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1.
A feeding trial was performed in the laboratory with the catfish species Pterygoplichthys disjunctivus to determine stable carbon (13C) and nitrogen (15 N) turnover rates and discrimination factors in non-lethally sampled tissues (red blood cells, plasma solutes, and fin).
A second feeding trial was conducted to determine what P. disjunctivus could assimilate from low-quality wood-detritus—refractory polysaccharides (e.g., cellulose), or soluble wood-degradation products inherent in wood-detritus. This was performed
by feeding the fish an artificial wood-detritus diet with fibrous (δ13C = −26.36‰; δ15
N = 2.13‰) and soluble portions (δ13C = −11.82‰; δ15
N = 3.39‰) that had different isotopic signatures and monitoring the dynamics of isotopic incorporation in the different tissues
over time. Plasma solutes turned over more quickly than red blood cells for 13C and 15 N. However, in contrast to previous studies of juvenile fishes, C and N incorporation was primarily driven by catabolic tissue
turnover as opposed to growth rate. Tissue-diet discrimination factors for 15 N varied from 4.08 to 5.17‰, whereas they were <2‰ for 13C (and less than 0.3‰ for plasma and red blood cells). The results of trial two suggested that P. disjunctivus could not assimilate refractory polysaccharides. Moreover, the δ13C and δ15 N signatures of wild-caught P. disjunctivus from Florida confirmed their detrital trophic standing in Floridian aquatic ecosystems. 相似文献
2.
Interseasonal comparison of CO2 concentrations, isotopic composition, and carbon dynamics in an Amazonian rainforest (French Guiana) 总被引:2,自引:0,他引:2
Canopy CO2 concentrations in a tropical rainforest in French Guiana were measured continuously for 5 days during the 1994 dry season
and the 1995 wet season. Carbon dioxide concentrations ([CO2]) throughout the canopy (0.02–38 m) showed a distinct daily pattern, were well-stratified and decreased with increasing height
into the canopy. During both seasons, daytime [CO2] in the upper and middle canopy decreased on average 7–10 μmol mol−1 below tropospheric baseline values measured at Barbados. Within the main part of the canopy (≥ 0.7 m), [CO2] did not differ between the wet and dry seasons. In contrast, [CO2] below 0.7 m were generally higher during the dry season, resulting in larger [CO2] gradients. Supporting this observation, soil CO2 efflux was on average higher during the dry season than during the wet season, either due to diffusive limitations and/or
to oxygen deficiency of root and microbial respiration. Soil respiration rates decreased by 40% after strong rain events,
resulting in a rapid decrease in canopy [CO2] immediately above the forest floor of about 50␣μmol mol−1. Temporal and spatial variations in [CO2]canopy were reflected in changes of δ13Ccanopy and δ18Ocanopy values. Tight relationships were observed between δ13C and δ18O of canopy CO2 during both seasons (r
2 > 0.86). The most depleted δ13Ccanopy and δ18Ocanopy values were measured immediately above the forest floor (δ13C = −16.4‰; δ18O = 39.1‰ SMOW). Gradients in the isotope ratios of CO2 between the top of the canopy and the forest floor ranged between 2.0‰ and 6.3‰ for δ13C, and between 1.0‰ and 3.5‰ for δ18O. The δ13Cleaf and calculated c
i/c
a of foliage at three different positions were similar for the dry and wet seasons indicating that the canopy maintained a
constant ratio of photosynthesis to stomatal conductance. About 20% of the differences in δ13Cleaf within the canopy was accounted for by source air effects, the remaining 80% must be due to changes in c
i/c
a. Plotting 1/[CO2] vs. the corresponding δ13C ratios resulted in very tight, linear relationships (r
2 = 0.99), with no significant differences between the two seasons, suggesting negligible seasonal variability in turbulent
mixing relative to ecosystem gas exchange. The intercepts of these relationships that should be indicative of the δ13C of respired sources were close to the measured δ13C of soil respired CO2 and to the δ13C of litter and soil organic matter. Estimates of carbon isotope discrimination of the entire ecosystem, Δe, were calculated as 20.3‰ during the dry season and as 20.5‰ during the wet season.
Received: 3 March 1996 / Accepted: 19 October 1996 相似文献
3.
We studied the nutritional modes of the orchid Serapias strictiflora and its mycorrhizal fungus Epulorhiza sp. using the differences in carbon isotopic composition (δ13C) of C3 orchid and C4 maize tissues. We found that if cultivated in substrate lacking any organic compounds, the mycorrhizal extraradical mycelia
(δ13C = −26.3 ± 0.2 ‰) developed well, despite being fully dependent on nutrition from orchid roots (δ13C = −28.6 ± 0.1 ‰). If the mycorrhizal fungus had additional access to and colonized decaying maize roots (δ13C = −14.6 ± 0.1 ‰), its isotopic composition (δ13C = −21.6 ± 0.4 ‰) reflected a mixture of biotrophy and saprotrophy. No statistically significant differences in δ13C of new storage tubers were found between Epulorhiza-associated orchids with (δ13C = -28.2 ± 0.1 ‰) and without access to maize roots (δ13C = −28.6 ± 0.2 ‰). We conclude that autotrophy is the predominant nutritional mode of mature S. strictiflora plants and that they supply their mycorrhizal fungus with substantial amount of carbon (69 ± 3 % of the fungus demand), even
if the fungus feeds saprotrophically. 相似文献
4.
Desert plants have unique strategies for survival and growth to cope with the limited water availability in arid regions.
The stable carbon isotope (δ
13C) provides an integrated measurement of internal plant physiological and external environmental properties affecting photosynthetic
gas exchange and water use efficiency. The δ
13C values of 84 species in the Junggar Basin were categorized into two groups (ranged from −30.1 to −23.3‰ for C3 and −14.9 to −9.9‰ for C4 species, respectively). No life form differences in δ
13C values were detected in C3 (p = 0.78) and C4 plants (p = 0.63). Small differences among life forms were observed in δ
13C values in C4 species with shrubs slightly depleted (−13.3‰) relative to perennials (−13.1‰) and annuals (−12.5‰). These differences suggested
that δ
13C value could not represent a plant functional group classification based on life forms in C4 plants in extremely arid regions. Ephemerals are all using C3 photosynthetic pathway and no significant differences (p = 0.92) in δ
13C values were observed between annuals (−26.5‰) and perennials (−26.4‰). The δ
13C values of Tulipa iliensis (an important ephemeral species distributed widely in the Junggar Basin) among nine natural populations were positively correlated
with leaf (r
2 = 0.46, p = 0.046) and soil (r
2 = 0.67, p = 0.007) total nitrogen content, and negatively correlated with leaf (r
2 = 0.48, p = 0.039) and soil (r
2 = 0.79, p = 0.001) water content. This indicated that the variation in δ
13C values of T. iliensis was probably caused by both water availability associated stomatal openness and nitrogen availability associated photosynthetic
capacity. T. iliensis is very sensitive to water and nitrogen availability in soil. 相似文献
5.
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
6.
Tom Moens Sandra Vanhove Ilse De Mesel Bea Kelemen Thierry Janssens Ann Dewicke Ann Vanreusel 《Polar Biology》2007,31(1):1-13
δ13C of nematode communities in 27 sites was analyzed, spanning a large depth range (from 130 to 2,021 m) in five Antarctic regions,
and compared to isotopic signatures of sediment organic matter. Sediment organic matter δ13C ranged from −24.4 to −21.9‰ without significant differences between regions, substrate types or depths. Nematode δ13C showed a larger range, from −34.6 to −19.3‰, and was more depleted than sediment organic matter typically by 1‰ and by up
to 3‰ in silty substrata. These, and the isotopically heavy meiofauna at some stations, suggest substantial selectivity of
some meiofauna for specific components of the sedimenting plankton. However, 13C-depletion in lipids and a potential contribution of chemoautotrophic carbon in the diet of the abundant genus Sabatieria may confound this interpretation. Carbon sources for Antarctic nematodes were also explored by means of an experiment in
which the fate of a fresh pulse of labile carbon to the benthos was followed. This organic carbon was remineralized at a rate
(11–20 mg C m−2 day−1) comparable to mineralization rates in continental slope sediments. There was no lag between sedimentation and mineralization;
uptake by nematodes, however, did show such a lag. Nematodes contributed negligibly to benthic carbon mineralization. 相似文献
7.
Abstract
Freshwater ecosystems derive organic carbon from both allochthonous and autochthonous sources. We studied the relative contributions
of different carbon sources to zooplankton in a small, polyhumic, steeply stratified lake, using six replicate surface-to-sediment
enclosures established during summer and autumn 2004. We added 13C-enriched bicarbonate to the epilimnion of half the enclosures for three weeks during each season and monitored carbon stable
isotope ratios of DIC, DOC, POC and Daphnia, along with physical, chemical and biological variables. During summer, 13C-enriched DIC (δ13C up to 44 ± 7.2‰) was soon taken up by phytoplankton (δ13C up to −5.1 ± 13.6‰) and was transmitted to Daphnia (δ13C up to −1.7 ± 7.2‰), demonstrating consumption of phytoplankton. In contrast, during autumn, 13C-enriched DIC (δ13C up to 56.3 ± 9.8‰) was not transmitted to Daphnia, whose δ13C became progressively lower (δ13C down to −45.6 ± 3.3‰) concomitant with decreasing methane concentration. Outputs from a model suggested phytoplankton contributed
64–84% of Daphnia diet during summer, whereas a calculated pelagic carbon mass balance indicated only 30–40% could have come from phytoplankton.
Although autumn primary production was negligible, zooplankton biomass persisted at the summer level. The model suggested
methanotrophic bacteria contributed 64–87% of Daphnia diet during autumn, although the calculated carbon mass balance indicated a contribution of 37–112%. Thus methanotrophic
bacteria could supply virtually all the carbon requirement of Daphnia during autumn in this lake. The strongly 13C-depleted Daphnia values, together with the outputs from the models and the calculated carbon mass balance showed that methanotrophic bacteria
can be a greater carbon source for Daphnia in lakes than previously suspected. 相似文献
8.
The vertical profile of stable carbon isotope ratios (δ13C) of leaves was analyzed for 13 tree species in a cool-temperate deciduous forest in Japan. The vertical distribution of
long-term averaged δ13C in atmospheric CO2 (δa) was estimated from δ13C of dry matter from NADP-malic enzyme type C4 plant (Zea mays L. var. saccharata Sturt.) grown at a tower in the forest for 32␣days, assuming constant Δ value (3.3‰) in Z. mays against height. The δa value obtained from δ13C in Z.␣mays was lowest at the forest floor (−9.30 ± 0.03‰), increased with height, and was almost constant above 10␣m (−7.14 ± 0.14‰).
Then leaf Δ values for the tree species were calculated from tree leaf δ13 C andδa. Mean leaf Δ values for the three tall deciduous species (Fraxinus mandshurica, Ulmus davidiana, and Alnus hirsuta) were significantly different among three height levels in the forest: 23.1 ± 0.7‰ at the forest floor (understory), 21.4 ± 0.5‰
in lower canopy, and 20.5 ± 0.3‰ in upper canopy. The true difference in tree leaf Δ among the forest height levels might
be even greater, because Δ in Z. mays probably increased with shading by up to ∼‰. The difference in tree leaf Δ among the forest height levels would be mainly
due to decreasing intercellular CO2 (C
i) with the increase in irradiance. Potential assimilation rate for the three tree species probably increased with height,
since leaf nitrogen content on an area basis for these species also increased with height. However, the increase in stomatal
conductance for these tree species would fail to meet the increase in potential assimilation rate, which might lead to increasing
the degree of stomatal limitation in photosynthesis with height.
Received: 30 September 1995 / Accepted: 25 October 1996 相似文献
9.
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
10.
Leaf carbon isotope ratios (δ13C) and photosynthetic gas exchange were measured on plants growing in hanging garden communities in southern Utah, USA. Hanging
gardens are unusual, mesic cliff communities occurring where water seeps from the sandstone bedrock in an otherwise extremely
arid region; there is very limited overlap in species distributions inside and outside these gardens. Solar exposure in hanging
gardens varied with orientation and one of the gardens (Ribbon Garden) was shaded throughout the day. The leaf δ13C values of plants in hanging gardens were significantly more negative than for plants from either nearby ephemeral wash or
riparian communities. In Ribbon Garden, the observed δ13C values were as low as −34.8‰, placing them among the most negative values reported for any terrestrial plant species growing
in a natural environment. Hanging garden plants were exposed to normal atmospheric CO2 with an average δ13C value of −7.9‰ and so the low leaf δ13C values could not be attributed to exposure to a CO2 source with low 13C content. There was a seasonal change toward more negative leaf δ13C values at the end of the growing season. The observed leaf δ13C values were consistent with photosynthetic gas exchange measurements that indicated unusually high leaf intercellular CO2 concentrations associated with the relatively low light levels in hanging gardens. Thus, extremely negative leaf δ13C values would be expected if significant amounts of the seasonal carbon gain occur at light levels low enough to be near
the light compensation point. Maximum observed photosynthetic rates varied with light levels at each of the gardens, with
maximum rates averaging 20.3, 14.6, and 3.1 μmol m−2 s−1 at Double Garden, Lost Garden, and Ribbon Garden, respectively. Leaf nitrogen contents averaged 18.5 mg g−1 in species from the more shaded hanging gardens (Lost and Ribbon). When expressed on a leaf area basis, nitrogen contents
averaged 117 mmol N m−2 at Lost Garden and 65 mmol N m−2 at Ribbon Garden (shadiest of the two gardens). Leaf nitrogen isotope ratios averaged −2.3‰ (range of −0.7 to −6.1‰), suggesting
that most of the nitrogen was derived from a biological fixation source which is most likely the Nostoc growing on the sandstone walls at the seep. These values contrast with leaf nitrogen isotope ratios of 5–9‰ which have been
previously reported for arid zone plants in nearby ecosystems.
Received: 19 January 1997 / Accepted: 19 April 1997 相似文献
11.
Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural
carbon isotope ratio (δ
13C) and short-term carbon uptake rates (13C tracer study) of size-fractionated nannoplankton (<10 μm) and net plankton (>10 μm) samples. Short-term photosynthetic rates,
which represent the physiological state of algae, were variable regardless of standing stock sizes. Theδ
13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction
(−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more
negativeδ
13C values (−22 to −18‰). Highδ
13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the
increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the
nannoplankton fractions with higher POC values have relatively lowδ
13C values. 相似文献
12.
William E. Magnusson M. Carmozina de Araújo Renato Cintra Albertina P. Lima Luiz A. Martinelli Tânia M. Sanaiotti Heraldo L. Vasconcelos Reynaldo L. Victoria 《Oecologia》1999,119(1):91-96
We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential
food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (xˉ = −30.8, SD = 1.2), vines (xˉ = −30.7, SD = 0.46) and trees (xˉ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (xˉ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (xˉ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate
values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing,
the frogs and lizards generally had higher values of δ13C (xˉ = −21.7, SD = 1.6; xˉ = −21.9, SD = 1.8, respectively) than the birds (xˉ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (xˉ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
Received: 7 May 1998 / Accepted: 30 November 1998 相似文献
13.
Influence of stand structure on carbon-13 of vegetation, soils, and canopy air within deciduous and evergreen forests in Utah, United States 总被引:15,自引:0,他引:15
Carbon isotope ratios (δ13C) were studied in evergreen and deciduous forest ecosystems in semi-arid Utah (Pinus contorta, Populus tremuloides, Acer negundo and Acer grandidentatum). Measurements were taken in four to five stands of each forest ecosystem differing in overstory leaf area index (LAI) during
two consecutive growing seasons. The δ13Cleaf (and carbon isotope discrimination) of understory vegetation in the evergreen stands (LAI 1.5–2.2) did not differ among canopies
with increasing LAI, whereas understory in the deciduous stands (LAI 1.5–4.5) exhibited strongly decreasing δ13Cleaf values (increasing carbon isotope discrimination) with increasing LAI. The δ13C values of needles and leaves at the top of the canopy were relatively constant over the entire LAI range, indicating no
change in intrinsic water-use efficiency with overstory LAI. In all canopies, δ13Cleaf decreased with decreasing height above the forest floor, primarily due to physiological changes affecting c
i/c
a (> 60%) and to a minor extent due to δ13C of canopy air (< 40%). This intra-canopy depletion of δ13Cleaf was lowest in the open stand (1‰) and greatest in the denser stands (4.5‰). Although overstory δ13Cleaf did not change with canopy LAI, δ13C of soil organic carbon increased with increasing LAI in Pinus contorta and Populus tremuloides ecosystems. In addition, δ13C of decomposing organic carbon became increasingly enriched over time (by 1.7–2.9‰) for all deciduous and evergreen dry temperate
forests. The δ13Ccanopy of CO2 in canopy air varied temporally and spatially in all forest stands. Vertical canopy gradients of δ13Ccanopy, and [CO2]canopy were larger in the deciduous Populus tremuloides than in the evergreen Pinu contorta stands of similar LAI. In a very wet and cool year, ecosystem discrimination (Δe) was similar for both deciduous Populus tremulodies (18.0 ± 0.7‰) and evergreen Pinus contorta (18.3 ± 0.9‰) stands. Gradients of δ13Ccanopy and [CO2]canopy were larger in denser Acer spp. stands than those in the open stand. However, 13C enrichment above and photosynthetic draw-down of [CO2]canopy below tropospheric baseline values were larger in the open than in the dense stands, due to the presence of a vigorous understory
vegetation. Seasonal patterns of the relationship δ13Ccanopy versus 1/[CO2]canopy were strongly influenced by precipitation and air temperature during the growing season. Estimates of Δe for Acer spp. did not show a significant effect of stand structure, and averaged 16.8 ± 0.5‰ in 1933 and 17.4 ± 0.7‰ in 1994. However,
Δe varied seasonally with small fluctuations for the open stand (2‰), but more pronounced changes for the dense stand (5‰).
Received: 15 April 1996 / Accepted: 19 October 1996 相似文献
14.
The natural relationship13C/12C determined in three soil profiles under grass vegetation indicated a depletion in organic13C at depth: theδ
13C was between −18‰ and −15‰ in the A horizons and ranged from −18 to −22‰ at depth. Previous work showed that in forest soils,
whereδ
13C was near −28‰ in the upper horizon, there was, on the contrary, a relative enrichment of the lower strata. This meant thatδ
13C, initially different in the various topsoils, became more equal at depth. Comparison between dark, deep horizons (sombric
horizons), which are certainly of illuvial origine, would confirm this:δ
13C of grassland and a forest sombric horizon were almost equal at around −22‰. These results might mean that, in natural ecosystems,
the isotopic carbon composition of the soil underlying humus would be independent of the vegetation type. This would have
practical implications for the use of13C as a tracer for soil organic matter studies. 相似文献
15.
Nitrogen and carbon isotope responses of Chinese cabbage and chrysanthemum to the application of liquid pig manure 总被引:2,自引:0,他引:2
Sang-Sun Lim Woo-Jung Choi Jin-Hyeob Kwak Jae-Woon Jung Scott X. Chang Han-Yong Kim Kwang-Sik Yoon Soo-Myung Choi 《Plant and Soil》2007,295(1-2):67-77
The effects of the liquid pig manure (LM) used in organic farming on the natural abundance of 15N and 13C signatures in plant tissues have not been studied. We hypothesized that application of LM will (1) increase δ15N of plant tissues due to the high δ15N of N in LM as compared with soil N or inorganic fertilizer N, and (2) increase δ13C of plant tissues as a result of high salt concentration in LM that decreases stomatal conductance of plants. To test these
hypotheses, variations in the δ15N and δ13C of Chinese cabbage (Brassica campestris L.) and chrysanthemum (Chrysanthemum morifolium Ramatuelle) with two different LMs (with δ15N of +15.6 and +18.2‰) applied at two rates (323 and 646 kg N ha-1 for cabbage and 150 and 300 kg N ha-1 for chrysanthemum), or urea (δ15N = -2.7‰) applied at the lower rate above for the respective species, in addition to the control (no N input) were investigated
through a 60-day pot experiment. Application of LM significantly increased plant tissue δ15N (range +9.4 to +14.9‰) over the urea (+3.2 to +3.3‰) or control (+6.8 to 7.7‰) treatments regardless of plant species, strongly
reflecting the δ15N of the N source. Plant tissue δ13C were not affected by the treatments for cabbage (range −30.8 to −30.2‰) or chrysanthemum (−27.3 to −26.8‰). However, cabbage
dry matter production decreased while its δ13C increased with increasing rate of LM application or increasing soil salinity (P < 0.05), suggesting that salinity stress caused by high rate of LM application likely decreased stomatal conductance and
limited growth of cabbage. Our study expanded the use of the δ15N technique in N source (organic vs. synthetic fertilizer) identification and suggested that plant tissue δ13C maybe a sensitive indicator of plant response to salinity stress caused by high LM application rates. 相似文献
16.
J. M. Guehl A. M. Domenach M. Bereau T. S. Barigah H. Casabianca A. Ferhi J. Garbaye 《Oecologia》1998,116(3):316-330
Functional aspects of biodiversity were investigated in a lowland tropical rainforest in French Guyana (5°2′N, annual precipitation
2200 mm). We assessed leaf δ15N as a presumptive indicator of symbiotic N2 fixation, and leaf and wood cellulose δ13C as an indicator of leaf intrinsic water-use efficiency (CO2 assimilation rate/leaf conductance for water vapour) in dominant trees of 21 species selected for their representativeness
in the forest cover, their ecological strategy (pioneers or late successional stage species, shade tolerance) or their potential
ability for N2 fixation. Similar measurements were made in trees of native species growing in a nearby plantation after severe perturbation
(clear cutting, mechanical soil disturbance). Bulk soil δ15N was spatially quite uniform in the forest (range 3–5‰), whereas average leaf δ15N ranged from −0.3‰ to 3.5‰ in the different species. Three species only, Diplotropis purpurea, Recordoxylon speciosum (Fabaceae), and Sclerolobium melinonii (Caesalpiniaceae), had root bacterial nodules, which was also associated with leaf N concentrations higher than 20 mg g−1. Although nodulated trees displayed significantly lower leaf δ15N values than non-nodulated trees, leaf δ15N did not prove a straightforward indicator of symbiotic fixation, since there was a clear overlap of δ15N values for nodulated and non-nodulated species at the lower end of the δ15N range. Perturbation did not markedly affect the difference δ15Nsoil − δ15Nleaf, and thus the isotopic data provide no evidence of an alteration in the different N acquisition patterns. Extremely large
interspecific differences in sunlit leaf δ13C were observed in the forest (average values from −31.4 to −26.7‰), corresponding to intrinsic water-use efficiencies (ratio
CO2 assimilation rate/leaf conductance for water vapour) varying over a threefold range. Wood cellulose δ13C was positively related to total leaf δ13C, the former values being 2–3‰ higher than the latter ones. Leaf δ13C was not related to leaf δ15N at either intraspecific or interspecific levels. δ13C of sunlit leaves was highest in shade hemitolerant emergent species and was lower in heliophilic, but also in shade-tolerant
species. For a given species, leaf δ13C did not differ between the pristine forest and the disturbed plantation conditions. Our results are not in accord with the
concept of existence of functional types of species characterized by common suites of traits underlying niche differentiation;
rather, they support the hypothesis that each trait leads to a separate grouping of species.
Received: 18 August 1997 / Accepted: 14 April 1998 相似文献
17.
Giedrius Trakimas Timothy D. Jardine Rūta Barisevi?iūt? Andrius Garbaras Raminta Skipityt? Vidmantas Remeikis 《Hydrobiologia》2011,675(1):87-95
During migrations and ontogeny amphibians change their habitat and feeding, and thus are important in linking terrestrial
and aquatic ecosystems. We measured δ
13C and δ
15N values of early stages (egg, embryo, tadpole) and toes of adult frogs Rana temporaria, collected from a small wetland in Lithuania. We compared the isotopic composition of these tissues with potential food sources,
excrements of tadpoles, and filled intestinal tracts. We found that δ
13C values in R. temporaria tadpoles were markedly depleted in comparison to adults, eggs or embryos, demonstrating a terrestrial to aquatic shift in
energy sources. After the onset of feeding, tadpoles approached isotopic equilibrium with available food (algae and litter).
Tadpoles had higher δ
15N than both algae and litter, differing by 3.6 and 2.4‰, respectively, and similar δ
13C to these sources. However, tadpole excrements and body tissue diverged, with mean δ
13C values of excrements (−30.3 ± 1.6‰ SD) more similar to litter (−31.7 ± 1.2‰ SD) and body tissue δ
13C (−34.8 ± 0.7‰ SD) more similar to algae (−34.2 ± 4.1‰ SD). This suggests that algal resources are critical in early life
stages of this anuran, particularly at stages characterized by high growth and low development (stages: 25–35). 相似文献
18.
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
19.
The use of stable isotopes to investigate animal diets, habitat use, and trophic level requires understanding the rate at
which animals incorporate the 13C and 15N from their diets and the factors that determine the magnitude of the difference in isotopic composition between the animal’s
diet and that of its tissues. We determined the contribution of growth and catabolic turnover to the rate of 13C and 15N incorporation into several tissues that can be sampled non-invasively (skin, scute, whole blood, red blood cells, and plasma
solutes) in two age classes of a rapidly growing ectotherm (loggerhead turtles, Caretta caretta). We found significant differences in C and N incorporation rates and isotopic discrimination factors (Δ13C = δ13Ctissues − δ13Cdiet and Δ15N = δ15Ntissues − δ15Ndiet) among tissues and between age classes. Growth explained from 26 to 100% of the total rate of incorporation in hatchling
turtles and from 15 to 52% of the total rate of incorporation in juvenile turtles. Because growth contributed significantly
to the rate of isotopic incorporation, variation in rates among tissues was lower than reported in previous studies. The contribution
of growth can homogenize the rate of isotopic incorporation and limit the application of stable isotopes to identify dietary
changes at contrasting time scales and to determine the timing of diet shifts. The isotopic discrimination factor of nitrogen
ranged from −0.64 to 1.77‰ in the turtles’ tissues. These values are lower than the commonly assumed average 3.4‰ discrimination
factors reported for whole body and muscle isotopic analyses. The increasing reliance on non-invasive and non-destructive
sampling in animal isotopic ecology requires that we recognize and understand why different tissues differ in isotopic discrimination
factors. 相似文献
20.
Water availability is an important factor limiting the productivity of desert plants but little is known about the impact
of water-limiting conditions on the physiology of plants in mesic environments. Riparian ecosystems of the western US receive
significantly more water than the surrounding desert environments but experience dramatic interannual fluctuations in water
availability because both stream flow and precipitation are highly variable over time. This variability results in different
growing conditions each year which may influence the physiology of riparian species such as Fremont cottonwood (Populus fremontii), the dominant, native canopy tree species in lowland southwestern US river systems. We wished to determine if the physiology
of this species varies among years, what climatic parameters are related to any observed physiological variation and if individuals
within a P. fremontii population differ in their physiological response to variation through time. We collected tree ring cores from a central
New Mexico cottonwood population and analyzed carbon isotope composition (δ13C) in each year from 1981 to 1995. We used δ13C analysis in this study because it allowed us to obtain multi-year estimates of physiological activity. During these years,
mean stream flow at our study site ranged over two orders of magnitude from 0.82 to 80.94 m3 s−1, precipitation ranged fourfold from 49 to 215 ccmm and mean temperature ranged from 20.5 to 22.6°C during the growing season.
δ13C varied from a low of −26.7‰ in 1984 to a high of −24.7‰ in 1981. Low δ13C values were associated with years in which stream flow and/or precipitation were high and temperature was low. The opposite
was true of years with high δ13C values. We observed a strong linear relationship between δ13C and stream flow during years when stream flow was <25 m3 s−1 but no significant relationship between these variables when stream flow was >25 m3 s−1. Additionally, there was a linear relationship between δ13C and precipitation during years when stream flow was <25 m3 s−1 but not in years when stream flow was >25 m3 s−1. These data suggest that above a threshold of total stream flow, increased flow does not influence physiology. Below this
threshold, precipitation can be an important water source. The ten individuals within our study population varied significantly
in mean δ13C values but responded to interannual variation in a similar manner (i.e., all individuals had low δ13C values when water was abundant). These results suggest that precipitation as well as stream flow are important factors influencing
the physiology of this riparian tree.
Received: 25 November 1998 / Accepted: 9 February 1999 相似文献