共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
Natural 15N abundances (δ15N) in plant and soil can be used as a powerful marker to reveal the history of N fertilization. To investigate whether N fertilizer source and timing of fertilization leave specific δ15N signals in plant tissue and soil inorganic N, Chinese cabbage (Brassica campestris L. cv. Maeryok), one of the most popular vegetables in Asia, was grown in pots for 60 days with a single or split N applications of organic (composted manure; δ15N=+16.4‰) or inorganic N (urea; δ15N=−0.7‰). Seven N treatments were studied: (1) a single basal fertilization with compost or (2) urea; (3) a basal urea application followed by an additional (at 40 days after transplant, same below) compost or (4) urea application; (5) a basal compost application followed by an additional compost or (6) urea application; and (7) no N fertilization. Regardless of the time of N application, δ15N of cabbage treated with compost was higher (>+9.0‰) than that (< +1.0‰) treated with urea, reflecting the effect of isotopically different N sources. In split N fertilization, only the addition of isotopically different N sources in the middle of the growth period significantly affected the δ15N of the whole plant. Specific δ15N signals of basal N inputs were detected in outer cabbage parts formed in the early growth stage, while those of additional N inputs were detected in inner cabbage parts formed in the latter growth stage. We conclude that measurements of temporal variations in δ15N of plant parts formed in different growth stages could reveal the history of N fertilization. 相似文献
3.
Here we present δ13C and δ2H data of long-chained, even-numbered (C27-C31) n-alkanes from C3 (trees) and C4 (grasses) plants and from the corresponding soils from a grassland-woodland vegetation sequence in central Queensland, Australia. Our data show that δ13C values of the C4 grassland species were heavier relative to those of C3 tree species from the woodland (Acacia leaves) and woody grassland (Atalaya leaves). However, n-alkanes from the C4 grasses had lighter δ2H values relative to the Acacia leaves, but showed no significant difference in δ2H values when compared with C3 Atalaya leaves. These results differ from those of previous studies, showing that C4 grasses had heavier δ2H values relative to C3 grasses and trees. Those observations have been explained by C4 plants accessing the more evaporation-influenced and isotopically heavier surface water and tree roots sourcing deeper, isotopically lighter soil water (“Two-layered soil-water system”). By comparison, our data suggest that ecosystem changes (vegetation “thickening”) can significantly alter the soil hydrological characteristics. This is shown by the heavier δ2H values in the woodland soil compared with lighter δ2H values in the grassland soil, implying that the recent vegetation change (increased tree biomass) in the woodland had altered soil hydrological conditions. Estimated δ2H values of the source-water for vegetation in the grassland and woodland showed that both trees and grasses in open settings accessed water with lighter δ2H values (avg. −46‰) compared with water accessed by trees in the woodland vegetation (avg. −7‰). These data suggest that in semi-arid environments the “two-layer” soil water concept might not apply. Furthermore, our data indicate that compound-specific δ2H and δ13C analyses of n-alkanes from soil organic matter can be used to successfully differentiate between water sources of different vegetation types (grasses versus trees) in natural ecosystems. 相似文献
4.
Boron (B) is a sensitive stable isotope tracer which allows identification of different anthropogenic contaminant sources, originating from man-made boron products manufactured from non-marine borates (δ11B ≤ +10‰), in near-surface fluids which are characterized by a different natural background signature of predominantly meteoric origin. The data presented show that the boron isotopic composition of uncontaminated groundwater at the study site (δ11B = +12.0‰) is similar to that of local precipitation and significantly different from two distinct anthropogenic contaminant sources, identified as Ca- and/or Na/Ca-borates and Na-borates in `low-δ11B' (–6.0‰) and `high-δ11B' (+7.5 to +9.0‰) municipalsolid waste landfill leachates, respectively. The boron isotopic signature of contaminants can remain preserved over several decades, in contrast to aqueous B concentrations which are less diagnostic due to their sensitivity to dilution with low-B meteoric waters. 相似文献
5.
《Pedobiologia》2014,57(4-6):215-222
Seasonal changes in environmental conditions and biotic interactions are often ignored when using stable isotope analysis for reconstructing the trophic structure of soil communities in temperate ecosystems. In this study, we estimated seasonal and age-related changes in δ13C and δ15N values in three epigeic species of collembolans (Pogonognathellus longicornis, Orchesella flavescens and Isotoma viridis) and two litter-dwelling species of millipedes (Polydesmus denticulatus and Leptoiulus proximus) in deciduous and coniferous forest stands in central Russia. Age-related changes in δ13C or δ15N values were either absent or negligible (within 1‰) in L. proximus, but adult and subadult specimens of P. denticulatus were enriched in 15N compared to early larval stages. Since the adults of P. denticulatus were generally more enriched in 15N than adults of L. proximus, they presumably occupy more distinct trophic niches than juveniles do. Age-related changes in isotopic composition were small or absent in collembolans studied. Neither δ13C nor δ15N values of millipedes changed significantly during the vegetation season. In contrast, consistent seasonal changes in δ13C and δ15N values were found in collembolans. Increased δ13C values coincided with the period of minimum soil moisture and correlated with a decreased C/N ratio in collembolan tissues. These changes can largely be attributed to the depletion of lipid-rich storage tissues. Seasonal changes in δ15N values were similar among collembolan species, yet slightly varied between habitats. A general trend of increasing δ15N values from June to September–October may indicate either a reduced importance of non-vascular plants (algae and lichen) in collembolan diet or variation in the isotopic composition of these plants. Overall, our data show that seasonal variations should be taken into account when estimating the isotopic composition of epigeic collembolans in forest soils. 相似文献
6.
Rodrigues C Brunner M Steiman S Bowen GJ Nogueira JM Gautz L Prohaska T Máguas C 《Journal of agricultural and food chemistry》2011,59(18):10239-10246
Green coffee bean isotopes have been used to trace the effects of different climatic and geological characteristics associated with the Hawaii islands. Isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry ((MC)-ICP-SFMS and ICP-QMS) were applied to determine the isotopic composition of carbon (δ13C), nitrogen (δ15N), sulfur (δ34S), and oxygen (δ18O), the isotope abundance of strontium (87Sr/86Sr), and the concentrations of 30 different elements in 47 green coffees. The coffees were produced in five Hawaii regions: Hawaii, Kauai, Maui, Molokai, and Oahu. Results indicate that coffee plant seed isotopes reflect interactions between the coffee plant and the local environment. Accordingly, the obtained analytical fingerprinting could be used to discriminate between the different Hawaii regions studied. 相似文献
7.
降水中稳定氢氧同位素（18O）和（D）是水循环过程的重要组成部分,也是气候的天然示踪剂。为了模拟不同时空尺度上降水稳定氢氧同位素的变化,大气环流模式（GCM）已经成为研究全球或区域水循环的有效途径。本文基于全球大汽降水同位素网络（GNIP）提供的实测数据和第2次稳定水同位素比较小组（SWING2）的模拟数据,运用回归分析法和同位素GCM对比分析了西北干旱区1986—2003年大气降水中稳定氢氧同位素的年际变化特征。结果表明:3个同位素监测站点乌鲁木齐、张掖和和田的年均δ18Ow线性倾向率分别为0.041,0.207,0.915‰/a,δDw线性倾向率分别为0.767,0.026,0.120‰/a;如果只考虑暖季（5—9月）,则δ18Ow线性倾向率分别为-0.008,0.085,0.306‰/a,δDw线性倾向率分别为-0.331,-1.390,-1.503‰/a。同时,采用SWING2中的GISS-E（MERRA）,GISS-E（NCEP）,isoGSM（NCEP）,LMDZ（free）,LMDZ（ECMWF）和MIROC（free）共6种同位素GCM模式得出的δ18Ow和δDw的线性倾向率与回归分析法得到的结果相反。此外,分析了两种模拟方法得到的大气水线,发现各模拟结果中和田的大气水线斜率均高于乌鲁木齐和张掖。 相似文献
8.
Morphological and functional characteristics of flowers may have major effects on their reproductive success. Here, we report a study on the characteristics of flowers of Petrocoptis viscosa, a herb species endemic to the northwest Iberian Peninsula, restricted to crevices in limestone outcrops, and currently occurring in only three populations within an area of less than 30 km2. We also investigated the effects of pollen source on indicators of reproductive success. The results show that Petrocoptis viscosa flowers are well adapted to autogamy. Inbreeding depression (as determined by comparison of results obtained after selfing and outcrossing) was negligible for fruit production (δ=−0.05) and mean seed number (δ=−0.11), low for seed germination percentage (δ=0.08), but relatively high for mean seed weight (δ=0.23). The spatial structure and small size of population of Petrocoptis viscosa may mean that inbreeding is frequent in natural habitats. Adaptation of plants to autogamy may therefore be energetically beneficial (i.e. less wasted expenditure on rewards and flowers). 相似文献
9.
为探究稳定同位素在黑木耳产地溯源中的可行性,本研究从东北(黑龙江、吉林、辽宁)、浙江产地采集74份代表性黑木耳样品,从新疆采集11份代表性黑木耳样品作为外部验证,采用元素分析-稳定同位素比率质谱仪测定δ13C、δ15N、δ2H、δ18O值,结合化学计量学方法进行产地溯源判定。结果表明,东北黑木耳δ13C、δ15N、δ2H、δ18O值分别为-24.5‰～-22.7‰、-0.9‰～3.1‰、-62.2‰～-34.6‰、15.9‰～19.4‰;浙江黑木耳δ13C、δ15N、δ2H、δ18O值分别为-26.2‰～-24.5‰、-0.9‰～1.2‰、-24.9‰～-9.0‰、19.9‰～22.2‰,两产地黑木耳δ15N值差异不显著(P>0.05),δ13C、δ2H和... 相似文献
10.
《Agricultural and Forest Meteorology》2006,136(1-2):56-75
Quantifying and understanding the uncertainty in isotopic mixing relationships is critical to isotopic applications in carbon cycle studies at all spatial and temporal scales. Studies that depend on stable isotope approaches must also address quantification of uncertainty for parameters derived from isotopic studies. An important application of isotopic mixing relationships is determination of the isotopic content of ecosystem respiration (δ13CS) via an inverse relationship (a Keeling plot) between atmospheric CO2 concentrations ([CO2]) and carbon isotope ratios of CO2 (δ13C). Alternatively, a linear relationship between [CO2] and the product of [CO2] and δ13C (a Miller/Tans plot) can also be applied.We used three datasets of [CO2] and δ13C in air to examine contrasting approaches to determine δ13CS and its uncertainty. These datasets were from the Niwot Ridge, Colorado, AmeriFlux site, the Biosphere-Atmosphere Stable Isotope Network (BASIN), and from the Grünschwaige Grassland Research Station in Germany. The analysis of this data included Keeling plots and Miller/Tans plots fit with both Model I (ordinary least squares) and Model II regressions (geometric mean regression and orthogonal distance regression).Our analysis confirms previous observations that increasing the range of the measurements ([CO2] range) used for a mixing line reduces the uncertainty associated with δ13CS. Using a Model II regression technique to determine δ13CS introduces a negatively skewed bias in δ13CS which is especially significant for small [CO2] ranges. This bias arises from comparatively greater variability in the dependent variable than the independent variable for a linear regression. For carbon isotope studies, uncertainty in the isotopic measurements has a greater effect on the uncertainty of δ13CS than the uncertainty in [CO2]. As a result, studies that estimate parameters via a Model II regression technique maybe biased in their conclusions. In contrast to earlier studies, we advocate Model I (ordinary least squares) regression to calculate δ13CS and its uncertainty. Reducing the uncertainty of isotopic measurements reduces the uncertainty of δ13CS, even when the [CO2] range of samples is small (<20 ppm). As a result, improvement in isotope (rather than [CO2]) measuring capability is presently needed to substantially reduce uncertainty in δ13CS. We find for carbon isotope studies no inherent advantage or disadvantage to using either a Keeling or Miller/Tans approach to determine δ13CS. We anticipate that the mathematical methods developed in this paper can be applied to other applications where linear regression is utilized. 相似文献
11.
The hypothesis that the biological availability of soil organic matter (SOM) pools is inversely proportional to their thermal stability was tested using the isotopic difference between the atmospheric CO2 (δ13C = ?8.0‰) and 13C-enriched CO2 (δ13C = ?47‰) fertilizers, as well as 15N-labeled fertilizers. The soil samples from spring wheat plots subjected to treatment with ambient (370 ppm) and elevated (540 ppm) CO2 concentrations for three years were analyzed by the thermogravimetric method. Based on the weight loss, five SOM pools were distinguished where the total C and N contents and isotopic compositions (δ13C and (δ15N) were determined. The contents of new C and N and their mean residence times in pools were calculated. The incorporation of 13C and 15N and their turnover rates did not depend on the thermal stability of the SOM pools, which disproved the hypothesis being tested. 相似文献
12.
Ayato Kohzu Toshihiro Miyajima Takashi Watanabe Eitaro Wada 《Soil biology & biochemistry》2005,37(9):1598-1607
Factors that affect the δ13C values of fungi need to be analyzed for the progress of isotope-based studies of food-chain or organic matter dynamics in soils. To analyze the factors that control δ13C values of the fungal body, basidiomycete and ascomycete species were grown on a beechwood substrate (six species) and in glucose medium (nine species), and the δ13C value of produced fungal body was compared to that of the carbon source. The 13C enrichment (Δδ13C) in the fungal aggregates compared to the decomposed wood varied from 1.2 to 6.3‰ among six species. In the glucose substrate experiment, the degree of 13C enrichment in the hyphal mat was relatively small and varied from −0.1 to 2.8‰ among nine basidiomycetes species depending on their growth stage. Calculated δ13C values of the respired CO2 were lower than those of the hyphal mat, organic metabolites and the glucose used. The degree of 13C enrichment was affected by fungal species, substrate and growth stage. Fungal internal metabolic processes are the plausible mechanism for the observed isotopic discrimination between fungal bodies and substrates. Especially, dark fixation of ambient CO2 and kinetic isotope fractionation during assimilation and dissimilation reactions could well explain Δδ13C dynamics in our experiments. Through the analysis of field Δδ13C, we could know undisturbed fungal status about starvation, aeration and type of decomposition. 相似文献
13.
K.E. Anders Ohlsson Bhupinderpal Singh Anders Nordgren Peter Högberg 《Soil biology & biochemistry》2005,37(12):2273-2276
The δ13C of soil-respired CO2 (δr) is frequently determined using static closed chamber methods. δr is obtained as the intercept of the least squares linear regression of δ vs 1/C*, where measured δ13C-CO2 (δ) and volume fraction of CO2 (C*) values of chamber headspace samples are used. Theoretically, we show that the variance of the estimate of δr can be reduced by extending the 1/C* interval of the regression towards (i) higher or (ii) lower values, or (iii) distributing the 1/C* values optimally within the pre-selected headspace CO2 sampling time period. Experimental applications of these approaches indicated that: (1) lowering the initial CO2 level, thereby increasing 1/C*, yielded a positive bias to the δr result. (2) It was feasible to obtain lower variance in the δr estimate by lowering 1/C* values through extended CO2 sampling time. We also recommend that each chamber is sampled only once, mainly because this allows freedom to select the sampling times, in order to optimize the distribution of 1/C* values. 相似文献
14.
By measuring the isotopic signature of soil respiration, we seek to learn the isotopic composition of the carbon respired in the soil (δ13CR-s) so that we may draw inferences about ecosystem processes. Requisite to this goal is the need to understand how δ13CR-s is affected by both contributions of multiple carbon sources to respiration and fractionation due to soil gas transport. In this study, we measured potential isotopic sources to determine their contributions to δ13CR-s and we performed a series of experiments to investigate the impact of soil gas transport on δ13CR-s estimates. The objectives of these experiments were to: i) compare estimates of δ13CR-s derived from aboveground and belowground techniques, ii) evaluate the roles of diffusion and advection in a forest soil on the estimates of δ13CR-s, and iii) determine the contribution of new and old carbon sources to δ13CR-s for a Douglas-fir stand in the Pacific Northwest during our measurement period. We found a maximum difference of −2.36‰ between estimates of δ13CR-s based on aboveground vs. belowground measurements; the aboveground estimate was enriched relative to the belowground estimate. Soil gas transport during the experiment was primarily by diffusion and the average belowground estimate of δ13CR-s was enriched by 3.8-4.0‰ with respect to the source estimates from steady-state transport models. The affect of natural fluctuations in advective soil gas transport was little to non-existent; however, an advection-diffusion model was more accurate than a model based solely on diffusion in predicting the isotopic samples near the soil surface. Thus, estimates made from belowground gas samples will improve with an increase in samples near the soil surface. We measured a −1‰ difference in δ13CR-s as a result of an experiment where advection was induced, a value which may represent an upper limit in fractionation due to advective gas transport in forest ecosystems. We found that aboveground measurements of δ13CR-s may be particularly susceptible to atmospheric incursion, which may produce estimates that are enriched in 13C. The partitioning results attributed 69-98% of soil respiration to a source with a highly depleted isotopic signature similar to that of water-soluble carbon from foliage measured at our site. 相似文献
15.
《Soil Science and Plant Nutrition》2013,59(3):422-426
Abstract The natural 13C abundance (δ 13C) of plant leaves collected from fields in Thailand and the Philippines (Asian Monsoon tropics) was analyzed, and changes in the δ 13C values of C3 and C4 plants in wet and dry seasons were characterized. In Thailand, the δ 13C values of C3 plants were ?29.2?±?1.04 (mean?±?standard deviation) ‰ in July and August (wet season) and ?28.6?±?1.05‰ in February and March (dry season): these values are not significantly different, whereas the values of C4 plants were ?12.7?±?0.56‰ in the wet season and ?14.5?±?0.68‰ in the dry season (P?<?0.01, t-test). In the Philippines, where plants were collected only in October (late wet season), the δ 13C values of C3 plants were ?29.5?±?1.28‰, whereas those of C4 plants were ?12.6?±?1.11‰. These results suggest that under an Asian Monsoon climate, C4 plants exhibit more negative δ 13C values in the dry season than in the wet season, whereas C3 plants as a whole show no clear seasonal changes in δ 13C values. 相似文献
16.
17.
This study was conducted to examine whether the applications of N-inputs (compost and fertilizer) having different N isotopic compositions (δ15N) produce isotopically different inorganic-N and to investigate the effect of soil moisture regimes on the temporal variations in the δ15N of inorganic-N in soils. To do so, the temporal variations in the concentrations and the δ15N of NH4+ and NO3− in soils treated with two levels (0 and 150 mg N kg−1) of ammonium sulfate (δ15N=−2.3‰) and compost (+13.9‰) during a 10-week incubation were compared by changing soil moisture regime after 6 weeks either from saturated to unsaturated conditions or vice versa. Another incubation study using 15N-labeled ammonium sulfate (3.05 15N atom%) was conducted to estimate the rates of nitrification and denitrification with a numerical model FLUAZ. The δ15N values of NH4+ and NO3− were greatly affected by the availability of substrate for each of the nitrification and denitrification processes and the soil moisture status that affects the relative predominance between the two processes. Under saturated conditions for 6 weeks, the δ15N of NH4+ in soils treated with fertilizer progressively increased from +2.9‰ at 0.5 week to +18.9‰ at 6 weeks due to nitrification. During the same period, NO3− concentrations were consistently low and the corresponding δ15N increased from +16.3 to +39.2‰ through denitrification. Under subsequent water-unsaturated conditions, the NO3− concentrations increased through nitrification, which resulted in the decrease in the δ15N of NO3−. In soils, which were unsaturated for the first 6-weeks incubation, the δ15N of NH4+ increased sharply at 0.5 week due to fast nitrification. On the other hand, the δ15N of NO3− showed the lowest value at 0.5 week due to incomplete nitrification, but after a subsequence increase, they remained stable while nitrification and denitrification were negligible between 1 and 6 weeks. Changing to saturated conditions after the initial 6-weeks incubation, however, increased the δ15N of NO3− progressively with a concurrent decrease in NO3− concentration through denitrification. The differences in δ15N of NO−3 between compost and fertilizer treatments were consistent throughout the incubation period. The δ15N of NO3− increased with the addition of compost (range: +13.0 to +35.4‰), but decreased with the addition of fertilizer (−10.8 to +11.4‰), thus resulting in intermediate values in soils receiving both fertilizer and compost (−3.5 to +20.3‰). Therefore, such differences in δ15N of NO3− observed in this study suggest a possibility that the δ15N of upland-grown plants receiving compost would be higher than those treated with fertilizer because NO3− is the most abundant N for plant uptake in upland soils. 相似文献
18.
The natural 15N abundance (δ15N) of different ecosystem compartments is considered to be an integrator of nitrogen (N) cycle processes. Here we investigate the extent to which patterns of δ15N in grassland plants and soils reflect the effect of different management practices on N cycling processes and N balance. Investigations were conducted in long-term experimental plots of permanent montane meadows with treatments differing in the amount and type of applied fertilizer (0-200 kg N ha−1 yr−1; mineral fertilizer, cattle slurry, stable manure) and/or the cutting frequency (1-6 cuts per season). The higher δ15N values of organic fertilizers compared to mineral fertilizer were reflected by higher δ15N values in soils and harvested plant material. Furthermore, δ15N of top soils and plant material increased with the amount of applied fertilizer N. N balances were calculated from N input (fertilization, atmospheric N deposition and symbiotic N2 fixation) and N output in harvest. ‘Excess N’—the fraction of N input not harvested—was assumed to be lost to the environment or accumulated in soil. Taking fertilizer type into account, strong positive correlations between δ15N of top soils and the N input-output balance were found. In plots receiving mineral N fertilizer this indicates that soil processes which discriminate against 15N (e.g. nitrification, denitrification, ammonia volatilization) were stimulated by the increased supply of readily available N, leading to loss of the 15N depleted compounds and subsequent 15N enrichment of the soils. By contrast, in plots with organic fertilization this correlation was partly due to accumulation of 15N-enriched fertilizer N in top soils and partly due to the occurrence of significant N losses. Cutting frequency appeared to have no direct effect on δ15N patterns. This study for the first time shows that the natural abundance of 15N of agricultural systems does not only reflect the type (organic or mineral fertilizer) or amount of annual fertilizer amendment (0-200 kg ha−1 yr−1) but that plant and soil δ15N is better described by N input-output balances. 相似文献
19.
Eurasian Soil Science - Isotopic composition of nitrogen in soil microbial biomass (δ15Nmicr) is connected with the transformation of nitrogen compounds and with the balance of carbon and... 相似文献
20.
Valery J. Terwilliger Zewdu Eshetu Yongsong Huang Marcelo Alexandre Mohammed Umer Tsige Gebru 《CATENA》2011
The Tigray Plateau of Ethiopia and Eritrea is vulnerable to environmental change, yet environmental influences on the rise and fall of the civilizations that once existed there are almost unexplored. We sampled sections of gully walls for palaeoenvironmental proxies from two sites: 1) Adi Kolen on the southern outskirts of the Plateau's most developed former empire, the Aksumite, and 2) Adigrat near polities dating to at least ca. 3000 cal yr BP. A multi-proxy approach for examining local variation in palaeoenvironments was evaluated that included stable isotopic and elemental analyses (δ13CSOM, δ15N, %TOC, and %TN) of soil, and charcoal identification. An increase in δ15N values from older soils in Adi Kolen (4400 cal yr BP) and Adigrat (2900 cal yr BP) until 1200 cal yr BP is not explained by changes in δ15N that occur with time in an unchanging environment. It may instead indicate an overall decrease in rainfall from the earlier times until 1200 cal yr BP. In one Adigrat section, the decreases in organic δ13C and increases in C/N molar ratios from older to younger soil could have resulted from changes that occur over time, per se. In the remaining sections, however, δ13CSOM trends more likely reflect changes in the biomass of C4 relative to C3 plants (% C4 biomass). Changes in% C4 biomass may reflect climate and/or land use. Deciphering which may be aided by analyses of the other proxies. Identified charcoal suggests that both sites supported some juniper forest types until very recently but that forests may have been a more important and dynamic component of Adigrat's vegetation history than Adi Kolen's. If environment affected the trajectories of the kingdoms of the Tigray Plateau, these results suggest that the exact nature of the changes in climate differed among kingdoms. The kingdoms prior to 1200 cal yr BP may have been exposed to increasing aridity punctuated with relatively wetter intervals. Thereafter, general changes in climate are not apparent. Land clearing dynamics are likely to have had a more consistent effect on the trajectories of kingdoms than climate changes. 相似文献