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1.
Stable isotopes (δD and δ13C) are geographic indicators of natal origins of monarch butterflies in eastern North America 总被引:1,自引:0,他引:1
Wing membranes of laboratory and field-reared monarch butterflies (Danaus plexippus) were analyzed for their stable-hydrogen (δD) and carbon (δ13C) isotope ratios to determine whether this technique could be used to identify their natal origins. We hypothesized that
the hydrogen isotopic composition of monarch butterfly wing keratin would reflect the hydrogen isotope patterns of rainfall
in areas of natal origin where wings were formed. Monarchs were reared in the laboratory on milkweed plants (Asclepias sp.) grown with water of known deuterium content, and, with the assistance of volunteers, on native milkweeds throughout
eastern North America. The results show that the stable hydrogen isotopic composition of monarch butterflies is highly correlated
with the isotopic composition of the milkweed host plants, which in turn corresponds closely with the long-term geographic
patterns of deuterium in rainfall. Stable-carbon isotope values in milkweed host plants were similarly correlated with those
values in monarch butterflies and showed a general pattern of enrichment along a southwest to northeast gradient bisecting
the Great Lakes. These findings indicate that natal origins of migratory and wintering monarchs in Mexico can be inferred
from the combined δD and δ13C isotopic signatures in their wings. This relationship establishes that analysis of hydrogen and carbon isotopes can be used
to answer questions concerning the biology of migratory monarch butterflies and provides a new approach to tracking similar
migratory movements of other organisms.
Received: 1 July 1998 / Accepted: 11 November 1998 相似文献
2.
C. P. Chamberlain J. D. Blum R. T. Holmes Xiahong Feng T. W. Sherry G. R. Graves 《Oecologia》1996,109(1):132-141
To determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we
examined the isotopic composition of hydrogen (deuterium, δD), carbon (δ13C), and strontium (δ87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. δD and δ13C values in feathers, which are grown in the breeding area, varied systematically along a latitudinal gradient, being highest
in samples from the southern end of the species’ breeding range in Georgia and lowest in southern Canada. In addition, δD
decreased from east to west across the northern part of the breeding range, from New Brunswick to Michigan. δ87Sr ratios were highest in the Appalachian Mountains, and decreased towards the west. These patterns are consistent with geographical
variation in the isotopic composition of the natural environment, i.e., with that of precipitation, plants, and soils for
δD, δ13C, and δ87Sr, respectively. Preliminary analyses of the δD and δ13C composition of feathers collected from warblers in their Caribbean winter grounds indicate that these individuals were mostly
from northern breeding populations. Furthermore, variances in isotope ratios in samples from local areas in winter tended
to be larger than those in summer, suggesting that individuals from different breeding localities may mix in winter habitats.
These isotope markers, therefore, have the potential for locating the breeding origins of migratory species on their winter
areas, for quantifying the degree of mixing of breeding populations on migratory and wintering sites, and for documenting
other aspects of the population structure migratory animals – information needed for studies of year-round ecology of these
species as well as for their conservation. Combining information from several stable isotopes will help to increase the resolution
for determining the geographic origins of individuals in such highly vagile populations.
Received: 24 April 1995 / Accepted: 2 June 1996 相似文献
3.
Spatial patterns of foliar stable carbon isotope compositions of C<Subscript>3</Subscript> plant species in the Loess Plateau of China 总被引:1,自引:0,他引:1
The spatial pattern of foliar stable carbon isotope compositions (δ13C) of dominant species and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian,
Ansai, Mizhi and Shenmu, standing from south to north in the Loess Plateau of China, was studied. The results showed that
in the 121 C3 plant samples collected from the Loess Plateau, the foliar δ13C value ranged from −22.66‰ to −30.70‰, averaging −27.04‰. The foliar δ13C value varied significantly (P<0.01) among the seven sites, and the average δ13C value increased by about 1.69‰ from Yangling in the south to Shenmu in the north as climatic drought increased. There was
a significant difference in foliar δ13C value among three life-forms categorized from all the plant samples in the Loess Plateau (P<0.001). The trees (−26.74‰) and shrubs (−26.68‰) had similar mean δ13C values, both significantly (P<0.05) higher than the mean δ13C value of herbages (−27.69‰). It was shown that the trees and shrubs had higher WUEs and employed more conservative water-use
patterns to survive drier habitats in the Loess Plateau. Of all the C3 species in the Loess Plateau, the foliar δ13C values were significantly and negatively correlated with the mean annual rainfall (P<0.001) and mean annual temperature (P<0.05), while being significantly and positively correlated with the latitude (P<0.001) and the annual solar radiation (P<0.01). In general, the foliar δ13C values increased as the latitude and solar radiation increased and the rainfall and temperature decreased. The annual rainfall
as the main influencing factor could explain 13.3% of the spatial variations in foliar δ13C value. A 100 mm increment in annual rainfall would result in a decrease by 0.88‰ in foliar δ13C values. 相似文献
4.
Using stable hydrogen and oxygen isotope measurements of feathers to infer geographical origins of migrating European birds 总被引:1,自引:0,他引:1
Successful application of stable-hydrogen isotope measurements (Df) of feathers to track origins of migratory birds and other wildlife requires a fundamental understanding of the correlation between Df and deuterium patterns in rainfall (Dp) over continental scales. A strong correlation between Dp and Df has been confirmed for birds and insects in North America, but not yet for other continents. Here, we compare Df data from resident European birds to new Dp basemaps for Europe. Three maps, representing growing-season and mean annual Dp estimates from an elevation-explicit, detrended interpolation model and growing-season Dp estimates from simple Kriging, all indicate that strong isotope gradients occur across Europe with a general depletion occurring in a northeast direction. The feather data, representing 141 individuals of 25 avian species from 38 sites, ranged from –131 to –38. Regression analysis showed that strong correlations existed between both mean annual and growing-season Dp estimated by detrended interpolation and Df of non-aquatic and non-corvid birds (r2=0.66 and 0.65, respectively). We also examined mean annual and growing-season 18Op vs. 18Of for our samples. Both oxygen regressions were similar (r2=0.56 and 0.57, respectively) but poorer than for deuterium. Our study reveals that D measurements of feathers from migratory birds in Europe may be used to track their origin and movements, and so provide a powerful investigative tool for avian migration research in Europe. 相似文献
5.
Variations and controls of nitrogen stable isotopes in particulate organic matter of lakes 总被引:3,自引:0,他引:3
B. Gu 《Oecologia》2009,160(3):421-431
Nitrogen stable isotope (δ15N) data of particulate organic matter (POM) from the literature were analyzed to provide an understanding of the variations
and controls of δ15NPOM in lakes at the global scale. The δ15NPOM variability characterized by seasonal mean, minimum, maximum, and amplitude (defined as δ15NPOM maximum − δ15NPOM minimum) from 36 lakes with seasonal data did not change systematically with latitude, but was significantly lower in small
lakes than in large lakes. The seasonal mean δ15NPOM increased from oligotrophic lakes to eutrophic lakes despite large variations that are attributed to the occurrences of nitrogen
fixation across the trophic gradient and the differences in δ15N of dissolved inorganic nitrogen (DIN) in individual lakes. Seasonal mean δ15NPOM was significantly correlated with DIN concentration and δ15NDIN in two subsets of lakes. Seasonal minimum δ15NPOM in individual lakes is influenced by nitrogen fixation and δ15NDIN while seasonal maximum δ15NPOM is influenced by lake trophic state and δ15NDIN. As a result of the dominance of non-living POM in the unproductive surface waters, seasonal δ15NPOM amplitude was small (mean = 4.2‰) in oligotrophic lakes of all latitudes. On the other hand, seasonal δ15NPOM amplitude in eutrophic lakes was large (mean = 10.3‰), and increased from low to high latitudes, suggesting that the seasonal
variability of δ15N in the phytoplankton-dominated POM pool was elevated by the greater spans of solar radiation and thermal regimes at high
latitudes. The δ15NPOM from 42 lakes with no seasonal data revealed no consistent patterns along latitude, lake area, and trophic gradients, and
a greater than 2‰ depletion compared to the lakes with seasonal data. Along with the large seasonal variability of δ15NPOM within lakes, these results provide insightful information on sampling design for the studies of food web baseline in lakes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Use of saguaro fruit by white-winged doves: isotopic evidence of a tight ecological association 总被引:1,自引:0,他引:1
We report the use of stable isotope and crop content analyses to quantify the use of saguaro (Carnegiea gigantea) nectar and fruit by migratory desert white-winged doves (Zenaida asiatica mearsnii). Saguaro resources had characteristically 13C-enriched CAM values (δ13C=–12.8±0.7‰ SD VPDB and –13.1±0.5‰ SD VPDB for nectar and fruit, respectively) relative to other food plants used by doves
(δ13CC3=–24.9±3.3‰ SD VPDB). The water contained in saguaro nectar and fruit was deuterium enriched (δD=19.6±2.0‰ SD VSMOW and 48.4±1.6‰
SD VSMOW for nectar and fruit, respectively) relative to other water sources (ranging from –41 to –19‰ VSMOW). During the
fruiting season, there was a positive correlation between δ13C in dove liver tissues and percent of saguaro in crop contents. A two-point mixing model indicated that during the peak of
saguaro fruit use, most of the carbon incorporated in dove tissues was from saguaro. Desert white-winged doves appear to be
saguaro specialists. Averaged over the period when doves were resident, saguaro comprised about 60% of the total carbon incorporated
into dove tissues. Tissue δ13C and δD of body water showed a significant positive correlation, indicating that doves were using saguaro as a source of
both nutrients and water. However, at the peak of saguaro utilization, the doves’ body-water δD was more positive (by about
20‰) than saguaro fruit water. We hypothesize that this enrichment is due to fractionated evaporative water losses by doves.
Using dove carbon isotope data and a two end-point mixing model we estimate that, on average, doves consume the equivalent
of 128 saguaro fruits per season; each fruit contains on average 26.0±14.8 g SD of pulp (wet mass) of which 19.4 g is water.
Stable isotopes have been used to produce qualitative re-constructions of animal diets. Our study shows that they can be used
to provide quantitative estimates of the flow of nutrients from resources into consumers as well.
Received: 30 September 1999 / Accepted: 23 March 2000 相似文献
7.
Stable isotopes are being increasingly used in wildlife forensics as means of determining the origin and movement of animals. The heavy isotope content of precipitated water and snow (Dp, 18Op) varies widely and systematically across the globe, providing a label that is incorporated through diet into animal tissue. As a result, these isotopes are potentially ideal tracers of geographic origin. The hydrogen and oxygen isotope tracer method has excellent potential where (1) spatial variation of precipitation isotopes exist, and (2) strong, mechanistic relationships link precipitation and isotope ratios in biological tissue. Here, we present a method for interpolation of precipitation isotope values and use it to create global basemaps of growing-season (GS) and mean annual (MA) Dp and 18Op. The use of these maps for forensic application is demonstrated using previously published isotope data for bird feathers (Df) in North America and Europe. The precipitation maps show that the greatest potential for applying hydrogen and oxygen isotope forensics exists in mid- to high-latitude continental regions, where strong spatial isotope gradients exist. We demonstrate that Df/Dp relationships have significant predictive power both in North America and Europe, and show how zones of confidence for the assignment of origin can be described using these predictive relationships. Our analysis focuses on wildlife forensics, but the maps and approaches presented here will be equally applicable to criminal forensic studies involving biological materials. These maps are available in GIS format at . 相似文献
8.
This study explores the giant oyster Hyotissa hyotis as a novel environmental archive in tropical reef environments of the Indo-Pacific. The species is a typical accessory component
in coral reefs, can reach sizes of tens of centimetres, and dates back to the Late Pleistocene. Here, a 70.2-mm-long oxygen
and carbon isotope transect through the shell of a specimen collected at Safaga Bay, northern Red Sea, in May 1996, is presented.
The transect runs perpendicularly to the foliate and vesicular layers of the inner ostracum near the ligament area of the
oyster. The measured δ18O and δ13C records show sinusoidal fluctuations, which are independent of shell microstructure. The δ13C fluctuations exhibit the same wavelength as the δ18O fluctuations but are phase shifted. The δ18O record reflects the sea surface temperature variations from 1957 until 1996, possibly additionally influenced by the local
evaporation. Due to locally enhanced evaporation in the semi-enclosed Safaga Bay, the δ18Oseawater value is estimated at 2.17‰, i.e., 0.3–0.8‰ higher than published open surface water δ18O values (1.36–1.85‰) from the region. The mean water temperature deviates by only 0.4°C from the expected value, and the
minimum and maximum values are 0.5°C lower and 2.9°C higher, respectively. When comparing the mean monthly values, however,
the sea surface temperature discrepancy between reconstructed and global grid datasets is always <1.0°C. The δ13C signal is weakly negatively correlated with regional chlorophyll a concentration and with the sunshine duration, which may
reflect changes in the bivalve’s respiration. The study emphasises the palaeogeographic context in isotope studies based on
fossils, because coastal embayments might not reflect open-water oceanographic conditions. 相似文献
9.
Keith A. Hobson 《Oecologia》1999,120(3):314-326
To understand the ecology of migratory animals it is important to link geographic regions used by individuals including breeding,
wintering, and intermediate stopover sites. Previous conventional approaches used to track animal movements have relied on
extrinsic markers and typically the subsequent recovery of individuals. This approach has generally been inappropriate for
most small, or non-game animals. The use of intrinsic markers such as fatty acid profiles, molecular DNA analyses, and the
measurement of naturally occurring stable isotopes in animal tissues offer alternative approaches. This paper reviews the
use of stable isotope analyses (primarily δ13C, δ15N, δ34S, δD, δ87Sr) to trace nutritional origin and migration in animals. This approach relies on the fact that foodweb isotopic signatures
are reflected in the tissues of organisms and that such signatures can vary spatially based on a variety of biogeochemical
processes. Organisms moving between isotopically distinct foodwebs can carry with them information on the location of previous
feeding. Such an approach has been used to track animal use of inshore versus offshore, marine versus freshwater, terrestrial
C3 versus marine, terrestrial mesic versus xeric, and C3 versus C4 or Crassulacean acid metabolism foodwebs. More recently, the use of stable hydrogen isotope analyses (δD) to link organisms
to broad geographic origin in North America is based on large-scale isotopic contours of growing-season average δD values
in precipitation. This technique, especially when combined with the assay of other stable isotopes, will be extremely useful
in helping to track migration and movement of a wide range of animals from insects to birds and mammals. Future research to
refine our understanding of natural and anthropogenic-induced isotopic gradients in nature, and to explore the use of stable
isotopes of other elements, is recommended.
Received: 1 July 1998 / Accepted: 9 December 1998 相似文献
10.
Keirith A. Snyder Robert Monnar Simon R. Poulson Peter Hartsough Franco Biondi 《Trees - Structure and Function》2010,24(3):585-595
Diurnal fluctuations of leaf water isotope ratios (δ18O and δD) were measured for Jeffrey (Pinus jeffreyi Balf.) and lodgepole (Pinus contorta Douglas ex Louden) pine. Two trees per species were sampled every few hours on 15–16 October 2005 and 19–20 June 2006. Diurnal
gas exchange was measured during the summer sampling. In fall 2005, leaf water δ18O ranged from 0.7 to 9.0‰, and leaf water δD ranged from −70 to −50‰. In summer 2006, leaf water δ18O ranged from 7.7 to 20.7‰, and leaf water δD ranged from −61 to −24‰. Diurnal variation of leaf water isotope values typically
reached a maximum in early afternoon, began decreasing around midnight, and reached a minimum in mid-morning. Both periods
showed a high degree of enrichment relative to source water, with leaf water–source water enrichments ranging up to 37.8‰
for δ18O, and up to 95‰ for δD. Leaf water enrichment varied by season with summer enrichment being greater than fall enrichment.
A steady-state model (i.e., modified Craig–Gordon modeling) for leaf water isotope compositions did not provide a good fit
to measured values of leaf water. In summer, a non-steady state model provided a better fit to the measured data than the
steady-state model. Our findings demonstrate substantial leaf water enrichment above source water and diurnal variations in
the isotopic composition of leaf water, which has application to understanding short-term variability of atmospheric gases
(water vapor, CO2, O2), climate studies based on the isotopic composition of tree rings, and ecosystem water fluxes. 相似文献
11.
Hong Yang Mark Pagani Derek E. G. Briggs M. A. Equiza Richard Jagels Qin Leng Ben A. LePage 《Oecologia》2009,160(3):461-470
The effect of low intensity continuous light, e.g., in the High Arctic summer, on plant carbon and hydrogen isotope fractionations
is unknown. We conducted greenhouse experiments to test the impact of light quantity and duration on both carbon and hydrogen
isotope compositions of three deciduous conifers whose fossil counterparts were components of Paleogene Arctic floras: Metasequoia glyptostroboides, Taxodium distichum, and Larix laricina. We found that plant leaf bulk carbon isotopic values of the examined species were 1.75–4.63‰ more negative under continuous
light (CL) than under diurnal light (DL). Hydrogen isotope values of leaf n-alkanes under continuous light conditions revealed a D-enriched hydrogen isotope composition of up to 40‰ higher than in
diurnal light conditions. The isotope offsets between the two light regimes is explained by a higher ratio of intercellular
to atmospheric CO2 concentration (C
i/C
a) and more water loss for plants under continuous light conditions during a 24-h transpiration cycle. Apparent hydrogen isotope
fractionations between source water and individual lipids (εlipid–water) range from −62‰ (Metasequoia C27 and C29) to −87‰ (Larix C29) in leaves under continuous light. We applied these hydrogen fractionation factors to hydrogen isotope compositions of in
situ n-alkanes from well-preserved Paleogene deciduous conifer fossils from the Arctic region to estimate the δD value in ancient precipitation. Precipitation in the summer growing season yielded a δD of −186‰ for late Paleocene, −157‰ for early middle Eocene, and −182‰ for late middle Eocene. We propose that high-latitude
summer precipitation in this region was supplemented by moisture derived from regionally recycled transpiration of the polar
forests that grew during the Paleogene warming. 相似文献
12.
Carbon-13 abundance, expressed as δ13C in ‰, was measured in wheat straw grown between 1984 and 1989 on the Broadbalk Continuous Wheat Experiment at Rothamsted.
In all six years, straw grown without fertilizer N contained less carbon-13 (i.e.δ13C was more negative) than straw grown with fertilizer, although the magnitude of this difference varied with year. In a dry
year, when dry matter response to fertilizer N was relatively small, there was a large difference between the δ13C of straw grown with and without N. Conversely, in a wet year, when there was a marked response to N, there was little difference
in the isotopic composition of N-fertilized and unfertilized straw. Over the six years, the difference between the δ13C value of straw grown with and without nitrogen (D
13C, in ‰) was related to drought, measured as the calculated soil water deficit on 15 July (Wj, in mm), by the equation D
13C=−0.299+0.01034 Wj (r=0.87). H Lambers Section editor 相似文献
13.
Isotopic signature of nitrate in two contrasting watersheds of Brush Brook,Vermont, USA 总被引:2,自引:0,他引:2
We used the dual isotope method to study differences in nitrate export in two subwatersheds in Vermont, USA. Precipitation,
soil water and streamwater samples were collected from two watersheds in Camels Hump State Forest, located within the Green
Mountains of Vermont. These samples were analyzed for the δ15N and δ18O of NO3−. The range of δ15N–NO3− values overlapped, with precipitation −4.5‰ to +2.0‰ (n = 14), soil solution −10.3‰ to +6.2‰ (n = 12) and streamwater +0.3‰ to +3.1‰ (n = 69). The δ18O of precipitation NO3− (mean 46.8 ± 11.5‰) was significantly different (P < 0.001) from that of the stream (mean 13.2 ± 4.3‰) and soil waters (mean 14.5 ± 4.2‰) even during snowmelt periods. Extracted
soil solution and streamwater δ18O of NO3− were similar and within the established range of microbially produced NO3−, demonstrating that NO3− was formed by microbial processes. The δ15N and δ18O of NO3− suggests that although the two tributaries have different seasonal NO3− concentrations, they have a similar NO3− source. 相似文献
14.
The Canadian Migration Monitoring Network consists of several fixed migration monitoring stations (MMS) that apply constant-effort
protocols to track changes in the abundance of migratory birds. Such monitoring will be important for tracking long-term population
trends of songbirds, especially for species breeding in remote areas such as the North American boreal forest. The geographical
catchment sampled by individual MMS, however, remains largely unknown. Here, we used hydrogen isotope measurements (δD) of feathers of white-throated sparrows (Zonotrichia albicollis) moving through Delta Marsh MMS in Manitoba, Canada, to determine both wintering and breeding ground catchment areas monitored
by this station. The δD of tail feathers, collected from spring and fall migrants delineated previous breeding or natal latitudes, ranging from the
northern to the southern extremes of the western boreal forest. The δD values of head feathers grown on the wintering grounds and collected during spring migration revealed that individuals wintered
in a broad region of the southeastern United States. The isotope data showed no relationship between estimated breeding/natal
and wintering latitudes of white-throated sparrow populations. Stable isotope data provided little information on longitude.
Band-encounter analyses, however, indicated a clear east–west segregation of these sparrows across Canada, supporting connectivity
among breeding/natal and wintering longitudes over the entire scale of this species' range. Isotope analyses of multiple feather
types representing different periods and geographic regions of the annual cycle can provide key information on migratory connectivity
for species moving through dedicated MMS. 相似文献
15.
Patterns and controls of seasonal variability of carbon stable isotopes of particulate organic matter in lakes 总被引:2,自引:0,他引:2
Carbon stable isotopes (δ13C) of particulate organic matter (POM) have been used as indicators for energy flow, primary productivity and carbon dioxide
concentration in individual lakes. Here, we provide a synthesis of literature data from 32 freshwater lakes around the world
to assess the variability of δ13CPOM along latitudinal, morphometric and biogeochemical gradients. Seasonal mean δ13CPOM, a temporally integrated measure of the δ13CPOM, displayed weak relationships with all trophic state indices [total phosphorus (TP), total nitrogen (TN), and chlorophyll
a (Chl a)], but decreased significantly with the increase in latitude, presumably in response to the corresponding decrease
in water temperature and increase in CO2 concentration. The seasonal minimum δ13CPOM also correlated negatively with latitude while seasonal maximum δ13CPOM correlated positively with all trophic state indices, pH, and δ13C of dissolved inorganic carbon (DIC). Seasonal amplitude of δ13CPOM (the difference between seasonal maximum and minimum values) correlated significantly with pH, TP and Chl a concentrations
and displayed small variations in oligotrophic, mesotrophic and low latitude eutrophic lakes, which is attributed to low primary
productivity and abundant non-living POM in the low trophic state lakes and relatively stable environmental conditions in
the subtropics. Seasonal amplitude of δ13CPOM was the greatest in high latitude eutrophic lakes. Greater seasonal changes in solar energy and light regime may be responsible
for the large seasonal variability in high latitude productive lakes. This synthesis provides new insights on the factors
controlling variations in stable carbon isotopes of POM among lakes on the global scale. 相似文献
16.
Carbon isotopic composition of soils subjected to C3–C4 vegetation change can be used to estimate C turnover in bulk soil and in soil organic matter (SOM) pools with fast and intermediate
turnover rates. We hypothesized that the biological availability of SOM pools is inversely proportional to their thermal stability,
so that thermogravimetry can be used to separate SOM pools with contrasting turnover rates. Soil samples from a field plot
cultivated for 10.5 years with the perennial C4 plant Miscanthus×gigantheus were analyzed by thermogravimetry coupled with differential scanning calorimetry (DSC). Three SOM fractions were distinguished
according to the differential weight losses and exothermic or endothermic reactions measured by DSC. The δ13C and δ15N values of these three fractions obtained by gradual soil heating were measured by IRMS. The weight losses up to 190 °C mainly
reflected water evaporation because no significant C and N losses were detected and δ13C and δ15N values of the residual SOM remained unchanged. The δ13C values (−16.4‰) of SOM fraction decomposed between 190 and 390 °C (containing 79% of total soil C) were slightly closer
to that of the Miscanthus plant tissues (δ13C = −11.8‰) compared to the δ13C values (−16.8‰) of SOM fraction decomposed above 390 °C containing the residual 21% of SOM. Thus, the C turnover in the
thermally labile fraction was faster than that in thermally stable fractions, but the differences were not very strong. Therefore,
in this first study combining TG-DSC with isotopic analysis, we conclude that the thermal stability of SOM was not very strongly
related to biological availability of SOM fractions. In contrast to δ13C, the δ15N values strongly differed between SOM fractions, suggesting that N turnover in the soil was different from C turnover. More
detailed fractionation of SOM by thermal analysis with subsequent isotopic analysis may improve the resolution for δ13C. 相似文献
17.
Concentrations and natural isotope abundance of total sulfur and nitrogen as well as sulfate and nitrate concentrations were
measured in needles of different age classes and in soil samples of different horizons from a healthy and a declining Norway
spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), in order to study the fate of atmospheric depositions of
sulfur and nitrogen compounds.
The mean δ15N of the needles ranged between −3.7 and −2.1 ‰ and for δ34S a range between −0.4 and +0.9 ‰ was observed. δ34S and sulfur concentrations in the needles of both stands increased continuously with needle age and thus, were closely correlated.
The δ15N values of the needles showed an initial decrease followed by an increase with needle age. The healthy stand showed more
negative δ15N values in old needles than the declining stand. Nitrogen concentrations decreased with needle age.
For soil samples at both sites the mean δ15N and δ34S values increased from −3 ‰ (δ15N) or +0.9 ‰ (δ34S) in the uppermost organic layer to about +4 ‰ (δ15N) or +4.5 ‰ (δ34S) in the mineral soil. This depth-dependent increase in abundance of 15N and 34S was accompanied by a decrease in total nitrogen and sulfur concentrations in the soil. δ15N values and nitrogen concentrations were closely correlated (slope −0.0061 ‰ δ15N per μmol eq N gdw
−1), and δ34S values were linearly correlated with sulfur concentrations (slope −0.0576 ‰ δ34S per μmol eq S gdw
−1). It follows that in the same soil samples sulfur concentrations were linearly correlated with the nitrogen concentrations
(slope 0.0527), and δ34S values were linearly correlated with δ15N values (slope 0.459). A correlation of the sulfur and nitrogen isotope abundances on a Δ basis (which considers the different
relative frequencies of 15N and 34S), however, revealed an isotope fractionation that was higher by a factor of 5 for sulfur than for nitrogen (slope 5.292).
These correlations indicate a long term synchronous mineralization of organic nitrogen and sulfur compounds in the soil accompanied
by element-specific isotope fractionations.
Based on different sulfur isotope abundance of the soil (δ34S=0.9 ‰ for total sulfur of the organic layer was assumed to be equivalent to about −1.0 ‰ for soil sulfate) and of the atmospheric
SO2 deposition (δ34S=2.0 ‰ at the healthy site and 2.3 ‰ at the declining site) the contribution of atmospheric SO2 to total sulfur of the needles was estimated. This contribution increased from about 20 % in current-year needles to more
than 50 % in 3-year-old needles. The proportion of sulfur from atmospheric deposition was equivalent to the age dependent
sulfate accumulation in the needles. In contrast to the accumulation of atmospheric sulfur compounds nitrogen compounds from
atmospheric deposition were metabolized and were used for growth. The implications of both responses to atmospheric deposition
are discussed. 相似文献
18.
Photoperiodic time measurement regulating larval diapause in the pitcher-plant mosquito, Wyeomyia smithii, varies in a close relationship with latitude. The critical photoperiod mediating the maintenance and termination of diapause
is positively correlated with latitude (r
2 = 0.977) among six populations from southern (30–31° N), intermediate (40° N), and northern (46–49° N) latitudes in North
America. The developmental response to unnaturally short and to unnaturally long photoperiods declines with increasing latitude,
so that longer critical photoperiods are associated with a downward rather than a lateral shift in the photoperiodic response
curve. Exotic light and dark cycles of varying period (T) with a short (10 h) photophase and a scotophase ranging from 14
(T = 24) to 62 (T = 72) h, reveal two geographic patterns: a decline in perturbability of the photoperiodic clock with increasing
latitude, and no change with latitude in the 21-h period of rising and falling development with increasing T. These results
show (1) that there is a rhythmic component to photoperiodic time measurement in W. smithii, (2) that the period of this rhythm is about 21 h in all populations, and (3) that more northern populations show decreasing
responsiveness to photoperiod and increasing stability against perturbation by exotic period lengths (T > 24). Previous studies
on W.␣smithii indicate that this single temperate species of a tropical and subtropical genus has evolved from south to north. We therefore
conclude that the evolution of increasing critical photoperiod in W. smithii during its adaptive radiation into North America has more likely involved the amplitude and not the period of the underlying
circadian pacemaker.
Received: 22 July 1996 / Accepted: 30 September 1996 相似文献
19.
Linking breeding and wintering grounds of neotropical migrant songbirds using stable hydrogen isotopic analysis of feathers 总被引:1,自引:0,他引:1
Recent studies have shown that stable hydrogen isotope ratios (δD) in the tissues of animals often correlate with δD of local
precipitation. Here we examined the relationship between δD in feathers and growing season precipitation for neotropical migrant
songbirds breeding over a continent-wide isotopic gradient. δD values were determined on feathers of 140 individuals of 6
species of wild insectivorous forest songbirds (Setophaga ruticilla, Empidonax minimus, Vermivora peregrinus, Catharus ustulatus, Seiurus aurocapillus, Hylocichla mustelina) taken from 14 breeding locations across North America. The δD of feathers was strongly correlated with the δD of growing
season precipitation at breeding sites across North America. As feather hydrogen is metabolically inert after growth, this
relationship was then used to assess the breeding origins of wintering migrants. Deuterium values of feathers from 64 individuals
representing 5 species of migrants (Helmitheros vermivorus, Wilsonia citrina, Hylocichla mustelina, Dumetella carolinensis, Seirus aurocapillus) at a wintering site in Guatemala were consistent with those predicted from the known breeding ranges of these species. This
study demonstrates hydrogen isotopes may become a powerful tool for linking breeding and wintering grounds of neotropical
migrant songbirds, as well as other migratory species moving between isotopically distinct regions.
Received: 25 August 1995 / Accepted: 28 May 1996 相似文献
20.
The mechanisms behind the 13C enrichment of organic matter with increasing soil depth in forests are unclear. To determine if 13C discrimination during respiration could contribute to this pattern, we compared δ13C signatures of respired CO2 from sieved mineral soil, litter layer and litterfall with measurements of δ13C and δ15N of mineral soil, litter layer, litterfall, roots and fungal mycelia sampled from a 68-year-old Norway spruce forest stand
planted on previously cultivated land. Because the land was subjected to ploughing before establishment of the forest stand,
shifts in δ13C in the top 20 cm reflect processes that have been active since the beginning of the reforestation process. As 13C-depleted organic matter accumulated in the upper soil, a 1.0‰ δ13C gradient from −28.5‰ in the litter layer to −27.6‰ at a depth of 2–6 cm was formed. This can be explained by the 1‰ drop
in δ13C of atmospheric CO2 since the beginning of reforestation together with the mixing of new C (forest) and old C (farmland). However, the isotopic
change of the atmospheric CO2 explains only a portion of the additional 1.0‰ increase in δ13C below a depth of 20 cm. The δ13C of the respired CO2 was similar to that of the organic matter in the upper soil layers but became increasingly 13C enriched with depth, up to 2.5‰ relative to the organic matter. We hypothesise that this 13C enrichment of the CO2 as well as the residual increase in δ13C of the organic matter below a soil depth of 20 cm results from the increased contribution of 13C-enriched microbially derived C with depth. Our results suggest that 13C discrimination during microbial respiration does not contribute to the 13C enrichment of organic matter in soils. We therefore recommend that these results should be taken into consideration when
natural variations in δ13C of respired CO2 are used to separate different components of soil respiration or ecosystem respiration. 相似文献