同位素示踪技术在丛枝菌根真菌生态学研究中的应用

丛枝菌根(arbuscular mycorrhizal,AM)真菌是生态系统中重要的土壤微生物之一。AM真菌菌丝体网络是由AM真菌菌丝体在土壤生态系统中连接两株或两株以上植物根系所形成的菌丝体网络。随着菌根学研究的深入,如何直观的揭示AM真菌的生态学功能已经成为相关领域关注的热点问题。研究发现,利用同位素示踪技术可以开展AM真菌与宿主植物对土壤矿质营养的吸收、转运等方面的研究,以及菌丝体网络对不同宿主植物之间营养物质的分配研究和AM真菌在生态系统生态学中的功能研究。基于此,为了阐明同位素示踪技术在AM真菌研究中的价值,围绕菌根学最新研究进展,系统回顾了利用同位素示踪技术探究AM共生体对不同元素吸收和转运的机制、同位素示踪技术在AM真菌菌丝体网络研究中的价值和利用同位素示踪技术研究AM真菌在生态系统中的功能,为AM真菌生态学功能的研究提供理论基础,并对本领域未来的研究方向和应用前景进行展望。     

土壤-植物-大气连续体系中氮的研究进展

氮素是植物最需要的重要养分元素之一.近年来,土壤-植物-大气这一连续体系(SPAC)中的氮循环成为研究的热点之一.大气中的氮素可以通过生物固定和N沉降等作用进入土壤和植物内,同时土壤和植物内的氮素又会以氨挥发和氮氧化物等方式排放到大气中.氮素通过生物固持和植物吸收等方式进入植物体内,植物器官脱落使植物损失一部分的氮素,另外雨水的淋洗和植物溢出液也会造成植物的N损失.植物氮素在植物体内的积累和分布随着生长时期和各营养器官而有所不同.另外,植物吸收氮素的过程又受到大气状况和土壤状况的制约.土壤中氮素经过矿化作用、硝化作用和反硝化作用进行转化,一部分把氮素转化成植物能吸收的营养形态,另一部分则从土壤中损失.凋落物的分解和N沉降能补充土壤中的氮素,而植物吸收、微生物固持、水文流失和N溢出等方式使氮素从土壤中损失出去.另外,凋落物的分解和根际土壤、CO2浓度和臭氧对氮素循环有着重要的作用.N污染、N沉降、碳氮循环的耦合作用是今后研究的热点问题.     

青藏高原东部高山植物的水分利用效率与氮素利用效率研究

对生长在青藏高原东部隶属于23科、49属的71种高山植物(包括多年生和一年生植物)的稳定碳同位素比值、氮含量以及碳/氮比率进行了分析,并以稳定碳同位素比值及碳/氮比率来分别指示植物的水分利用效率和氮素利用效率.结果表明:(1)多年生植物稳定碳同位素比值显著高于一生年植物,而碳/氮比率显著低于一年生植物(P<0.01),氮含量两者无显著性差异.(2)多年生植物和一年生植物的稳定碳同位素比值均与碳/氮比率呈显著负相关(-0.643**和-0.707),而与氮含量均无明显相关性.研究证实,在自然条件下多年生植物的水分利用效率比一年生植物更高,而氮素利用效率却更低;高山植物水分利用效率和氮素利用效率存在明显的权衡",即植物不能同时提高水分利用效率和氮素利用效率,高水分利用效率的代价是降低氮素利用效率,青藏高原不同植物即使在相同环境条件下具有不同适应对策.     

碳同位素示踪技术及其在陆地生态系统碳循环研究中的应用与展望

碳同位素示踪技术具有高度的专一性和灵敏度, 经过几十年的发展, 形成了一系列成熟的标记方法, 在陆地生态系统碳循环过程的研究中已得到广泛应用。目前, 自然丰度法、与¹³C贫化示踪技术结合的自由空气中气体浓度增加(FACE)实验、脉冲与连续标记法以及碳同位素高丰度底物富集标记法是研究陆地生态系统碳循环过程常用的碳同位素示踪方法; 通过将长期定位实验和室内模拟实验结合, 量化光合碳在植物-土壤系统的传输与分配特征, 明确植物光合碳对土壤有机质的来源、稳定化过程的影响及其微生物驱动机制; 阐明土壤碳动态变化(迁移与转化)和新碳与老碳对土壤碳库储量的相对贡献, 评估有机碳输入、转化与稳定的生物与非生物微观界面过程机制。然而, 生态系统碳循环受气候、植被、人为活动等多因素影响, 碳同位素技术需要结合质谱、光谱技术实现原位示踪, 结合分子生物学技术阐明其微生物驱动机制, 从而构建灵敏、准确、多尺度、多方位的同位素示踪技术体系。因此, 该文以稳定碳同位素为主, 综述了碳同位素示踪技术的原理、分析方法和在陆地生态系统碳循环过程中的应用进展, 归纳总结了碳同位素示踪技术结合原位检测技术和分子生物学技术的研究进展和应用前景, 并对碳同位素示踪技术存在的问题进行了分析和展望。     

碳同位素示踪技术及其在陆地生态系统碳循环研究中的应用与展望

碳同位素示踪技术具有高度的专一性和灵敏度,经过几十年的发展,形成了一系列成熟的标记方法,在陆地生态系统碳循环过程的研究中已得到广泛应用。目前,自然丰度法、与13C贫化示踪技术结合的自由空气中气体浓度增加(FACE)实验、脉冲与连续标记法以及碳同位素高丰度底物富集标记法是研究陆地生态系统碳循环过程常用的碳同位素示踪方法;通过将长期定位实验和室内模拟实验结合,量化光合碳在植物-土壤系统的传输与分配特征,明确植物光合碳对土壤有机质的来源、稳定化过程的影响及其微生物驱动机制;阐明土壤碳动态变化(迁移与转化)和新碳与老碳对土壤碳库储量的相对贡献,评估有机碳输入、转化与稳定的生物与非生物微观界面过程机制。然而,生态系统碳循环受气候、植被、人为活动等多因素影响,碳同位素技术需要结合质谱、光谱技术实现原位示踪,结合分子生物学技术阐明其微生物驱动机制,从而构建灵敏、准确、多尺度、多方位的同位素示踪技术体系。因此,该文以稳定碳同位素为主,综述了碳同位素示踪技术的原理、分析方法和在陆地生态系统碳循环过程中的应用进展,归纳总结了碳同位素示踪技术结合原位检测技术和分子生物学技术的研究进展和应用前景,并对碳同位素示踪技术存在的问题进行了分析和展望。     

碳同位素技术在森林生态系统碳循环研究中的应用

碳同位素技术对碳素在生态系统中的迁移动态具有很好的示踪作用,在生态学各领域研究中应用广泛。土壤、大气、植物是森林生态系统的重要碳库,植物是大气和土壤交换碳元素的重要介质。本文简要总结了碳同位素技术在研究碳元素在植物体内以及植物、土壤、大气碳库之间的迁移规律和生态学过程中的应用,展望了该技术在森林界面学中的应用前景。     

苔藓新老组织及其根际土壤的碳氮元素含量和同位素组成(δ13C和δ15N)对比

 对细叶小羽藓(Haplocladium microphyllum)新老组织及其根际土壤的碳氮含量和同位素组成进行了分析,探讨了苔藓衰老过程控制元素和同位 素变化的机制以及苔藓对土壤的贡献。同种组织碳氮含量之间的相关性反映了苔藓固碳能力和氮需求的相互联系。新生组织碳氮含量明显高于 衰老组织且存在相关性,反映了苔藓衰老过程体内碳氮物质向新生组织迁移的生理特征。两种组织之间同位素组成(δ¹³C和δ¹⁵N)没有明显差 异,说明组织间的物质迁移没有产生明显的同位素分馏,其原因可能在于细叶小羽藓形态结构简单,体内物质迁移对碳氮同位素组成的影响较 小。相反,苔藓组织与根际土壤之间的有机碳/ 氮信息没有相关性,这可能与苔藓植物长期滞留营养物质、缓慢的分解和成土速度有关,反映了 该研究区苔藓层对土壤碳氮累积的贡献较小。     

C和δ15N)对比

对细叶小羽藓(Haplocladium microphyllum)新老组织及其根际土壤的碳氮含量和同位素组成进行了分析,探讨了苔藓衰老过程控制元素和同位 素变化的机制以及苔藓对土壤的贡献。同种组织碳氮含量之间的相关性反映了苔藓固碳能力和氮需求的相互联系。新生组织碳氮含量明显高于 衰老组织且存在相关性,反映了苔藓衰老过程体内碳氮物质向新生组织迁移的生理特征。两种组织之间同位素组成(δ¹³C和δ¹⁵N)没有明显差 异,说明组织间的物质迁移没有产生明显的同位素分馏,其原因可能在于细叶小羽藓形态结构简单,体内物质迁移对碳氮同位素组成的影响较 小。相反,苔藓组织与根际土壤之间的有机碳/ 氮信息没有相关性,这可能与苔藓植物长期滞留营养物质、缓慢的分解和成土速度有关,反映了 该研究区苔藓层对土壤碳氮累积的贡献较小。     

稳定碳同位素技术在土壤-植物系统碳循环中的应用

碳作为重要的生命元素,在土壤-植物系统物质循环中发挥重要作用.作为一种天然的示踪物,稳定碳同位素（13C）较放射性同位素具有安全、无污染、易控制的优点,在土壤-植物生态系统碳循环研究中得到广泛应用.通过检测土壤-植物体系中稳定碳同位素的自然丰度或采用稳定碳同位素标记有机材料,能够较真实地了解植物的光合特性、光合产物在土壤-植物体系中的运转及其在土壤中的分解、转化等过程.本文概述了稳定碳同位素技术在植物光合作用及光合产物运转、古气候重建、土壤有机质周转以及植物-根际微生物相互作用等方面的研究进展,并针对当前研究中存在的问题提出了今后的研究展望.     

稳定碳同位素技术在土壤-植物系统碳循环中的应用

碳作为重要的生命元素,在土壤 植物系统物质循环中发挥重要作用.作为一种天然的示踪物,稳定碳同位素（¹³C）较放射性同位素具有安全、无污染、易控制的优点,在土壤 植物生态系统碳循环研究中得到广泛应用.通过检测土壤 植物体系中稳定碳同位素的自然丰度或采用稳定碳同位素标记有机材料,能够较真实地了解植物的光合特性、光合产物在土壤 植物体系中的运转及其在土壤中的分解、转化等过程.本文概述了稳定碳同位素技术在植物光合作用及光合产物运转、古气候重建、土壤有机质周转以及植物 根际微生物相互作用等方面的研究进展,并针对当前研究中存在的问题提出了今后的研究展望.     

Measuring the trophic ecology of ants using stable isotopes

Ants are prominent components of most terrestrial arthropod food webs, yet due to their highly variable diet, the role ants play in arthropod communities can be difficult to resolve. Stable isotope analysis is a promising method for determining the dietary history of an organism, and has the potential to advance our understanding of the food web ecology of social insects. However, some unique characteristics of eusocial organisms can complicate the application of this technique to the study of their trophic ecology. Using stable isotopes of N and C, we investigated levels of intraspecific variation both within and among colonies. We also examined the effect of a common preservation technique on δ¹⁵N and δ¹³C values. We discuss the implications of our results on experimental design and sampling methods for studies using stable isotopes to investigate the trophic ecology of social insects. Received 4 February 2005; revised 23 June 2005; accepted 4 July 2005.     

Stable Isotope Ratios as a Tool for Assessing Changes in Carbon and Nutrient Sources in Antarctic Terrestrial Ecosystems

Samples of an angiosperm species, nine lichen species and a terrestrial alga, were collected from a variety of Antarctic terrestrial habitats, and were analysed for C and N stable isotope composition. Collections were made along natural gradients, the marine gradient, running from the sea coast inland and the moisture gradient, determined by melt water and precipitation runoff, and running towards the sea coast. Considerable variation in stable isotope ratios was found; δ¹³C values ranged between −16 and −32‰ and δ¹⁵N values between −23 and +23‰ The variation in stable carbon isotope ratios could be attributed in part to species specific differences, but differences in water availability also played a role, as was shown for the terrestrial alga Prasiola crispa and the lichen species Usnea antarctica. The differences in the isotope ratios of nitrogen could be retraced to the origin of nitrogen: marine or terrestrial. The nitrogen stable isotope ratios were influenced by both the marine gradient from the sea inland and the melt water and precipitation flow running in the opposite direction, towards the sea. This was shown for the lichen species Turgidosculum complicatulum and the angiosperm species Deschampsia antarctica. The variation in the C and N stable isotope ratios can be used to determine sources and pathways of N and changes in the water availability in Antarctic terrestrial ecosystems. Contrary to earlier reports the use of stable N isotope ratios is possible in this case because of the relative simplicity of the structure of the Antarctic terrestrial ecosystems.     

Use of compound-specific nitrogen isotope analysis of amino acids in trophic ecology: assumptions,applications, and implications

Knowledge of the diet source and trophic position of organisms is fundamental in food web science. Since the 1980s, stable isotopes of light elements such as ¹³C and ¹⁵N have provided unique information on the food web structure in a variety of ecosystems. More recently, novel isotope tools such as stable isotopes of heavy elements, radioisotopes, and compound-specific isotope analysis, have been examined by researchers. Here I reviewed the use of compound-specific nitrogen isotope analysis of amino acids (CSIA-AA) as a useful dietary tracer in food web ecology. Its three key features—(1) offsetting against isotopic variation; (2) universality of the trophic discrimination factor; and (3) sensitivity to source mixing—were compared with conventional isotope analysis for the bulk tissue of organisms. These three advantages of CSIA-AA will allow future researchers to (1) estimate the integrated trophic position (iTP) of animal communities; (2) infer trophic transfer efficiency (TTE) in food webs; and (3) quantify contributions from different resources to animals, all of which are crucial for understanding the relationship between biodiversity and multi-trophic ecosystem functioning. Further development of trophic ecology will be facilitated by both methodological refinement of CSIA-AA and its application to a wider range of organisms, food webs, and ecosystems.     

15N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     

Stable isotope analyses provide new insights into ecological plasticity in a mixohaline population of European eel

Recent studies have shown that anguillid eel populations in habitats spanning the marine–freshwater ecotone can display extreme plasticity in the range of catadromy expressed by individual fishes. Carbon and nitrogen stable isotope analysis was used to differentiate between European eels (Anguilla anguilla) collected along a short (2 km) salinity gradient ranging from <1‰ to ~30‰ in Lough Ahalia, a tidal Atlantic lake system. Significant differences were recorded in mean δ¹³C, δ¹⁵N and C:N values from eels collected from fresh, brackish and marine-dominated basins. A discriminant analysis using these predictor variables correctly classified ca. 85% of eels to salinity zone, allowing eels to be classified as freshwater (FW), brackish (BW) or marine (MW) residents. The results of the discriminant analysis also suggested that a significant proportion of eels moved between habitats (especially between FW and BW). Comparisons of several key population parameters showed significant variation between eels resident in different salinity zones. Mean condition and estimated age was significantly lower in MW eels, whilst observed length at age (a correlate of growth) was significantly higher in MW eels, intermediate in BW and lowest in FW eels. This study has demonstrated that the ecology of eels found along a short salinity gradient can be extremely plastic and that stable isotope analysis has considerable utility in demonstrating intra-population variation in diadromous fishes.     

Application of stable isotopes to examine N proportions within a simulated Aegiceras corniculatum wetland

Salinity levels and drought status of coastal wetlands may be strongly affected by climate change, and changes in the nitrogen cycle of mangrove wetlands may also be affected. We established combinations of three salinity and water levels with applied stable isotope ¹⁵N to study the δ¹⁵N distributions in the sediment and plants of a greenhouse-based simulated mangrove Aegiceras corniculatum wetland system. The stable isotope ¹³C and ¹⁵N, C and N contents and the C:N ratio were determined. Results showed that increasing in salinity significantly increased the δ¹³C value in plant organs. The δ¹⁵N value of plant organs increased with increasing water level in low salinity (10‰) and medium salinity (20‰) treatment groups but not in the high salinity (30‰) treatment group. This may attributed to A. corniculatum adjusting the δ¹⁵N distribution in different organs in response to high salinity stress. Compared to the δ¹³C, the δ¹⁵N values of plant were strongly affected by salinity and water level treatments, indicating that the behavior of N cycle was somewhat different than the C cycle, and affected by the combined effects of both salinity and water level. Most of ¹⁵N absorbed by plant tissues were in leaves except for the highest salinity and high water level treatment, showing at increasing water level, the proportion of ¹⁵N increased in root. Overall, the measured indicators exhibited different responses to salinity level and water level, suggesting that the changes in salinity and water levels have an impact on N cycling processes of wetland systems.     

NMR analysis of plant nitrogen metabolism

The analysis of primary and secondary nitrogen metabolism in plants by nuclear magnetic resonance (NMR) spectroscopy is comprehensively reviewed. NMR is a versatile analytical tool, and the combined use of ¹H, ²H, ¹³C, ¹⁴N and ¹⁵N NMR allows detailed investigation of the acquisition, assimilation and metabolism of nitrogen. The analysis of tissue extracts can be complemented by the in vivo NMR analysis of functioning tissues and cell suspensions, and by the application of solid state NMR techniques. Moreover stable isotope labelling with ²H-, ¹³C- and ¹⁵N-labelled precursors provides direct insight into specific pathways, with the option of both time-course and steady state analysis increasing the potential value of the approach. The scope of the NMR method, and its contribution to studies of plant nitrogen metabolism, are illustrated with a wide range of examples. These include studies of the GS/GOGAT pathway of ammonium assimilation, investigations of the metabolism of glutamate, glycine and other amino acids, and applications to tropane alkaloid metabolism. The continuing development of the NMR technique, together with potential applications in the emerging fields of metabolomics and metabolic flux analysis, leads to the conclusion that NMR will play an increasingly valuable role in the analysis of plant nitrogen metabolism.     

Nitrogen fixation,transfer and turnover in upland and lowland grass-clover swards,using15N isotope dilution

The stable isotope¹⁵N is particularly valuable in the field for measuring N fixation by isotope dilution. At the same time other soil-plant processes can be studied, including¹⁵N recovery, and nitrogen transfer between clover and grass. Three contrasting sites and soils were used in the present work: a lowland soil, an upland soil, and an upland peat. Nitrogen fixation varied from 12 gm^–2 on lowland soil to 2.7 gm^–2 on upland peat. Most N transfer occurred on upland soil (4.2 gm^–2) which, added to nitrogen fixed, made a total of 8.7 gm² input during summer 1985.¹⁵N recovery for the whole experiment was small, around 25%.Measurement of dead and dying leaves, stubble and roots, suggests that plant organ death is the first stage in N transfer from white clover to ryegrass, through the decomposer cycle. Decomposition was fastest on lowland soils, slowest on peat. On lowland soil this decomposer nitrogen is apparently subverted before transfer, probably by soil microbes.Variations in natural abundance of¹⁵N in plants were found in the two species on the different soils. These might be used to measure nitrogen fixation without adding isotope, but the need for many replicates and repeat samples would limit throughput.     

A comparison between the acetylene reduction method,the isotope dilution method and the total nitrogen difference method for measuring nitrogen fixation in lucerne (Medicago sativa L.)

Summary In view of the increasing need for the exact estimation of the input of nitrogen in agroecosystems, an application of the acetylene-reduction technique was developed. The technique, consisting of a plastic bag incubation system, using propane as an internal standard of the apparent volume, made it possible to carry out repeated incubations on the same plant system. The evaluated technique included studies of the diffusion of ethylene and propane in a soil column, as well as studies of the optimal substrate concentration and grade of purity of the substrate. In addition, the conversion factor between amounts of reduced acetylene as compared wtih reduced dinitrogen was determined by¹⁵N₂ incubations to be 4.41. The developedin situ acetylene-reduction technique was compared with an isotope dilution method and a total nitrogen difference method. By comparing the derived total nitrogen fixation values from each with the value derived from the acetylene-reduction method; it was shown that the values differed significantly. The acetylene-reduction method gave the highest nitrogen fixation values, the isotope dilution the lowest values and the total nitrogen difference method was intermediate. No statistical significant difference existed between the two different reference crops used in the isotope dilution method.     

Dual‐tracer‐based isotope turnover rates in a highly invasive mysid Limnomysis benedeni from Lake Constance

Understanding the ecological patterns of invasive species and their habitats require an understanding of the species’ foraging ecology. Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values provide useful information into the study of animal ecology and evolution, since the isotope ratios of consumers reflect consumer's dietary patterns. Nevertheless, the lack of species‐ and element‐specific laboratory‐derived turnover rates could limit their application. Using a laboratory‐based dual stable isotope tracer approach (Na¹⁵NO₃ and NaH¹³CO₃), we evaluated the δ¹⁵N and δ¹³C isotope turnover rates in full‐grown adult invasive Limnomysis benedeni from Lake Constance. We provide δ¹⁵N and δ¹³C turnover rates based on nonlinear least‐squares regression and posterior linear regression models. Model precisions and fit were evaluated using Akaike's information criterion. Within a couple of days, the δ¹⁵N and δ¹³C of mysids began to change. Nevertheless, after about 14 days, L. benedeni did not reach equilibrium with their new isotope values. Since the experiment was conducted on adult subjects, it is evident that turnover was mainly influenced by metabolism (in contrast to growth). Unlike traditional dietary shifts, our laboratory‐based dual stable isotope tracer approach does not shift the experimental organisms into a new diet and avoids dietary effects on isotope values. Results confirm the application of isotopic tracers to label mysid subpopulations and could be used to reflect assimilation and turnover from the labeled dietary sources. Field‐based stable isotope studies often use isotopic mixing models commonly assuming diet‐tissue steady state. Unfortunately, in cases where the isotopic composition of the animal is not in equilibrium with its diet, this can lead to highly misleading conclusions. Thus, our laboratory‐based isotopic incorporation rates assist interpretation of the isotopic values from the field and provide a foundation for future research into using isotopic tracers to investigate invasion ecology.