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 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 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 13 C labeled technique, the effects of elevated CO 2 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 15 N 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 15 N 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 ( 34 S) 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.

Carbon and nitrogen isotopes analysis and sources of organic matter in surface sediments from the Sanggou Bay and its adjacent areas, China

Naturally existing stable carbon and nitrogen isotopes are important in the study of sedimentary organic matter sources. To identify the sources of sedimentary organic matter in Sanggou Bay and its adjacent areas, which is characterized by high-density shellfish and seaweed aquaculture, the grain size, organic carbon （OC）, total nitrogen （TN）, carbon and nitrogen isotopic composition （δ13C andδ15N） of organic matter in the surface sediment were determined. The results showed that, in August, sedimentary OC and TN ranged from 0.17% to 0.76% and 0.04% to 0.14%, respectively. In November, OC and TN ranged from 0.23% to 0.87% and 0.05% to 0.14%, respectively. There was a significant positive correlation between OC and TN （R=0.98, P＆lt;0.0001）, indicating that OC and TN were homologous. In August, theδ13C andδ15N of organic matter varied from -23.06‰ to -21.59‰ and 5.10‰ to 6.31‰, respectively. In November,δ13C andδ15N ranged from -22.87‰ to -21.34‰ and 5.13‰ to 7.31‰, respectively. This study found that the major sources of sedimentary organic matter were marine shellfish biodeposition, seaweed farming, and soil organic matter. Using a three-end-member mixed model, we estimated that the dominant source of sedimentary organic matter was shellfish biodeposition, with an average contribution rate of 65.53% in August and 43.00% in November. Thus, shellfish farming had a significant influence on the coastal carbon cycle.

Effect of dietary stable isotopic ratios of carbon and nitrogen on the extent of their incorporation into tissues of rats

This study was conducted to investigate the effect of different dietary ratios of 13C to 12C or 15 N to 14N on their relative incorporation into tissues. Eighty male rats were used in two 21-day feeding trials in which they were fed diets with either high δ13C levels （δ13C=-13.89%o and δ15N =2.37%o in experiment 1 and δ13C=-19.34%o and δ15N = 4.73%o in experiment 2） or low 613C levels （δ13C =-17.90%o and δ15N = 3.08%o in experiment 1 and δ13C =-21.76%o and δ15N = 0.53‰ in experiment 2）, meanwhile, the dietary δ15N levels were designed to two ranks Blood, liver, adipose and muscle tissues were collected on day 0, 3, 7, 14, and 21 for determination of 13C, 12C, 15N and 14 N isotopes. Rat growth rate, antioxidant capacity and metabolic parameters were also assessed. The results indicate that adipose tissue tend to deplete 13C before the stable isotopic ratios achieved final equilibrium. Therefore, feeds with different isotopic signatures had different incorporation rates into tissues. Low dietary 13C levels decreased tissue δ13C values whereas high dietary 13C levels did not alter tissue δ13C values during the 21-d experiment. Blood δ15N values were a reliable parameter in assessing the relative contribution of dietary nitrogen to tissues. This study revealed a relationship between dietary tissues. However, more studies are needed to illustrate the sotopic signatures and their incorporation rates into rat mechanism through which dietary isotopic ratios nfiuence the extent of isotopic incorporation into the tissues

Spatial distributions of organic carbon and nitrogen and their isotopic compositions in sediments of the Changjiang Estuary and its adjacent sea area

The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotopes in sediments show linear correlations with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratios can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （up to 50%） of terrestrial organic carbon appears near the Changjiang Estuary with isolines projecting towards northeast, indicating the influence of the Changjiang dilution water. Terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.

Distribution of organic carbon in sediments and its influences on adjacent sea area in the turbidity maximum of Changjiang Estuary in China

Distributions and sources of total organic carbon （TOC）in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects of estuary water on the continuously increasing terrigenous organic carbon from the Changjiang River are also explored through variations of organic carbon content and water quality indicators. Results show that, hydrodynamics exert important influences on distributions of organic carbon in the tur- bidity maximum of Changjiang Estuary. For their redistribution effect of terrigenous organic carbon within the moving layer in the whole region, variations from land to sea are not indicated by surficial and vertical average values of TOC and total nitrogen （TN） contents in core sediment, as well as organic stable carbon isotopes in surface sediments. However, on the long-time scale, the trend of terrigenous organic carbon decreasing from land to sea is still displayed by variations of stable carbon isotopic average values becoming heavier from land to sea. Previous studies have shown that high content of Chl a cannot appear in the Changjiang Estuary in despite of adequate nourishment supply, because photosynthesis of phytoplankton is constrained by high suspended sediment concentration（SSC）. However, an area with a high content of Chl a occurs, which may be caused by resuspended benthic algae with bottom fine grain-size sediments. Tremendous pressures are imposed on the environment of Changjiang Estuary, because of uhrophication trends and special hydrodynamics. Phytoplankton bloom area tends to extend from the outer sea to the mouth of Changjiang River.

Carbon Sources of Sediment and Epifaunal Food Sources in a Tropical Mangrove Forest in North Sulawesi, Indonesia

The stable isotope ratios of nitrogen(δ^(15)N) and carbon(δ^(13)C) were applied in this study to analyze sediment carbon sources and primary food sources of epifauna in an oceanic mangrove forest in tropical North Sulawesi, Indonesia. Proportional contribution of mangrove-derived carbon to the food sources was compared among epifauna belonging to different feeding guilds. The sediment in the mangrove site with a depleted δ^(13)C signature(-28.02‰± 0.24‰) mainly consists of mangrove-derived carbon. Analysis using Bayesian stable isotope mixing model in the R program shows that mangrove-derived carbon can dominate the food sources of a majority of the epifauna(11 out of the total 18 species), especially 2 sesarmid crabs Parasesarma semperi and Sesarma sp., crab Epixanthus dentatus, and snails Terebralia sulcata and Optediceros breviculum, which belong to various feeding guilds. Mangrove-derived carbon has a proportional contribution to the food sources of fiddle crab Tubuca coarctata and 3 littorinid snails(Littoraria spp.) close to that of suspended particulate organic matter. Three planktophagous bivalve species(Anadara antiquata, Anadara sp. and Callista erycina) were found to mainly feed on seagrass-derived materials. Mean proportional contributions of mangrove-derived carbon to the food sources were 50.15%, 59.60%, 46.20% and 27.58% for the carnivorous, omnivorous, phytophagous and planktophagous groups, respectively. The results suggest that mangrove-derived carbon can directly(via grazing plant tissues) or indirectly(via deposit feedings) make an important contribution to the food sources of epifauna in the oceanic mangrove forest where the allochthonous input of organic carbon is low.

Distribution and Sources of Organic Matter in Surface Sediments of the Karachi Coast,Pakistan

Under the steadily intensifying human activities in coastal areas,it is crucial to distinguish the sources of organic matter(OM)in sediments for better understanding of the environmental change.In this study,25 surface sediments collected along the harbor and creeks areas off Karachi coast were used for total organic carbon(TOC),total nitrogen(TN),stable carbon(δ^(13)C)and nitrogen(δ^(15)N)isotopic compositions,phytoplankton biomarkers(brassicasterol,dinosterol and cholesterol)and glycerol dialkyl glycerol tetraethers(GDGTs)analyses,to trace the distribution of OM and identify its sources.TOC,TN,δ^(13)C,and δ^(15)N are in the range of 0.04% to 5.28%,0.01% to 0.57%,-17.55‰ to -26.31‰,and 2.83‰ to 6.04‰,respectively.C/N values range from 4.24 to 21.04.The δ^(13)C,δ^(15)N,C/N,BIT(Branched Isoprenoid Tetraether)index together with phytoplankton biomarkers show both marine and terrestrial OM input to the creeks and Harbor stations.In contrast,the stations from Western Coast indicate a marine source predominance.A clearly impact of human activities is seen from sediments near river mouths.

Preliminary attempt to distinguish the domesticated pigs from wild boars by the methods of carbon and nitrogen stable isotope analysis

Despite great achievements in the origins of domestic pigs made by the methods of zooarchaeology and molecular biology,how to scientifically distinguish the domesticated pigs from wild boars during the early stage of pig domestication is still poorly understood.Compared to wild boar's diets which come from the natural environment,the diets of domestic pigs are more easily influenced by human feeding activities.Therefore,in principle,exploration of the dietary differences among pigs and understanding the impact on pig diets fed by humans can have great potential to differentiate between wild boars and domesticated pigs.To reveal dietary differences among pigs and distinguish the domesticated pigs from wild boars based on comparison with the diets of humans and other animals,we analyzed the carbon and nitrogen stable isotopes of human bones from Xiaojingshan Site and animal bones from Yuezhuang Site,both of which belong to Houli Culture in Shandong Province and date to about 8500―7500 years ago.The mean δ 13C value((-17.8 ± 0.3)‰) and δ 15N value((9.0±0.6)‰) in human collagen indicate that although millet agriculture began it was not the main subsistence strategy as millets are typical of C4 plants and that humans made a living mainly by gathering,hunting or raising some domesticated animals.The δ 13C value(-16.1‰) and δ 15N value(6.9‰) in the bovine suggest that C3 plants were dominant in its diet with some C4 plants complemented.The fish has lower δ 13C value(-24.9‰) and higher δ 15N value(8.8‰) than the bovine,which is the characteristic of the isotopic values from Eurasian freshwater fish.Based on the differences in carbon and nitrogen isotope values,the pigs can be divided into three groups.A group,composed of two pigs,has low δ 13C values(-18.1‰,-20.0‰) and low δ 15N values(4.7‰,6.0‰).B group,only one pig,has the highest δ 13C value(-10.6‰) and mediate δ 15N value(6.4‰).As for the C group,also only one pig,low δ 13C value(-19.0‰) and the highest δ 15N value(9.1‰) are observed.Previous studies on the stable isotopes from modern or ancient wild boars' bones have suggested that C3 plants are predominated in their diets and that their δ 15N values are close to those in herbivores and far from those in carnivores.Based on the comparison with the isotope values from humans,the wild boars and the domestic pigs from Xipo Site in Henan 6000―5500 years ago and Kangjia Site in Shaanxi 4500―4000 years ago,we conclude that A pig group belongs to wild boars while B and C groups can be attributed to domesticated pigs.

Determination of the geographical origin of Chinese teas based on stable carbon and nitrogen isotope ratios

The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong(GD),Guangxi(GX),Hainan(HA),Fujian(FJ),Shandong(SD),Sichuan(SC),Chongqing(CQ),and Henan(HN) provinces was high,while in Zhejiang(ZJ),Hubei(HB),Yunnan(YN),and Anhui(AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.

The subsistence patterns of the Shengedaliang site(-4,000 yr BP)revealed by stable carbon and nitrogen isotopes in northern Shaanxi,China

In order to explore subsistence patterns in northern Shaanxi Province around 4,000 yr BP,28 human and 24 animal bones from the Shengedaliang site were sampled for stable carbon and nitrogen isotope ratio analysis.The results show that most people primarily subsisted on C_4 resources,e.g.millet and millet-related animal products,despite the fact that there was some intake of C_3 plants by some individuals.Stable nitrogen isotope values indicate that there were differences in meat consumption between individuals at the site.Pigs were mainly foddered with millet and millet byproducts,as well as some cattle,according to their highδ^(13)C values.However,most cattle and the sheep/goats consumed wild C_3 plants at Shengedaliang.Our above findings indicates that subsistence patterns in northern Shaanxi around 4,000 yr BP were characterized by millet farming,while the grassland animal husbandry,e.g.cattle and sheep/goats raising,displayed very little contribution to local economy.The intensive millet farming in northern Shaanxi provided enough food for population growth,ensured the accumulation of wealth,and consequently accelerated social differentiation and complexity.

The influence of agriculture in the process of population integration and cultural interaction during the Eastern Zhou Period in central-south, Inner Mongolia: Carbon and nitrogen stable isotope analysis of human bones from the Dabaoshan cemetery, Helingee

Central-south Inner Mongolia, China, is highly sensitive to the cultural interactions between sedentary agriculturalists and nomadic pastoralists during the Eastern Zhou Period(770–256 BC). The previous pattern of multiple cultures and diverse ethnic groups has been transformed to the increasingly dominated cultural system of Central Plain since the middle and late Warring States Period, when the states of Zhao and Qin have conquered the most parts of central-south Inner Mongolia.However, the variation of subsistence strategies during this historical process has never been evaluated. Particularly, as the typical representative of Central Plain cultures, the effect of intensive millet agriculture is still unknown in the process of population integration and culture interaction. Thus, to explore the shift of subsistence pattern, carbon and nitrogen stable isotope analysis of bone collagen from Dabaoshan site(410–180 BC) have been performed. The isotopic result indicates a large amount of C_4-based animal protein consumed by Dabaoshan humans. According to the archaeological backgrounds, we propose the Dabaoshan persons intensively relied on the millet agriculture and developed the agro-pastoral economy, which hinted the comprehensive influences from Central plain civilizations in late Warring States Period. Further compared with other published isotopic data in the same region during different periods, we suggest the millet agriculture has played the positive role in the process of population integration and culture fusion in central-south Inner Mongolia during the Eastern Zhou Period.

Sewage pollution in Negril, Jamaica: effects on nutrition and ecology of coral reef macroalgae

Coral reefs in the Negril Marine Park （NMP）, Jamaica, have been increasingly impacted by nutrient pollution and macroalgal blooms following decades of intensive development as a major tourist destination. A baseline survey of DIN and SRP concentrations, C：N：P and stable nitrogen isotope ratios （δ^15N） of abundant reef macroalgae on shallow and deep reefs of the NMP in 1998 showed strong P-limitation and evidence of increasing sewage pollution. In 1999, a sewage collection and treatment project began diverting wastewater from the resort and urban areas to a pond system that discharged partially-treated effluent into the South Negril River （SNR）. These sewage discharges significantly increased concentrations of NH2 and SRP （N：P -13） in the SNR, which flows into Long Bay and around Negril＇s ＂West End＂. Concentrations of SRP, the primary limiting nutrient, were higher on shallow reefs of the West End in 2001 compared to 1998. Stable nitrogen isotope ratios （δ^15N） of abundant reef macroalgae on both shallow and deep reefs of the West End in 2002 were significantly higher than baseline values in 1998, indicating an escalating impact of sewage nitrogen pollution over this timeframe. The increased nutrient concentrations and δ^15N enrichment of reef macroalgae correlated with blooms of the chlorophyte Chaetornorpha linum in shallow waters of Long Bay and Codium isthrnocladum and Caulerpa cupressoides on deep reefs of the West End. Sewage treatment systems adjacent to coral reefs must include nutrient removal to ensure that DIN and SRP concentrations, after dilution, are below the low thresholds noted for these oligotrophic ecosystems.

Food web structure and trophic levels in polyculture ricecrab fields

Stable carbon and nitrogen isotopes were used to investigate nutrient pathways and trophic relationships from the rice-crab system in Panjin, Liaoning Province, China. Values of 313C ranged from -27.38%±0.44%o to -18.34%±0.26%o and δ^15N ranged from 1.10%o4-0.88%o to 9.33%±0.57%. Pseudorasbora parva （Stone moroko） had the highest δ^13C and 8tSN values. The lowest δ^13C values were obtained for the macrophytes and the lowest δ^15N value was found in sediments. Stable carbon and nitrogen isotopes were used to determine the contribution of different food items to the diets of crabs. The δ^13C results indicated that the Pseudorasbora parva made the greatest contribution to the diet of Eriocheir sinensis （Chinese mitten crab）, while the δ^15N results indicated that most food items contributed more than 10% to the diet of the crab. There were three trophic levels identified in the system （Levels 0-2）. The crab Eriocheir sinensis, fish Pseudorasbora parva and Misgurnus anguillicaudatus （Oriental weatherfish）, and the oligochaete Limnodrilus hoffmeisteri （Limnodrilus worm）, were at the second level, zooplankton were at the first level and suspended particulate matter and macrophytes were at trophic position 0.

Evaluation of Accuracy and Precision of IRMS by Using Standard Materials and Applications

The isotope ratio mass spectrometer (IRMS) is an instrument that measures both of the elemental contents and isotope ratios of hydrogen, oxygen, carbon, nitrogen and sulfur in environmental samples at the same time. In this study, we want to try to get two main goals;first, to make up for setting the analytical conditions such as accuracy and precision, second, to apply for comparing of the carbon and nitrogen isotope ratio of sediments in the abandoned mine located in middle province of Korea. For the first goal, a recently introduced IRMS was used to analyze CRM (certified reference materials), which helped to make up the analytical conditions of carbon and nitrogen isotope ratios. So, the accuracy and precision of isotope ratios and elemental contents were also assessed simultaneously, and also the results were very satisfactory. The analytical results of carbon reference materials (EMA-P2) showed an accuracy of -2.801 × 10‰ ± 0.01‰ (2σ) and a precision of 0.009‰ in the mass range from 0.008 μg - 0.162 μg. For nitrogen reference materials (EMA-P2), an accuracy of -1.632‰ ± 0.72‰ (2σ) was obtained in the mass range from 0.082 - 0.162 mg. These values of accuracy and precision are higher than those reported by other studies. For the second goal, carbon and nitrogen isotopes in river sediment near abandoned mines were analyzed based on the established analytical conditions. The result suggested that carbon isotope ratios ranged from -22.5‰ - -7.5‰ and nitrogen isotope ratios from -1.9‰ - 7.9‰. By comparing the isotope ratios and sampling sites of sediment, we know that the nitrogen isotope values in samples of entrance area of mine are greater than those of the farm house area, which is indicating the effects of organic materials. So, we could guess that the newly accumulated organic materials were much more in the farm house area than mine entrance area. And a result of this study, the accuracy and precision tests of IRMS using certified reference materials were very satisfactory and optimum analytical conditions were established well. And also, it was found that the applications of isotopic analysis for environmental samples by using the IRMS could be very useful for the studies on tracing pollution sources.

Patterns of δ^(13) C and δ^(15) N in wolverine Gulo gulo tissues from the Brooks Range,Alaska

Knowledge of carnivore diets is essential to understand how carnivore populations respond demographically to variations in prey abundance. Analysis of stable isotopes is a useful complement to traditional methods of analyzing carnivore diets. We used data on δ^13C and δ^15N in wolverine tissues to investigate patterns of seasonal and annual diet variation in a wolverine Gulo gulo population in the western Brooks Range, Alaska, USA. The stable isotope ratios in wolverine tissues generally reflected that of terrestrial carnivores, corroborating previous diet studies on wolverines. We also found variation in δ^13C and δ^15N both between muscle samples collected over several years and between tissues with different assimilation rates, even after correcting for isotopic fractionation. This suggests both annual and seasonal diet variation. Our results indicate that data on δ^13C and δ^15N holds promise for qualitative assessments of wolverine diet changes over time. Such temporal variation may be important indicators of ecological responses to environmental perturbations, and we suggest that more refined studies of stable isotopes may be an important tool when studying temporal change in diets of wolverines and similar carnivores [ Current Zoology 55 （3）： 188- 192, 2009].

How <i>Betula ermanii</i>Maintains a Positive Carbon Balance at the Individual Leaf Level at High Elevations

Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA against environmental stresses. Therefore, plants need to increase both LMA and photosynthesis at high elevations. To examine how deciduous plants maintain a positive carbon balance at high elevations, photosynthesis and related leaf traits for deciduous broad-leaved tree Betula ermanii were measured at three elevations. LMA was greater at middle and high elevations than at low elevation. Leaf δ13C was greater at higher elevations, and positively correlated with LMA, indicating greater long-term deficiency of CO2 in leaves at higher elevations. However, the Ci/Ca ratio at photosynthetic measurement was not low at high elevations. Nitrogen content per leaf mass and stomatal conductance were greater at higher elevations. Photosynthetic rates and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three elevations. Photosynthetic rate showed a strong positive correlation with stomatal conductance on a leaf area basis (R2 = 0.83, P < 0.001). Therefore, this study suggests B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing stomatal conductance, and maintains photosynthesis and PNUE at high elevation as much as at low elevation.

放牧对不同类型草原土壤碳氮及其稳定同位素的影响

为探究不同草原类型生态系统碳氮元素对重度放牧的响应,本研究以平原丘陵草原、平原丘陵荒漠草原和沙地荒漠草原3种草原类型为对象,通过测定围封和重度放牧下土壤有机碳、全氮、稳定碳氮同位素及土壤温湿度等指标,探究放牧处理对不同类型草原碳氮元素的影响。结果表明:(1)重度放牧显著降低了3种类型草原土壤有机碳、全氮含量(P<0.05),重度放牧条件下土壤稳定碳同位素和土壤稳定氮同位素值有降低的趋势;(2)土壤稳定碳同位素值与土壤含水量存在极显著负相关性(P<0.01),土壤有机碳、全氮含量及土壤稳定氮同位素值均与土壤含水量存在极显著正相关性(P<0.01)。重度放牧对不同类型草原碳氮养分含量造成了不同程度的影响,其中对平原丘陵草原影响较大,不利于土壤有机碳和全氮的积累。

基于碳、氮稳定同位素特征的国产绿茶产地溯源研究

目的研究我国多省出产绿茶碳、氮稳定同位素比率特征。优化基于稳定同位素比率差异的绿茶产地溯源模型。方法运用同位素质谱检测我国多省出产的169份代表性绿茶样本。采用方差分析比较各产地样本是否具有显著性差异。按7:3划分训练集和测试集,使用训练集构建基于线性判别分析(linear discriminant analysis,LDA)、支持向量机(support vector machine,SVM)和K-最近邻算法(K-nearest neighbor algorithm,KNN)的产地溯源判别模型。采用K折交叉验证的方法进行模型内部验证,采用测试集进行模型外部验证。结果各地绿茶样品的碳、氮稳定同位素比率存在显著性差异。建立基于LDA、SVM、KNN的判别模型,对测试集预测的整体准确率分别为76.5%、86.3%和84.3%。非线性模型对此样本的总体判别效果优于线性模型。结论碳、氮稳定同位素比率特征结合非线性判别模型可以用于绿茶产地溯源。本研究为绿茶溯源及判别模型参数优化提供了一定的参考。

苏铁蕨在广东的分布概况及其中药饮片溯源分析

为给苏铁蕨(Brainea insignis)资源的保护和可持续利用提供依据,采用样线法对广东省内的苏铁蕨种群进行较全面的野外调查,测定稳定碳和氮同位素比值及碳和氮含量,对其中药饮片进行初步溯源。结果表明,苏铁蕨在广东主要分布在北江以东的惠州市、河源市、梅州市和深圳市;在北江以西分布较少;苏铁蕨分布点纬度为22°36'~24°39'N,经度为112°35'~116°48'E,海拔高度为26~706 m。2批次中药饮片的初步溯源结果显示,这些中药饮片可能源自广东罗浮山省级自然保护区、广东惠东莲花山白盆珠省级自然保护区和广东和平黄石坳省级自然保护区。

广东毛茶资源及其生理生态特征研究

为了解毛茶资源及其生理生态特征,采用样线法对广东67个自然保护地的毛茶资源进行了野外调查,测定了毛茶的净光合速率、蒸腾速率及环境因子的日变化、叶绿度、植物及生境的碳氮含量、稳定碳氮同位素组成。结果表明:在10个保护地的123个生境记录到280株毛茶,其中珠海担杆岛和二洲岛、斗门黄杨山和锅盖栋、台山上川岛为毛茶新增分布点,以深圳三洲田的62处148株为最多。毛茶植物体的碳、氮含量显著高于生境土壤和岩石;叶片δ^(13)C、δ^(15)N比率分别为-34.51‰和-0.94‰,显著低于或高于根、茎的相应值。正常绿色叶片叶绿度(SPAD值)为41.0,显著高于黄叶的17.6;测定日的净光合速率平均为5.55μmol·m^(-2)·s^(-1);蒸腾速率平均为0.59 mmol·m^(-2)·s^(-1);水分利用效率平均为9.13,显示毛茶在冬季气温和大气相对湿度相对较低的情况下,以较低的净光合速率、蒸腾速率但较高的水分利用效率维持正常的生理活动。