Isotopic Composition Of Plants Research Articles

Pasture usage by ancient pastoralists in the northern Kazakh steppe informed by carbon and nitrogen isoscapes of contemporary floral biomes

Identification of variation in pasture use by domesticated livestock has important implications for understanding the scale of animal husbandry and landscape use in modern and ancient societies alike. Here, we explore the influence of pasture floral composition, salinity, and water availability on the carbon (δ13C) and nitrogen (δ15N) isotopic composition of plants from the steppes of Kazakhstan. Our findings demonstrate geospatially defined differences in the isotopic composition of sedge marshes, saline marshes, and meadow steppes, information which we then use to inform animal management strategies used in the past. We then examine pasture usage by ancient livestock through carbon and nitrogen isotope analyses of bone collagen from animals that grazed in the northern Kazakh steppe. Pasturing strategies varied according to livestock taxa, with horses exhibiting lower δ13C and δ15N values relative to cattle, sheep, and goat. We argue that horses, which are highly mobile and freely graze over pastures extending over wide areas, were grazed under an extensive pasturing system. These data suggest that the isotopic composition of contemporary vegetation communities can help inform animal management strategies used in the past.

Effects of landscape configuration on the exchange of materials in seagrass ecosystems

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 532:89-100 (2015) - DOI: https://doi.org/10.3354/meps11384 Effects of landscape configuration on the exchange of materials in seagrass ecosystems Aurora M. Ricart*, Andreu Dalmau, Marta Pérez, Javier Romero Facultat de Biologia, Departament d’Ecologia, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain *Corresponding author: auroramartinez@ub.edu ABSTRACT: Landscape (or seascape) attributes play an important role in modulating the flow rates of materials between habitats in the coastal marine environment. Seagrass meadows are known to both export and import organic matter, thus establishing links with other habitats. Most of those links remain unexplored, and little is known about the relevance of landscape configuration on these flows. We studied the relationships between landscape configuration (continuous meadows, patchy meadows in a sand matrix and patchy meadows in a rock matrix) and the exchange and accumulation of detrital material. Moreover, we evaluated the impact of landscape configuration on (1) plant nutrient content and (2) the diet of a model deposit feeder (holothurians). We determined detritus stocks in seagrass meadows as well as the carbon and nitrogen elemental and isotopic composition of plants, detritus and other food sources (e.g. suspended organic matter). Based on this, we identified, by applying mixing models, the different contributions of these sources to the diets of deposit feeders. Our results showed that landscape configuration influences the exchange of materials across the coastal seascape. Less accumulation of detrital seagrass leaves was found in patchy meadows, although no effects were found for allochthonous materials. In addition, patchy seagrass meadows showed significantly lower nitrogen concentrations in leaves compared to continuous meadows. Landscape configuration had no effect on the diet of the deposit feeder studied. These findings highlight the importance of landscape-level processes in coastal waters and specifically warn of the possible effects of changes in meadow size on seagrass performance. KEY WORDS: Coastal seascape · Habitat linkages · Spatial subsidy · Deposit feeder diets · Stable isotopes · Holothuria Full text in pdf format Supplementary material PreviousNextCite this article as: Ricart AM, Dalmau A, Pérez M, Romero J (2015) Effects of landscape configuration on the exchange of materials in seagrass ecosystems. Mar Ecol Prog Ser 532:89-100. https://doi.org/10.3354/meps11384 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 532. Online publication date: July 21, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Carbon and nitrogen isotopic survey of northern peruvian plants: baselines for paleodietary and paleoecological studies.

The development of isotopic baselines for comparison with paleodietary data is crucial, but often overlooked. We review the factors affecting the carbon (δ13C) and nitrogen (δ15N) isotopic compositions of plants, with a special focus on the carbon and nitrogen isotopic compositions of twelve different species of cultivated plants (n = 91) and 139 wild plant species collected in northern Peru. The cultivated plants were collected from nineteen local markets. The mean δ13C value for maize (grain) was −11.8±0.4 ‰ (n = 27). Leguminous cultigens (beans, Andean lupin) were characterized by significantly lower δ15N values and significantly higher %N than non-leguminous cultigens. Wild plants from thirteen sites were collected in the Moche River Valley area between sea level and ∼4,000 meters above sea level (masl). These sites were associated with mean annual precipitation ranging from 0 to 710 mm. Plants growing at low altitude sites receiving low amounts of precipitation were characterized by higher δ15N values than plants growing at higher altitudes and receiving higher amounts of precipitation, although this trend dissipated when altitude was >2,000 masl and MAP was >400 mm. For C3 plants, foliar δ13C was positively correlated with altitude and precipitation. This suggests that the influence of altitude may overshadow the influence of water availability on foliar δ13C values at this scale.

A high-resolution stable isotopic record from the Junggar Basin (NW China): Implications for the paleotopographic evolution of the Tianshan Mountains

This study presents high-resolution oxygen and carbon isotopic records of paleosol carbonates from fluvial sediments and lacustrine carbonates, sampled from the Jingou He and Kuitun He stratigraphic sections, located in the northern Tianshan piedmont. These sections expose remarkable outcrops of Junggar foreland basin sediments that have been previously dated by high-resolution magnetostratigraphy to between ∼23.6 and ∼1Ma, and ∼10.5 and ∼3.1Ma. A total of 216 samples of fluvio-lacustrine sediments were collected from which isotopic analyses yield δ18O (SMOW) values that range from 13.7‰ to 29.9‰ in the Jingou He section, and 16.3‰ to 21.0‰ in the Kuitun He section. δ13C (PDB) values range from −12.9‰ to 3.0‰ in the Jingou He section and from −7.8‰ to −4.0% in the Kuitun He section. δ18O values decrease between ∼25 and 23Ma, and then remain relatively steady, with the exception of one period that contains samples with higher oxygen isotope values at ∼16Ma. During the periods when there are samples that overlap in time from the Kuitun He and Jingou He sections, we observe a difference of ∼1.7% between values from the two locales. The δ13C values also decrease between ∼25 and 23Ma, and then remain relatively steady until ∼10Ma with, again, one short period of higher values at ∼16Ma. Then, between ∼10 and 3.1Ma, carbon isotope values progressively increase. We interpret that δ18O and δ13C isotopic values during lacustrine periods (∼25–23Ma and ∼16Ma) as largely controlled by evaporation and opening/closing of the lake to external inputs. We interpret the δ18O values of paleosol carbonate in the Junggar Basin to be influenced by the hypsometry of the high Tianshan range while the δ13C values may record the uplift history of the depositional area in the foreland basin itself as well as the isotopic composition of plants. Consequently, we conclude that the Jingou He and Kuitun He drainage basins in the Central Tianshan have remained at relatively unchanged elevations for the past ∼20Ma. We also suggest that the elevation of the southern part of the foreland basin increased between ∼10 and ∼3.1Ma, probably as a result of tectonic deformation in the piedmont and sedimentary filling of the sedimentary basin. The carbon isotope record remains relatively stable through time, and isotopic values suggest that there was little or no expansion of C4 plants in this region in the late Miocene.

Development and Validation of a Method to Determine the Boron Isotopic Composition of Crop Plants

We present a comprehensive chemical and mass spectrometric method to determine boron isotopic compositions of plant tissue. The method including dry ashing, a three-step ion chromatographic boron-matrix separation, and (11)B/(10)B isotope ratio determinations using the Cs(2)BO(2)(+) graphite technique has been validated using certified reference and quality control materials. The developed method is capable to determine δ(11)B values in plant tissue down to boron concentrations of 1 mg/kg with an expanded uncertainty of ≤1.7‰ (k = 2). The determined δ(11)B values reveal an enormous isotopic range of boron in plant tissues covering three-quarters of the natural terrestrial occurring variation in the boron isotopic composition. As the local environment and anthropogenic activity mainly control the boron intake of plants, the boron isotopic composition of plants can be used for food provenance studies.

Nitrogen fixation and metabolism by groundwater-dependent perennial plants in a hyperarid desert.

The Central Asian Taklamakan desert is characterized by a hyperarid climate with less than 50 mm annual precipitation but a permanent shallow groundwater table. The perched groundwater (2-16 m) could present a reliable and constant source of nitrogen throughout the growing season and help overcome temporal nitrogen limitations that are common in arid environments. We investigated the importance of groundwater and nitrogen fixation in the nitrogen metabolism of desert plants by assessing the possible forms and availability of soil N and atmospheric N and the seasonal variation in concentration as well as isotopic composition of plant N. Water availability was experimentally modified in the desert foreland through simulated flooding to estimate the contribution of surface water and temporally increased soil moisture for nutrient uptake and plant-water relations. The natural vegetation of the Taklamakan desert is dominated by plants with high foliar nitrogen concentrations (2-3% DM) and leaf nitrate reductase activity (NRA) (0.2-1 micromol NO2- g(-1) FW h(-1)). There is little evidence that nitrogen is a limiting resource as all perennial plants exhibited fast rates of growth. The extremely dry soil conditions preclude all but minor contributions of soil N to total plant N so that groundwater is suggested as the dominant source of N with concentrations of 100 microM NO3-. Flood irrigation had little beneficial effect on nitrogen metabolism and growth, further confirming the dependence on groundwater. Nitrogen fixation was determined by the 15N natural abundance method and was a significant component of the N-requirement of the legume Alhagi, the average contribution of biologically fixed nitrogen in Alhagi was 54.8%. But nitrogen fixing plants had little ecological advantage owing to the more or less constant supply of N available from groundwater. From our data we conclude that the perennial species investigated have adapted to the environmental conditions through development of root systems that access groundwater to satisfy demands for both water and nutrients. This is an ecologically favourable strategy since only groundwater is a predictable and stable resource.

Delta13C values of grasses as a novel indicator of pollution by fossil-fuel-derived greenhouse gas CO2 in urban areas.

A novel fossil fuel pollution indicator based on the 13C/12C isotopic composition of plants has been designed. This bioindicator is a promising tool for future mapping of the sequestration of fossil fuel CO2 into urban vegetation. Theoretically, plants growing in fossil-fuel-CO2-contaminated areas, such as major cities, industrial centers, and highway borders, should assimilate a mixture of global atmospheric CO2 of delta13C value of -8.02 per thousand and of fossil fuel CO2 of average delta13C value of -27.28 per thousand. This isotopic difference should, thus, be recorded in plant carbon. Indeed, this study reveals that grasses growing near a major highway in Paris, France, have strikingly depleted delta13C values, averaging at -35.08 per thousand, versus rural grasses that show an average delta13C value of -30.59 per thousand. A simple mixing model was used to calculate the contributions of fossil-fuel-derived CO2 to the plant tissue. Calculation based on contaminated and noncontaminated isotopic end members shows that urban grasses assimilate up to 29.1% of fossil-fuel-CO2-derived carbon in their tissues. The 13C isotopic composition of grasses thus represents a promising new tool for the study of the impact of fossil fuel CO2 in major cities.

Oxygen isotope corrections for online delta(34)S analysis.

Elemental analyzers have been successfully coupled to stable-isotope-ratio mass spectrometers for online measurements of the delta(34)S isotopic composition of plants, animals and soils. We found that the online technology for automated delta(34)S isotopic determinations did not yield reproducible oxygen isotopic compositions in the SO(2) produced, and as a result calculated delta(34)S values were often 1-3 per thousand too high versus their correct values, particularly for plant and animal samples with high C/S ratio. Here we provide empirical and analytical methods for correcting the S isotope values for oxygen isotope variations, and further detail a new SO(2)-SiO(2) buffering method that minimizes detrimental oxygen isotope variations in SO(2).

The effect of soil hydrology on the oxygen and hydrogen isotopic compositions of plants’ source water

Abstract Many studies have demonstrated that the isotopic composition of plants’ source water is the main factor affecting the isotopic composition of tree rings. Because of soil hydrological processes, soil water as the source water for plants may isotopically differ from precipitation that contains climatic information (such as surface temperature). This study addresses the effects of soil hydrological processes on the isotopic compositions of soil water and discusses how these effects affect interpretations of tree ring data in isotopic dendroclimatology. We collected precipitation, soil gas at two depths (20 and 50 cm), and twigs from a maple tree ( Acer saccharum ) on a biweekly basis during the growing season in 1997–1999 at Hanover, NH, USA. Water was extracted from the twig samples by vacuum distillation. All water samples were analyzed for both δD and δ 18 O. Soil CO 2 was extracted from soil gas and measured for the δ 18 O values, and using the soil temperature and assuming isotopic equilibrium between CO 2 and H 2 O, we calculated the δ 18 O values of soil water. Comparisons among the isotopic time series of each type of sample indicate the following. (1) The isotopic composition of soil water is much less variable than that of precipitation, suggesting isotopic mixing between waters of different precipitation events. (2) In early spring, soil water at all depths is isotopically similar to winter precipitation, but with time the surface soil water becomes progressively enriched in deuterium and 18 O due to infiltration of summer rain and enrichment through soil water evaporation. (3) The influence of summer precipitation decreases with increasing depth, and soil at 50 cm can only receive water from large storms. (4) Replacement of old soil water with new infiltrating water is dependent upon frequency and intensity of growing season precipitation, and it is generally more efficient in a wet year than in a dry year. (5) The tree we studied uses water mainly from near-surface soil layers. (6) The δD–δ 18 O relationship in twig water indicates that soil water has experienced isotopic enrichment by evaporation. These results have important implications for selecting sites for paleoclimatic studies using isotopic data of tree rings.

Relationships between soil nitrogen dynamics and natural 15N abundance in plant foliage from Great Smoky Mountains National Park

We tested the hypothesis that naturally occurring nitrogen (N) isotope ratios in foliage (from plants that do not symbiotically fix atmospheric N2) are an indicator of soil N dynamics in forests. Replicate plots were established at eight locations ranging in elevation from 615 to 1670 m in Great Smoky Mountains National Park in eastern Tennessee, U.S.A. The locations selected ranged from N-poor (low-elevation) to N-rich (high-elevation) forest stands. Soils were sampled in June 1992; plants, forest floors, and upper mineral soils were sampled in August 1992. Net N mineralization and net nitrification potentials for surface mineral soils and organic matter layers at each site were determined by aerobic laboratory incubations. Soils and organic layers from high-elevation sites had greater net N mineralization and nitrification potentials than soils from low-elevation sites. There were significant (P ≤ 0.05) differences between study sites in soil 15N abundance. Therefore, we examined correlations between measures of soil N availability and both mean foliar δ15N values and mean enrichment factors (εp−s = δ15Nleaf − δ15Nsoil). In evergreens, maples, and ferns, mean foliar δ15N values and mean enrichment factors were positively correlated with net N mineralization and net nitrification potentials in soil. The observed relationships between natural 15N abundance in plant leaves and soil N availability were explained by a simple model of soil N dynamics. The model predicts how the isotopic composition of plant N is affected by the following factors: (i) varying uptake of soil NH4-N and NO3-N, (ii) the isotopic composition of different soil N pools, and (iii) relative rates of soil N transformations.

The 15N/14N ratios of plants in South Africa and Namibia: relationship to climate and coastal/saline environments

Data are presented for the 15N/14N ratios of 140 indigenous terrestrial plants from a wide variety of natural habitats in South Africa and Namibia. Over much of the area, from high-rainfall mountains to arid deserts, the δ 15N values of plants lie typically in the range -1 to +6‰; with no evident differences between C3 plants and C4 grasses. There is a slight correlation between δ 15N and aridity, but this is less marked than the correlation between the δ 15N values of animal bones and aridity. At coastal or saline sites, however, the mean δ 15N values for plants are higher than those at nearby inland or non-saline sites-e.g.: arid Namib coast (10‰ higher than inland Namib); wet Natal beach (5‰ higher than inland Natal); saline soils 500 km from coast (4‰ higher than non-saline soils). High values were also found at one site where there were no marked coastal or saline influences. These environmental effects on the isotopic composition of plants will extend upwards to the animals and humans they support. They therefore have important consequences for the use of nitrogen isotope data in the study of the dietary habits and trophic structures of modern and prehistoric communities.