil native nitrogen. One hundred days after emergence of the corn, velvet bean provided higher accumulation of nitrogen in the soil, higher absorption by corn plants and accumulation in the aerial part. The green manure decomposition was more intense in the medium textured soil. In this soil, highest nitrogen losses were also observed. The sugarcane (Saccharum spp.) was cultivated for five years in the field and was harvested three times;15N recovery was evaluated in the first two harvests. The combination of inorganic fertilizer and green manure resulted in higher sugarcane yields than either N source applied separately;however, in the second cutting the yields were higher where sunn hemp was used than in plots with ammonium sulfate. The recovery of N by the first two consecutive harvests accounted for 19% to 21% of the N applied as sunn hemp and 46% to 49% of the N applied as ammonium sulfate. Very little inorganic N was present in the 0-40 cm soil layer with both N sources.