Carbon Isotope Ratios Of Plants Research Articles

Carbon isotope fractionation including photosynthetic and post-photosynthetic processes in C3 plants: Low [CO2] matters

Carbon isotope ratios of plants are highly informative for the reconstruction of ancient environments and for the interpretation of plant physiological processes to climate, but their responses to changing atmospheric CO2 concentration are currently debated. Moreover, plants in the geological past have experienced long-term low CO2 concentration (LC). However, the effects of LC on the plant C isotope ratios are still elusive.To investigate effects of atmospheric CO2 concentration ([CO2]) and drought on isotope ratios of plant metabolites we grew winter wheat (Triticum aestivum) in climate-controlled chambers under different [CO2] covering glacial, pre-industrial, and present concentrations (170, 280, and 400 ppm) and water regimes (well-watered and drought).First, we quantified total C isotope discrimination between plant and atmosphere (Δ) using 13C on-line measurements of plant gas exchange and 13C values of plant metabolites, i.e., cellulose, n-alkane, and phospholipid fatty acids (PLFA). We found that LC yielded a higher Δ regardless of water regime, i.e. more 13C-depleted values were found under LC; the effect was stronger for n-C29 alkane (1.5‰/100 ppm) and C16:0 PLFA (1.1‰/100 ppm) than that for cellulose (0.6‰/100 ppm). We then calculated post-photosynthetic C isotope shift (ɛ) between specific metabolites and plant bulk isotope values. δ13Cn-C29 alkane and δ13CPLFA were 8.3‰ and 7.3‰ lighter than the δ13Cbulk under 400 ppm; these depletions became higher (9.8‰ and 8.2‰ lighter than the δ13Cbulk for n-C29 alkane and PLFA, respectively) under 170 ppm. In contrast, δ13Ccellulose was 1.2‰ heavier than the δ13Cbulk under 400 ppm while this enrichment became higher (1.6‰) under 170 ppm.Changes in atmospheric [CO2] affected C fractionation not only via photosynthetic but also post-photosynthetic processes and thus must be taken into account when interpreting C isotopes for paleoclimate reconstruction and future global C cycle prediction.

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Variations in carbon isotope ratios of plants across a temperature gradient along the 400 mm isoline of mean annual precipitation in north China and their relevance to paleovegetation reconstruction

Carbon isotope values (δ13C) of plants reflect the balance between photosynthesis and stomatal conductance and vary with environmental conditions. Temperature is an important influential factor for plant δ13C; however, variations of plant δ13C across temperature gradients have yet to be quantified. This impedes interpretation of variability of δ13C in ancient terrestrial organic matter and reconstructions of paleoclimate and paleoecology. In this study, the effect of temperature on δ13C of C3 and C4 plants was assessed by comprehensive investigation of a large number of species (118 C3 plants and 17 C4 plants) from 29 sites across a temperature gradient along the 400 mm mean annual precipitation isoline in north China. After deducting the effects of precipitation on plant δ13C, a strong positive relationship is found between δ13C values of C3 plants averaged for each site and mean annual temperature, with a coefficient of 0.104‰/°C; however, no significant correlation is found for C4 plants. Based on our results, we conduct a sample reconstruction of paleovegetation of the central Chinese Loess Plateau and demonstrate that, to a certain extent, our paleovegetation reconstruction is affected by temperature corrections.

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Background and Aim Nitrogen (N) and carbon (C) isotopic signatures (δ15N and δ13C) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood.

Limitations of stable carbon isotope analysis for determining natal host origins of tobacco budworm, Heliothis virescens

AbstractDifferences in the stable carbon isotope ratios of plants utilizing the C3 vs. C4 photosynthetic pathway have been used to broadly identify the natal host origins of herbivorous insects. This study explored whether adequate variation exists between the carbon isotope ratios of different C3 plants in the host range of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) to enable accurate identification of natal host‐plant species. Isotope ratio mass spectrometry (IRMS) analysis of 13C/12C ratios of moths reared on four crop plant species [Gossypium hirsutum (L.), Nicotiana tabacum L., Glycine max (L.) Merrill, and Arachis hypogaea L.] and two common weed species [Geranium carolinianum L. and Linaria canadensis (L.) Chaz.] revealed a range of δ13C values within that expected for plants utilizing the C3 photosynthetic pathway. Analysis of vegetative and reproductive tissues from the plants utilized in the study resulted in statistically different δ13C values for some plant species; nevertheless, the range of δ13C values observed for many plant species overlapped. Significant differences in mean δ13C values were detected between groups of moths reared on different host‐plant species, but there was no significant correlation between the δ13C values of moths vs. the δ13C value of plant tissue on which they were reared. Feral tobacco budworm moths collected over 3 years were found to have carbon isotope ratios consistent with those having fed on C3 plants, confirming little utilization of C4 plant species by the insect. Results demonstrate that within the range of C3 host plants tested, carbon isotope signatures are not sufficiently unique to enable a reliable determination of natal origin of feral tobacco budworm with current IRMS technology.

Carbon isotope ratios of plants and occurrences of C4 species under different soil moisture regimes in arid region of Northwest China

Carbon isotope ratio of leaf dry matter, δ13C, was measured on species occurring within Baiyin desert community, consisting of valley, slope and ridge microhabitats, and within Shandan desert community, consisting of Gobi desert and seasonal flooded creek microhabitats, in Northwest China. δ13C of C3 species increased with a decrease in soil water availability, suggesting that water‐use efficiency (WUE) increased with decreasing soil moisture, whereas for all C4 species, δ13C tended to decrease with decreasing soil water availability, suggesting that WUE also increased with decreasing soil moisture. Above results indicated that water‐use pattern was conservative under drought for C4 and C3 plants. In this present study, C4 species' occurrences within different microhabitats were investigated and C4 plants were observed to be absent and/or scarce within relatively lower soil moisture microhabitats, whereas they occurred and/or even had a high abundance within relatively higher soil moisture microhabitats, suggesting limited moisture available was a key factor of limiting C4 distribution in arid region of Northwest China.

Leaf carbon isotope composition of fossil and extant oaks grown under differing atmospheric CO2 levels

The aim of this study is to investigate the effects of long-term variations in atmospheric CO 2 levels ( p CO 2 ) on stable carbon isotope ratios in plants. Isotope measurements were undertaken on two kinds of oak leaves: fossil leaves originating from two Miocene levels of well-documented and differing p CO 2 (i.e., 280 and 360 ppmv), and extant leaves of the same species coming from plants experimentally grown under contrasted p CO 2 . Measurements were performed separately on sun and shade leaves to avoid bias linked to leaf morphotype, and on bulk leaves and individual n -alkanes extracted from the leaves, to detect possible diagenetic alteration of the isotope signal. Although extant oaks exhibit no significant trend in isotope discrimination with varying p CO 2 , fossil oaks from the high p CO 2 level tend to exhibit slightly smaller isotope discrimination than those from the low p CO 2 level. However, the difference in fossil discrimination is only of 0.5‰ and its origin cannot be unequivocally assessed since other environmental parameters could be responsible for it. Therefore, it appears that if plant carbon isotope composition is sensitive to long-term p CO 2 variations, its response is rather minimal.

Leaf carbon isotope composition of fossil and extant oaks grown under differing atmospheric CO 2 levels

The aim of this study is to investigate the effects of long-term variations in atmospheric CO 2 levels ( pCO 2) on stable carbon isotope ratios in plants. Isotope measurements were undertaken on two kinds of oak leaves: fossil leaves originating from two Miocene levels of well-documented and differing pCO 2 (i.e., 280 and 360 ppmv), and extant leaves of the same species coming from plants experimentally grown under contrasted pCO 2. Measurements were performed separately on sun and shade leaves to avoid bias linked to leaf morphotype, and on bulk leaves and individual n-alkanes extracted from the leaves, to detect possible diagenetic alteration of the isotope signal. Although extant oaks exhibit no significant trend in isotope discrimination with varying pCO 2, fossil oaks from the high pCO 2 level tend to exhibit slightly smaller isotope discrimination than those from the low pCO 2 level. However, the difference in fossil discrimination is only of 0.5‰ and its origin cannot be unequivocally assessed since other environmental parameters could be responsible for it. Therefore, it appears that if plant carbon isotope composition is sensitive to long-term pCO 2 variations, its response is rather minimal.

New chronology and organic matter paleoclimatic significance of Nußloch loess sequence (Rhine Valley, Germany)

Due to its high accumulation rate, the loess sequence of Nu{loch (Rhine Valley, Germany) is well suited to a high-resolution study of continental paleoenvironmental changes over the last climatic cycle for northwestern Europe. As carbon isotope ratios of plants depend on environmental variations, C of loess-derived organic matter constitute reliable paleoclimatic proxies. We present here a new chronology of Nu{loch loess sequence based on several C and TL-dates. Our data show high correlations with global climate e!ects (Vostok-[CO ]) or semi-global (GISP2-O) and thus o!er, in this way, a new approach to establish accurate chronologies in continental sequences. Furthermore, using a deconvolution of the C signal would provide a quantitative proxy of moisture supply and permit paleoprecipitation reconstructions. 2000 Elsevier Science Ltd and INQUA. All rights reserved.

Unusually low carbon isotope ratios in plants from hanging gardens in southern Utah.

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.

Influence of Nitrogen Supply and Temperature on Stable Carbon Isotope Ratios in Plants of Different Photosynthetic Pathways (C3, C4, CAM)

Abstract One representative species of each of the three photosynthetic pathways (C3, C4, CAM) were cultivated in growth chambers with high and low nitrogen nutrition level respectively once at 20°C day/13°C night temperature, once at 30°C day/13°C night. Leaf conductances and δ13C values of the leaves of each plant were determined. At 20°C day temperature the C3 species showed higher leaf conductance with low nitrogen nutrition level than with high nitrogen level, which is also reflected in a more negative δ13C value, whereas both C4 and CAM plants did not respond in this manner to nitrogen supply. An increase of day temperature to 30°C diminished the significant response of the C3 plant, while the response of C4 and CAM representatives to nitrogen nutrition did not change markedly.

Carbon Isotope Ratios of Plants of a Tropical Dry Forest in Mexico

Carbon isotope ratios were measured on leaves of the dominant species within a tropical dry forest in Mexico, which was characterized as being strongly drought deciduous. A variety of succulent epiphytes from diverse microsites had carbon isotope ratios indicating obligate crassulacean acid metabolism. All woody species examined had isotope ratios indicative of the C3 photosynthetic pathway, although there was a wide range of isotopic values. Two of the woody species that retained leaves during the dry season showed a large variation in carbon isotope ratios (up to 6 %o) that was dependent on microsite location. Key-words: Epiphytes, isotope ratios, crassulacean acid metabolism, water-use-efficiency, succulents

Leaf carbon isotope ratios of plants from a subtropical monsoon forest.

Carbon isotope ratios were used to survey the distribution of photosynthetic pathways among taxa, the relationship between photosynthetic pathway and habitat light levels, and the relationship between intercellular CO2 levels of C3 plants and habitat light levels within a subtropical monsoon forest in southern China. Of 128 species, most (94) possessed the C3 photosynthetic pathway; 33 species possessed the C4 pathway and all of these were restricted to high light locations. There was one epiphytic CAM species. The C3 species were classified as occurring in open, intermediate, and closed canopy sites. Among C3 species, carbon isotope ratios tended to become more negative with decreasing light availability in the habitat.