Application Of Stable Isotope Techniques Research Articles

Application of Stable Isotope Techniques in Tracing the Sources of Atmospheric NOX and Nitrate

Nitrate is an important component of PM2.5, and its dry deposition and wet deposition can have an impact on ecosystems. Nitrate in the atmosphere is mainly transformed by nitrogen oxides (NOX = NO + NO2) through a number of photochemical processes. For effective management of the atmosphere’s environment, it is crucial to understand the sources of atmospheric NOX and the processes that produce atmospheric nitrate. The stable isotope method is an effective analytical method for exploring the sources of NO3− in the atmosphere. This study discusses the range and causes of δ15N data from various sources of NOX emissions, provides the concepts of stable isotope techniques applied to NOX traceability, and introduces the use of Bayesian mixture models for the investigation of NOX sources. The combined application of δ15N and δ18O to determine the pathways of nitrate formation is summarized, and the contribution of Δ17O to the atmospheric nitrate formation pathway and the progress of combining Δ17O simulations to reveal the atmospheric oxidation characteristics of different regions are discussed, respectively. This paper highlights the application results and development trend of stable isotope techniques in nitrate traceability, discusses the advantages and disadvantages of stable isotope techniques in atmospheric NOX traceability, and looks forward to its future application in atmospheric nitrate pollution. The research results could provide data support for regional air pollution control measures.

Application of stable isotope technique to authenticate the geographical origin of imported apple products

Application of stable isotope technique to authenticate the geographical origin of imported apple products

High Spatiotemporal Dynamics of Methane Production and Emission in Oxic Surface Water.

The discovery of methane (CH4) accumulation in oxic marine and limnic waters has redefined the role of aquatic environments in the regional CH4 cycle. Although CH4 accumulation in oxic surface waters became apparent in recent years, the sources are still subject to controversial discussions. We present high-resolution in situ measurements of CH4 concentration and its stable isotope composition in a stratified mesotrophic lake. We show that CH4 accumulation in surface waters originates from a highly dynamic interplay between (oxic) CH4 production and emission to the atmosphere. Laboratory incubations of different phytoplankton types and application of stable isotope techniques provide a first unambiguous evidence that major phytoplankton classes in Lake Stechlin per se produce CH4 under oxic conditions. Combined field and lab results show that the photoautotroph community is an important driver for CH4 production and its highly dynamic accumulation in oxic surface waters.

Using stable isotope analysis to answer fundamental questions in invasion ecology: Progress and prospects

Abstract What makes some species successful invaders while others fail, and why some invaders have major impacts in invaded ecosystems are pivotal questions that are attracting major research effort. The increasing availability of high resolution, georeferenced stable isotope landscapes (‘isoscapes’), coupled with the commercialization of stable isotope‐enriched tracer molecules and the development of new analytical approaches, is facilitating novel applications of stable isotope techniques in ecology. We can now address ecological questions that were previously intractable. We review and discuss how stable isotope analysis (SIA) can complement fundamental research themes in the study of biological invasions, especially in answering questions relating to the physiological and ecological mechanisms underlying invasion processes and invader impacts. SIA was first used for simply describing the diet of invaders but, more recently, SIA‐informed metrics of population and community trophic structure have been advanced. These approaches now permit the comparison of diets across space and time and provide quantitative tools to compare food webs across different stages of invasion. SIA has also been pivotal in quantifying competition for resources between native and non‐native species (e.g. competition for food, water, or nutrient use). Specific questions related to modes of dispersal (e.g. origin and distance/direction travelled) and mechanisms of establishment can also be addressed using SIA in diverse taxa. An overarching goal is to highlight examples of recent studies that have used SIA in key areas of invasion ecology and use these to synthesize testable predictions where SIA could be applied to future studies. We conclude by highlighting several paths forward and describing how unresolved challenges in quantifying the rates, impacts, and mechanisms underlying invasions could potentially benefit from the use of SIA.

Toxic effect of oil spill on the growth of Ulva pertusa by stable isotope analysis

The oil spills occur frequently during the offshore oil exploration and transportation, resulting in the destruction of the marine environment. After an oil spill, petroleum can stay in the sea for a long time and pose a toxic effect on marine organism. Under the action of the waves, oil continues to diffuse, flows to the intertidal zone of the coast, where it accumulates. Ulva pertusa Kjellman (Ulvales, Chlorophyta) is the marine green algae and is widely distributed and easy to breed in the intertidal zone. The study investigated the growth rates, chlorophyll-a, and carbon and nitrogen stable isotopes of U. pertusa under the stress of the water accommodated fraction (WAF) for two kinds of oils (0# diesel oil and Russian crude oil). The results showed that the growth rate and chlorophyll-a initially increased and then decreased under the stress of WAF. High concentration of WAF posed the obviously inhibitory effect on algae; and oil spill also causes the distinct fraction of carbon and nitrogen stable isotopes of U. pertusa, especially for carbon stable isotope. The change trends of bulk carbon and nitrogen isotopes were similar to those of growth rates of U. pertusa. Therefore, the application of stable isotope techniques can quickly evaluate the toxic effects of petroleum on algae and can be used as a new method to evaluate the toxicity of the oil spill in marine environment.

The continuous trophic spectrum of food web in Dalian marine area, China.

This study analyzed the values of δ13C and δ15N by the application of stable isotope technique from the marine mammals (Phoca largha, Neophocaena asiaorientalis sunameri, Balaenoptera acutorostrata) and major biological species in Dalian marine area based on the animals collected due to stranding and death after bycatch from January, 2008 to June, 2017, and the fisheries resources investigation between autumn, 2016 and spring, 2017 in the same area. The trophic level was then calculated in order to establish the continuous trophic spectrum of the food web in Dalian marine area. The results showed that the value of δ15N ranged from 8.0‰ to 14.7‰ and the value of δ13C ranged from -21.1‰ to -16.7‰ of the food web in Dalian marine area. The major biological species could be categorized into three groups, namely primary consumer, secondary consumer and top predator. The analysis of δ15N revealed that the trophic level ranged from 2.63 to 4.59 for the major biological species. The trophic level of B. acutorostrata, N. asiaorientalis sunameri, P. largha, echinoderm, cephalopods, gastropod, bivalve, crustacean and fish were 3.16, 4.11, 4.25, 3.24-3.84, 3.81-3.93, 3.65-4.13, 2.63-3.15, 3.58-4.12 and 3.20-4.59, respectively. The characteristics of the trophic structure demonstrated that the primary consumer was bivalve, the secondary consumers were B. acutorostrata, cephalopods, Echinoderms, gastropod and crustacean, and top predators were N. asiaorientalis sunameri, P. largha and fish. The value of δ15N increased with the increase in the body length, indicating the feeding of N. asiaorientalis sunameri tended to be at a higher trophic level with the growth and feeding ability enhanced. This study established the continuous trophic spectrum of food web in Dalian marine area and would provide the information for the marine mammal and fisheries resources protection.

A review of water and carbon flux partitioning and coupling in SPAC using stable isotope techniques

Soil-vegetation-atmosphere continuum (SPAC) is one of the important research objects in the field of terrestrial hydrology, ecology and global change. The process of water and carbon cycling, and their coupling mechanism are frontier issues. With characteristics of tracing, integration and indication, stable isotope techniques contribute to the estimation of the relationship between carbon sequestration and water consumption in ecosystems. In this review, based on a brief introduction of stable isotope principles and techniques, the applications of stable isotope techniques to water and carbon exchange in SPAC using optical stable isotope techniques were mainly explained, including: partitioning of net carbon exchange into photosynthesis and respiration; partitioning of evapotranspiration into transpiration and evaporation; coupling of water and carbon cycle at the ecosystem scale. Advanced techniques and methods provided long-term and high frequency measurements for isotope signals at the ecosystem scale, but the issues about the precision and accuracy for measurements, partitioning of ecosystem respiration, adaptability for models under non-steady state, scaling up, coupling mechanism of water and carbon cycles, were challenging. The main existing research findings, limitations and future research prospects were discussed, which might help new research and technology development in the field of stable isotope ecology.

Mining the isotopic complexity of nitrous oxide: a review of challenges and opportunities

Nitrous oxide (N2O) is an important focus of international greenhouse gas accounting agreements and mitigation of emissions will likely depend on understanding the mechanisms of its formation and reduction. Consequently, applications of stable isotope techniques to understand N2O cycling are proliferating and recent advances in technology are enabling (1) increases in the frequency of isotope analyses and (2) analyses not previously possible. The two isotopes of N and 3 isotopes of O combine to form a total of 12 possible isotopic molecules of N2O. Consequently, this remarkably simple molecule contains a wealth of isotopic information in the form of bulk (δ15N, δ18O), position dependent (site preference), mass independent (Δ17O) and multiply-substituted or clumped isotope compositions. With recent developments in high-mass resolution double sector instruments all 12 isotopic molecules will likely be resolved in the near future. Advances in spectroscopic instruments hold the promise of substantial increases in sample throughput; however, spectroscopic analyses require corrections due to interferences from other gases and frequent and accurate calibration. Mass spectrometric approaches require mass overlap corrections that are not uniform between research groups and interlaboratory comparisons remain imprecise. The continued lack of attention to calibration by both funding agencies and investigators can only perpetuate disagreement between laboratories in reported isotope values for N2O that, in turn, will compromise global assessments of N2O sources and sinks based on isotope ratios. This review discusses the challenges and opportunities offered by the isotopic complexity of N2O.

应用碳氮稳定同位素技术研究江豚(Neophocaena asiaeorientalisssp.sunameri)食性

PDF HTML阅读 XML下载 导出引用 引用提醒 应用碳氮稳定同位素技术研究江豚(Neophocaena asiaeorientalis ssp. sunameri)食性 DOI: 10.5846/stxb201407071390 作者: 作者单位: 中国海洋大学海洋生物多样性与进化研究所,辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院,中国海洋大学海洋生物多样性与进化研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 辽宁省海洋与渔业科研项目(201417);海洋公益性行业科研专项经费项目(201105011) Using stable isotope technique to study feeding habits of the finless porpoise (Neophocaena asiaeorientalis ssp. sunameri) Author: Affiliation: Institute of Evolution DdDd Marine Biodiversity;Ocean University of China,,,,Liaoning Ocean and Fisheries Science Research Institute,Institute of Evolution DdDd Marine Biodiversity;Ocean University of China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:稳定同位素技术已广泛地用于分析生态系统中食物网的食物来源和营养级关系,但在海洋哺乳动物食性方面应用较少。通过分析2012年4-6月在辽东湾沿岸海域搁浅而死亡的江豚样本和同时期(6月)取自辽东湾海域主要渔获物的碳氮稳定同位素比值,研究了江豚(Neophocaena asiaeorientalis ssp. sunameri)及其可能摄食饵料的碳氮稳定同位素组成。结果表明:江豚δ13C值为(-18.4±0.3)‰,δ15N值为(13.8±0.4)‰。28种可能生物饵料的δ13C值的范围为-19.5‰--17.0‰,δ15N值的范围为11.4‰-14.0‰。江豚的营养级为4.5,高于传统胃含物分析法的研究结果。28种测试生物的营养级位于3.8-4.6之间。江豚的食物来源主要以鱼类为主,对食物种类的喜食顺序为中上层鱼类>中下层鱼类 > 底层鱼类 > 头足类 > 虾类 > 蟹类,其平均贡献率分别为43.9%、18.2%、13.1%、10.0%、8.8%、6.0%。江豚碳氮稳定同位素比值与体长无明显的线性关系,碳营养源较为稳定,氮营养源复杂多变。 Abstract:Stable isotope technique has been widely applied for identification of animal food sources and reconstruction of food chains and food webs in marine ecosystems, but it has been sparingly used in the research on feeding habits of marine mammals. Compared to the traditional stomach content analysis, which is lengthy, requires a large number of samples, and can only reflect the present state of the sampled organism, the stable isotope technique can reveal its extended biological activity, accurately measure biological source of nutrition, and truthfully identify the biological relationship among populations and the energy flow of the entire ecosystem. Various studies have applied the stable isotope method to investigate feeding in marine mammals such as pinnipeds, polar bears, and others. At present, research of finless porpoise has focused on morphology, behavior, age identification, population dynamics, etc. The previous diet studies mainly use the traditional methods to examine stomach content, whereas feeding studies of the finless porpoise in Liaodong Bay using stable isotopes have not been reported yet. Finless porpoise (genus Neophocaena) is a coastal, small-teethed cetacean inhabiting estuaries and rivers. It is broadly distributed in China, from the northern to the southern coastal areas and into the Yangtze River. The finless porpoise, which is listed as vulnerable in the IUCN list, includes Neophocaena phocaenoides and Neophocaena asiaeorientalis, with two subspecies (Neophocaena asiaeorientalis ssp. asiaeorientalis and Neophocaena asiaeorientalis ssp. sunameri) within the latter species. In the present study, we evaluated carbon and nitrogen stable isotope ratios in samples obtained from finless porpoises that were stranded and died on the coast of the Liaodong Bay and from those obtained from main fishing catches from the same area from April to June in 2012. We also evaluated the isotope ratio in the potential prey organisms. The mean values of δ13C and δ15N in samples of finless porpoise were (-18.4 ± 0.3)‰ and (13.8 ± 0.4)‰, respectively, whereas δ13C and δ15N in samples of 28 kinds of potential prey organisms ranged from -19.5‰ to -17.0‰ and from 11.4‰ to 14.0‰, respectively. The trophic level of finless porpoise was 4.5, which was higher than that obtained by traditional stomach content analysis. The trophic level of the 28 types of potential forages ranged from 3.8 to 4.6. Fish was the main prey of the finless porpoise; the contribution rate of prey organisms, from the biggest to the smallest, was as follows: pelagic fishes > mesodemersal fishes > demersal fishes > cephalopoda > shrimps > crabs, with the average contribution rate of 43.9%, 18.2%, 13.1%, 10.0%, 8.8%, and 6.0%, respectively. There was no significant linear correlation between the ratio of δ13C and δ15N and the body length of finless porpoise; the carbon sources were stable and the nitrogen sources were complex. Overall, the application of stable isotope technique to study feeding habits in finless porpoise can improve our understanding of the biology of this species, and provide some essential information for its conservation. 参考文献 相似文献 引证文献

Application of stable isotope techniques to the study of soil salinization

Application of stable isotope techniques to the study of soil salinization

Application of stable isotope techniques in studies of carbon and nitrogen biogeochemical cycles of ecosystem

Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the C-13 natural abundance technique, ecologists are able to understand the photosynthetic path and CO2 fixation of plants, the CO2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the C-13 labeled technique, the effects of elevated CO2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the N-15 natural abundance technique, ecologists are able to analyze the biological N-2-fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the N-15 labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope (S-34) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future.

Isotopic labeling and antifungal resistance as tracers of gut passage of the sea fan pathogen Aspergillus sydowii

Vectors play a critical role in the ecology of infectious disease by facilitating between host transmission, emphasizing the multi-species nature of disease. Corals are suffering an onslaught of infectious diseases, yet we know little about the role of vector species in the ecology of these epizootics. The infection of octocorals by the fungus Aspergillus sydowii is a widespread Caribbean coral disease. The snail Cyphoma gibbosum is a likely vector species because it is a specialist predator of octocorals, moves regularly among coral colonies, and aggregates on diseased corals. We used a novel application of stable isotope techniques and antifungal-resistant strains of A. sydowii to identify the potential for this snail to vector disease. The use of both isotopically labeled and hygromycin-resistant fungus was successful in definitively tracing A. sydowii through the guts of C. gibbosum from ingestion to feces. Further, we demonstrated in laboratory experiments that snails fed antifungal-resistant A. sydowii excrete viable spores and hyphae in their feces. Overall, this study demonstrates the usefulness of isotopic labeling and antifungal-resistant fungi to trace the movement of pathogen propagules in microbially diverse environments, and suggests that C. gibbosum may be able to spread aspergillosis between octocoral hosts.

Applications of stable isotope techniques to the ecology of mammals

ABSTRACT Stable isotope analysis (SIA) has the potential to become a widespread tool in mammalian ecology, because of its power in resolving the ecological and behavioural characteristics of animals. Although applications of the technique have enhanced our understanding of mammalian biology, it remains underused. Here we provide a review of previous applications to the study of extant mammals, drawing when appropriate on examples from the wider ecological literature, to identify the potential for future development of the approach. Stable isotope analysis has been applied successfully to understanding the basic foraging decisions of mammals. However, SIA generates quantitative data on a continuous scale meaning that the approach can be particularly powerful in the characterization of community metrics, such as dimensions of resource partitioning within species assemblages or nutrient dynamics in food chains. Resolving spatial and temporal patterns of individual, intraspecific and interspecific resource use is of fundamental importance in animal ecology and evolutionary biology and SIA will emerge as a critical tool in these fields. Geographical differences in naturally occurring stable isotopes have allowed ecologists to describe large‐scale mammal migrations. Several isotopic gradients exist at smaller spatial scales, which can provide finer resolution of spatial ecology. A combination of foraging and movement decisions is of prime importance in the study of ecotoxicology, since this discipline requires quantitative understanding of exposure risk.

The effects of flow regulation on food-webs of Boreal Shield Rivers

Alteration of flow regimes is a major threat to the functioning of lotic food-webs and is responsible for a wide range of ecological responses, including biodiversity loss (BUNN & ARTHINGTON 2002), reduction of food-chain length at lower trophic levels (MARKS et al. 2000), or diversion of energy flow from top consumers (WOOTTON et al. 1996). Despite growing recognition of the effects of flow disturbances on biota, quantitative understanding and/or predictive models of biotic responses to altered flow regimes are lacking. Consequently, environmental regulations that help to sustain lotic ecosystem ecological integrity are weakened. Such difficulty may stem from ignoring the complexity of flow as a combination of many variables including magnitude, frequency, timing, duration, or rate of change (ARTHINGTON et al. 2006), which have differing consequences on the biota (POWER et al. 1996). We applied a stable isotope (SI) approach to determine the impacts of a flow perturbation on food-web structure in rivers. The carbon and nitrogen isotopic compositions of organisms (δC and δN) are useful to characterize main sources of carbon and positions in the food-web because of the consistent fractionation between consumers and diet (FRY & SHERR 1984, FRANCE 1996, VANDER ZANDEN & RASMUSSEN 2001). In natural streams, the application of SI techniques revealed the importance of flow as a key variable driving the variation in δC of primary producers (FINLAY et al. 1999, MCCUTCHAN & LEWIS 2001, TRUDEAU & RASMUSSEN 2003). The controlling effect of flow at the base of the food-web has been further detected at higher trophic levels based on cross-ecosystem studies showing relationships between the carbon isotopic composition of consumers and basin characteristics such as drainage area (MCNEELY et al. 2006) and geochemistry (JEPSEN & WINEMILLER 2007). Stable isotope techniques have also been successfully applied to study the response of food-web structure to anthropogenic perturbations such as nutrient loading (ANDERSON & CABANA 2006) or contaminant accumulation (CABANA & RASMUSSEN 1994). Despite the great potential of SI techniques to identify impoundment and flow-related perturbations, they are rarely used to quantify food-web structure in regulated systems. We report on the effect of flow regulation on carbon sources and food-web structure of boreal streams based on a large-scale in situ experiment. We related variations in the flow regime to the carbon and nitrogen stable isotope composition of aquatic vegetation, invertebrates, and fish. This study aimed to determine the effects of (1) impoundment and (2) variation in the ramping rate (RR – or rate of change) regime on the food-web of a regulated stream.

Seasonal variations in fish δ13C and δ15N in two West African reservoirs, Sélingué and Manantali (Mali): Modifications of trophic links in relation to water level§

Most regions in the tropics undergo high seasonal precipitation that produces cyclic patterns of riverine discharge, resulting in periods characterized by low and high water levels. Many chemical and bio-logical factors are affected by this hydrologic seasonality, and it therefore appeared to be very likely that aquatic food webs would also differ during the low and high water periods. Available carbon sources for fish are thought to be less varied during low water periods, but flooding during high water periods could bring fish into contact with a greater abundance and diversity of food sources such as terrestrial plants or the biofilms that grow on submerged terrestrial plants. At low water levels, higher fish densities may lead to more piscivory and less omnivory when compared with the high water periods. Therefore, trophic links within the fish communities may then be modified by water level changes in tropical reservoirs. To address this prediction, we performed stable isotope analyses of the most common species in Sélingué and Manantali, two large reservoirs in Mali (West Africa). Allochthonous and littoral carbon sources were shown to support fish production to a significant extent, even during low water periods. However, the allochthonous or littoral carbon contributions that sustained the top-predators production were indeed greater during the high water periods as expected. The expected higher omnivory in the high water period might have shortened the food chain when compared with the low water period. Some carnivorous fish species were shown to feed at lower trophic levels during high water periods in both reservoirs, but this was not a general pattern. Flooding did not, therefore, necessarily result in a shorter food chain when water levels were high. § Revised version of a paper presented at the 4th International Conference on Applications of Stable Isotope Techniques to Ecological Studies, April 19–23, 2004, Wellington, New Zealand.

Differential isotopic enrichment and half-life among tissues in Japanese temperate bass (Lateolabrax japonicus) juveniles: implications for analyzing migration

As a first step for field applications of stable isotope techniques to investigate the migration of Japanese temperate bass (Lateolabrax japonicus) (Perciformes) juveniles, we conducted a diet switch experiment and fitted an exponential model to changes in stable carbon (δ13C) and nitrogen (δ15N) isotope ratios for muscle, fin, and liver. The trophic enrichment values were ranked liver < muscle < fin for δ13C (range –0.80‰ to +3.66‰) and liver < fin < muscle for δ15N (+0.59‰ to +3.12‰). The half-life values were similar for muscle and fin for both δ13C and δ15N (19.3–25.7 days), while those for liver were 5.3 days for δ13C and 14.4 days for δ15N. Both the δ13C and δ15N values of muscle reached the asymptotic value after a threefold body weight increase, reflecting the diet after the switch. These results suggest that fin is a useful substitute for muscle in field applications of stable isotope techniques and that liver, with a shorter half-life, has the potential to provide more recent information about migration.

Selected papers of the 4th International Conference on “Applications of stable Isotope Techniques to Ecological Studies”, April 19–23, 2004, Wellington, New Zealand

Selected papers of the 4th International Conference on “Applications of stable Isotope Techniques to Ecological Studies”, April 19–23, 2004, Wellington, New Zealand

APPLICATIONS OF STABLE ISOTOPE TECHNIQUES AND KEELING PLOT APPROACH TO CARBON AND WATER EXCHANGE STUDIES OF TERRESTRIAL ECOSYSTEMS

Stable isotopes are used as both natural integrators and tracers of complicated biological, ecological and biogeochemical processes, and their responses to environmental changes at different spatial and temporal scales. In this article, the application of stable isotopes and the Keeling plot approach to carbon and water exchange studies of terrestrial ecosystems were reviewed. We focused mainly on the current applications and potential development of stable isotope techniques and the Keeling plot approach in conjunction with concentration and flux measurements of CO_2 and water in terrestrial ecosystems. For these applications it is critical to know the isotopic identities of specific ecosystem components, such as the isotopic compositions of CO_2, organic matter, liquid water, and water vapor, as well as the associated isotopic fractionations, in the soil-plant-atmosphere continuum. Based on the principle of mass conservation, the Keeling plot approach combines measurements of stable isotope ratios and concentrations of CO_2, water or other trace gases, and allows the identification of the contributions of various ecosystems, or ecosystem components, to the net exchange fluxes between the terrestrial biosphere and atmosphere, and the estimation of net ecosystem isotopic discrimination and disequilibrium effect. Net ecosystem carbon fluxes can be partitioned into C uptake during photosynthesis and C release during respiration or evapotranspiration into leaf transpiration and soil evaporation by the Keeling plot technique. This approach also allows partitioning urban CO_2 sources into gasoline combustion, natural gas combustion and biogenic respiration. Recent modifications of the Keeling plot approach permit examination of CO_2 recycling in forest ecosystems. At the global scale, we can estimate relative contributions of terrestrial and ocean ecosystems to the global carbon cycle by combining stable isotope techniques, the Keeling plot approach and terrestrial ecosystem models. However, applications of stable isotope techniques and the Keeling plot approach to ecological research are sometimes constrained by the heterogeneity of terrestrial ecosystems. In addition, selection of suitable isotopic sampling protocols is another factor that we should consider in its application. Nevertheless, with new improvements in analytic protocols in the near future, stable isotope techniques and the Keeling plot approach will become one of the most effective techniques for understanding carbon and water relationships in terrestrial ecosystems.

Applications of stable isotopes to study plant-animal relationships in terrestrial ecosystems

As natural tracers, stable isotopes have been extensively used in plant physiological, ecological and environmental research. Recently, animal physiological ecologists have also applied stable isotope techniques to study plantanimal relationships. The isotopic compositions of animal body generally reflect and integrate their diets over a time period ranging from hours to years to the lifetime of an individual. When animal living habitat changes or animals move to a new environment, the animal isotopic compositions will shift accordingly. Thus, stable isotope signatures of an animal can truly reflect its food sources, habitat, distribution and movement patterns during a given time period. Moreover, by analyzing animal-tissue isotopic compositions at different temporal scales, we can improve our understanding of animal adaptation to environmental changes. Stable isotope technique also provides an ideal tool to study animal foodweb relationship and community structure because of isotopic fractionation during the processes of nutrient assimilation by animals. Stable isotope technique can continuously measure animal trophic position in a foodweb, which can eventually reveal the predator-prey relationship and its role in determining matter balance and energy flow in the entire ecosystem. Stable isotope technique has been one of the most important and efficient tools in studying plant-animal relationship. In this paper, we first review recent advances in the application of stable isotope techniques to plant-animal relationship research then evaluate their advantages and disadvantages, and finally discuss some future directions associated with stable isotope applications to plant-animal relationship research.

Stable isotope techniques in the study of biological processes and functioning of ecosystems. Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.

Stable isotope techniques in the study of biological processes and functioning of ecosystems. Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.