Stable Carbon Isotope Discrimination Research Articles

Morphological change and genome-wide transcript analysis of Haloxylon ammodendron leaf development reveals morphological characteristics and genes associated with the different C3 and C4 photosynthetic metabolic pathways.

C4 photosynthesis outperforms C3 photosynthesis in natural ecosystems by maintaining a high photosynthetic rate and affording higher water-use and nitrogen-use efficiencies. C4 plants can survive in environments with poor living conditions, such as high temperatures and arid regions, and will be crucial to ecological and agricultural security in the face of global climate change in the future. However, the genetic architecture of C4 photosynthesis remains largely unclear, especially the genetic regulation of C4 Kranz anatomy. Haloxylon ammodendron is an important afforestation tree species and a valuable C4 wood plant in the desert region. The unique characteristic of H. ammodendron is that, during the seedling stage, it utilizes C3 photosynthesis, while in mature assimilating shoots (maAS), it switches to the C4 pathway. This makes an exceptional opportunity for studying the development of the C4 Kranz anatomy and metabolic pathways within individual plants (identical genome). To provide broader insight into the regulation of Kranz anatomy and non-Kranz leaves of the C4 plant H. ammodendron, carbon isotope values, anatomical sections and transcriptome analyses were used to better understand the molecular and cellular processes related to the development of C4 Kranz anatomy. This study revealed that H. ammodendron conducts C3 in the cotyledon before it switches to C4 in AS. However, the switching requires a developmental process. Stable carbon isotope discrimination measurements on three different developmental stages showed that young AS have a C3-like δ13C even though C4 Kranz anatomy is found, which is inconsistent with the anatomical findings. A C4-like δ13C can be measured in AS until they are mature. The expression analysis of C4 key genes also showed that the maAS exhibited higher expression than the young AS. In addition, many genes that may be related to the development of Kranz anatomy were screened. Comparison of gene expression patterns with respect to anatomy during leaf ontogeny provided insight into the genetic features of Kranz anatomy. This study helps with our understanding of the development of Kranz anatomy and provides future directions for studies on key C4 regulatory genes.

Variations of deep water uptake and water use efficiency indicated divergence in tree growth stability

Insights into forest growth stability in response to intensified climate change and disturbances is critical to maintain the continued flow and stability of forest services. However, the underlying drivers for tree growth stability remain poorly understood. In this study, we quantified the spatiotemporal pattern in tree growth stability of Chinese pine (Pinus tabulaeformis) plantations and its relationship to diverse driving factors (climate, stand structure, ecophysiological traits, soil properties, and topography) across a great climatic gradient in northern China in the period of 1979–2018. We calculated the coefficient of variation of tree ring chronology (TRIcv) to characterize tree growth stability and revealed that the TRIcv increased significantly with increasing multiyear mean aridity index (MAI) and vapor pressure deficit (VPD) spatially. Temporally, TRIcv displayed increasing trend in 25 of 40 study sites. Constrained redundancy analysis revealed that TRIcv was strongly mediated by water availability, water uptake from different soil layers, wood density, tree height, leaf stable carbon isotope discrimination (δ13C), and leaf nutrients. The ratio of water uptake from 60 to 80 cm soil layer and leaf δ13C were the two most important ecohydrological-related factors determining TRIcv, highlighting that the water uptake strategy and leaf water use efficiency play critical role in reshaping the tree growth stability of Chinese pine to cope with the intensifying climate change.

Tissue‐ and diet‐dependent stable carbon and nitrogen isotope discrimination: a calibration study in a captive shorebird species

In ecology, stable‐isotope ratios are widely used to determine diets of organisms and reconstruct food webs. This is usually done by analyzing the stable‐isotope ratios of nitrogen (δ15N), which increase with increasing trophic level, and those of carbon (δ13C), which correlate with the δ13C value of food source(s) and generally differ between terrestrial and marine food sources. Assimilation of food changes stable‐isotope ratios, resulting in different values between the food source and its consumer. These differences are known as isotope trophic discrimination factors and, if known, can be used to determine from the stable‐isotope ratios in the consumer's tissue what the consumer has been eating. What is often ignored is that discrimination factors can differ between consumer's food sources and also between tissue types. Therefore, we performed a controlled feeding study in red knots Calidris canutus to determine discrimination factors between different food sources and red knot tissues. We kept two groups of red knots in captivity on a stable diet, one group feeding on mudsnails and the other on Trouvit pellets, for several months, during which the birds molted their feathers. We analyzed δ13C and δ15N in both food sources and in five red knot tissues (blood cells, blood plasma and three feather types) and subsequently calculated the isotope discrimination factors. We confirmed that the discrimination factors differed between tissues, and also between diets. Our values deviated from general averages reported in reviews on a wide range of animals/birds, but were very similar to values from previous red knot and dunlin studies. We therefore think that our discrimination factors can be used in future stable isotope studies, not only on red knots, but also on other marine shorebird species and plea for careful consideration of using the right discrimination factors.Keywords: δ13C, δ15N, discrimination factor, red knot, shorebird, stable isotope

Toxicity and Starvation Induce Major Trophic Isotope Variation in Daphnia Individuals: A Diet Switch Experiment Using Eight Phytoplankton Species of Differing Nutritional Quality.

Stable isotope values can express resource usage by organisms, but their precise interpretation is predicated using a controlled experiment-based validation process. Here, we develop a stable isotope tracking approach towards exploring resource shifts in a key primary consumer species Daphnia magna. We used a diet switch experiment and model fitting to quantify the stable carbon (δ13C) and nitrogen (δ15N) isotope turnover rates and discrimination factors for eight dietary sources of the plankton species that differ in their cellular organization (unicellular or filamentous), pigment and nutrient compositions (sterols and polyunsaturated fatty acids), and secondary metabolite production rates. We also conduct a starvation experiment. We evaluate nine tissue turnover models using Akaike's information criterion and estimate the repetitive trophic discrimination factors. Using the parameter estimates, we calculate the hourly stable isotope turnover rates. We report an exceedingly faster turnover value following dietary switching (72 to 96 h) and a measurable variation in trophic discrimination factors. The results show that toxic stress and the dietary quantity and quality induce trophic isotope variation in Daphnia individuals. This study provides insight into the physiological processes that underpin stable isotope patterns. We explicitly test multiple alternative dietary sources and fasting and discuss the parameters that are fundamental for field- and laboratory-based stable isotope studies.

Application of biomarker recovery method for oil–source correlation in severe to extreme biodegradation in eastern Chepaizi Uplift, Junggar Basin (NW China)

Biodegradation always alters the original characteristics of biomarkers, thereby limiting the identification of heavy oil sources. The eastern Chepaizi Uplift is a typical heavy oil-producing unit in northwestern China, most of heavy oils were discovered in Lower Neogene Shawan Formation, Lower Cretaceous Tugulu Group, and Upper Carboniferous Xibeikulasi Formation, the source of heavy oils is a controversial issue. This study adopted a biomarker recovery method based on the quality conservation principle that uses the sum of the mass of the residual biomarkers and their corresponding biodegradation products to obtain the mass of the original biomarkers. The 25–norhopane and the 17–nortricyclic terpane homologs, which were detected in severely to extremely biodegraded oils in the Chepaizi Uplift, while the corresponding hopanes (H) and tricyclic terpanes (TT) were eliminated, which are therefore an excellent option for biomarker recovery. A total of 13 relevant parameters were selected for recovery, the results indicated that the effect is particularly notable: the standard deviations of the tricyclic terpenes-related parameters (for example, (C20+C24) TT/(C23+C24) TT) and the hopanes-related parameters (for example, C30H/G (Gammacerane)) were 0.258–0.268, 0.400–0.540 before the parameter recovery, then they changed to 0.174–0.260, 0.176–0.273 after the parameter recovery, which indicates the dispersion of those parameter sets are significantly reduced and them numerical characteristics are more clearly highlighted. And the recovery result shows that the characteristics of 13 parameters are more consistent with the Carboniferous source rocks in this region and the Permian source rocks in Shawan Sag, indicating genetic affinity of heavy oil with these source kitchens. The reliability of oil source determination was verified using the stepwise discriminant analysis method and stable carbon isotope discrimination. Therefore, we believe that the biomarker recovery method is an effective method for oil–source correlation of heavy oil and can help deep oil exploration in biodegradation regions.

Direct evidence of drought stress memory in mulberry from a physiological perspective: Antioxidative, osmotic and phytohormonal regulations

Drought stress commonly happens more than once during the life cycle of perennial trees. Stress memory endows better capacity to cope with repeated stresses for plants, while the underlying mechanisms are not fully elucidated. In this study, 2-month-old saplings of two mulberry cultivars (Husang32 and 7307 of Morus multicaulis) with or without an early soil water deficit were subjected to subsequent drought for 9 days. The shoot height growth, biomass production, stable carbon isotope discrimination, phytohormones, reactive oxygen species (ROS), osmotic substances and antioxidant enzymes were analyzed after the first and the second drought, respectively. Drought priming saplings sustained comparable or slightly higher biomass accumulation under the second drought than those non-priming. They also exhibited decreased levels of soluble sugars, free proline and soluble proteins, lower accumulation of malonaldehyde (MDA) and superoxide anion (O2•−), reduced activities of superoxide dismutase (SOD) and peroxidase (POD) compared to non-priming plants. Moreover, cultivar Husang32 exhibited elevated abscisic acid (ABA) and jasmonic acid (JA) where 7307 displayed opposite changes. PCA suggests that MDA, H2O2, free proline, SOD and POD in roots, and ROS, soluble sugars and glutamate reductase in leaves are dominant factors influenced by stress memory. ABA and JA in leaves also play important roles in exerting drought imprints. Collectively, stress memory can confer mulberry resistance to recurrent drought via combined regulations of antioxidative protection, osmotic adjustment and phytohormonal responses.

Stable Carbon Isotope Discrimination (<i>δ</i><sup>13</sup>C) of Cotton Burrs and Seeds as a Season-Long Integrator of Crop Water Stress

Plant-based irrigation management schemes typically use surrogates such as canopy temperature, alone, or in conjunction with environmental variables, to infer the degree of “crop stress” (biological strain) induced by drought. Few systematic studies of the relationship between “crop stress”, as defined by such surrogates, and physiological estimates of water use efficiency (WUE) exist over both daily and seasonal time scales relevant to agronomic irrigation control. The systematic application of stable carbon isotope discrimination (δ13C) might allow post hoc evaluation of irrigation scheduling schemes and might also be a useful germplasm screening tool if the source(s) of variability can be uncovered and/or controlled. Results from preliminary efforts comparing leaf and cotton seed δ13C to season-long water deficits showed that seeds are more useful indicators of season-long water stress and water use efficiency during crop development.

Tree-Ring Width and Carbon Isotope Chronologies Track Temperature, Humidity, and Baseflow in the Tianshan Mountains, Central Asia

Concerns have been raised about the negative impacts of global warming on the hydrological climate change and ecosystems of Asia. Research on the high-altitude mountainous regions of Asia with relatively short meteorological and hydrological records relies on paleoclimate proxy data with long time scales. The stable isotopes of tree-rings are insightful agents that provide information on pre-instrumental climatic and hydrological fluctuations, yet the variability of these data from different regions along the Tianshan Mountains has not been fully explored. Herein, we related climate data with tree-ring width (TRW) chronologies and δ13C (stable carbon isotope discrimination) series to discern if the Picea schrenkiana in the Ili and Manas River Basins are sensitive to climatic factors and baseflow (BF). The results show significant correlations between temperature and TRW chronologies, temperature and δ13C, relative humidity and TRW chronologies, and BF and δ13C. Temperature, particularly the mean late summer to early winter temperature, is a pronounced limiting factor for the tree-ring and the δ13C series in the Manas River Basin, located in the middle of the North Tianshan Mountains. Meanwhile, mean early spring to early autumn temperature is a limiting factor for that of the Ili River Basin, located on the southern slope of the North Tianshan Mountains. We conclude that different seasonal variations in temperature and precipitation of the two river basins exerted significant control on tree growth dynamics. Tree-ring width and tree-ring δ13C differ in their sensitivity to climate and hydrological parameters to which tree-ring δ13C is more sensitive. δ13C showed significant lag with precipitation, and the lag correlation showed that BF, temperature, and precipitation were the most affected factors that are often associated with source water environments. δ13C series correlated positively to winter precipitation, suggesting baseflow was controlling the length of the growing season. The tree-ring δ13C provided information that coincided with TRW chronologies, and supplied some indications that were different from TRW chronologies. The carbon stable isotopes of tree-rings have proven to be powerful evidence of climatic signals and source water variations.

Relationship between stable carbon isotope discrimination and water use efficiency under deficit drip irrigation of kiwifruit in the humid areas of South China

In order to explore the application value of the stable carbon isotope discrimination method in improving water use efficiency (WUE) and productivity of kiwifruit under deficit drip irrigation, five water deficit levels (55 %, 65 %, 75 %, 85 % and 100 % of full irrigation) with thirteen treatments were established at three growth stages in field-grown kiwifruit. The leaf stable carbon isotope discrimination (ΔL) at different growth stages and fruit stable carbon isotope discrimination (ΔF) at fruit maturation stage of kiwifruit were determined; the changes of WUE at leaf and yield levels were analyzed, and the indicating effect of carbon isotope discrimination (Δ13C) on the WUE of kiwifruit was also verified. The results showed that moderate water deficit improved the WUEi (photosynthesis rate/transpiration rate, Pn/Tr) and WUEn (photosynthesis rate/stomatal conductance, Pn/gs) of kiwifruit at each growth stage. Compared with full irrigation (CK), the yield (Y) and WUEy (yield/crop evapotranspiration, Y/ET) of low water deficit treatment (LD) at fruit maturation stage increased by 14.75 % and 23.74 %, respectively. There were significant relationships between ΔL and ΔF versus WUE, Ci/Ca (the specific value of intercellular CO2 concentration and ambient atmosphere CO2 concentration), CE (carboxylation rate), ET (crop evapotranspiration) and Y under deficit drip irrigation, respectively. ΔL was negatively correlated with WUEn (coefficient of determination, R2=0.4844, P<0.01) over the whole growth period, whereas ΔF was positively correlated with Y (R2=0.2805, P<0.05) and ET (R2=0.9267, P<0.01), respectively. Overall, this study verifies that ΔL can be used as a useful evaluation index of WUEn, and ΔF is an important indicator of quantifying Y and ET of kiwifruit under deficit drip irrigation.

Growth decline of Pinus Massoniana in response to warming induced drought and increasing intrinsic water use efficiency in humid subtropical China

Pinus Massoniana is the most widely distributed coniferous species in southern China and one of the most distributed species for plantation in China. It is not uncertain about the responses of tree growth to the combined effects of regional drying and the increase in the intrinsic water-use efficiency (iWUE) due to increased atmospheric CO2. This study addressed this issue by comparing the tree growth patterns as represented by three tree-ring width chronologies with climate variables and three iWUE series derived from three tree-ring stable carbon isotope discrimination chronologies (Δ13C) from Pinus Massoniana in Daiyun Mountain, central Fujian province of China. Among these chronologies, we reported the first tree-ring carbon isotope discrimination chronologies (Δ13C) from Fuzhou area spanning last 210 years. It was found that tree radial growth is mainly limited by dry condition from May to October. Growth limitation by cold condition was only found in one high altitude site (780m) in early spring and late autumn. The tree-ring carbon discrimination was enhanced under conditions with low relative humidity and sufficient sunshine in late summer and autumn. In general, the iWUE showed a significantly increasing trend since the 1850s for all the sites in response to the increase in atmospheric CO2. However, the growth promotion of the increased iWUE on tree growth could not compensate the growth limitation caused by drought. Especially since the 1960s, a growth decline was found at two drought stressed sites at low altitudes. On the other hand, the increase in temperature of spring and autumn and iWUE has most likely enhanced tree growth at the high altitude site.

Instantaneous and long-term CO2 assimilation of Platycladus orientalis estimated from 13C discrimination

• A simple, nondestructive method to estimate CO 2 assimilation. • The method combined sap flow measurements and stable carbon isotope discrimination. • The method could estimate CO 2 assimilation on different time scales. Long-term forest productivity and carbon sequestration capacity are affected by climate change, and have become a global concern. In this study, we provide a simple and nondestructive method to determine tree CO 2 assimilation across multiple time scales. The new method combines sap flow and stable carbon isotope discrimination ( Δ 13 C) measurements to estimate carbon assimilation. We analyzed variability and conducted paired-sample t -tests to compare CO 2 assimilation estimated from gas exchange measurements and the new approach to verify its accuracy and applicability. Gas exchange and isotopic measurements both showed that the CO 2 assimilation rate in the morning was higher than in the afternoon, and peak values occurred around 10–11 a.m., which may have been due to nocturnal water storage and higher stomatal conductance in the morning. Diurnal, monthly, and annual CO 2 assimilation of P. orientalis variations were related to water supply conditions. Compared with previous research, we experimented using tree-ring stable carbon isotope discrimination ( Δ 13 C) and sap flow measurement to estimate annual CO 2 assimilation and the results were consistent with other traditional methods. Platycladus orientalis is effective and responsive to water supply, which explained why it adapts well in semi-arid areas. The new method for estimating CO 2 assimilation was accurate and applicable in semi-arid areas around Beijing.

The response of mesophyll conductance to short- and long-term environmental conditions in chickpea genotypes.

. Mesophyll conductance (gm) has been shown to vary between genotypes of a number of species and with growth environments, including nitrogen availability, but understanding of gm variability in legumes is limited. We might expect gm in legumes to respond differently to limited nitrogen availability, due to their ability to fix atmospheric N2. Using online stable carbon isotope discrimination method, we quantified genetic variability in gm under ideal conditions, investigated gm response to N source (N2-fixation or inorganic N) and determined the effects of N source and water availability on the rapid response of gm to photosynthetic photon flux density (PPFD) and radiation wavelength in three genotypes of chickpea (Cicer arietinum). Genotypes varied 2-fold in gm under non-limiting environments. N-fed plants had higher gm than N2-fixing plants in one genotype, while gm in the other two genotypes was unaffected. gm response to PPFD was altered by N source in one of three genotypes, in which the gm response to PPFD was statistically significant in N-fed plants but not in N2-fixing plants. There was no clear effect of moderate water stress on the gm response to PPFD and radiation wavelength. Genotypes of a single legume species differ in the sensitivity of gm to both long- and short-term environmental conditions, precluding utility in crop breeding programmes.

Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 76:115-130 (2018) - DOI: https://doi.org/10.3354/cr01526 Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China Guoyang Guo1, Keyan Fang1,2,*, Jinbao Li3, Hans W. Linderholm2, Dawen Li1, Feifei Zhou1, Zhipeng Dong1, Yingjun Li1, Lei Wang1 1Institute of Geography, Key Laboratory of Humid Subtropical Eco-geographical Process (Ministry of Education), College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, PR China 2Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Box 460, 405 30 Gothenburg, Sweden 3Department of Geography, University of Hong Kong, Pokfulam, Hong Kong SAR *Corresponding author: kfang@fjnu.edu.cn ABSTRACT: Understanding the responses of tree growth and intrinsic water-use efficiency (iWUE) to anthropogenic CO2 increase and climate warming provides important benchmarks for evaluating future forest dynamics under different scenarios of warming and CO2 changes. Relative to the short period of instrumental data of the past few decades, long-term tree-ring width and stable carbon isotopic (δ13C) data are invaluable in fully comprehending their interactions during the entire industrial era, since ~1850. Here, we present a tree-ring width chronology (1856 to 2015) and δ13C series (1876-2015) of Pinus massoniana for Yongtai county of Fujian province, in humid subtropical China, a ‘green island’ relative to other dry subtropical areas of the world. Tree growth was limited by precipitation of the hydrological year (previous November to current October) (r = 0.568, p < 0.001), and the stable carbon isotope discrimination (Δ13C) was strongly correlated with relative humidity in September-October (r = -0.677, p < 0.001) of the current growing season. We found that the iWUE increased by 40.9% since 1876. Specifically, we found that the ci:ca ratio decreased during the study period whereas intercellular CO2 concentration (ci) increased. The negative relationship between basal area increment (BAI) and iWUE indicated that increasing iWUE may not lead to long-term enhancement of tree growth. Our results indicated a drought-induced limitation to tree growth in response to rising CO2, and that trees may mitigate the negative effects of a decrease in water availability through a reduction in stomatal conductance. KEY WORDS: Tree-ring · Stable carbon isotope · Intrinsic water-use efficiency · Pinus massoniana · Humid subtropical China Full text in pdf format PreviousNextCite this article as: Guo G, Fang K, Li J, Linderholm HW and others (2018) Increasing intrinsic water-use efficiency over the past 160 years does not stimulate tree growth in southeastern China. Clim Res 76:115-130. https://doi.org/10.3354/cr01526 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 76, No. 2. Online publication date: October 10, 2018 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2018 Inter-Research.

Tree-Ring Carbon Isotope Records from the Western Oregon Cascade Mountains Primarily Record Summer Maximum Temperatures

Abstract Here we examine climatic influences on inter-annual variation in latewood tree growth (i.e. ring-width indices, RWILW) and stable-carbon isotope discrimination (Δ13CLW) from 1950 to 2013 at two SNOTEL snowpack monitoring sites in the Oregon Cascade Mountains. Douglas-fir and mountain hemlock trees were sampled at the lower and upper elevation sites where annual peak snow water equivalent (SWE) averaged 467 and 1128 mm, respectively. RWILW chronologies were poorly correlated among sites/species (r = 0.23, P = 0.063) and neither exhibited strong correlations with monthly or seasonal climate variables. By contrast, Δ13CLW chronologies were significantly correlated (r = 0.69, P < 0.001) and exhibited stronger climate responses. Multiple regression analyses identified summertime maximum temperature (Tmax) and/or vapor pressure deficit (VPD) as the primary drivers of Δ13CLW. Secondary influences included summertime precipitation, specific humidity, cloud cover, and SWE from the previous fall and winter...

Stable isotope discrimination factors and between-tissue isotope comparisons for bone and skin from captive and wild green sea turtles (Chelonia mydas).

The ecological application of stable isotope analysis (SIA) relies on taxa- and tissue-specific stable carbon (Δ13 C) and nitrogen (Δ15 N) isotope discrimination factors, determined with captive animals reared on known diets for sufficient time to reflect dietary isotope ratios. However, captive studies often prohibit lethal sampling, are difficult with endangered species, and reflect conditions not experienced in the wild. We overcame these constraints and determined the Δ13 C and Δ15 N values for skin and cortical bone from green sea turtles (Chelonia mydas) that died in captivity and evaluated the utility of a mathematical approach to predict discrimination factors. Using stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios from captive and wild turtles, we established relationships between bone stable isotope (SI) ratios and those from skin, a non-lethally sampled tissue, to facilitate comparisons of SI ratios among studies using multiple tissues. The mean (±SD) Δ13 C and Δ15 N values (‰) between skin and bone from captive turtles and their diet (non-lipid-extracted) were 2.3 ± 0.3 and 4.1 ± 0.4 and 2.1 ± 0.6 and 5.1 ± 1.1, respectively. The mathematically predicted Δ13 C and Δ15 N values were similar (to within 1‰) to the experimentally derived values. The mean δ15 N values from bone were higher than those from skin for captive (+1.0 ± 0.9‰) and wild (+0.8 ± 1.0‰) turtles; the mean δ13 C values from bone were lower than those from skin for wild turtles (-0.6 ± 0.9‰), but the same as for captive turtles. We used linear regression equations to describe bone vs skin relationships and create bone-to-skin isotope conversion equations. For sea turtles, we provide the first (a) bone-diet SI discrimination factors, (b) comparison of SI ratios from individual-specific bone and skin, and (c) evaluation of the application of a mathematical approach to predict stable isotope discrimination factors. Our approach opens the door for future studies comparing different tissues, and relating SI ratios of captive to wild animals.

Evolutionary differences in Δ13C detected between spore and seed bearing plants following exposure to a range of atmospheric O2:CO2 ratios; implications for paleoatmosphere reconstruction

The stable carbon isotopes of fossil plants are a reflection of the atmosphere and environment in which they grew. Fossil plant remains have thus stored information about the isotopic composition and concentration of atmospheric carbon dioxide (pCO2) and possibly pO2 through time. Studies to date, utilizing extant plants, have linked changes in plant stable carbon isotopes (δ13Cp) or carbon isotope discrimination (Δ13C) to changes in pCO2 and/or pO2. These studies have relied heavily on angiosperm representatives, a phylogenetic group only present in the fossil record post-Early Cretaceous (∼140million years ago (mya)), whereas gymnosperms, monilophytes and lycophytes dominated terrestrial ecosystems prior to this time. The aim of this study was to expand our understanding of carbon isotope discrimination in all vascular plant groups of C3 plants including lycophytes, monilophytes, gymnosperms and angiosperms, under elevated CO2 and sub-ambient O2 to explore their utility as paleo-atmospheric proxies. To achieve this goal, plants were grown in controlled environment chambers under a range of O2:CO2 ratio treatments. Results reveal a strong phylogenetic dependency on Δ13C, where spore-bearing (lycophytes and monilophytes) have significantly higher 13C discrimination than seed plants (gymnosperms and angiosperms) by ∼5‰. We attribute this strong phylogenetic signal to differences in Ci/Ca likely mediated by fundamental differences in how spore and seed bearing plants control stomatal aperture. Decreasing O2:CO2 ratio in general resulted in increased carbon isotope discrimination in all plant groups. Notably, while all plant groups respond unidirectionally to elevated atmospheric CO2 (1900ppm and ambient O2), they do not respond equally to sub-ambient O2 (16%). We conclude that (1) Δ13C has a strong phylogenetic or ‘reproductive grade’ bias, whereby Δ13C of spore reproducing plants is significantly different to seed reproducing taxa. (2) Δ13C increases with decreasing O2:CO2 ratios (where significant) but is more likely a result of mechanistically uncoupled responses to elevated pCO2 and sub-ambient O2; and (3) due to this response we find δ13Ca cannot be calculated from δ13Cp unless environmental influences such as O2:CO2 ratio can be independently constrained. Therefore, interpretations of trends in fossil plant δ13Cp to reconstruct paleoatmospheric CO2 concentration should include cross calibration based on a nearest living relative, appropriate nearest living equivalent, or utilizing the phylogenetic corrections produced from this study.

Growth, Morphological, and Physiological Responses to Drought Stress in Bothriochloa ischaemum.

Water shortage in the arid-semiarid regions of China seriously hampers ecosystem construction. Therefore, elucidation of the mechanisms by which vegetation in that area responds to drought stress may enable us to improve utilization of limited water resources and thus contend with the problem of drought and water shortage. We studied Bothriochloa ischaemum, a native grass species, conducted potting control tests to compare several indicators of B. ischaemum grown under three different moisture conditions (80%, 60%, 40% Field capacity represent sufficient water supply, mild water stress, and serious water stress, respectively). Plant response parameters measured included biomass accumulation, root morphology, transient water use efficiency (WUE), stable carbon isotope ratio (δ13C), and stable carbon isotope discrimination (Δ13C) of various plant organs and their interrelationships. B. ischaemum had the greatest WUE under mild drought stress. However, serious drought stress resulted in considerable decline in overall biomass but substantial increase in root-to-shoot ratio and fine-root biomass. Coarse-root biomass dropped appreciably, indicating that serious drought stress leads to allocation non-uniformity of the carbon “sink.” δ13C and Δ13C of stem correlated considerably with root morphology, suggesting the feasibility of characterizing WUE, biomass, and root morphology of B. ischaemum via the stable carbon isotope approach. Our evaluation of 21 drought resistance indicators of B. ischaemum showed that under a given moisture treatment gradient one can isolate an optimal indicator to express growth, morphology, and physiology, to improve the accuracy of depicting plant drought resistance and simplify the drought resistance indicator system. This study elucidates the response mechanism of B. ischaemum to drought stress and provides theoretical support to screening of drought-resistant plants across the arid-semiarid regions of China.

Landscape transformations at the dawn of agriculture in southern Syria (10.7–9.9 ka cal. BP): Plant-specific responses to the impact of human activities and climate change

In southwest Asia, the accelerated impact of human activities on the landscape has often been linked to the development of fully agricultural societies during the middle and late Pre-Pottery Neolithic B (PPNB) period (around 10.2–7.9 ka cal. BP). This work contributes to the debate on the environmental impact of the so-called Neolitisation process by identifying the climatic and anthropogenic factors that contributed to change local and regional vegetation at the time when domesticated plants appeared and developed in southern Syria (around 10.7–9.9 ka cal. BP). In this work a multidisciplinary analysis of plant microremains (pollen and phytoliths) and macroremains (wood charcoal) is carried out along with stable carbon isotope discrimination of wood charcoals in an early PPNB site (Tell Qarassa North, west of the Jabal al-Arab area). Prior to 10.5 ka cal. BP, the results indicate a dynamic equilibrium in the local and regional vegetation, which comprised woodland-steppe, Mediterranean evergreen oak-woodlands, wetland vegetation and coniferous forests. Around 10.5–9.9 ka cal. BP, the elements that regulated the vegetation system changed, resulting in reduced proportions of arboreal cover and the spread of cold-tolerant and wetlands species. Our data show that reinforcing interaction between the elements of the anthropogenic (e.g. herding, fire-related activities) and climatic systems (e.g. temperature, rainfall) contributed to the transformation of early Holocene vegetation during the emergence of fully agricultural societies in southern Syria.

Basal area growth, carbon isotope discrimination, and intrinsic water use efficiency after fertilization of Douglas-fir in the Oregon Coast Range

Many hectares of intensively managed Douglas-fir (Pseudotsuga menziesii Mirb. Franco) stands in western North America are fertilized with nitrogen (N) to increase growth rates, but only about ⅔ of all stands respond. Understanding the mechanisms of response facilitates prioritization of stands for treatment. The primary objective of this study was to test the hypothesis that the short-term basal area growth response to a single application of 224kgNha−1 as urea was associated with reduced stable carbon isotope discrimination (Δ13C) and increased intrinsic water use efficiency (iWUE) in a 20-yr-old plantation of Douglas-fir in the Oregon Coast Range, USA. Increment cores were measured to estimate earlywood, latewood, and total basal area increment over a time series from 1997 to 2015. Stable carbon isotope discrimination and iWUE were estimated using earlywood and latewood stable carbon isotope concentrations in tree-ring holocellulose starting seven years before fertilization in early 2009 and ending seven years after treatment. A highly significant (p<0.01) interaction effect between fertilization treatment and year was found for total basal area growth and earlywood basal area increment. Specifically, fertilized trees showed significant responses (p<0.05) in total basal area growth and earlywood basal area increment in the first (2009) and second (2010) growing seasons after fertilization in 2009. A marginally significant (p<0.10) fertilization effect was found for latewood basal area increment only in the first growing season after treatment. A significant treatment×year interaction was also found for Δ13C and iWUE in earlywood and latewood. Fertilization significantly reduced earlywood Δ13C and increased earlywood iWUE in the first and second growing seasons after fertilization. Only a marginally significant fertilization effect was detected for latewood Δ13C and iWUE in the second growing season after treatment. Previous studies of N fertilization of Douglas-fir forests have reported consistently increased growth and iWUE on low productivity sites treated with relatively high fertilization rates. This study suggested that these responses can also be observed on highly productive sites despite their lower frequency and apparently shorter duration. Other key mechanisms driving growth responses appear less important than iWUE, including an increase in LAI and shift from belowground to aboveground carbon allocation.

采用稳定碳同位素法分析白羊草在不同干旱胁迫下的水分利用效率

PDF HTML阅读 XML下载 导出引用 引用提醒 采用稳定碳同位素法分析白羊草在不同干旱胁迫下的水分利用效率 DOI: 10.5846/stxb201601180112 作者: 作者单位: 西安理工大学,西安理工大学,西安理工大学,西安理工大学,西安理工大学,西安理工大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41330858）；国家自然科学基金（41471226，41271290）；校级基金（310-252071506） Effects of drought stress on Bothriochloa ischaemum water-use efficiency based on stable carbon isotope Author: Affiliation: Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:本研究以黄土高原乡土草种白羊草（Bothriochloa ischaemum （L.）Keng.）为研究对象，采用盆栽控制实验，比较白羊草在3个水分处理（CK80%FC、MS60%FC和SS 40%FC）下的生物量积累和分配模式、瞬时水分利用效率（WUE）、不同部位（新叶、老叶、茎、细根、粗根）的稳定碳同位素组成（δ13C）和碳同位素分辨率（Δ13C）及其相互关系，以及干旱胁迫下影响水分利用效率的主导环境因子。结果表明：1）重度干旱胁迫显著降低植物整体生物量，显著增加根冠比和细根生物量比例；2）随着干旱胁迫加剧，白羊草各器官的δ13C均呈上升趋势，Δ13C呈减小趋势，SS处理不同器官δ13C和Δ13C没有显著差异，CK和MS处理的各器官δ13C均值表现分别为细根 > 粗根 > 老叶 > 新叶 > 茎、细根 > 新叶 > 老叶 > 粗根 > 茎，CK和MS处理Δ13C的值总体呈根 < 叶 < 茎。3）新叶的δ13CNL和Δ13CNL与WUE的相关系数均最大，说明利用稳定碳同位素方法测定白羊草水分利用效率具有可行性。4）不同水分处理的WUE的主导影响因子不同，CK、MS、SS水分处理WUE分别受到叶面温度、大气水汽压亏缺和空气温度的影响最大。为采用稳定碳同位素方法指示白羊草水分利用效率可行性及阐明植物的胁迫响应机制提供理论依据。 Abstract:Owing to low precipitation and high inter-annual variability, the Loess hilly and valley region experiences frequent drought, which significantly affects plant growth. Studying the response mechanism of plants to water stress is important with respect to improving water-use efficiency (WUE) in this arid and semi-arid area. In the present research, Bothriochloa ischaemum (L.) Keng., a typical native species in the Loess hilly-gully region, was selected to investigate biomass accumulation and allocation, instantaneous WUE, stable carbon isotope composition (δ13C), and stable carbon isotope discrimination (Δ13C) in different organs under three water regimes: control [CK, 80% field capacity (FC)], mild water stress (MS, 60% FC), and severe stress (SS, 40% FC). Photosynthetic parameters of B. ischaemum were measured at 09:00-11:00 on sunny windless days (Aug 3, 10, and 13,2014), using a portable photosynthesis determination system (Li-6400; Li-Cor, USA). On Nov 11, when the experiment ended, the new leaf, old leaf, stem, fine root, and coarse root parts of seedlings were sampled carefully and weighed (with accuracy 0.001 g) after drying at 65℃. The root-to-shoot ratio was then calculated as the ratio of the belowground dry biomass to aboveground dry biomass. The δ13C of different plant parts was measured using a CCIA-36d-EP Carbon isotope ratio mass spectrometer (Los Gatos Research, USA). The Δ13C of different plant parts was calculated based on δ13C and the carbon isotope ratio of atmospheric CO2. Many environmental factors that might affect WUE were analyzed to explore the response mechanisms of B. ischaemum under drought conditions. The following results were obtained. (1) The total biomass of B. ischaemum was significantly decreased under the SS condition, whereas the root-to-shoot ratio and fine root biomass were significantly increased under this water regime. (2) The δ13C and Δ13C in different plant parts showed different trends. Drought stress led to an increase in the δ13C value and decrease in the Δ13C value. There was no significant difference in the δ13C and Δ13C of different plant parts under the SS condition. The δ13C values under CK and MS conditions were in the order of fine root > coarse root > old leaf > new leaf > stem, and fine root > new leaf > old leaf > coarse root > stem, respectively. Furthermore, the Δ13C values under CK and MS conditions were all in the order of root < leaf δ13C and Δ13C values of new leaves had the highest correlation coefficients with respect to WUE, which indicated that the stable carbon isotope technique is suitable for the determination of the WUE of B. ischaemum. (4) The WUE was affected by different environmental factors under different water regimes. Leaf temperature, atmospheric water vapor pressure, and air temperature were the most important factors affecting WUE under CK, MS, and SS conditions, respectively. This research provides a theoretical basis for the feasibility of using the stable carbon isotope method to determine the WUE of B. ischaemum, and for elucidating the mechanism underlying the response of B. ischaemum to water stress. 参考文献 相似文献 引证文献